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Sample records for lake malawi cichlid

  1. Geographical ancestry of Lake Malawi's cichlid fish diversity.

    PubMed

    Genner, Martin J; Ngatunga, Benjamin P; Mzighani, Semvua; Smith, Alan; Turner, George F

    2015-06-01

    The Lake Malawi haplochromine cichlid flock is one of the largest vertebrate adaptive radiations. The geographical source of the radiation has been assumed to be rivers to the south and east of Lake Malawi, where extant representatives of the flock are now present. Here, we provide mitochondrial DNA evidence suggesting the sister taxon to the Lake Malawi radiation is within the Great Ruaha river in Tanzania, north of Lake Malawi. Estimates of the time of divergence between the Lake Malawi flock and this riverine sister taxon range from 2.13 to 6.76 Ma, prior to origins of the current radiation 1.20-4.06 Ma. These results are congruent with evaluations of 2-3.75 Ma fossil material that suggest past faunal connections between Lake Malawi and the Ruaha. We propose that ancestors of the Malawi radiation became isolated within the catchment during Pliocene rifting that formed both Lake Malawi and the Kipengere/Livingstone mountain range, before colonizing rivers to the south and east of the lake region and radiating within the lake basin. Identification of this sister taxon allows tests of whether standing genetic diversity has predisposed Lake Malawi cichlids to rapid speciation and adaptive radiation. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  2. Identification of Cichlid Fishes from Lake Malawi Using Computer Vision

    PubMed Central

    Joo, Deokjin; Kwan, Ye-seul; Song, Jongwoo; Pinho, Catarina; Hey, Jody; Won, Yong-Jin

    2013-01-01

    Background The explosively radiating evolution of cichlid fishes of Lake Malawi has yielded an amazing number of haplochromine species estimated as many as 500 to 800 with a surprising degree of diversity not only in color and stripe pattern but also in the shape of jaw and body among them. As these morphological diversities have been a central subject of adaptive speciation and taxonomic classification, such high diversity could serve as a foundation for automation of species identification of cichlids. Methodology/Principal Finding Here we demonstrate a method for automatic classification of the Lake Malawi cichlids based on computer vision and geometric morphometrics. For this end we developed a pipeline that integrates multiple image processing tools to automatically extract informative features of color and stripe patterns from a large set of photographic images of wild cichlids. The extracted information was evaluated by statistical classifiers Support Vector Machine and Random Forests. Both classifiers performed better when body shape information was added to the feature of color and stripe. Besides the coloration and stripe pattern, body shape variables boosted the accuracy of classification by about 10%. The programs were able to classify 594 live cichlid individuals belonging to 12 different classes (species and sexes) with an average accuracy of 78%, contrasting to a mere 42% success rate by human eyes. The variables that contributed most to the accuracy were body height and the hue of the most frequent color. Conclusions Computer vision showed a notable performance in extracting information from the color and stripe patterns of Lake Malawi cichlids although the information was not enough for errorless species identification. Our results indicate that there appears an unavoidable difficulty in automatic species identification of cichlid fishes, which may arise from short divergence times and gene flow between closely related species. PMID:24204918

  3. Genetic population structure indicates sympatric speciation of Lake Malawi pelagic cichlids.

    PubMed Central

    Shaw, P W; Turner, G F; Idid, M R; Robinson, R L; Carvalho, G R

    2000-01-01

    Allopatric processes of speciation have routinely been presented to explain the extraordinary radiation of the East African Great Lakes cichlid fish species flocks. The 21 or more species of pelagic cichlids within the Lake Malawi flock appear to have lake-wide distributions that challenge such a concept. Data from six microsatellite DNA loci indicate single, panmictic populations across the lake of three Diplotaxodon species. Levels of variability at these loci suggest that populations have been large and stable. Mitochondrial DNA sequence data (872 bp of control region + 981 bp of the NADH-2) from 90 species, representing all major clades within the Lake Malawi flock, indicate reciprocal monophyly of the pelagic clade. We suggest that these data support a hypothesis that speciation in sympatry is more plausible (and widespread) within the cichlid species flocks than previously thought. PMID:11413643

  4. Geography disentangles introgression from ancestral polymorphism in Lake Malawi cichlids.

    PubMed

    Mims, Meryl C; Darrin Hulsey, C; Fitzpatrick, Benjamin M; Streelman, J Todd

    2010-03-01

    Phenotypically diverse Lake Malawi cichlids exhibit similar genomes. The extensive sharing of genetic polymorphism among forms has both intrigued and frustrated biologists trying to understand the nature of diversity in this and other rapidly evolving systems. Shared polymorphism might result from hybridization and/or the retention of ancestrally polymorphic alleles. To examine these alternatives, we used new genomic tools to characterize genetic differentiation in widespread, geographically structured populations of Labeotropheus fuelleborni and Metriaclima zebra. These phenotypically distinct species share mitochondrial DNA (mtDNA) haplotypes and show greater mtDNA differentiation among localities than between species. However, Bayesian analysis of nuclear single nucleotide polymorphism (SNP) data revealed two distinct genetic clusters corresponding perfectly to morphologically diagnosed L. fuelleborni and M. zebra. This result is a function of the resolving power of the multi-locus dataset, not a conflict between nuclear and mitochondrial partitions. Locus-by-locus analysis showed that mtDNA differentiation between species (F(CT)) was nearly identical to the median single-locus SNP F(CT). Finally, we asked whether there is evidence for gene flow at sites of co-occurrence. We used simulations to generate a null distribution for the level of differentiation between co-occurring populations of L. fuelleborni and M. zebra expected if there was no hybridization. The null hypothesis was rejected for the SNP data; populations that co-occur at rock reef sites were slightly more similar than expected by chance, suggesting recent gene flow. The coupling of numerous independent markers with extensive geographic sampling and simulations utilized here provides a framework for assessing the prevalence of gene flow in recently diverged species.

  5. Genetic sex determination in Astatotilapia calliptera, a prototype species for the Lake Malawi cichlid radiation

    NASA Astrophysics Data System (ADS)

    Peterson, Erin N.; Cline, Maggie E.; Moore, Emily C.; Roberts, Natalie B.; Roberts, Reade B.

    2017-06-01

    East African cichlids display extensive variation in sex determination systems. The species Astatotilapia calliptera is one of the few cichlids that reside both in Lake Malawi and in surrounding waterways. A. calliptera is of interest in evolutionary studies as a putative immediate outgroup species for the Lake Malawi species flock and possibly as a prototype ancestor-like species for the radiation. Here, we use linkage mapping to test association of sex in A. calliptera with loci that have been previously associated with genetic sex determination in East African cichlid species. We identify a male heterogametic XY system segregating at linkage group (LG) 7 in an A. calliptera line that originated from Lake Malawi, at a locus previously shown to act as an XY sex determination system in multiple species of Lake Malawi cichlids. Significant association of genetic markers and sex produce a broad genetic interval of approximately 26 megabases (Mb) using the Nile tilapia genome to orient markers; however, we note that the marker with the strongest association with sex is near a gene that acts as a master sex determiner in other fish species. We demonstrate that alleles of the marker are perfectly associated with sex in Metriaclima mbenjii, a species from the rock-dwelling clade of Lake Malawi. While we do not rule out the possibility of other sex determination loci in A. calliptera, this study provides a foundation for fine mapping of the cichlid sex determination gene on LG7 and evolutionary context regarding the origin and persistence of the LG7 XY across diverse, rapidly evolving lineages.

  6. An Evaluation of the Role of Sensory Drive in the Evolution of Lake Malawi Cichlid Fishes

    PubMed Central

    Smith, Adam R.; van Staaden, Moira J.; Carleton, Karen L.

    2012-01-01

    Although the cichlids of Lake Malawi are an important model system for the study of sensory evolution and sexual selection, the evolutionary processes linking these two phenomena remain unclear. Prior works have proposed that evolutionary divergence is driven by sensory drive, particularly as it applies to the visual system. While evidence suggests that sensory drive has played a role in the speciation of Lake Victoria cichlids, the findings from several lines of research on cichlids of Lake Malawi are not consistent with the primary tenets of this hypothesis. More specifically, three observations make the sensory drive model implausible in Malawi: (i) a lack of environmental constraint due to a broad and intense ambient light spectrum in species rich littoral habitats, (ii) pronounced variation in receiver sensory characteristics, and (iii) pronounced variability in male courtship signal characteristics. In the following work, we synthesize the results from recent studies to draw attention to the importance of sensory variation in cichlid evolution and speciation, and we suggest possible avenues of future research. PMID:22779029

  7. An evaluation of the role of sensory drive in the evolution of lake Malawi cichlid fishes.

    PubMed

    Smith, Adam R; van Staaden, Moira J; Carleton, Karen L

    2012-01-01

    Although the cichlids of Lake Malawi are an important model system for the study of sensory evolution and sexual selection, the evolutionary processes linking these two phenomena remain unclear. Prior works have proposed that evolutionary divergence is driven by sensory drive, particularly as it applies to the visual system. While evidence suggests that sensory drive has played a role in the speciation of Lake Victoria cichlids, the findings from several lines of research on cichlids of Lake Malawi are not consistent with the primary tenets of this hypothesis. More specifically, three observations make the sensory drive model implausible in Malawi: (i) a lack of environmental constraint due to a broad and intense ambient light spectrum in species rich littoral habitats, (ii) pronounced variation in receiver sensory characteristics, and (iii) pronounced variability in male courtship signal characteristics. In the following work, we synthesize the results from recent studies to draw attention to the importance of sensory variation in cichlid evolution and speciation, and we suggest possible avenues of future research.

  8. Similar morphologies of cichlid fish in Lakes Tanganyika and Malawi are due to convergence.

    PubMed

    Kocher, T D; Conroy, J A; McKaye, K R; Stauffer, J R

    1993-06-01

    The species flocks of cichlid fishes in the lakes of East Africa are the most spectacular example of adaptive radiation among living vertebrates. Similar highly derived morphologies are found among species in different lakes. These similarities have been variously interpreted either as evidence for migration of ancestral species between the lakes, or of striking convergence of morphology. To distinguish among these competing hypotheses we sequenced a portion of the mitochondrial DNA control region from six pairs of morphologically similar taxa from Lakes Malawi and Tanganyika. Our results clearly indicate a separate origin of these morphologies in the two lakes. They also suggest that the Tanganyikan radiation is relatively old, and that the species flocks in lakes Malawi and Victoria are derived from one of the ancient lineages found in Lake Tanganyika. These findings have important implications for understanding the pattern of morphological and behavioral evolution in these fish.

  9. Intraspecific cone opsin expression variation in the cichlids of Lake Malawi.

    PubMed

    Smith, Adam R; D'Annunzio, Lindsay; Smith, Abbi E; Sharma, Anit; Hofmann, Christopher M; Marshall, N J; Carleton, Karen L

    2011-01-01

    The expression of cone opsin genes is a primary determinant of the characteristics of colour vision. Interspecific variation in opsin expression is common in African cichlids. It is correlated with foraging among cichlids from Lake Malawi, and with ambient light environment among cichlids from Lake Victoria. In this study, we tested whether gene expression varied within species such that it might be important in contributing to divergence. We hypothesized that light attenuation with depth would be correlated with predictable changes in gene expression in Lake Malawi, and that this variation would tune visual sensitivities to match the ambient light environment. We observed significant differences in cone opsin expression in three different comparisons among populations of the same species. Higher LWS expression was found in shallow versus deep Copadichromis eucinostomus. In Metriaclima zebra, individuals from Zimbawe Rock expressed significantly more SWS2B than those from Thumbi West Island, although these locales have similar ambient light environments. Finally, Tropheops gracilior from deeper water had significantly more variation in expression than their shallow counterparts. These results support that gene expression varies significantly between populations of the same species. Surprisingly, these results could not be explained by predicted visual performance as models predicted that differential expression patterns did not confer sensitivity advantages at different depths. This suggested that expression variation did not confer a local sensitivity advantage. Therefore, our findings were contrary to a primary requirement of the sensory bias hypothesis. As such, other explanations for intraspecific gene expression variation need to be tested.

  10. Phylogenomic analysis of Lake Malawi cichlid fishes: Further evidence that the three-stage model of diversification does not fit.

    PubMed

    Hulsey, Christopher Darrin; Zheng, Jimmy; Faircloth, Brant C; Meyer, Axel; Alfaro, Michael E

    2017-09-01

    Adaptive radiations could often occur in discrete stages. For instance, the species flock of ∼1000 species of Lake Malawi cichlid fishes might have only diverged once between rocky and sandy environments during the initial stage of their diversification. All further diversification within the rock-dwelling (mbuna) or sand-dwelling (utaka) cichlids would have occurred during a subsequent second stage of extensive trophic evolution that was followed by a third stage of sexual trait divergence. We provide an improved phylogenetic framework for Malawi cichlids to test this three-stage hypothesis based on newly reconstructed phylogenetic relationships among 32 taxonomically disparate Malawi cichlids species. Using several reconstruction methods and 1037 ultra-conserved element (UCE) markers, we recovered a molecular phylogeny that confidently resolved relationships among most of the Malawi lineages sampled when a bifurcating framework was enforced. These bifurcating reconstructions also indicated that the sand-dwelling species Cyathochromis obliquidens was well-nested within the primarily rock-dwelling radiation known as the mbuna. In contrast to predictions from the three-stage model of vertebrate diversification, the recovered phylogeny reveals an initial colonization of rocky reefs, followed by substantial diversification of rock-dwelling lineages, and then at least one instance of subsequent evolution back into sandy habitats. This repeated evolution into major habitat types provides further evidence that the three-stage model of Malawi cichlid diversification has numerous exceptions. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Major-histocompatibility-complex variation in two species of cichlid fishes from Lake Malawi.

    PubMed

    Ono, H; O'hUigin, C; Tichy, H; Klein, J

    1993-09-01

    Lake Malawi in eastern Africa harbors > 500 endemic species of cichlid fishes, all of which are believed to have emerged from a single founding population in the past 2 Myr. Molecular characterization of differences among the species could provide important information about the nature of speciation in the period of adaptive radiation. Because of the close relationship, however, molecular variation among the species has been difficult to ascertain. In this communication, we provide evidence for extensive differences, in major-histocompatibility-complex (Mhc) class II genes, between two related species, Pseudotropheus zebra and Melanochromis auratus. We used specific primers to amplify and sequence intron 1 and exon 2 of the class II genes from 18 individuals. Although we found 20 different sequences among the 42 that we produced, there was not a single sequence shared by the two species. Thus the study suggests that different cichlid species of Lake Malawi have different profiles of class II alleles, presumably because the polymorphism present in the ancestral founding population segregated differentially into the various species. These results make Mhc genes an important tool for elucidating speciation.

  12. Mix and match color vision: tuning spectral sensitivity by differential opsin gene expression in Lake Malawi cichlids.

    PubMed

    Parry, Juliet W L; Carleton, Karen L; Spady, Tyrone; Carboo, Aba; Hunt, David M; Bowmaker, James K

    2005-10-11

    Cichlid fish of the East African Rift Lakes are renowned for their diversity and offer a unique opportunity to study adaptive changes in the visual system in rapidly evolving species flocks. Since color plays a significant role in mate choice, differences in visual sensitivities could greatly influence and even drive speciation of cichlids. Lake Malawi cichlids inhabiting rock and sand habitats have significantly different cone spectral sensitivities. By combining microspectrophotometry (MSP) of isolated cones, sequencing of opsin genes, and spectral analysis of recombinant pigments, we have established the cone complements of four species of Malawi cichlids. MSP demonstrated that each of these species predominately expresses three cone pigments, although these differ between species to give three spectrally different cone complements. In addition, rare populations of spectrally distinct cones were found. In total, seven spectral classes were identified. This was confirmed by opsin gene sequencing, expression, and in vitro reconstitution. The genes represent the four major classes of cone opsin genes that diverged early in vertebrate evolution. All four species possess a long-wave-sensitive (LWS), three spectrally distinct green-sensitive (RH2), a blue-sensitive (SWS2A), a violet-sensitive (SWS2B), and an ultraviolet-sensitive (SWS1) opsin. However, African cichlids determine their spectral sensitivity by differential expression of primarily only three of the seven available cone opsin genes. Phylogenetic analysis suggests that all percomorph fish have similar potential.

  13. Dynamic Sequence Evolution of a Sex-Associated B Chromosome in Lake Malawi Cichlid Fish.

    PubMed

    Clark, Frances E; Conte, Matthew A; Ferreira-Bravo, Irani A; Poletto, Andreia B; Martins, Cesar; Kocher, Thomas D

    2017-01-01

    B chromosomes are extra chromosomes found in many species of plants, animals, and fungi. B chromosomes often manipulate common cellular processes to increase their frequency, sometimes to the detriment of organismal fitness. Here, we characterize B chromosomes in several species of Lake Malawi cichlid fish. Whole genome sequencing of Metriaclima zebra "Boadzulu" individuals revealed blocks of sequence with unusually high sequence coverage, indicative of increased copy number of those sequences. These regions of high sequence coverage were found only in females. SNPs unique to the high copy number sequences permitted the design of specific amplification primers. These primers amplified fragments only in Metriaclima lombardoi individuals that carried a cytologically identified B chromosome (B-carriers), indicating these extra copies are located on the B chromosome. These same primers were used to identify B-carrying individuals in additional species from Lake Malawi. Across 7 species, a total of 43 B-carriers were identified among 323 females. B-carriers were exclusively female; no B chromosomes were observed in the 317 males surveyed from these species. Quantitative analysis of the copy number variation of B-specific sequence blocks suggests that B-carriers possess a single B chromosome, consistent with previous karyotyping of M. lombardoi A single B chromosome in B-carriers is consistent with 2 potential drive mechanisms: one involving nondisjunction and preferential segregation in a mitotic division prior to the germ-line, and the other involving preferential segregation during meiosis I.

  14. Sensory basis for detection of benthic prey in two Lake Malawi cichlids.

    PubMed

    Schwalbe, Margot A B; Webb, Jacqueline F

    2014-04-01

    The adaptive radiations of African cichlids resulted in a diversity of feeding morphologies and strategies, but the role of sensory biology in prey detection and feeding ecology remains largely unexplored. Two endemic Lake Malawi cichlid genera, Tramitichromis and Aulonocara, feed on benthic invertebrates, but differ in lateral line morphology (narrow and widened lateral line canals, respectively) and foraging strategy. The hypothesis that they use their lateral line systems differently was tested by looking at the relative contribution of the lateral line system and vision in prey detection by Tramitichromis sp. and comparing results to those from a complementary study using Aulonocara stuartgranti (Schwalbe et al., 2012). First, behavioral trials were used to assess the ability of Tramitichromis sp. to detect live (mobile) and dead (immobile) benthic prey under light and dark conditions. Second, trials were run before, immediately after, and several weeks after chemical ablation of the lateral line system to determine its role in feeding behavior. Results show that Tramitichromis sp. is a visual predator that neither locates prey in the dark nor depends on lateral line input for prey detection and is thus distinct from A. stuartgranti, which uses its lateral line or a combination of vision and lateral line to detect prey depending on light condition. Investigating how functionally distinctive differences in sensory morphology are correlated with feeding behavior in the laboratory and determining the role of sensory systems in feeding ecology will provide insights into how sensory capabilities may contribute to trophic niche segregation.

  15. Extensive Introgression among Ancestral mtDNA Lineages: Phylogenetic Relationships of the Utaka within the Lake Malawi Cichlid Flock

    PubMed Central

    Anseeuw, Dieter; Nevado, Bruno; Busselen, Paul; Snoeks, Jos; Verheyen, Erik

    2012-01-01

    We present a comprehensive phylogenetic analysis of the Utaka, an informal taxonomic group of cichlid species from Lake Malawi. We analyse both nuclear and mtDNA data from five Utaka species representing two (Copadichromis and Mchenga) of the three genera within Utaka. Within three of the five analysed species we find two very divergent mtDNA lineages. These lineages are widespread and occur sympatrically in conspecific individuals in different areas throughout the lake. In a broader taxonomic context including representatives of the main groups within the Lake Malawi cichlid fauna, we find that one of these lineages clusters within the non-Mbuna mtDNA clade, while the other forms a separate clade stemming from the base of the Malawian cichlid radiation. This second mtDNA lineage was only found in Utaka individuals, mostly within Copadichromis sp. “virginalis kajose” specimens. The nuclear genes analysed, on the other hand, did not show traces of divergence within each species. We suggest that the discrepancy between the mtDNA and the nuclear DNA signatures is best explained by a past hybridisation event by which the mtDNA of another species introgressed into the ancestral Copadichromis sp. “virginalis kajose” gene pool. PMID:22655216

  16. A genetic demographic analysis of Lake Malawi rock-dwelling cichlids using spatio-temporal sampling.

    PubMed

    Husemann, Martin; Nguyen, Rachel; Ding, Baoqing; Danley, Patrick D

    2015-06-01

    We estimated the effective population sizes (Ne ) and tested for short-term temporal demographic stability of populations of two Lake Malawi cichlids: Maylandia benetos, a micro-endemic, and Maylandia zebra, a widespread species found across the lake. We sampled a total of 351 individuals, genotyped them at 13 microsatellite loci and sequenced their mitochondrial D-loop to estimate genetic diversity, population structure, demographic history and effective population sizes. At the microsatellite loci, genetic diversity was high in all populations. Yet, genetic diversity was relatively low for the sequence data. Microsatellites yielded mean Ne estimates of 481 individuals (±99 SD) for M. benetos and between 597 (±106.3 SD) and 1524 (±483.9 SD) individuals for local populations of M. zebra. The microsatellite data indicated no deviations from mutation-drift equilibrium. Maylandia zebra was further found to be in migration-drift equilibrium. Temporal fluctuations in allele frequencies were limited across the sampling period for both species. Bayesian Skyline analyses suggested a recent expansion of M. zebra populations in line with lake-level fluctuations, whereas the demographic history of M. benetos could only be estimated for the very recent past. Divergence time estimates placed the origin of M. benetos within the last 100 ka after the refilling of the lake and suggested that it split off the sympatric M. zebra population. Overall, our data indicate that micro-endemics and populations in less favourable habitats have smaller Ne , indicating that drift may play an important role driving their divergence. Yet, despite small population sizes, high genetic variation can be maintained. © 2015 John Wiley & Sons Ltd.

  17. A small number of genes underlie male pigmentation traits in Lake Malawi cichlid fishes.

    PubMed

    O'Quin, Claire T; Drilea, Alexi C; Roberts, Reade B; Kocher, Thomas D

    2012-05-01

    Pigmentation patterns are one of the most recognizable forms of phenotypic diversity and an important component of organismal fitness. While much progress has been made in understanding the genes controlling pigmentation in model systems, many questions remain about the genetic basis of pigment traits observed in nature. Lake Malawi cichlid fishes are known for their diversity of male pigmentation patterns, which have been shaped by sexual selection. To begin the process of identifying the genes underlying this diversity, we quantified the number of pigment cells on the body and fins of two species of the genus Metriaclima and their hybrids. We then used the Castle-Wright equation to estimate that differences in individual pigmentation traits between these species are controlled by one to four genes each. Different pigmentation traits are highly correlated in the F(2) , suggesting shared developmental pathways and genetic pleiotropy. Melanophore and xanthophore traits fall on opposite ends of the first principal component axis of the F(2) phenotypes, suggesting a tradeoff during the development of these two pigment cell types.

  18. An allelic series at pax7a is associated with colour polymorphism diversity in Lake Malawi cichlid fish.

    PubMed

    Roberts, Reade B; Moore, Emily C; Kocher, Thomas D

    2016-12-27

    Despite long-standing interest in the evolution and maintenance of discrete phenotypic polymorphisms, the molecular genetic basis of such polymorphism in the wild is largely unknown. Female sex-associated blotched colour polymorphisms found in cichlids of Lake Malawi, East Africa, represent a highly successful polymorphic phenotype, found and maintained in four genera across the geographic expanse of the lake. Previously, we identified an association with an allelic variant of the paired-box transcription factor gene pax7a and blotched colour morphs in Lake Malawi cichlid fishes. Although a diverse range of blotched phenotypes are present in Lake Malawi cichlid species, they all appeared to result from an allele of pax7a that produces increased levels of transcript. Here, we examine the developmental and genetic basis of variation among blotched morphs. First, we confirm that pax7a-associated blotch morphs result primarily from modulation of melanophore development and survival. From laboratory crosses and natural population studies, we identify at least three alleles of pax7a associated with discrete subtypes of blotched morphs, in addition to the ancestral pax7a allele. Genotypes at pax7a support initial evolution of a novel pax7a allele to produce the blotched class of morphs, followed by subsequent evolution of that pax7a blotched allele to produce additional alleles associated with discrete colour morphs. Variant alleles of pax7a produce different levels of pax7a transcript, correlating with pigmentation phenotype at the cellular level. This naturally selected allelic series should serve as a case study for understanding the molecular genetic control of pax7a expression and the evolution of sex-associated alleles.

  19. Variation in habitat preference and population structure among three species of the Lake Malawi cichlid genus Protomelas.

    PubMed

    Pereyra, Ricardo; Taylor, Martin I; Turner, George F; Rico, Ciro

    2004-09-01

    Several studies have demonstrated strong population structuring over small distances in the rocky-shore mbuna cichlid fishes from Lake Malawi, suggesting the potential for allopatric speciation. However, many endemic Lake Malawi cichlids are neither mbuna, nor confined to rocky shores. Using microsatellites, we investigated the population structure in three species of the non-mbuna genus Protomelas. The rocky-shore P. taeniolatus showed high levels of population structure even over distances of less than 1 km, while the sandy-shore species P. similis showed no significant structure over distances up to 21 km. Protomelas fenestratus, which is generally found at the interface between rocks and sand, also showed low levels of population structure. Our results suggest that the model of allopatric speciation based on habitat fragmentation within the current lake basin may be equally applicable to rocky-shore non-mbuna as to mbuna, but that an alternative model is required to explain speciation among sandy-shore species as well as the deep-water and pelagic species.

  20. Environmental change explains cichlid adaptive radiation at Lake Malawi over the past 1.2 million years.

    PubMed

    Ivory, Sarah J; Blome, Margaret W; King, John W; McGlue, Michael M; Cole, Julia E; Cohen, Andrew S

    2016-10-18

    Long paleoecological records are critical for understanding evolutionary responses to environmental forcing and unparalleled tools for elucidating the mechanisms that lead to the development of regions of high biodiversity. We use a 1.2-My record from Lake Malawi, a textbook example of biological diversification, to document how climate and tectonics have driven ecosystem and evolutionary dynamics. Before ∼800 ka, Lake Malawi was much shallower than today, with higher frequency but much lower amplitude water-level and oxygenation changes. Since ∼800 ka, the lake has experienced much larger environmental fluctuations, best explained by a punctuated, tectonically driven rise in its outlet location and level. Following the reorganization of the basin, a change in the pacing of hydroclimate variability associated with the Mid-Pleistocene Transition resulted in hydrologic change dominated by precession rather than the high-latitude teleconnections recorded elsewhere. During this time, extended, deep lake phases have abruptly alternated with times of extreme aridity and ecosystem variability. Repeated crossings of hydroclimatic thresholds within the lake system were critical for establishing the rhythm of diversification, hybridization, and extinction that dominate the modern system. The chronology of these changes closely matches both the timing and pattern of phylogenetic history inferred independently for the lake's extraordinary array of cichlid fish species, suggesting a direct link between environmental and evolutionary dynamics.

  1. Environmental change explains cichlid adaptive radiation at Lake Malawi over the past 1.2 million years

    PubMed Central

    Blome, Margaret W.; King, John W.; McGlue, Michael M.; Cole, Julia E.

    2016-01-01

    Long paleoecological records are critical for understanding evolutionary responses to environmental forcing and unparalleled tools for elucidating the mechanisms that lead to the development of regions of high biodiversity. We use a 1.2-My record from Lake Malawi, a textbook example of biological diversification, to document how climate and tectonics have driven ecosystem and evolutionary dynamics. Before ∼800 ka, Lake Malawi was much shallower than today, with higher frequency but much lower amplitude water-level and oxygenation changes. Since ∼800 ka, the lake has experienced much larger environmental fluctuations, best explained by a punctuated, tectonically driven rise in its outlet location and level. Following the reorganization of the basin, a change in the pacing of hydroclimate variability associated with the Mid-Pleistocene Transition resulted in hydrologic change dominated by precession rather than the high-latitude teleconnections recorded elsewhere. During this time, extended, deep lake phases have abruptly alternated with times of extreme aridity and ecosystem variability. Repeated crossings of hydroclimatic thresholds within the lake system were critical for establishing the rhythm of diversification, hybridization, and extinction that dominate the modern system. The chronology of these changes closely matches both the timing and pattern of phylogenetic history inferred independently for the lake’s extraordinary array of cichlid fish species, suggesting a direct link between environmental and evolutionary dynamics. PMID:27698127

  2. Retroposition of the AFC family of SINEs (short interspersed repetitive elements) before and during the adaptive radiation of cichlid fishes in Lake Malawi and related inferences about phylogeny.

    PubMed

    Takahashi, K; Nishida, M; Yuma, M; Okada, N

    2001-01-01

    Lake Malawi is home to more than 450 species of endemic cichlids, which provide a spectacular example of adaptive radiation. To clarify the phylogenetic relationships among these fish, we examined the presence and absence of SINEs (short interspersed repetitive elements) at orthologous loci. We identified six loci at which a SINE sequence had apparently been specifically inserted by retroposition in the common ancestor of all the investigated species of endemic cichlids in Lake Malawi. At another locus, unique sharing of a SINE sequence was evident among all the investigated species of endemic non-Mbuna cichlids with the exception of Rhamphochromis sp. The relationships were in good agreement with those deduced in previous studies with various different markers, demonstrating that the SINE method is useful for the elucidation of phylogenetic relationships among cichlids in Lake Malawi. We also characterized a locus that exhibited transspecies polymorphism with respect to the presence or absence of the SINE sequence among non-Mbuna species. This result suggests that incomplete lineage sorting and/or interspecific hybridization might have occurred or be occurring among the species in this group, which might potentially cause misinterpretation of phylogenetic data, in particular when a single-locus marker, such as a sequence in the mitochondrial DNA, is used for analysis.

  3. The effect of light intensity on prey detection behavior in two Lake Malawi cichlids, Aulonocara stuartgranti and Tramitichromis sp.

    PubMed

    Schwalbe, Margot A B; Webb, Jacqueline F

    2015-04-01

    Two sand-dwelling cichlids from Lake Malawi (Aulonocara stuartgranti, Tramitichromis sp.) that feed on benthic invertebrates, but have different lateral line phenotypes, use lateral line and/or visual cues to detect prey under light versus dark conditions. The current study examined how ecologically relevant variation in light intensity [0-800 lux (lx)] influences detection of prey (mobile, immobile) in each species by analyzing six behavioral parameters. Both species fed at light intensities ≥1 lx and trends in behavior among light intensities were informative. However, prey type and/or time of day (but not light intensity) predicted all four parameters analyzed with generalized linear mixed models in A. stuartgranti, whereas the interaction of light intensity and time of day predicted three of these parameters in Tramitichromis sp. Data suggest that the critical light intensity is 1-12 lx for both species, that the integration of visual and lateral line input explains differences in detection of mobile and immobile prey and behavioral changes at the transition from 1 to 0 lx in A. stuartgranti, and that Tramitichromis sp. likely uses binocular vision to locate prey. Differences in the sensory biology of species that exploit similar prey will have important implications for the trophic ecology of African cichlid fishes.

  4. Population structure and colour variation of the cichlid fishes Labeotropheus fuelleborni Ahl along a recently formed archipelago of rocky habitat patches in southern Lake Malawi

    PubMed Central

    Arnegard, M. E.; Markert, J. A.; Danley, P. D.; Stauffer, J. R.; Ambali, A. J.; Kocher, T. D.

    1999-01-01

    Extremely fine-scale genetic partitioning has recently been detected among populations of Lake Malawi's rock-dwelling cichlids through the study of microsatellite loci. Understanding the mechanisms of genetic differentiation that operate in this rapidly speciating group requires further investigation of the geographic patterns of gene flow and the congruence between morphological and genetic divergence. In pursuit of this goal, genetic variation at four microsatellite loci and variation in male breeding coloration were examined in several populations of Labeotropheus fuelleborni from southern Lake Malawi. Significant genetic differentiation exists among populations (overall FST = 0.063; p = 0.0002). While migration appears unrestricted within continuous rocky patches, deep waters and sandy bays more than 2 km wide act as strong barriers to gene flow. Dispersal of L. fuelleborni appears to follow a stepping-stone model in which the distribution of habitats often constrains migration to one dimension. It is hypothesized that clinal colour variation in the study area has resulted from the secondary contact of divergent lineages, although reproductive isolation between colour variants is not apparent. Relative to shoreline populations, reduced levels of gene flow among populations inhabiting isolated, deep-water islands provides greater opportunities for drift, adaptation to local conditions, or sexual selection to effect genetic differentiation in this species.

  5. Schistosomiasis in Lake Malawi.

    PubMed

    Cetron, M S; Chitsulo, L; Sullivan, J J; Pilcher, J; Wilson, M; Noh, J; Tsang, V C; Hightower, A W; Addiss, D G

    1996-11-09

    Schistosomiasis is a parasitic infection caused by trematodes. Humans are infected through skin contact with free-swimming cercariae which develop in freshwater snails. Schistosomiasis has been endemic to Malawi for several decades, but the open waters and shores of Lake Malawi have long been thought to be risk-free with regard to schistosomiasis transmission. However, in 1992, two US Peace Corps volunteers developed central nervous system schistosomiasis due to infection with Schistosoma haematobium following recreational water exposure at Cape Maclear on Lake Malawi. In light of these infections, a cross-sectional survey of resident expatriates and visitors to Malawi was subsequently conducted during March-April 1993 to determine the transmission potential and risk for acquiring schistosomiasis in the lake. 305 US citizens and 650 non-US foreign nationals participated in the study. Serological evidence of current or past schistosome infection was identified in 303 subjects. Indeed, seroprevalence was 32% among expatriates whose freshwater exposure was limited to Lake Malawi; S. haematobium antibodies were found in 135 of 141 seropositive specimens. The risk of seropositivity increased with the number of freshwater exposures at Lake Malawi resorts. While many resort areas in the southwestern lake region posed a significant risk, Cape Maclear was the location most strongly associated with seropositivity. Schistosome-infected Bulinus globosus, the snail vector of S. haematobium in Malawi, were found at Cape Maclear and other locations along the lakeshore.

  6. Tempo and mode of diversification of lake Tanganyika cichlid fishes.

    PubMed

    Day, Julia J; Cotton, James A; Barraclough, Timothy G

    2008-03-05

    Understanding the causes of disparities in species diversity across taxonomic groups and regions is a fundamental aim in evolutionary biology. Addressing these questions is difficult because of the need for densely sampled phylogenies and suitable empirical systems. Here we investigate the cichlid fish radiation of Lake Tanganyika and show that per lineage diversification rates have been more than six times slower than in the species flocks of Lakes Victoria and Malawi. The result holds even at peak periods of diversification in Lake Tanganyika, ruling out the age of the lake as an explanation for slow average rates, and is robust to uncertainties over the calibration of cichlid radiations in geological time. Moreover, Lake Tanganyika lineages, irrespective of different biological characteristics (e.g. sexually dichromatic versus sexually monochromatic clades), have diversified at similar rates, falling within typical estimates across a range of plant and animal clades. For example, the mostly sexually dichromatic haplochromines, which have speciated explosively in Lakes Victoria and Malawi, have displayed modest rates in Lake Tanganyika (where they are called Tropheini). Our results show that either the Lake Tanganyika environment is less conducive for cichlid speciation or the remarkable diversifying abilities of the haplochromines were inhibited by the prior occupancy of older radiations. Although the results indicate a dominant role for the environment in shaping cichlid diversification, differences in the timing of diversification among the Tanganyikan tribes indicate that biological differences were still important for the dynamics of species build-up in the lake. While we cannot resolve the timing of the radiation relative to the origin of the lake, because of the lack of robust geological date calibrations for cichlids, our results are consistent with a scenario that the different clades reflect independent adaptive radiations into different broad niches in

  7. Tempo and Mode of Diversification of Lake Tanganyika Cichlid Fishes

    PubMed Central

    Day, Julia J.; Cotton, James A.; Barraclough, Timothy G.

    2008-01-01

    Background Understanding the causes of disparities in species diversity across taxonomic groups and regions is a fundamental aim in evolutionary biology. Addressing these questions is difficult because of the need for densely sampled phylogenies and suitable empirical systems. Methodology/Principal Findings Here we investigate the cichlid fish radiation of Lake Tanganyika and show that per lineage diversification rates have been more than six times slower than in the species flocks of Lakes Victoria and Malawi. The result holds even at peak periods of diversification in Lake Tanganyika, ruling out the age of the lake as an explanation for slow average rates, and is robust to uncertainties over the calibration of cichlid radiations in geological time. Moreover, Lake Tanganyika lineages, irrespective of different biological characteristics (e.g. sexually dichromatic versus sexually monochromatic clades), have diversified at similar rates, falling within typical estimates across a range of plant and animal clades. For example, the mostly sexually dichromatic haplochromines, which have speciated explosively in Lakes Victoria and Malawi, have displayed modest rates in Lake Tanganyika (where they are called Tropheini). Conclusion/Significance Our results show that either the Lake Tanganyika environment is less conducive for cichlid speciation or the remarkable diversifying abilities of the haplochromines were inhibited by the prior occupancy of older radiations. Although the results indicate a dominant role for the environment in shaping cichlid diversification, differences in the timing of diversification among the Tanganyikan tribes indicate that biological differences were still important for the dynamics of species build-up in the lake. While we cannot resolve the timing of the radiation relative to the origin of the lake, because of the lack of robust geological date calibrations for cichlids, our results are consistent with a scenario that the different clades

  8. Sexually dimorphic levels of color trait integration and the resolution of sexual conflict in Lake Malawi cichlids.

    PubMed

    Brzozowski, Frances; Roscoe, Jennifer; Parsons, Kevin; Albertson, Craig

    2012-06-01

    East African cichlids are renowned for their propensity to radiate, and variation in color patterns accounts for much of endemic cichlid diversity. Sexual dimorphism in color among cichlid species likely represents the outcome of different selective regimes acting on each sex, and is a classic example of sexual conflict. It is generally assumed that this conflict has been mitigated through the evolution of sex-linked color polymorphisms. Here, we propose that the evolution of sex-specific differences in levels of color trait integration may represent an additional mechanism through which sexual conflict has been resolved in this group. Specifically, we predict: (1) that general patterns of integration are influenced by early developmental events and thus conserved across sexes and (2) that male color is less integrated than females, and thus more evolvable in terms of producing an elaborate palette (i.e., in response to sexual selection), whereas female color is more integrated, facilitating wholesale shifts in color for background matching (i.e., in response to natural selection for crypsis). We tested these hypotheses using an F(2) design to compare the segregation of male and female color patterns. Both exploratory methods and hypothesis-driven analyses of integration demonstrate that the covariance structure of color traits in males and females is distinct, and that males are significantly less integrated than females. We suggest that the ability of species to promote different levels, and to a lesser extent patterns, of phenotypic integration between males and females may have contributed to the evolutionary success of this group.

  9. High prevalence of non-synonymous substitutions in mtDNA of cichlid fishes from Lake Victoria.

    PubMed

    Shirai, Kazumasa; Inomata, Nobuyuki; Mizoiri, Shinji; Aibara, Mitsuto; Terai, Yohey; Okada, Norihiro; Tachida, Hidenori

    2014-12-01

    When a population size is reduced, genetic drift may fix slightly deleterious mutations, and an increase in nonsynonymous substitution is expected. It has been suggested that past aridity has seriously affected and decreased the populations of cichlid fishes in Lake Victoria, while geographical studies have shown that the water levels in Lake Tanganyika and Lake Malawi have remained fairly constant. The comparably stable environments in the latter two lakes might have kept the populations of cichlid fishes large enough to remove slightly deleterious mutations. The difference in the stability of cichlid fish population sizes between Lake Victoria and the Lakes Tanganyika and Malawi is expected to have caused differences in the nonsynonymous/synonymous ratio, ω (=dN/dS), of the evolutionary rate. Here, we estimated ω and compared it between the cichlids of the three lakes for 13 mitochondrial protein-coding genes using maximum likelihood methods. We found that the lineages of the cichlids in Lake Victoria had a significantly higher ω for several mitochondrial loci. Moreover, positive selection was indicated for several codons in the mtDNA of the Lake Victoria cichlid lineage. Our results indicate that both adaptive and slightly deleterious molecular evolution has taken place in the Lake Victoria cichlids' mtDNA genes, whose nonsynonymous sites are generally conserved. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. The schistosome intermediate host, Bulinus nyassanus, is a 'preferred' food for the cichlid fish, Trematocranus placodon, at Cape Maclear, Lake Malawi.

    PubMed

    Evers, B N; Madsen, H; McKaye, K M; Stauffer, J R

    2006-01-01

    Over the last decade, transmission of the schistosome parasites of humans has increased in parts of Lake Malawi, possibly because over-fishing has led to a decline in the numbers of molluscivorous fish. The stomach contents of 51 wild-caught Trematocranus placodon from the Cape Maclear area of Lake Malawi have now been investigated and compared with the field abundance of snail species at two sites, close to where the fish were caught. The snails found in the fish stomachs were identified to genus or species on the basis of their shell fragments and/or opercula. The sizes of the prosobranchs consumed by the T. placodon were determined from their operculum sizes whereas the Bulinus nyassanus ingested by the fish were categorized as small (<4 mm) or large (> or =4 mm) on the basis of their shell fragments. The proportion of the Bu. nyassanus ingested that were categorized as large increased with fish size. Furthermore, the relative abundance of Bu. nyassanus in the guts of the fish was considerably higher than in the field, indicating that the T. placodon had a 'preference' for Bu. nyassanus over the Melanoides species that dominated the snail fauna. Small specimens of Bellamya species were also consumed in a greater proportion than found in field.

  11. Persistence of neutral polymorphisms in Lake Victoria cichlid fish

    PubMed Central

    Nagl, Sandra; Tichy, Herbert; Mayer, Werner E.; Takahata, Naoyuki; Klein, Jan

    1998-01-01

    Phylogenetic trees for groups of closely related species often have different topologies, depending on the genes used. One explanation for the discordant topologies is the persistence of polymorphisms through the speciation phase, followed by differential fixation of alleles in the resulting species. The existence of transspecies polymorphisms has been documented for alleles maintained by balancing selection but not for neutral alleles. In the present study, transspecific persistence of neutral polymorphisms was tested in the endemic haplochromine species flock of Lake Victoria cichlid fish. Putative noncoding region polymorphisms were identified at four randomly selected nuclear loci and tested on a collection of 12 Lake Victoria species and their putative riverine ancestors. At all loci, the same polymorphism was found to be present in nearly all the tested species, both lacustrine and riverine. Different polymorphisms at these loci were found in cichlids of other East African lakes (Malawi and Tanganyika). The Lake Victoria polymorphisms must have therefore arisen after the flocks now inhabiting the three great lakes diverged from one another, but before the riverine ancestors of the Lake Victoria flock colonized the Lake. Calculations based on the mtDNA clock suggest that the polymorphisms have persisted for about 1.4 million years. To maintain neutral polymorphisms for such a long time, the population size must have remained large throughout the entire period. PMID:9826684

  12. Persistence of neutral polymorphisms in Lake Victoria cichlid fish.

    PubMed

    Nagl, S; Tichy, H; Mayer, W E; Takahata, N; Klein, J

    1998-11-24

    Phylogenetic trees for groups of closely related species often have different topologies, depending on the genes used. One explanation for the discordant topologies is the persistence of polymorphisms through the speciation phase, followed by differential fixation of alleles in the resulting species. The existence of transspecies polymorphisms has been documented for alleles maintained by balancing selection but not for neutral alleles. In the present study, transspecific persistence of neutral polymorphisms was tested in the endemic haplochromine species flock of Lake Victoria cichlid fish. Putative noncoding region polymorphisms were identified at four randomly selected nuclear loci and tested on a collection of 12 Lake Victoria species and their putative riverine ancestors. At all loci, the same polymorphism was found to be present in nearly all the tested species, both lacustrine and riverine. Different polymorphisms at these loci were found in cichlids of other East African lakes (Malawi and Tanganyika). The Lake Victoria polymorphisms must have therefore arisen after the flocks now inhabiting the three great lakes diverged from one another, but before the riverine ancestors of the Lake Victoria flock colonized the Lake. Calculations based on the mtDNA clock suggest that the polymorphisms have persisted for about 1.4 million years. To maintain neutral polymorphisms for such a long time, the population size must have remained large throughout the entire period.

  13. Fish predation as a factor in the distribution of Lake Malawi gastropods.

    PubMed

    McKaye, K R; Stauffer, J R; Louda, S M

    1986-01-01

    Gastropod densities in Lake Malawi, Africa drop dramatically below 4.5 m water depth. Weed beds disappear and the number of molluscivorous cichlids increases below this depth. When molluscivores were excluded from open sand habitat by cages, due to migration and reduced predation, the density of snails increased by 40-60% within a week. Alternatively, when adult Cyrtocara placodon were placed into the cages, snail density equaled the controls. The molluscivores disproportionately consumed snails of the genus Bulinus relative to those of the more heavily armoured genus, Melanoides. Cichlid molluscivores are hypothesized to be responsible for preventing the thin shelled bilharzia vector snail, Bulinus globosus, from successfully invading the open shore areas of Lake Malawi. Lake Malawi may be relatively free of this human disease because of snail predation by cichlids.

  14. Mitochondrial phylogeny of the endemic mouthbrooding lineages of cichlid fishes from Lake Tanganyika in eastern Africa.

    PubMed

    Sturmbauer, C; Meyer, A

    1993-07-01

    Of the three cichlid species flocks in eastern Africa, Lake Tanganyika harbors the oldest species assemblage, which is also the most diverse morphologically and behaviorally. For 12 species (20 individuals) of 12 genera of the tribe Ectodini, 852 bp from two segments (cytochrome b and control region) of the mitochondrial genome were sequenced. In addition, orthologous sequences were obtained from eight species (11 individuals) representing other mouthbrooding lineages from Lake Tanganyika. Comparisons of sequence divergences revealed that the single Tanganyikan tribe Ectodini appears to be approximately five times older than the whole Lake Malawi cichlid species flock, suggesting that the radiation of the Tanganyikan mouthbrooding lineages took place long before the species flocks of Lakes Malawi and Victoria evolved. Seven of nine surveyed tribes of Tanganyikan cichlids appear to be approximately equally divergent, and this seems to corroborate the hypothesis of a rapid simultaneous formation of lineages at an early stage in the history of the Lake Tanganyika species flock. The close genetic relationship between the endemic Tropheus lineage and a nonendemic "Haplochromine," Astatotilapia burtoni, indicates that members of the tribe Tropheini may be the sister group of the cichlid flocks of Lakes Malawi and Victoria. The phylogenetic analyses demonstrate the monophyly of the Ectodini and identify the Cyprichromini as their sister group among the Tanganyikan cichlids. Within the tribe Ectodini the molecular data suggest both a branching pattern different than that previously proposed and a subdivision of the Ectodini into four clades, instead of the two originally described. The previously postulated model of morphological transformations believed to be responsible for the drastically different types of ecological specialization found among the Ectodini might therefore be in need of reinterpretation. Characters immediately related to foraging and nutrition seem to

  15. Lake level fluctuations synchronize genetic divergences of cichlid fishes in African lakes.

    PubMed

    Sturmbauer, C; Baric, S; Salzburger, W; Rüber, L; Verheyen, E

    2001-02-01

    Water level fluctuations are important modulators of speciation processes in tropical lakes, in that they temporarily form or break down barriers to gene flow among adjacent populations and/or incipient species. Time estimates of the most recent major lowstands of the three African Great Lakes are thus crucial to infer the relative timescales of explosive speciation events in cichlid species flocks. Our approach combines geological evidence with genetic divergence data of cichlid fishes from the three Great East African Lakes derived from the fastest-evolving mtDNA segment. Thereby, we show for each of the three lakes that individuals sampled from several populations which are currently isolated by long geographic distances and/or deep water form clusters of equally closely related haplotypes. The distribution of identical or equally closely related haplotypes in a lake basin allows delineation of the extent of lake level fluctuations. Our data suggest that the same climatic phenomenon synchronized the onset of genetic divergence of lineages in all three species flocks, such that their most recent evolutionary history seems to be linked to the same external modulators of adaptive radiation. A calibration of the molecular clock of the control region was elaborated by gauging the age of the Lake Malawi species flock through the divergence among the utaka-cichlid and the mbuna-cichlid lineages to minimally 570,000 years and maximally 1 Myr. This suggests that the low-lake-level period which established the observed patterns of genetic relatedness dates back less than 57,000 years, probably even to 17,000-12,400 years ago, when Lake Victoria dried up and Lakes Malawi and Tanganyika were also low. A rapid rise of all three lakes about 11,000 years ago established the large-scale population subdivisions observed today. Over that period of time, a multitude of species originated in Lakes Malawi and Victoria with an impressive degree of morphological and ecological

  16. A microsatellite-based genetic linkage map and putative sex-determining genomic regions in Lake Victoria cichlids.

    PubMed

    Kudo, Yu; Nikaido, Masato; Kondo, Azusa; Suzuki, Hikoyu; Yoshida, Kohta; Kikuchi, Kiyoshi; Okada, Norihiro

    2015-04-15

    Cichlid fishes in East Africa have undergone extensive adaptive radiation, which has led to spectacular diversity in their morphology and ecology. To date, genetic linkage maps have been constructed for several tilapias (riverine), Astatotilapia burtoni (Lake Tanganyika), and hybrid lines of Lake Malawi cichlids to facilitate genome-wide comparative analyses. In the present study, we constructed a genetic linkage map of the hybrid line of Lake Victoria cichlids, so that maps of cichlids from all the major areas of East Africa will be available. The genetic linkage map shown here is derived from the F2 progeny of an interspecific cross between Haplochromis chilotes and Haplochromis sauvagei and is based on 184 microsatellite and two single-nucleotide polymorphism (SNP) markers. Most of the microsatellite markers used in the present study were originally designed for other genetic linkage maps, allowing us to directly compare each linkage group (LG) among different cichlid groups. We found 25 LGs, the total length of which was 1133.2cM with an average marker spacing of about 6.09cM. Our subsequent linkage mapping analysis identified two putative sex-determining loci in cichlids. Interestingly, one of these two loci is located on cichlid LG5, on which the female heterogametic ZW locus and several quantitative trait loci (QTLs) related to adaptive evolution have been reported in Lake Malawi cichlids. We also found that V1R1 and V1R2, candidate genes for the fish pheromone receptor, are located very close to the recently detected sex-determining locus on cichlid LG5. The genetic linkage map study presented here may provide a valuable foundation for studying the chromosomal evolution of East African cichlids and the possible role of sex chromosomes in generating their genomic diversity. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Parallelism of amino acid changes at the RH1 affecting spectral sensitivity among deep-water cichlids from Lakes Tanganyika and Malawi.

    PubMed

    Sugawara, Tohru; Terai, Yohey; Imai, Hiroo; Turner, George F; Koblmüller, Stephan; Sturmbauer, Christian; Shichida, Yoshinori; Okada, Norihiro

    2005-04-12

    Many examples of the appearance of similar traits in different lineages are known during the evolution of organisms. However, the underlying genetic mechanisms have been elucidated in very few cases. Here, we provide a clear example of evolutionary parallelism, involving changes in the same genetic pathway, providing functional adaptation of RH1 pigments to deep-water habitats during the adaptive radiation of East African cichlid fishes. We determined the RH1 sequences from 233 individual cichlids. The reconstruction of cichlid RH1 pigments with 11-cis-retinal from 28 sequences showed that the absorption spectra of the pigments of nine species were shifted toward blue, tuned by two particular amino acid replacements. These blue-shifted RH1 pigments might have evolved as adaptations to the deep-water photic environment. Phylogenetic evidence indicates that one of the replacements, A292S, has evolved several times independently, inducing similar functional change. The parallel evolution of the same mutation at the same amino acid position suggests that the number of genetic changes underlying the appearance of similar traits in cichlid diversification may be fewer than previously expected.

  18. Parallel life history evolution in mouthbrooding cichlids from the African Great Lakes

    PubMed Central

    Duponchelle, Fabrice; Paradis, Emmanuel; Ribbink, Anthony J.; Turner, George F.

    2008-01-01

    The existence of ancient deep-water lakes provides an opportunity to study the independent adaptation of aquatic organisms to pelagic, benthic, and rocky shore habitats. With improving resolution of their phylogenetic relationships, the many cichlid fish species endemic to the African Great Lakes Malawi, Tanganyika, and Victoria provide a significant resource for the comparative study of such evolutionary processes. Here, we show that cichlid lineages colonizing rocky shores and pelagic habitats in the different lakes have independently evolved larger eggs and lower fecundities than benthic lineages, suggesting parallel adaptive life-history evolution. By contrast, other pelagic teleost fishes in both marine and freshwater habitats, including African lakes, typically produce large numbers of very small eggs. Our results also suggest that decreased fecundity and increased egg size not only occurred independently in each lake but occurred independently in the colonization of rocky and pelagic habitats. PMID:18824688

  19. Parallel life history evolution in mouthbrooding cichlids from the African Great Lakes.

    PubMed

    Duponchelle, Fabrice; Paradis, Emmanuel; Ribbink, Anthony J; Turner, George F

    2008-10-07

    The existence of ancient deep-water lakes provides an opportunity to study the independent adaptation of aquatic organisms to pelagic, benthic, and rocky shore habitats. With improving resolution of their phylogenetic relationships, the many cichlid fish species endemic to the African Great Lakes Malawi, Tanganyika, and Victoria provide a significant resource for the comparative study of such evolutionary processes. Here, we show that cichlid lineages colonizing rocky shores and pelagic habitats in the different lakes have independently evolved larger eggs and lower fecundities than benthic lineages, suggesting parallel adaptive life-history evolution. By contrast, other pelagic teleost fishes in both marine and freshwater habitats, including African lakes, typically produce large numbers of very small eggs. Our results also suggest that decreased fecundity and increased egg size not only occurred independently in each lake but occurred independently in the colonization of rocky and pelagic habitats.

  20. A tribal level phylogeny of Lake Tanganyika cichlid fishes based on a genomic multi-marker approach.

    PubMed

    Meyer, Britta S; Matschiner, Michael; Salzburger, Walter

    2015-02-01

    The species-flocks of cichlid fishes in the East African Great Lakes Victoria, Malawi and Tanganyika constitute the most diverse extant adaptive radiations in vertebrates. Lake Tanganyika, the oldest of the lakes, harbors the morphologically and genetically most diverse assemblage of cichlids and contains the highest number of endemic cichlid genera of all African lakes. Based on morphological grounds, the Tanganyikan cichlid species have been grouped into 12-16 distinct lineages, so-called tribes. While the monophyly of most of the tribes is well established, the phylogenetic relationships among the tribes remain largely elusive. Here, we present a new tribal level phylogenetic hypothesis for the cichlid fishes of Lake Tanganyika that is based on the so far largest set of nuclear markers and a total alignment length of close to 18kb. Using next-generation amplicon sequencing with the 454 pyrosequencing technology, we compiled a dataset consisting of 42 nuclear loci in 45 East African cichlid species, which we subjected to maximum likelihood and Bayesian inference phylogenetic analyses. We analyzed the entire concatenated dataset and each marker individually, and performed a Bayesian concordance analysis and gene tree discordance tests. Overall, we find strong support for a position of the Oreochromini, Boulengerochromini, Bathybatini and Trematocarini outside of a clade combining the substrate spawning Lamprologini and the mouthbrooding tribes of the 'H-lineage', which are both strongly supported to be monophyletic. The Eretmodini are firmly placed within the 'H-lineage', as sister-group to the most species-rich tribe of cichlids, the Haplochromini. The phylogenetic relationships at the base of the 'H-lineage' received less support, which is likely due to high speciation rates in the early phase of the radiation. Discordance among gene trees and marker sets further suggests the occurrence of past hybridization and/or incomplete lineage sorting in the cichlid

  1. A tribal level phylogeny of Lake Tanganyika cichlid fishes based on a genomic multi-marker approach

    PubMed Central

    Meyer, Britta S.; Matschiner, Michael; Salzburger, Walter

    2015-01-01

    The species-flocks of cichlid fishes in the East African Great Lakes Victoria, Malawi and Tanganyika constitute the most diverse extant adaptive radiations in vertebrates. Lake Tanganyika, the oldest of the lakes, harbors the morphologically and genetically most diverse assemblage of cichlids and contains the highest number of endemic cichlid genera of all African lakes. Based on morphological grounds, the Tanganyikan cichlid species have been grouped into 12–16 distinct lineages, so-called tribes. While the monophyly of most of the tribes is well established, the phylogenetic relationships among the tribes remain largely elusive. Here, we present a new tribal level phylogenetic hypothesis for the cichlid fishes of Lake Tanganyika that is based on the so far largest set of nuclear markers and a total alignment length of close to 18 kb. Using next-generation amplicon sequencing with the 454 pyrosequencing technology, we compiled a dataset consisting of 42 nuclear loci in 45 East African cichlid species, which we subjected to maximum likelihood and Bayesian inference phylogenetic analyses. We analyzed the entire concatenated dataset and each marker individually, and performed a Bayesian concordance analysis and gene tree discordance tests. Overall, we find strong support for a position of the Oreochromini, Boulengerochromini, Bathybatini and Trematocarini outside of a clade combining the substrate spawning Lamprologini and the mouthbrooding tribes of the ‘H-lineage’, which are both strongly supported to be monophyletic. The Eretmodini are firmly placed within the ‘H-lineage’, as sister-group to the most species-rich tribe of cichlids, the Haplochromini. The phylogenetic relationships at the base of the ‘H-lineage’ received less support, which is likely due to high speciation rates in the early phase of the radiation. Discordance among gene trees and marker sets further suggests the occurrence of past hybridization and/or incomplete lineage sorting in

  2. Monophyletic origin of Lake Victoria cichlid fishes suggested by mitochondrial DNA sequences.

    PubMed

    Meyer, A; Kocher, T D; Basasibwaki, P; Wilson, A C

    1990-10-11

    Lake Victoria, together with its satellite lakes, harbours roughly 200 endemic forms of cichlid fishes that are classified as 'haplochromines' and yet the lake system is less than a million years old. This 'flock' has attracted attention because of the possibility that it evolved within the lake from one ancestral species and that biologists are thus presented with a case of explosive evolution. Within the past decade, however, morphology has increasingly emphasized the view that the flock may be polyphyletic. We sequenced up to 803 base pairs of mitochondrial DNA from 14 representative Victorian species and 23 additional African species. The flock seems to be monophyletic, and is more akin to that from Lake Malawi than to species from Lake Tanganyika; in addition, it contains less genetic variation than does the human species, and there is virtually no sharing of mitochondrial DNA types among species. These results confirm that the founding event was recent.

  3. Body shape differences in a pair of closely related Malawi cichlids and their hybrids: Effects of genetic variation, phenotypic plasticity, and transgressive segregation.

    PubMed

    Husemann, Martin; Tobler, Michael; McCauley, Cagney; Ding, Baoqing; Danley, Patrick D

    2017-06-01

    Phenotypic differences may have genetic and plastic components. Here, we investigated the contributions of both for differences in body shape in two species of Lake Malawi cichlids using wild-caught specimens and a common garden experiment. We further hybridized the two species to investigate the mode of gene action influencing body shape differences and to examine the potential for transgressive segregation. We found that body shape differences between the two species observed in the field are maintained after more than 10 generations in a standardized environment. Nonetheless, both species experienced similar changes in the laboratory environment. Our hybrid cross experiment confirmed that substantial variation in body shape appears to be genetically determined. The data further suggest that the underlying mode of gene action is complex and cannot be explained by simple additive or additive-dominance models. Transgressive phenotypes were found in the hybrid generations, as hybrids occupied significantly more morphospace than both parentals combined. Further, the body shapes of transgressive individuals resemble the body shapes observed in other Lake Malawi rock-dwelling genera. Our findings indicate that body shape can respond to selection immediately, through plasticity, and over longer timescales through adaptation. In addition, our results suggest that hybridization may have played an important role in the diversification of Lake Malawi cichlids through creating new phenotypic variation.

  4. Mitochondrial phylogeography of rock-dwelling cichlid fishes reveals evolutionary influence of historical lake level fluctuations of Lake Tanganyika, Africa.

    PubMed

    Verheyen, E; Rüber, L; Snoeks, J; Meyer, A

    1996-06-29

    The East African Lakes Tanganyika, Malawi and Victoria each harbour hundreds of endemic invertebrate and vertebrate species. Inferences about the ecological and evolutionary processes responsible for the origin of these species flocks will only be possible when they are made within historical and comparative frameworks. Specifically, the relative importance of intrinsic characteristics and extrinsic factors may offer information about the processes that drive diversification and speciation in these species. We investigated the sequence variation of a segment of the mitochondrial DNA control region of 32 populations representing all four nominal species in the three genera of eretmodine cichlids from Lake Tanganyika. Based on a phylogenetic analysis of these data we attempted to evaluate the importance of major lake level fluctuations on patterns of intralacustrine speciation. The geography of genetic variation reveals a high degree of within-lake endemism among genetically well-separated lineages distributed along the inferred shore lines of three historically intermittent lake basins. Seismic data indicate that extreme lowering of water levels in the Pleistocene caused the single Lake Tanganyika basin to split into three isolated ones. The strong phylogeographic structure of the Eretmodini, and the observation that some closely related populations occur on opposite shores of the lake, agree with this geological scenario. The three-clade-three-basin phylogeographic pattern was repeated twice within this tribe of cichlids. The phylogeographic pattern of eretmodine cichlids suggests that major fluctuations in the level of the lake have been important in shaping their adaptive radiation and speciation. The mitochondrially defined clades are in conflict with the current taxonomy of the group and suggest that there has been convergent evolution in trophic morphology, particularly in the shapes of oral teeth, taxonomically the most diagnostic characters of the three

  5. Mating and Parental Care in Lake Tanganyika's Cichlids

    PubMed Central

    Sefc, Kristina M.

    2011-01-01

    Cichlid fishes of Lake Tanganyika display a variety of mating and parental care behaviors, including polygamous and monogamous mouthbrooding and substrate breeding, cooperative breeding, as well as various alternative reproductive tactics such as sneaking and piracy. Moreover, reproductive behaviors sometimes vary within species both in space and in time. Here, I survey reports on mating and parenting behaviors of Lake Tanganyika cichlid species and address the evolution of mating and parental care patterns and sexual dimorphism. Notes on measures of sexual selection intensity and the difficulties of defining mating systems and estimating selection intensities at species level conclude the essay. PMID:21822482

  6. Mating and Parental Care in Lake Tanganyika's Cichlids.

    PubMed

    Sefc, Kristina M

    2011-01-01

    Cichlid fishes of Lake Tanganyika display a variety of mating and parental care behaviors, including polygamous and monogamous mouthbrooding and substrate breeding, cooperative breeding, as well as various alternative reproductive tactics such as sneaking and piracy. Moreover, reproductive behaviors sometimes vary within species both in space and in time. Here, I survey reports on mating and parenting behaviors of Lake Tanganyika cichlid species and address the evolution of mating and parental care patterns and sexual dimorphism. Notes on measures of sexual selection intensity and the difficulties of defining mating systems and estimating selection intensities at species level conclude the essay.

  7. Distinct population structure in a phenotypically homogeneous rock-dwelling cichlid fish from Lake Tanganyika.

    PubMed

    Duftner, Nina; Sefc, Kristina M; Koblmüller, Stephan; Nevado, Bruno; Verheyen, Erik; Phiri, Harris; Sturmbauer, Christian

    2006-08-01

    Several lineages of cichlid fishes in the East African Great Lakes display stunning levels of morphological diversification. The rapid evolution of rock-dwelling polygynous mouthbrooders in Lake Malawi, for example, was in part ascribed to their allopatric distribution on disjunct stretches of rocky coast, where even short habitat discontinuities reduce gene flow effectively. However, as seen in other cichlids, ecological barriers do not always prevent gene flow, whereas genetic structure can develop along continuous habitat, and morphological diversification does not necessarily accompany genetic differentiation. The present study investigates the population structure of Variabilichromis moorii, a monogamous substrate-brooding lamprologine of rocky coasts in Lake Tanganyika, which occurs over about 1000 km of shoreline almost without phenotypic variation. Phylogeographic analyses of mitochondrial DNA sequences indicated that dispersal is infrequent and generally occurs between adjacent locations only. Exceptions to this pattern are closely related haplotypes from certain locations on opposite lakeshores, a phenomenon which has been observed in other species and is thought to reflect lake crossing along an underwater ridge in times of low water level. Genetic population differentiation, estimated from mitochondrial DNA and microsatellite data in six adjacent populations, was equally high across localities separated by sandy shores and along uninterrupted stretches of rocky shore. Our results suggest that ecological barriers are not required to induce philopatric behavior in Variabilichromis, and that morphological stasis persists in the face of high levels of neutral genetic differentiation.

  8. Genomic islands of speciation separate cichlid ecomorphs in an East African crater lake.

    PubMed

    Malinsky, Milan; Challis, Richard J; Tyers, Alexandra M; Schiffels, Stephan; Terai, Yohey; Ngatunga, Benjamin P; Miska, Eric A; Durbin, Richard; Genner, Martin J; Turner, George F

    2015-12-18

    The genomic causes and effects of divergent ecological selection during speciation are still poorly understood. Here we report the discovery and detailed characterization of early-stage adaptive divergence of two cichlid fish ecomorphs in a small (700 meters in diameter) isolated crater lake in Tanzania. The ecomorphs differ in depth preference, male breeding color, body shape, diet, and trophic morphology. With whole-genome sequences of 146 fish, we identified 98 clearly demarcated genomic "islands" of high differentiation and demonstrated the association of genotypes across these islands with divergent mate preferences. The islands contain candidate adaptive genes enriched for functions in sensory perception (including rhodopsin and other twilight-vision-associated genes), hormone signaling, and morphogenesis. Our study suggests mechanisms and genomic regions that may play a role in the closely related mega-radiation of Lake Malawi. Copyright © 2015, American Association for the Advancement of Science.

  9. Genomic islands of speciation separate cichlid ecomorphs in an East African crater lake*

    PubMed Central

    Tyers, Alexandra M.; Schiffels, Stephan; Terai, Yohey; Ngatunga, Benjamin P.; Miska, Eric A.; Durbin, Richard; Genner, Martin J.; Turner, George F.

    2015-01-01

    The genomic causes and effects of divergent ecological selection during speciation are still poorly understood. Here, we report the discovery and detailed characterization of early-stage adaptive divergence of two cichlid fish ecomorphs in a small (700m diameter) isolated crater lake in Tanzania. The ecomorphs differ in depth preference, male breeding color, body shape, diet and trophic morphology. With whole genome sequences of 146 fish, we identify 98 clearly demarcated genomic ‘islands’ of high differentiation and demonstrate association of genotypes across these islands to divergent mate preferences. The islands contain candidate adaptive genes enriched for functions in sensory perception (including rhodopsin and other twilight vision associated genes), hormone signaling and morphogenesis. Our study suggests mechanisms and genomic regions that may play a role in the closely related mega-radiation of Lake Malawi. PMID:26680190

  10. Origins of Shared Genetic Variation in African Cichlids

    PubMed Central

    Loh, Yong-Hwee E.; Bezault, Etienne; Muenzel, Frauke M.; Roberts, Reade B.; Swofford, Ross; Barluenga, Marta; Kidd, Celeste E.; Howe, Aimee E.; Di Palma, Federica; Lindblad-Toh, Kerstin; Hey, Jody; Seehausen, Ole; Salzburger, Walter; Kocher, Thomas D.; Streelman, J. Todd

    2013-01-01

    Cichlid fishes have evolved tremendous morphological and behavioral diversity in the waters of East Africa. Within each of the Great Lakes Tanganyika, Malawi, and Victoria, the phenomena of hybridization and retention of ancestral polymorphism explain allele sharing across species. Here, we explore the sharing of single nucleotide polymorphisms (SNPs) between the major East African cichlid assemblages. A set of approximately 200 genic and nongenic SNPs was ascertained in five Lake Malawi species and genotyped in a diverse collection of ∼160 species from across Africa. We observed segregating polymorphism outside of the Malawi lineage for more than 50% of these loci; this holds similarly for genic versus nongenic SNPs, as well as for SNPs at putative CpG versus non-CpG sites. Bayesian and principal component analyses of genetic structure in the data demonstrate that the Lake Malawi endemic flock is not monophyletic and that river species have likely contributed significantly to Malawi genomes. Coalescent simulations support the hypothesis that river cichlids have transported polymorphism between lake assemblages. We observed strong genetic differentiation between Malawi lineages for approximately 8% of loci, with contributions from both genic and nongenic SNPs. Notably, more than half of these outlier loci between Malawi groups are polymorphic outside of the lake. Cichlid fishes have evolved diversity in Lake Malawi as new mutations combined with standing genetic variation shared across East Africa. PMID:23275489

  11. How many species of cichlid fishes are there in African lakes?

    PubMed

    Turner, G F; Seehausen, O; Knight, M E; Allender, C J; Robinson, R L

    2001-03-01

    The endemic cichlid fishes of Lakes Malawi, Tanganyika and Victoria are textbook examples of explosive speciation and adaptive radiation, and their study promises to yield important insights into these processes. Accurate estimates of species richness of lineages in these lakes, and elsewhere, will be a necessary prerequisite for a thorough comparative analysis of the intrinsic and extrinsic factors influencing rates of diversification. This review presents recent findings on the discoveries of new species and species flocks and critically appraises the relevant evidence on species richness from recent studies of polymorphism and assortative mating, generally using behavioural and molecular methods. Within the haplochromines, the most species-rich lineage, there are few reported cases of postzygotic isolation, and these are generally among allopatric taxa that are likely to have diverged a relatively long time in the past. However, many taxa, including many which occur sympatrically and do not interbreed in nature, produce viable, fertile hybrids. Prezygotic barriers are more important, and persist in laboratory conditions in which environmental factors have been controlled, indicating the primary importance of direct mate preferences. Studies to date indicate that estimates of alpha (within-site) diversity appear to be robust. Although within-species colour polymorphisms are common, these have been taken into account in previous estimates of species richness. However, overall estimates of species richness in Lakes Malawi and Victoria are heavily dependent on the assignation of species status to allopatric populations differing in male colour. Appropriate methods for testing the specific status of allopatric cichlid taxa are reviewed and preliminary results presented.

  12. Colour-assortative mating among populations of Tropheus moorii, a cichlid fish from Lake Tanganyika, East Africa.

    PubMed

    Salzburger, Walter; Niederstätter, Harald; Brandstätter, Anita; Berger, Burkhard; Parson, Walther; Snoeks, Jos; Sturmbauer, Christian

    2006-02-07

    The species flocks of cichlid fishes in the East African Lakes Tanganyika, Malawi and Victoria are prime examples of adaptive radiation and explosive speciation. Several hundreds of endemic species have evolved in each of the lakes over the past several thousands to a few millions years. Sexual selection via colour-assortative mating has often been proposed as a probable causal factor for initiating and maintaining reproductive isolation. Here, we report the consequences of human-mediated admixis among differentially coloured populations of the endemic cichlid fish Tropheus moorii from several localities that have accidentally been put in sympatry in a small harbour bay in the very south of Lake Tanganyika. We analysed the phenotypes (coloration) and genotypes (mitochondrial control region and five microsatellite loci) of almost 500 individuals, sampled over 3 consecutive years. Maximum-likelihood-based parenthood analyses and Bayesian inference of population structure revealed that significantly more juveniles are the product of within-colour-morph matings than could be expected under the assumption of random mating. Our results clearly indicate a marked degree of assortative mating with respect to the different colour morphs. Therefore, we postulate that sexual selection based on social interactions and female mate choice has played an important role in the formation and maintenance of the different colour morphs in Tropheus, and is probably common in other maternally mouthbrooding cichlids as well.

  13. The adaptive radiation of cichlid fish in lake tanganyika: a morphological perspective.

    PubMed

    Takahashi, Tetsumi; Koblmüller, Stephan

    2011-01-01

    Lake Tanganyika is the oldest of the Great Ancient Lakes in the East Africa. This lake harbours about 250 species of cichlid fish, which are highly diverse in terms of morphology, behaviour, and ecology. Lake Tanganyika's cichlid diversity has evolved through explosive speciation and is treated as a textbook example of adaptive radiation, the rapid differentiation of a single ancestor into an array of species that differ in traits used to exploit their environments and resources. To elucidate the processes and mechanisms underlying the rapid speciation and adaptive radiation of Lake Tanganyika's cichlid species assemblage it is important to integrate evidence from several lines of research. Great efforts have been, are, and certainly will be taken to solve the mystery of how so many cichlid species evolved in so little time. In the present review, we summarize morphological studies that relate to the adaptive radiation of Lake Tanganyika's cichlids and highlight their importance for understanding the process of adaptive radiation.

  14. The Adaptive Radiation of Cichlid Fish in Lake Tanganyika: A Morphological Perspective

    PubMed Central

    Takahashi, Tetsumi; Koblmüller, Stephan

    2011-01-01

    Lake Tanganyika is the oldest of the Great Ancient Lakes in the East Africa. This lake harbours about 250 species of cichlid fish, which are highly diverse in terms of morphology, behaviour, and ecology. Lake Tanganyika's cichlid diversity has evolved through explosive speciation and is treated as a textbook example of adaptive radiation, the rapid differentiation of a single ancestor into an array of species that differ in traits used to exploit their environments and resources. To elucidate the processes and mechanisms underlying the rapid speciation and adaptive radiation of Lake Tanganyika's cichlid species assemblage it is important to integrate evidence from several lines of research. Great efforts have been, are, and certainly will be taken to solve the mystery of how so many cichlid species evolved in so little time. In the present review, we summarize morphological studies that relate to the adaptive radiation of Lake Tanganyika's cichlids and highlight their importance for understanding the process of adaptive radiation. PMID:21716857

  15. Late Pleistocene Desiccation of Lake Victoria and Rapid Evolution of Cichlid Fishes

    NASA Astrophysics Data System (ADS)

    Johnson, Thomas C.; Scholz, Christopher A.; Talbot, Michael R.; Kelts, Kerry; Ricketts, R. D.; Ngobi, Gideon; Beuning, Kristina; Ssemmanda, Immacculate; McGill, J. W.

    1996-08-01

    Lake Victoria is the largest lake in Africa and harbors more than 300 endemic species of haplochromine cichlid fish. Seismic reflection profiles and piston cores show that the lake not only was at a low stand but dried up completely during the Late Pleistocene, before 12,400 carbon-14 years before the present. These results imply that the rate of speciation of cichlid fish in this tropical lake has been extremely rapid.

  16. Multiple colonisations of the Lake Malawi catchment by the genus Opsaridium (Teleostei: Cyprinidae).

    PubMed

    Sungani, Harold; Ngatunga, Benjamin P; Koblmüller, Stephan; Mäkinen, Tuuli; Skelton, Paul H; Genner, Martin J

    2017-02-01

    It has been proposed that the fish faunas of African rivers assemble through multiple colonisation events, while lake faunas form additionally through intralacustine speciation. While this pattern has been established for many lineages, most notably cichlids, there are opportunities to further investigate the concept using phylogenies of congeneric endemic species within ancient lake catchments. The Lake Malawi catchment contains three river-spawning cyprinids of the genus Opsaridium, two of which are endemic. These species differ in body size, migratory behaviour and habitat use, but it has never previously been tested if these represent a monophyletic radiation, or have instead colonised the lake independently. We placed these species in a broader phylogeny of Opsaridium and the related genus Raiamas, including all known species from the river systems surrounding Lake Malawi. Our results suggest that each of the species has independently colonised the lake catchment, with all three taxa having well-defined sister taxa outside of the lake, and all sharing a common ancestor ∼14.9million years ago, before the Lake Malawi basin started to form ∼8.6million years ago. Additionally, the results strongly support previous observations that Opsaridium is not a monophyletic group, but instead contains Raiamas from the Congo drainage. Together these results are supportive of the concept that river fish faunas within African catchments are primarily assembled through a process of accumulation from independent origins, rather than within-catchment speciation and adaptive radiation. In light of these results we also suggest there is scope for a re-evaluation of systematics of both Opsaridium and Raiamas.

  17. Climatic variability in combination with eutrophication drives adaptive responses in the gills of Lake Victoria cichlids.

    PubMed

    van Rijssel, Jacco C; Hecky, Robert E; Kishe-Machumu, Mary A; Meijer, Saskia E; Pols, Johan; van Tienderen, Kaj M; Ververs, Jan D; Wanink, Jan H; Witte, Frans

    2016-12-01

    Textbook examples of adaptive radiation often show rapid morphological changes in response to environmental perturbations. East Africa's Lake Victoria, famous for its stunning adaptive radiation of cichlids, has suffered from human-induced eutrophication over the past decades. This cultural eutrophication is thought to be partly responsible for the dramatically reduced cichlid biodiversity, but climatic variability in itself might also have contributed to the eutrophication which resulted in low oxygen levels and decreased water transparency. To determine how recent environmental changes have influenced the lake and its cichlids over the past 50 years, we gathered environmental and meteorological variables and compared these with gill surface area of four cichlid species. We found that during the period of severe eutrophication and temperature increase (1980s), reduced wind speeds coincided with a reduction in oxygen levels and a decrease in both water temperature and transparency. The gill surface area in three out of the four cichlid species increased during this period which is consistent with adaptive change in response to increased hypoxia. During the 2000s, wind speeds, oxygen levels, water transparency and water temperature increased again, while cichlid gill surface area decreased. Our results imply that climatic changes and especially wind speed and direction might play a crucial role in tropical lake dynamics. The changes in Lake Victoria's water quality coincide with fluctuations in cichlid gill surface area, suggesting that these fish can respond rapidly to environmental perturbations, but also that climatic variability, together with continued eutrophication, might be detrimental to the lake's cichlid biodiversity.

  18. Construction of chromosome markers from the Lake Victoria cichlid Paralabidochromis chilotes and their application to comparative mapping.

    PubMed

    Kuroiwa, A; Terai, Y; Kobayashi, N; Yoshida, K; Suzuki, M; Nakanishi, A; Matsuda, Y; Watanabe, M; Okada, N

    2014-01-01

    Cichlid fishes in the African Great Lakes are known as a spectacular example of adaptive radiation in vertebrates. Four linkage maps have been constructed to identify the genes responsible for adaptation and speciation, and the genetic linkages of those genes are assumed to play an important role during adaptive evolution. However, it is difficult to analyze such linkages because the linkage groups of one species do not match well with those of the other species. Chromosome markers are a powerful tool for the direct identification of linkage homology between different species. We used information about the linkage map of the Lake Malawi cichlid (Labeotropheus fuelleborni/Metriaclima zebra) to isolate bacterial artificial chromosome (BAC) clones from the BAC library of Paralabidochromis chilotes, Lake Victoria. We identified 18 of 22 P. chilotes chromosomes by single- and multi-color BAC fluorescence in situ hybridization using 19 BAC clones. Comparative mapping with the chromosome markers of P. chilotes in Astatotilapia burtoni (2n = 40) from Lake Tanganyika revealed the chromosome rearrangements that have occurred in this lineage. These chromosome markers will be useful for delineating the process of genome and chromosome evolution in African species. © 2013 S. Karger AG, Basel.

  19. Evolution of brain-body allometry in Lake Tanganyika cichlids.

    PubMed

    Tsuboi, Masahito; Kotrschal, Alexander; Hayward, Alexander; Buechel, Severine Denise; Zidar, Josefina; Løvlie, Hanne; Kolm, Niclas

    2016-07-01

    Brain size is strongly associated with body size in all vertebrates. This relationship has been hypothesized to be an important constraint on adaptive brain size evolution. The essential assumption behind this idea is that static (i.e., within species) brain-body allometry has low ability to evolve. However, recent studies have reported mixed support for this view. Here, we examine brain-body static allometry in Lake Tanganyika cichlids using a phylogenetic comparative framework. We found considerable variation in the static allometric intercept, which explained the majority of variation in absolute and relative brain size. In contrast, the slope of the brain-body static allometry had relatively low variation, which explained less variation in absolute and relative brain size compared to the intercept and body size. Further examination of the tempo and mode of evolution of static allometric parameters confirmed these observations. Moreover, the estimated evolutionary parameters indicate that the limited observed variation in the static allometric slope could be a result of strong stabilizing selection. Overall, our findings suggest that the brain-body static allometric slope may represent an evolutionary constraint in Lake Tanganyika cichlids. © 2016 The Author(s).

  20. Phylogeny of African cichlid fishes as revealed by molecular markers.

    PubMed

    Mayer, W E; Tichy, H; Klein, J

    1998-06-01

    The species flocks of cichlid fish in the three great East African Lakes, Victoria, Malawi, and Tanganyika, have arisen in each lake by explosive adaptive radiation. Various questions concerning their phylogeny have not yet been answered. In particular, the identity of the ancestral founder species and the monophyletic origin of the haplochromine cichlids from the East African lakes have not been established conclusively. In the present study, we used the anonymous nuclear DNA marker DXTU1 as a step towards answering these questions. A 280 bp-fragment of the DXTU1 locus was amplified by the polymerase chain reaction from East African lacustrine species, the East African riverine cichlid species Haplochromis bloyeti, H. burtoni and H. sparsidens, and other African cichlids. Sequencing revealed several indels and substitutions that were used as cladistically informative markers to support a phylogenetic tree constructed by the neighbor-joining method. The topology, although not supported by high bootstrap values, corresponds well to the geographical distribution and previous classification of the cichlids. Markers could be defined that: (i) differentiate East African from West African cichlids; (ii) distinguish the riverine and Lake Victoria/Malawi haplochromines from Lake Tanganyika cichlids; and (iii) indicate the existence of a monophyletic Lake Victoria cichlid superflock which includes haplochromines from satellite lakes and East African rivers. In order to resolve further the relationship of East African riverine and lacustrine species, mtDNA cytochrome b and control region segments were sequenced. The mtDNA-based trees support the notion of the monophyly of the Lake Victoria superflock but are ambiguous with respect to the phylogenetic position of the Lake Malawi flock.

  1. Complete mitochondrial DNA replacement in a Lake Tanganyika cichlid fish.

    PubMed

    Nevado, B; Koblmüller, S; Sturmbauer, C; Snoeks, J; Usano-Alemany, J; Verheyen, E

    2009-10-01

    We used nuclear and mitochondrial DNA (mtDNA) sequences from specimens collected throughout Lake Tanganyika to clarify the evolutionary relationship between Lamprologus callipterus and Neolamprologus fasciatus. The nuclear data support the reciprocal monophyly of these two shell-breeding lamprologine cichlids. However, mtDNA sequences show that (i) L. callipterus includes two divergent and geographically disjunct (North-South) mtDNA lineages; and that (ii) N. fasciatus individuals cluster in a lineage sister group to the northern lineage of L. callipterus. The two mtDNA lineages of L. callipterus diverged c. 684 kya to 1.2 Ma, coinciding with a major water level low stand in Lake Tanganyika, which divided the lake into isolated sub-lakes. This suggests that the two mtDNA lineages originated as the result of the separation of L. callipterus populations in different sub-basins. The incongruent phylogenetic position of N. fasciatus can best be explained by an ancient unidirectional introgression from L. callipterus into N. fasciatus. Remarkably, our data indicate that this event resulted in the complete mtDNA replacement in N. fasciatus. Our data suggest that hybridization occurred soon after the divergence of the two L. callipterus mtDNA lineages, probably still during the water level low stand, and that subsequently the invading mtDNA lineage spread throughout the lake.

  2. Bentho-pelagic divergence of cichlid feeding architecture was prodigious and consistent during multiple adaptive radiations within African rift-lakes.

    PubMed

    Cooper, W James; Parsons, Kevin; McIntyre, Alyssa; Kern, Brittany; McGee-Moore, Alana; Albertson, R Craig

    2010-03-08

    How particular changes in functional morphology can repeatedly promote ecological diversification is an active area of evolutionary investigation. The African rift-lake cichlids offer a calibrated time series of the most dramatic adaptive radiations of vertebrate trophic morphology yet described, and the replicate nature of these events provides a unique opportunity to test whether common changes in functional morphology have repeatedly facilitated their ecological success. Specimens from 87 genera of cichlid fishes endemic to Lakes Tanganyka, Malawi and Victoria were dissected in order to examine the functional morphology of cichlid feeding. We quantified shape using geometric morphometrics and compared patterns of morphological diversity using a series of analytical tests. The primary axes of divergence were conserved among all three radiations, and the most prevalent changes involved the size of the preorbital region of the skull. Even the fishes from the youngest of these lakes (Victoria), which exhibit the lowest amount of skull shape disparity, have undergone extensive preorbital evolution relative to other craniofacial traits. Such changes have large effects on feeding biomechanics, and can promote expansion into a wide array of niches along a bentho-pelagic ecomorphological axis. Here we show that specific changes in trophic anatomy have evolved repeatedly in the African rift lakes, and our results suggest that simple morphological alterations that have large ecological consequences are likely to constitute critical components of adaptive radiations in functional morphology. Such shifts may precede more complex shape changes as lineages diversify into unoccupied niches. The data presented here, combined with observations of other fish lineages, suggest that the preorbital region represents an evolutionary module that can respond quickly to natural selection when fishes colonize new lakes. Characterizing the changes in cichlid trophic morphology that have

  3. Phylogenetic analysis of cichlid fishes using nuclear DNA markers.

    PubMed

    Sültmann, H; Mayer, W E; Figueroa, F; Tichy, H; Klein, J

    1995-11-01

    The recent explosive adaptive radiation of cichlids in the great lakes of Africa has attracted the attention of both morphologists and molecular biologists. To decipher the phylogenetic relationships among the various taxa within the family Cichlidae is a prerequisite for answering some fundamental questions about the nature of the speciation process. In the present study, we used the random amplification of polymorphic DNA (RAPD) technique to obtain sequence differences between selected cichlid species. We then designed specific primers based on these sequences and used them to amplify template DNA from a large number of species by the polymerase chain reaction (PCR). We sequenced the amplified products and searched the sequences for indels and shared substitutions. We identified a number of such characters at three loci--DXTU1, DXTU2, and DXTU3--and used them for phylogenetic and cladistic analysis of the relationships among the various cichlid groups. Our studies assign an outgroup position to Neotropical cichlids in relation to African cichlids, provide evidence for a sister-group relationship of tilapiines to the haplochromines, group Cyphotilapia frontosa with the lamprologines of Lake Tanganyika, place Astatoreochromis alluaudi to an outgroup position with respect to other haplochromines of Lakes Victoria and Malawi, and provide additional support for the monophyly of the remaining Lake Victoria haplochromines and the Lake Malawi haplochromines. The described approach holds great promise for further resolution of cichlid phylogeny.

  4. Comparative phylogenetic analyses of the adaptive radiation of Lake Tanganyika cichlid fish: nuclear sequences are less homoplasious but also less informative than mitochondrial DNA.

    PubMed

    Clabaut, Céline; Salzburger, Walter; Meyer, Axel

    2005-11-01

    Over 200 described endemic species make up the adaptive radiation of cichlids in Lake Tanganyika. This species assemblage has been viewed as both an evolutionary reservoir of old cichlid lineages and an evolutionary hotspot from which the modern cichlid lineages arose, seeding the adaptive radiations in Lakes Victoria and Malawi. Here we report on a phylogenetic analysis of Lake Tanganyika cichlids combining the previously determined sequences of the mitochondrial ND2 gene (1047 bp) with newly derived sequences of the nuclear RAG1 gene (approximately 700 bp of intron 2 and approximately 1100 bp of exon 3). The nuclear data-in agreement with mitochondrial DNA-suggest that Lake Tanganyika harbors several ancient lineages that did not undergo rampant speciation (e.g., Bathybatini, Trematocarini). We find strong support for the monophyly of the most species-rich Tanganyikan group, the Lamprologini, and we propose a new taxonomic group that we term the C-lineage. The Haplochromini and Tropheini both have an 11-bp deletion in the intron of RAG1, strongly supporting the monophyly of this clade and its derived position. Mapping the phylogenetically informative positions revealed that, for certain branches, there are six times fewer apomorphies in RAG1. However, the consistency index of these positions is higher compared to the mitochondrial ND2 gene. Nuclear data therefore provide, on a per-base pair basis, less but more reliable phylogenetic information. Even if in our case RAG1 has not provided as much phylogenetic information as we expected, we suggest that this marker might be useful in the resolution of the phylogeny of older groups.

  5. Rapid radiation, ancient incomplete lineage sorting and ancient hybridization in the endemic Lake Tanganyika cichlid tribe Tropheini.

    PubMed

    Koblmüller, Stephan; Egger, Bernd; Sturmbauer, Christian; Sefc, Kristina M

    2010-04-01

    The evolutionary history of the endemic Lake Tanganyika cichlid tribe Tropheini, the sister group of the species flocks of Lake Malawi and the Lake Victoria region, was reconstructed from 2009 bp DNA sequence of two mitochondrial genes (ND2 and control region) and from 1293 AFLP markers. A period of rapid cladogenesis at the onset of the diversification of the Tropheini produced a multitude of specialized, predominantly rock-dwelling aufwuchs-feeders that now dominate in Lake Tanganyika's shallow habitat. Nested within the stenotopic rock-dwellers is a monophyletic group of species, which also utilize more sediment-rich habitat. Most of the extant species date back to at least 0.7 million years ago. Several instances of disagreement between AFLP and mtDNA tree topology are attributed to ancient incomplete lineage sorting, introgression and hybridization. A large degree of correspondence between AFLP clustering and trophic types indicated fewer cases of parallel evolution of trophic ecomorphology than previously inferred from mitochondrial data. (c) 2009 Elsevier Inc. All rights reserved.

  6. Incipient speciation in sympatric Nicaraguan crater lake cichlid fishes: sexual selection versus ecological diversification.

    PubMed Central

    Wilson, A B; Noack-Kunnmann, K; Meyer, A

    2000-01-01

    The growing body of empirical evidence for sympatric speciation has been complemented by recent theoretical treatments that have identified evolutionary conditions conducive to speciation in sympatry. The Neotropical Midas cichlid (Amphilophus citrinellum) fits both of the key characteristics of these models, with strong assortative mating on the basis of a colour polymorphism coupled with trophic and ecological differentiation derived from a polymorphism in their pharyngeal jaws. We used microsatellite markers and a 480 bp fragment of the mitochondrial DNA control region to study four polymorphic populations of the Midas cichlid from three crater lakes and one large lake in Nicaragua in an investigation of incipient sympatric speciation. All populations were strongly genetically differentiated on the basis of geography. We identified strong genetic separation based on colour polymorphism for populations from Lake Nicaragua and one crater lake (Lake Apoyo), but failed to find significant genetic structuring based on trophic differences and ecological niche separation in any of the four populations studied. These data support the idea that sexual selection through assortative mating contributes more strongly or earlier during speciation in sympatry than ecological separation in these cichlids. The long-term persistence of divergent cichlid ecotypes (as measured by the percentage sequence divergence between populations) in Central American crater lakes, despite a lack of fixed genetic differentiation, differs strikingly from the patterns of extremely rapid speciation in the cichlids in Africa, including its crater lakes. It is unclear whether extrinsic environmental factors or intrinsic biological differences, e.g. in the degree of phenotypic plasticity, promote different mechanisms and thereby rates of speciation of cichlid fishes from the Old and New Worlds. PMID:11413624

  7. Population-structure and genetic diversity in a haplochromine cichlid fish [corrected] of a satellite lake of Lake Victoria.

    PubMed

    Abila, Romulus; Barluenga, Marta; Engelken, Johannes; Meyer, Axel; Salzburger, Walter

    2004-09-01

    The approximately 500 species of the cichlid fish species flock of Lake Victoria, East Africa, have evolved in a record-setting 100,000 years and represent one of the largest adaptive radiations. We examined the population structure of the endangered cichlid species Xystichromis phytophagus from Lake Kanyaboli, a satellite lake to Lake Victoria in the Kenyan Yala wetlands. Two sets of molecular markers were analysed--sequences of the mitochondrial control region as well as six microsatellite loci--and revealed surprisingly high levels of genetic variability in this species. Mitochondrial DNA sequences failed to detect population structuring among the three sample populations. A model-based population assignment test based on microsatellite data revealed that the three populations most probably aggregate into a larger panmictic population. However, values of population pairwise FST indicated moderate levels of genetic differentiation for one population. Eleven distinct mitochondrial haplotypes were found among 205 specimens of X. phytophagus, a relatively high number compared to the total number of 54 haplotypes that were recovered from hundreds of specimens of the entire cichlid species flock of Lake Victoria. Most of the X. phytophagus mitochondrial DNA haplotypes were absent from the main Lake Victoria, corroborating the putative importance of satellite lakes as refugia for haplochromine cichlids that went extinct from the main lake in the last decades and possibly during the Late Pleistocene desiccation of Lake Victoria.

  8. Crustal Structure in Northern Malawi and Southern Tanzania surrounding Lake Malawi and the Rungwe Volcanic Province

    NASA Astrophysics Data System (ADS)

    Borrego, D.; Kachingwe, M.; Nyblade, A.; Shillington, D. J.; Gaherty, J. B.; Ebinger, C. J.; Accardo, N. J.; O'Donnell, J. P.; Mbogoni, G. J.; Mulibo, G. D.; Chindandali, P. R. N.; Mphepo, F.; Ferdinand-Wambura, R.; Tepp, G.

    2015-12-01

    Crustal Structure in Northern Malawi and Southern Tanzania surrounding Lake Malawi and the Rungwe Volcanic Province David Borrego, Marsella Kachingwe, Andrew Nyblade, Donna Shillington, James Gaherty, Cynthia Ebinger, Natalie Accardo, J.P. O'Donnell, Gabriel Mbogoni, Gabriel Mulibo, Richard Ferdinand, Patrick Chindandali, Felix Mphepo, Gabrielle Tepp, Godson Kamihanda We investigate crustal structure around the northern end of Lake Malawi and in the Rungwe Volcanic Province using teleseismic receiver functions from the SEGMeNT broadband seismic network. The SEGMeNT network includes 55 broadband stations deployed in northern Malawi and southern Tanzania, with station spacing of 20-50 km. Fourteen stations were deployed in August 2013, and an additional of 41 stations were added to the study region beginning June/July 2014. Fifteen stations are located in Malawi and 40 stations in Tanzania. Data from teleseismic earthquakes with magnitude 5.5 or greater in the 30 to 90 degrees distance range have been used to calculate P-wave receiver functions. Estimates of Moho depth and Vp/Vs ratios have been obtained by using the H-k stacking method and by jointly inverting the receiver functions with Rayleigh wave phase velocities. Preliminary results show an average Moho depth of 40 km and an average Vp/Vs ratio of 1.72. Little evidence is found for magmatic underplating beneath the Rungwe Volcanic Province.

  9. An extant cichlid fish radiation emerged in an extinct Pleistocene lake.

    PubMed

    Joyce, Domino A; Lunt, David H; Bills, Roger; Turner, George F; Katongo, Cyprian; Duftner, Nina; Sturmbauer, Christian; Seehausen, Ole

    2005-05-05

    The haplochromine cichlid fish of the East African Great Lakes represent some of the fastest and most species-rich adaptive radiations known, but rivers in most of Africa accommodate only a few morphologically similar species of haplochromine cichlid fish. This has been explained by the wealth of ecological opportunity in large lakes compared with rivers. It is therefore surprising that the rivers of southern Africa harbour many, ecologically diverse haplochromines. Here we present genetic, morphological and biogeographical evidence suggesting that these riverine cichlids are products of a recent adaptive radiation in a large lake that dried up in the Holocene. Haplochromine species richness peaks steeply in an area for which geological data reveal the historical existence of Lake palaeo-Makgadikgadi. The centre of this extinct lake is now a saltpan north of the Kalahari Desert, but it once hosted a rapidly evolving fish species radiation, comparable in morphological diversity to that in the extant African Great Lakes. Importantly, this lake seeded all major river systems of southern Africa with ecologically diverse cichlids. This discovery reveals how local evolutionary processes operating during a short window of ecological opportunity can have a major and lasting effect on biodiversity on a continental scale.

  10. Replicated divergence in cichlid radiations mirrors a major vertebrate innovation

    PubMed Central

    McGee, Matthew D.; Faircloth, Brant C.; Borstein, Samuel R.; Zheng, Jimmy; Darrin Hulsey, C.; Wainwright, Peter C.; Alfaro, Michael E.

    2016-01-01

    Decoupling of the upper jaw bones—jaw kinesis—is a distinctive feature of the ray-finned fishes, but it is not clear how the innovation is related to the extraordinary diversity of feeding behaviours and feeding ecology in this group. We address this issue in a lineage of ray-finned fishes that is well known for its ecological and functional diversity—African rift lake cichlids. We sequenced ultraconserved elements to generate a phylogenomic tree of the Lake Tanganyika and Lake Malawi cichlid radiations. We filmed a diverse array of over 50 cichlid species capturing live prey and quantified the extent of jaw kinesis in the premaxillary and maxillary bones. Our combination of phylogenomic and kinematic data reveals a strong association between biting modes of feeding and reduced jaw kinesis, suggesting that the contrasting demands of biting and suction feeding have strongly influenced cranial evolution in both cichlid radiations. PMID:26763694

  11. Separated by sand, fused by dropping water: habitat barriers and fluctuating water levels steer the evolution of rock-dwelling cichlid populations in Lake Tanganyika.

    PubMed

    Koblmüller, Stephan; Salzburger, Walter; Obermüller, Beate; Eigner, Eva; Sturmbauer, Christian; Sefc, Kristina M

    2011-06-01

    The conditions of phenotypic and genetic population differentiation allow inferences about the evolution, preservation and loss of biological diversity. In Lake Tanganyika, water level fluctuations are assumed to have had a major impact on the evolution of stenotopic littoral species, though this hypothesis has not been specifically examined so far. The present study investigates whether subtly differentiated colour patterns of adjacent Tropheus moorii populations are maintained in isolation or in the face of continuous gene flow, and whether the presumed influence of water level fluctuations on lacustrine cichlids can be demonstrated in the small-scale population structure of the strictly stenotopic, littoral Tropheus. Distinct population differentiation was found even across short geographic distances and minor habitat barriers. Population splitting chronology and demographic histories comply with our expectation of old and rather stable populations on steeper sloping shore, and more recently established populations in a shallower region. Moreover, population expansions seem to coincide with lake level rises in the wake of Late Pleistocene megadroughts ~100 KYA. The imprint of hydrologic events on current population structure in the absence of ongoing gene flow suggests that phenotypic differentiation among proximate Tropheus populations evolves and persists in genetic isolation. Sporadic gene flow is effected by lake level fluctuations following climate changes and controlled by the persistence of habitat barriers during lake level changes. Since similar demographic patterns were previously reported for Lake Malawi cichlids, our data furthermore strengthen the hypothesis that major climatic events synchronized facets of cichlid evolution across the East African Great Lakes. © 2011 Blackwell Publishing Ltd.

  12. Parallel evolution in Ugandan crater lakes: repeated evolution of limnetic body shapes in haplochromine cichlid fish.

    PubMed

    Machado-Schiaffino, Gonzalo; Kautt, Andreas F; Kusche, Henrik; Meyer, Axel

    2015-02-04

    The enormous diversity found in East African cichlid fishes in terms of morphology, coloration, and behavior have made them a model for the study of speciation and adaptive evolution. In particular, haplochromine cichlids, by far the most species-rich lineage of cichlids, are a well-known textbook example for parallel evolution. Southwestern Uganda is an area of high tectonic activity, and is home to numerous crater lakes. Many Ugandan crater lakes were colonized, apparently independently, by a single lineage of haplochromine cichlids. Thereby, this system could be considered a natural experiment in which one can study the interaction between geographical isolation and natural selection promoting phenotypic diversification. We sampled 13 crater lakes and six potentially-ancestral older lakes and, using both mitochondrial and microsatellite markers, discovered strong genetic and morphological differentiation whereby (a) geographically close lakes tend to be genetically more similar and (b) three different geographic areas seem to have been colonized by three independent waves of colonization from the same source population. Using a geometric morphometric approach, we found that body shape elongation (i.e. a limnetic morphology) evolved repeatedly from the ancestral deeper-bodied benthic morphology in the clear and deep crater lake habitats. A pattern of strong genetic and morphological differentiation was observed in the Ugandan crater lakes. Our data suggest that body shape changes have repeatedly evolved into a more limnetic-like form in several Ugandan crater lakes after independent waves of colonization from the same source population. The observed morphological changes in crater lake cichlids are likely to result from a common selective regime.

  13. A pharyngeal jaw evolutionary innovation facilitated extinction in Lake Victoria cichlids.

    PubMed

    McGee, Matthew D; Borstein, Samuel R; Neches, Russell Y; Buescher, Heinz H; Seehausen, Ole; Wainwright, Peter C

    2015-11-27

    Evolutionary innovations, traits that give species access to previously unoccupied niches, may promote speciation and adaptive radiation. Here, we show that such innovations can also result in competitive inferiority and extinction. We present evidence that the modified pharyngeal jaws of cichlid fishes and several marine fish lineages, a classic example of evolutionary innovation, are not universally beneficial. A large-scale analysis of dietary evolution across marine fish lineages reveals that the innovation compromises access to energy-rich predator niches. We show that this competitive inferiority shaped the adaptive radiation of cichlids in Lake Tanganyika and played a pivotal and previously unrecognized role in the mass extinction of cichlid fishes in Lake Victoria after Nile perch invasion. Copyright © 2015, American Association for the Advancement of Science.

  14. Big fish, little divergence: phylogeography of Lake Tanganyika's giant cichlid, Boulengerochromis microlepis.

    PubMed

    Koblmüller, Stephan; Odhiambo, Elizabeth A; Sinyinza, Danny; Sturmbauer, Christian; Sefc, Kristina M

    2015-04-01

    The largely endemic cichlid species flocks of the East African Great Lakes are among the prime examples for explosive speciation and adaptive radiation. Speciation rates differ among cichlid lineages, and the propensity to radiate has been linked to intrinsic and extrinsic factors such as sexual selection and ecological opportunity. Remarkably, only one cichlid tribe-the Boulengerochromini-comprises just a single species, Boulengerochromis microlepis, a predominantly piscivorous endemic of Lake Tanganyika and the world's largest cichlid. While the lineage diverged from its closest relatives at the onset of the Lake Tanganyika radiation >8 MYA, mitochondrial control region sequences collected in this study dated the most recent common ancestor of B. microlepis to ~60-110 KYA. There was no evidence of phylogeographic structure in the lake-wide sample. Patterns of genetic diversity and demographic analyses were consistent with slow and steady population growth throughout the reconstructed timescale. Additionally, the shallow divergence within the species may be related to a possibly large variance in reproductive success in this highly fecund species. Trophic niche space restriction by sympatric piscivores, lack of geographic structure, low potential for sexual selection arising from the monogamous mating system and extinction may have contributed to keeping the lineage monotypic.

  15. Big fish, little divergence: phylogeography of Lake Tanganyika’s giant cichlid, Boulengerochromis microlepis

    PubMed Central

    Koblmüller, Stephan; Odhiambo, Elizabeth A.; Sinyinza, Danny; Sturmbauer, Christian; Sefc, Kristina M.

    2014-01-01

    The largely endemic cichlid species flocks of the East African Great Lakes are among the prime examples for explosive speciation and adaptive radiation. Speciation rates differ among cichlid lineages, and the propensity to radiate has been linked to intrinsic and extrinsic factors such as sexual selection and ecological opportunity. Remarkably, only one cichlid tribe—the Boulengerochromini—comprises just a single species, Boulengerochromis microlepis, a predominantly piscivorous endemic of Lake Tanganyika and the world’s largest cichlid. While the lineage diverged from its closest relatives at the onset of the Lake Tanganyika radiation >8 MYA, mitochondrial control region sequences collected in this study dated the most recent common ancestor of B. microlepis to ~60–110 KYA. There was no evidence of phylogeographic structure in the lake-wide sample. Patterns of genetic diversity and demographic analyses were consistent with slow and steady population growth throughout the reconstructed timescale. Additionally, the shallow divergence within the species may be related to a possibly large variance in reproductive success in this highly fecund species. Trophic niche space restriction by sympatric piscivores, lack of geographic structure, low potential for sexual selection arising from the monogamous mating system and extinction may have contributed to keeping the lineage monotypic. PMID:25983338

  16. Phylogeny of the Lake Tanganyika cichlid species flock and its relationship to the Central and East African haplochromine cichlid fish faunas.

    PubMed

    Salzburger, Walter; Meyer, Axel; Baric, Sanja; Verheyen, Erik; Sturmbauer, Christian

    2002-02-01

    Lake Tanganyika, the oldest of the East African Great Lakes, harbors the ecologically, morphologically, and behaviorally most complex of all assemblages of cichlid fishes, consisting of about 200 described species. The evolutionary old age of the cichlid assemblage, its extreme degree of morphological differentiation, the lack of species with intermediate morphologies, and the rapidity of lineage formation have made evolutionary reconstruction difficult. The number and origin of seeding lineages, particularly the possible contribution of riverine haplochromine cichlids to endemic lacustrine lineages, remains unclear. Our phylogenetic analyses, based on mitochondrial DNA sequences of three gene segments of 49 species (25% of all described species, up to 2,400 bp each), yield robust phylogenies that provide new insights into the Lake Tanganyika adaptive radiation as well as into the origin of the Central- and East-African haplochromine faunas. Our data suggest that eight ancient African lineages may have seeded the Tanganyikan cichlid radiation. One of these seeding lineages, probably comprising substrate spawning Lamprologus-like species, diversified into six lineages that evolved mouthbrooding during the initial stage of the radiation. All analyzed haplochromines from surrounding rivers and lakes seem to have evolved within the radiating Tanganyikan lineages. Thus, our findings contradict the current hypothesis that ancestral riverine haplochromines colonized Lake Tanganyika to give rise to at least part of its spectacular endemic cichlid species assemblage. Instead, the early phases of the Tanganyikan radiation affected Central and East African rivers and lakes. The haplochromines may have evolved in the Tanganyikan basin before the lake became a hydrologically and ecologically closed system and then secondarily colonized surrounding rivers. Apparently, therefore, the current diversity of Central and East African haplochromines represents a relatively young and

  17. Parallel evolution of opsin gene expression in African cichlid fishes.

    PubMed

    O'Quin, Kelly E; Hofmann, Christopher M; Hofmann, Hans A; Carleton, Karen L

    2010-12-01

    Phenotypic evolution may occur either through alterations to the structure of protein-coding genes or their expression. Evidence for which of these two mechanisms more commonly contribute to the evolution of a phenotype can be garnered from examples of parallel and convergent evolution. The visual system of East African cichlid fishes is an excellent system with which to address this question. Cichlid fishes from Lakes Malawi (LM) and Victoria together exhibit three diverse palettes of coexpressed opsins and several important protein-coding mutations that both shift spectral sensitivity. Here we assess both opsin expression and protein-coding diversity among cichlids from a third rift lake, Lake Tanganyika (LT). We found that Tanganyikan cichlids exhibit three palettes of coexpressed opsins that largely overlap the short-, middle-, and long-wavelength-sensitive palettes of LM cichlids. Bayesian phenotypic clustering and ancestral state reconstructions both support the parallel evolution of the short- and middle-wavelength palettes among cichlids from LT and LM. In each case, these transitions occurred from different ancestors that expressed the same long-wavelength palette. We also identified similar but distinct patterns of correlated evolution between opsin expression, diet, and lens transmittance among cichlids from LT and LM as well. In contrast to regulatory changes, we identified few functional or potentially functional mutations in the protein-coding sequences of three variable opsins, with the possible exception of the SWS1 (ultraviolet) opsin. These results underscore the important contribution that gene regulation can make to rapid phenotypic evolution and adaptation.

  18. Alternative Reproductive Tactics in the Shell-Brooding Lake Tanganyika Cichlid Neolamprologus brevis

    PubMed Central

    Ota, Kazutaka; Aibara, Mitsuto; Morita, Masaya; Awata, Satoshi; Hori, Michio; Kohda, Masanori

    2012-01-01

    Alternative reproductive tactics (ARTs) are found in several Lake Tanganyika shell-brooding cichlids. Field studies were conducted in the Wonzye population to examine reproductive ecology and ARTs in the Lake Tanganyika shell-brooding cichlid Neolamprologus brevis. We discovered that this fish occurred in both rocky- and sandy-bottom habitats, but in rocky habitats, brood-caring females exclusively occurred in shell-patches that another cichlid species created. All N. brevis of both sexes in the patches were sexually mature, whereas immature males and females with unripe eggs were found frequently in sandy-bottom habitats. Males in sandy-bottom habitats were smaller, but fed more frequently and were in better somatic condition than males in the patches. Similar tendency was found in females. This indicates that N. brevis uses different habitats depending on the stage of its life history, with migration from sandy-bottom habitats to the shell-patches for reproduction. Males in the patches exhibited different behavior patterns: floating above the patches and lying in the patches. The former was larger, more aggressive, and invested less in gonads (relative to body size) than the latter. These results accord with those of other shell-brooding Lake Tanganyika cichlids with ARTs, and they therefore suggest the presence of ARTs in N. brevis. PMID:22888463

  19. The diversity of male nuptial coloration leads to species diversity in Lake Victoria cichlids.

    PubMed

    Miyagi, Ryutaro; Terai, Yohey

    2013-01-01

    The amazing coloration shown by diverse cichlid fish not only fascinates aquarium keepers, but also receives great attention from biologists interested in speciation because of its recently-revealed role in their adaptive radiation in an African lake. We review the important role of coloration in the speciation and adaptive evolution of Lake Victoria cichlids, which have experienced adaptive radiation during a very short evolutionary period. Mature male cichlids display their colors during mate choice. The color of their skin reflects light, and the reflected light forms a color signal that is received by the visual system of females. The adaptive divergence of visual perceptions shapes and diverges colorations, to match the adapted visual perceptions. The divergence of visual perception and coloration indicates that the divergence of color signals causes reproductive isolation between species, and this process leads to speciation. Differences in color signals among coexisting species act to maintain reproductive isolation by preventing hybridization. Thus, the diversity of coloration has caused speciation and has maintained species diversity in Lake Victoria cichlids.

  20. Alternative Reproductive Tactics in the Shell-Brooding Lake Tanganyika Cichlid Neolamprologus brevis.

    PubMed

    Ota, Kazutaka; Aibara, Mitsuto; Morita, Masaya; Awata, Satoshi; Hori, Michio; Kohda, Masanori

    2012-01-01

    Alternative reproductive tactics (ARTs) are found in several Lake Tanganyika shell-brooding cichlids. Field studies were conducted in the Wonzye population to examine reproductive ecology and ARTs in the Lake Tanganyika shell-brooding cichlid Neolamprologus brevis. We discovered that this fish occurred in both rocky- and sandy-bottom habitats, but in rocky habitats, brood-caring females exclusively occurred in shell-patches that another cichlid species created. All N. brevis of both sexes in the patches were sexually mature, whereas immature males and females with unripe eggs were found frequently in sandy-bottom habitats. Males in sandy-bottom habitats were smaller, but fed more frequently and were in better somatic condition than males in the patches. Similar tendency was found in females. This indicates that N. brevis uses different habitats depending on the stage of its life history, with migration from sandy-bottom habitats to the shell-patches for reproduction. Males in the patches exhibited different behavior patterns: floating above the patches and lying in the patches. The former was larger, more aggressive, and invested less in gonads (relative to body size) than the latter. These results accord with those of other shell-brooding Lake Tanganyika cichlids with ARTs, and they therefore suggest the presence of ARTs in N. brevis.

  1. Lake Tanganyika--a 'melting pot' of ancient and young cichlid lineages (Teleostei: Cichlidae)?

    PubMed

    Weiss, Juliane D; Cotterill, Fenton P D; Schliewen, Ulrich K

    2015-01-01

    A long history of research focused on the East Africa cichlid radiations (EAR) revealed discrepancies between mtDNA and nuclear phylogenies, suggesting that interspecific hybridisation may have been significant during the radiation of these fishes. The approximately 250 cichlid species of Lake Tanganyika have their roots in a monophyletic African cichlid assemblage, but controversies remain about the precise phylogenetic origin and placement of different lineages and consequently about L. Tanganyika colonization scenarios. 3312 AFLP loci and the mitochondrial ND2 gene were genotyped for 91 species representing almost all major lacustrine and riverine haplotilapiine east African cichlid lineages with a focus on L. Tanganyika endemics. Explicitly testing for the possibility of ancient hybridisation events, a comprehensive phylogenetic network hypothesis is proposed for the origin and diversification of L. Tanganyika cichlids. Inference of discordant phylogenetic signal strongly suggests that the genomes of two endemic L. Tanganyika tribes, Eretmodini and Tropheini, are composed of an ancient mixture of riverine and lacustrine lineages. For the first time a strong monophyly signal of all non-haplochromine mouthbrooding species endemic to L. Tanganyika ("ancient mouthbrooders") was detected. Further, in the genomes of early diverging L. Tanganyika endemics Trematocarini, Bathybatini, Hemibatini and Boulengerochromis genetic components of other lineages belonging to the East African Radiation appear to be present. In combination with recent palaeo-geological results showing that tectonic activity in the L. Tanganyika region resulted in highly dynamic and heterogeneous landscape evolution over the Neogene and Pleistocene, the novel phylogenetic data render a single lacustrine basin as the geographical cradle of the endemic L. Tanganyika cichlid lineages unlikely. Instead a scenario of a pre-rift origin of several independent L. Tanganyika precursor lineages which

  2. Lake Tanganyika—A 'Melting Pot' of Ancient and Young Cichlid Lineages (Teleostei: Cichlidae)?

    PubMed Central

    Weiss, Juliane D.; Cotterill, Fenton P. D.; Schliewen, Ulrich K.

    2015-01-01

    A long history of research focused on the East Africa cichlid radiations (EAR) revealed discrepancies between mtDNA and nuclear phylogenies, suggesting that interspecific hybridisation may have been significant during the radiation of these fishes. The approximately 250 cichlid species of Lake Tanganyika have their roots in a monophyletic African cichlid assemblage, but controversies remain about the precise phylogenetic origin and placement of different lineages and consequently about L. Tanganyika colonization scenarios. 3312 AFLP loci and the mitochondrial ND2 gene were genotyped for 91 species representing almost all major lacustrine and riverine haplotilapiine east African cichlid lineages with a focus on L. Tanganyika endemics. Explicitly testing for the possibility of ancient hybridisation events, a comprehensive phylogenetic network hypothesis is proposed for the origin and diversification of L. Tanganyika cichlids. Inference of discordant phylogenetic signal strongly suggests that the genomes of two endemic L. Tanganyika tribes, Eretmodini and Tropheini, are composed of an ancient mixture of riverine and lacustrine lineages. For the first time a strong monophyly signal of all non-haplochromine mouthbrooding species endemic to L. Tanganyika (“ancient mouthbrooders”) was detected. Further, in the genomes of early diverging L. Tanganyika endemics Trematocarini, Bathybatini, Hemibatini and Boulengerochromis genetic components of other lineages belonging to the East African Radiation appear to be present. In combination with recent palaeo-geological results showing that tectonic activity in the L. Tanganyika region resulted in highly dynamic and heterogeneous landscape evolution over the Neogene and Pleistocene, the novel phylogenetic data render a single lacustrine basin as the geographical cradle of the endemic L. Tanganyika cichlid lineages unlikely. Instead a scenario of a pre-rift origin of several independent L. Tanganyika precursor lineages which

  3. B Chromosomes Have a Functional Effect on Female Sex Determination in Lake Victoria Cichlid Fishes

    PubMed Central

    Yoshida, Kohta; Terai, Yohey; Mizoiri, Shinji; Aibara, Mitsuto; Nishihara, Hidenori; Watanabe, Masakatsu; Kuroiwa, Asato; Hirai, Hirohisa; Hirai, Yuriko; Matsuda, Yoichi; Okada, Norihiro

    2011-01-01

    The endemic cichlid fishes in Lake Victoria are a model system for speciation through adaptive radiation. Although the evolution of the sex-determination system may also play a role in speciation, little is known about the sex-determination system of Lake Victoria cichlids. To understand the evolution of the sex-determination system in these fish, we performed cytogenetic analysis in 11 cichlid species from Lake Victoria. B chromosomes, which are present in addition to standard chromosomes, were found at a high prevalence rate (85%) in these cichlids. In one species, B chromosomes were female-specific. Cross-breeding using females with and without the B chromosomes demonstrated that the presence of the B chromosomes leads to a female-biased sex ratio in this species. Although B chromosomes were believed to be selfish genetic elements with little effect on phenotype and to lack protein-coding genes, the present study provides evidence that B chromosomes have a functional effect on female sex determination. FISH analysis using a BAC clone containing B chromosome DNA suggested that the B chromosomes are derived from sex chromosomes. Determination of the nucleotide sequences of this clone (104.5 kb) revealed the presence of several protein-coding genes in the B chromosome, suggesting that B chromosomes have the potential to contain functional genes. Because some sex chromosomes in amphibians and arthropods are thought to be derived from B chromosomes, the B chromosomes in Lake Victoria cichlids may represent an evolutionary transition toward the generation of sex chromosomes. PMID:21876673

  4. B chromosomes have a functional effect on female sex determination in Lake Victoria cichlid fishes.

    PubMed

    Yoshida, Kohta; Terai, Yohey; Mizoiri, Shinji; Aibara, Mitsuto; Nishihara, Hidenori; Watanabe, Masakatsu; Kuroiwa, Asato; Hirai, Hirohisa; Hirai, Yuriko; Matsuda, Yoichi; Okada, Norihiro

    2011-08-01

    The endemic cichlid fishes in Lake Victoria are a model system for speciation through adaptive radiation. Although the evolution of the sex-determination system may also play a role in speciation, little is known about the sex-determination system of Lake Victoria cichlids. To understand the evolution of the sex-determination system in these fish, we performed cytogenetic analysis in 11 cichlid species from Lake Victoria. B chromosomes, which are present in addition to standard chromosomes, were found at a high prevalence rate (85%) in these cichlids. In one species, B chromosomes were female-specific. Cross-breeding using females with and without the B chromosomes demonstrated that the presence of the B chromosomes leads to a female-biased sex ratio in this species. Although B chromosomes were believed to be selfish genetic elements with little effect on phenotype and to lack protein-coding genes, the present study provides evidence that B chromosomes have a functional effect on female sex determination. FISH analysis using a BAC clone containing B chromosome DNA suggested that the B chromosomes are derived from sex chromosomes. Determination of the nucleotide sequences of this clone (104.5 kb) revealed the presence of several protein-coding genes in the B chromosome, suggesting that B chromosomes have the potential to contain functional genes. Because some sex chromosomes in amphibians and arthropods are thought to be derived from B chromosomes, the B chromosomes in Lake Victoria cichlids may represent an evolutionary transition toward the generation of sex chromosomes.

  5. Depth segregation and diet disparity revealed by stable isotope analyses in sympatric herbivorous cichlids in Lake Tanganyika.

    PubMed

    Hata, Hiroki; Shibata, Jyunya; Omori, Koji; Kohda, Masanori; Hori, Michio

    2015-01-01

    Lake Tanganyika in the African Great Rift Valley is known as a site of adaptive radiation in cichlid fishes. Diverse herbivorous fishes coexist on a rocky littoral of the lake. Herbivorous cichlids have acquired multiple feeding ecomorphs, including grazer, browser, scraper, and scooper, and are segregated by dietary niche. Within each ecomorph, however, multiple species apparently coexist sympatrically on a rocky slope. Previous observations of their behavior show that these cichlid species inhabit discrete depths separated by only a few meters. In this paper, using carbon (C) and nitrogen (N) stable isotope ratios as markers, we followed the nutritional uptake of cichlid fishes from periphyton in their feeding territories at various depths. δ(15)N of fish muscles varied among cichlid ecomorphs; this was significantly lower in grazers than in browsers and scoopers, although δ(15)N levels in periphyton within territories did not differ among territorial species. This suggests that grazers depend more directly on primary production of periphyton, while others ingest animal matter from higher trophic levels. With respect to δ(13)C, only plankton eaters exhibited lower values, suggesting that these fishes depend on production of phytoplankton, while the others depend on production of periphyton. Irrespective of cichlid ecomorph, δ(13)C of periphyton correlated significantly with habitat depth, and decreased as habitat depth became deeper. δ(13)C in territorial fish muscles was significantly related to that of periphyton within their territories, regardless of cichlid ecomorph, which suggests that these herbivorous cichlids depend on primary production of periphyton within their territories. Carbon and nitrogen stable isotope ratios varied among ecomorphs and among cichlid species in the same ecomorphs sympatrically inhabiting a littoral area of Lake Tanganyika, suggesting that these cichlids are segregated by nutrient source due to varying dependency on

  6. Local variation and parallel evolution: morphological and genetic diversity across a species complex of neotropical crater lake cichlid fishes

    PubMed Central

    Elmer, Kathryn R.; Kusche, Henrik; Lehtonen, Topi K.; Meyer, Axel

    2010-01-01

    The polychromatic and trophically polymorphic Midas cichlid fish species complex (Amphilophus cf. citrinellus) is an excellent model system for studying the mechanisms of speciation and patterns of phenotypic diversification in allopatry and in sympatry. Here, we first review research to date on the species complex and the geological history of its habitat. We analyse body shape variation from all currently described species in the complex, sampled from six crater lakes (maximally 1.2–23.9 kyr old) and both great lakes in Nicaragua. We find that Midas cichlid populations in each lake have their own characteristic body shape. In lakes with multiple sympatric species of Midas cichlid, each species has a distinct body shape. Across the species complex, most body shape change relates to body depth, head, snout and mouth shape and caudal peduncle length. There is independent parallel evolution of an elongate limnetic species in at least two crater lakes. Mitochondrial genetic diversity is higher in crater lakes with multiple species. Midas cichlid species richness increases with the size and age of the crater lakes, though no such relationship exists for the other syntopic fishes. We suggest that crater lake Midas cichlids follow the predicted pattern of an adaptive radiation, with early divergence of each crater lake colonization, followed by intralacustrine diversification and speciation by ecological adaptation and sexual selection. PMID:20439280

  7. Cognitive Abilities in Malawi Cichlids (Pseudotropheus sp.): Matching-to-Sample and Image/Mirror-Image Discriminations

    PubMed Central

    Gierszewski, Stefanie; Bleckmann, Horst; Schluessel, Vera

    2013-01-01

    The ability to recognize and distinguish between visual stimuli is fundamental for everyday survival of many species. While diverse aspects of cognition, including complex visual discrimination tasks were previously successfully assessed in fish, it remains unknown if fish can learn a matching-to-sample concept using geometrical shapes and discriminate between images and their mirror-image counterparts. For this purpose a total of nine Malawi cichlids (Pseudotropheus sp.) were trained in two matching-to-sample (MTS) and three two-choice discrimination tasks using geometrical, two-dimensional visual stimuli. Two out of the three discrimination experiments focused on the ability to discriminate between images and their mirror-images, the last was a general discrimination test. All fish showed quick associative learning but were unable to perform successfully in a simultaneous MTS procedure within a period of 40 sessions. Three out of eight fish learned to distinguish between an image and its mirror-image when reflected vertically; however none of the fish mastered the task when the stimulus was reflected horizontally. These results suggest a better discrimination ability of vertical compared to horizontal mirror-images, an observation that is widespread in literature on mirror-image discrimination in animals. All fish performed well in the general visual discrimination task, thereby supporting previous results obtained for this species. PMID:23437376

  8. Depth and substratum differentiations among coexisting herbivorous cichlids in Lake Tanganyika.

    PubMed

    Hata, Hiroki; Ochi, Haruki

    2016-11-01

    Cichlid fish in Lake Tanganyika represent a system of adaptive radiation in which eight ancestral lineages have diversified into hundreds of species through adaptation to various niches. However, Tanganyikan cichlids have been thought to be oversaturated, that is, the species number exceeds the number of niches and ecologically equivalent and competitively even species coexist. However, recent studies have shed light on niche segregation on a finer scale among apparently equivalent species. We observed depth and substratum preferences of 15 herbivorous cichlids from four ecomorphs (i.e. grazer, browser, scraper and scooper) on a rocky littoral slope for 14 years. Depth differentiation was detected among grazers that defended feeding territories and among browsers with feeding territories. Cichlid species having no feeding territory also showed specificity on depth and substratum, resulting in habitat segregation among species that belong to the same ecomorph. Phylogenetically close species did not occupy adjacent depths, nor the opposite depth zones. Our findings suggest that apparently equivalent species of the same ecomorph coexist parapatrically along depth on a few-metre scale, or coexist with different substratum preferences on the rocky shore, and this niche segregation may have been acquired by competition between encountering equivalent species through repetitive lake-level fluctuations.

  9. Depth and substratum differentiations among coexisting herbivorous cichlids in Lake Tanganyika

    PubMed Central

    Ochi, Haruki

    2016-01-01

    Cichlid fish in Lake Tanganyika represent a system of adaptive radiation in which eight ancestral lineages have diversified into hundreds of species through adaptation to various niches. However, Tanganyikan cichlids have been thought to be oversaturated, that is, the species number exceeds the number of niches and ecologically equivalent and competitively even species coexist. However, recent studies have shed light on niche segregation on a finer scale among apparently equivalent species. We observed depth and substratum preferences of 15 herbivorous cichlids from four ecomorphs (i.e. grazer, browser, scraper and scooper) on a rocky littoral slope for 14 years. Depth differentiation was detected among grazers that defended feeding territories and among browsers with feeding territories. Cichlid species having no feeding territory also showed specificity on depth and substratum, resulting in habitat segregation among species that belong to the same ecomorph. Phylogenetically close species did not occupy adjacent depths, nor the opposite depth zones. Our findings suggest that apparently equivalent species of the same ecomorph coexist parapatrically along depth on a few-metre scale, or coexist with different substratum preferences on the rocky shore, and this niche segregation may have been acquired by competition between encountering equivalent species through repetitive lake-level fluctuations. PMID:28018609

  10. Recent speciation between sympatric Tanganyikan cichlid colour morphs.

    PubMed

    Wagner, Catherine E; McCune, Amy R; Lovette, Irby J

    2012-07-01

    Lake Tanganyika, Africa's oldest lake, harbours an impressive diversity of cichlid fishes. Although diversification in its radiating groups is thought to have been initially rapid, cichlids from Lake Tanganyika show little evidence for ongoing speciation. In contrast, examples of recent divergence among sympatric colour morphs are well known in haplochromine cichlids from Lakes Malawi and Victoria. Here, we report genetic evidence for recent divergence between two sympatric Tanganyikan cichlid colour morphs. These Petrochromis morphs share mitochondrial haplotypes, yet microsatellite loci reveal that their sympatric populations form distinct genetic groups. Nuclear divergence between the two morphs is equivalent to that which arises geographically within one of the morphs over short distances and is substantially smaller than that among other sympatric species in this genus. These patterns suggest that these morphs diverged only recently, yet that barriers to gene flow exist which prevent extensive admixture despite their sympatric distribution. The morphs studied here provide an unusual example of active diversification in Lake Tanganyika's generally ancient cichlid fauna and enable comparisons of speciation processes between Lake Tanganyika and other African lakes.

  11. Rapid sympatric ecological differentiation of crater lake cichlid fishes within historic times

    PubMed Central

    2010-01-01

    Background After a volcano erupts, a lake may form in the cooled crater and become an isolated aquatic ecosystem. This makes fishes in crater lakes informative for understanding sympatric evolution and ecological diversification in barren environments. From a geological and limnological perspective, such research offers insight about the process of crater lake ecosystem establishment and speciation. In the present study we use genetic and coalescence approaches to infer the colonization history of Midas cichlid fishes (Amphilophus cf. citrinellus) that inhabit a very young crater lake in Nicaragua-the ca. 1800 year-old Lake Apoyeque. This lake holds two sympatric, endemic morphs of Midas cichlid: one with large, hypertrophied lips (~20% of the total population) and another with thin lips. Here we test the associated ecological, morphological and genetic diversification of these two morphs and their potential to represent incipient speciation. Results Gene coalescence analyses [11 microsatellite loci and mitochondrial DNA (mtDNA) sequences] suggest that crater lake Apoyeque was colonized in a single event from the large neighbouring great lake Managua only about 100 years ago. This founding in historic times is also reflected in the extremely low nuclear and mitochondrial genetic diversity in Apoyeque. We found that sympatric adult thin- and thick-lipped fishes occupy distinct ecological trophic niches. Diet, body shape, head width, pharyngeal jaw size and shape and stable isotope values all differ significantly between the two lip-morphs. The eco-morphological features pharyngeal jaw shape, body shape, stomach contents and stable isotopes (δ15N) all show a bimodal distribution of traits, which is compatible with the expectations of an initial stage of ecological speciation under disruptive selection. Genetic differentiation between the thin- and thick-lipped population is weak at mtDNA sequence (FST = 0.018) and absent at nuclear microsatellite loci (FST < 0

  12. The Integrated Genomic Architecture and Evolution of Dental Divergence in East African Cichlid Fishes (Haplochromis chilotes x H. nyererei).

    PubMed

    Hulsey, C Darrin; Machado-Schiaffino, Gonzalo; Keicher, Lara; Ellis-Soto, Diego; Henning, Frederico; Meyer, Axel

    2017-09-07

    The independent evolution of the two toothed jaws of cichlid fishes is thought to have promoted their unparalleled ecological divergence and species richness. However, dental divergence in cichlids could exhibit substantial genetic covariance and this could dictate how traits like tooth numbers evolve in different African Lakes and on their two jaws. To test this hypothesis, we used a hybrid mapping cross of two trophically divergent Lake Victoria species (Haplochromis chilotes × Haplochromis nyererei) to examine genomic regions associated with cichlid tooth diversity. Surprisingly, a similar genomic region was found to be associated with oral jaw tooth numbers in cichlids from both Lake Malawi and Lake Victoria. Likewise, this same genomic location was associated with variation in pharyngeal jaw tooth numbers. Similar relationships between tooth numbers on the two jaws in both our Victoria hybrid population and across the phylogenetic diversity of Malawi cichlids additionally suggests that tooth numbers on the two jaws of haplochromine cichlids might generally coevolve owing to shared genetic underpinnings. Integrated, rather than independent, genomic architectures could be key to the incomparable evolutionary divergence and convergence in cichlid tooth numbers. Copyright © 2017 Hulsey et al.

  13. Pleistocene desiccation in East Africa bottlenecked but did not extirpate the adaptive radiation of Lake Victoria haplochromine cichlid fishes.

    PubMed

    Elmer, Kathryn R; Reggio, Chiara; Wirth, Thierry; Verheyen, Erik; Salzburger, Walter; Meyer, Axel

    2009-08-11

    The Great Lakes region of East Africa, including Lake Victoria, is the center of diversity of the mega-diverse cichlid fishes (Perciformes: Teleostei). Paleolimnological evidence indicates dramatic desiccation of this lake ca. 18,000-15,000 years ago. Consequently, the hundreds of extant endemic haplochromine species in the lake must have either evolved since then or refugia must have existed, within that lake basin or elsewhere, from which Lake Victoria was recolonized. We studied the population history of the Lake Victoria region superflock (LVRS) of haplochromine cichlids based on nuclear genetic analysis (12 microsatellite loci from 400 haplochomines) of populations from Lake Kivu, Lake Victoria, and the connected and surrounding rivers and lakes. Population genetic analyses confirmed that Lake Kivu haplochromines colonized Lake Victoria. Coalescent analyses show a 30- to 50-fold decline in the haplochromine populations of Lake Victoria, Lake Kivu, and the region ca. 18,000-15,000 years ago. We suggest that this coincides with drastic climatic and geological changes in the late Pleistocene. The most recent common ancestor of the Lake Victoria region haplochromines was estimated to have existed about 4.5 million years ago, which corresponds to the first radiation of cichlids in Lake Tanganyika and the origin of the tribe Haplochrominii. This relatively old evolutionary origin may explain the high levels of polymorphism still found in modern haplochromines. This degree of polymorphism might have acted as a "genetic reservoir" that permitted the explosive radiation of hundreds of haplochromines and their array of contemporary adaptive morphologies.

  14. Replicated evolution of trophic specializations in an endemic cichlid fish lineage from Lake Tanganyika

    PubMed Central

    Rüber, Lukas; Verheyen, Erik; Meyer, Axel

    1999-01-01

    The current phylogenetic hypothesis for the endemic Lake Tanganyika cichlid fishes of the tribe Eretmodini is based solely on morphology and suggests that more complex trophic morphologies derived only once from a less specialized ancestral condition. A molecular phylogeny of eretmodine cichlids based on partial mitochondrial DNA cytochrome b and control-region sequences was used to reconstruct the evolutionary sequence of trophic adaptations and to test alternative models of morphological divergence. The six mitochondrial lineages found disagree with the current taxonomy and the morphology-based phylogeny. Mitochondrial lineages with similar trophic morphologies are not grouped monophyletically but are typically more closely related to lineages with different trophic phenotypes currently assigned to other genera. Our results indicate multiple independent origins of similar trophic specializations in these cichlids. A pattern of repeated divergent morphological evolution becomes apparent when the phylogeography of the mitochondrial haplotypes is analyzed in the context of the geological and paleoclimatological history of Lake Tanganyika. In more than one instance within Lake Tanganyika, similar morphological divergence of dentitional traits occurred in sympatric species pairs. Possibly, resource-based divergent selective regimes led to resource partitioning and brought about similar trophic morphologies independently and repeatedly. PMID:10468591

  15. Adult plasticity in African cichlids: Rapid changes in opsin expression in response to environmental light differences.

    PubMed

    Nandamuri, Sri Pratima; Yourick, Miranda R; Carleton, Karen L

    2017-09-19

    Phenotypic plasticity allows organisms to adapt quickly to local environmental conditions and could facilitate adaptive radiations. Cichlids have recently undergone an adaptive radiation in Lake Malawi where they inhabit diverse light environments and tune their visual sensitivity through differences in cone opsin expression. While cichlid opsin expression is known to be plastic over development, whether adults remain plastic is unknown. Adult plasticity in visual tuning could play a role in cichlid radiations by enabling survival in changing environments and facilitating invasion into novel environments. Here we examine the existence of and temporal changes in adult visual plasticity of two closely related species. In complementary experiments, wild adult Metriaclima mbenji from Lake Malawi were moved to the lab under UV-deficient fluorescent lighting; while lab raised M. benetos were placed under UV-rich lighting designed to mimic light conditions in the wild. Surprisingly, adult cichlids in both experiments showed significant changes in the expression of the UV-sensitive single cone opsin, SWS1, in only 3 days. Modeling quantum catches in the light environments revealed a possible link between the light available to the SWS1 visual pigment and SWS1 expression. We conclude that adult cichlids can undergo rapid and significant changes in opsin expression in response to environmental light shifts that are relevant to their habitat and evolutionary history in Lake Malawi. This could have contributed to the rapid divergence characteristic of these fantastic fishes. © 2017 John Wiley & Sons Ltd.

  16. Do constructional constraints influence cichlid craniofacial diversification?

    PubMed Central

    Hulsey, C.D; Mims, M.C; Streelman, J.T

    2007-01-01

    Constraints on form should determine how organisms diversify. Owing to competition for the limited space within the body, investment in adjacent structures may frequently represent an evolutionary compromise. For example, evolutionary trade-offs between eye size and jaw muscles in cichlid fish of the African great lakes are thought to represent a constructional constraint that influenced the diversification of these assemblages. To test the evolutionary independence of these structures in Lake Malawi cichlid fish, we measured the mass of the three major adductor mandibulae (AM) muscles and determined the eye volume in 41 species. Using both traditional and novel methodologies to control for resolved and unresolved phylogenetic relationships, we tested the evolutionary independence of these four structures. We found that evolutionary change in the AM muscles was positively correlated, suggesting that competition for space in the head has not influenced diversification among these jaw muscles. Furthermore, there was no negative relationship between change in total AM muscle mass and eye volume, indicating that there has been little effect of the evolution of eye size on AM evolution in Lake Malawi cichlids. The comparative approach used here should provide a robust method to test whether constructional constraints frequently limit phenotypic change in adaptive radiations. PMID:17519189

  17. Cholera outbreak in districts around Lake Chilwa, Malawi: lessons learned.

    PubMed

    Khonje, Amin; Metcalf, Carol Ann; Diggle, Emma; Mlozowa, Dudley; Jere, Chandiwira; Akesson, Ann; Corbet, Tom; Chimanga, Zachariah

    2012-06-01

    Cholera is endemic in Malawi with seasonal outbreaks during the wet season. People living around Lake Chilwa rely on the lake for their water supply. From May 2009 to May 2010, a cholera outbreak occurred in fishing communities around Lake Chilwa. This paper describes the outbreak response and lessons learned for prevention and management of future outbreaks. Starting in January 2010, Médecins Sans Frontières (MSF) helped District Health Management Teams (DHMTs) to distribute educational materials, water disinfectant and hygiene supplies, and oral rehydration solution (ORS) in fishing communities. MSF also supported case management by mentoring health workers and providing equipment and supplies. A total of 1,171 cholera cases and 21 deaths were reported in the districts around the lake, with cases also being reported on the Mozambican side of the lake. The attack rate was highest among people living on or around the lake, particularly among fishermen. Samples of lake water had high turbidity conducive to the propagation of Vibrio cholerae. A number of practical measures could be taken to prevent future outbreaks and to manage outbreaks more effectively. These measures should address surveillance, environmental management, outbreak preparedness, and case management.

  18. Back to Tanganyika: a case of recent trans-species-flock dispersal in East African haplochromine cichlid fishes.

    PubMed

    Meyer, Britta S; Indermaur, Adrian; Ehrensperger, Xenia; Egger, Bernd; Banyankimbona, Gaspard; Snoeks, Jos; Salzburger, Walter

    2015-03-01

    The species flocks of cichlid fishes in the East African Great Lakes are the largest vertebrate adaptive radiations in the world and illustrious textbook examples of convergent evolution between independent species assemblages. Although recent studies suggest some degrees of genetic exchange between riverine taxa and the lake faunas, not a single cichlid species is known from Lakes Tanganyika, Malawi and Victoria that is derived from the radiation associated with another of these lakes. Here, we report the discovery of a haplochromine cichlid species in Lake Tanganyika, which belongs genetically to the species flock of haplochromines of the Lake Victoria region. The new species colonized Lake Tanganyika only recently, suggesting that faunal exchange across watersheds and, hence, between isolated ichthyofaunas, is more common than previously thought.

  19. Symmetry perception in bamboo sharks (Chiloscyllium griseum) and Malawi cichlids (Pseudotropheus sp.).

    PubMed

    Schluessel, V; Beil, O; Weber, T; Bleckmann, H

    2014-09-01

    Several species have been shown to perceive symmetry as a measure of superior genetic quality, useful for assessing potential mates or mediating other visual activities such as the selection of food sources. The current study assessed whether Pseudotropheus sp. and Chiloscyllium griseum, two fish species from distantly related groups, possess symmetry perception. In alternative two choice experiments, individuals were tested for spontaneous preferences and trained to discriminate between abstract symmetrical and asymmetrical stimulus pairs. Pair discriminations were followed by extensive categorization experiments. Transfer tests elucidated whether bilaterally symmetrical and rotationally symmetrical stimuli could be distinguished. Sharks were also tested for the degree of dissimilarity between two symbols that could still be detected. While sharks showed both a spontaneous preference for symmetry as well as remarkable discrimination abilities by succeeding in all of the presented tasks, cichlids showed no spontaneous preference, had difficulties in discriminating between symbols and performed poorly in the categorization experiments. Sharks distinguished between bilaterally and rotationally symmetrical stimuli and easily differentiated between a four-armed cross (all arms 90° apart) and a cross where one of the arms was only 45° spaced from the one next to it. Performance did not decline when the separation was extended to 70°, but was significantly reduced at an 80° separation. Results indicate that the ability for symmetry perception varies across fish species and individuals, whereby some can detect even subtle differences in this respect.

  20. Nuclear markers reveal that inter-lake cichlids' similar morphologies do not reflect similar genealogy.

    PubMed

    Kassam, Daud; Seki, Shingo; Horic, Michio; Yamaoka, Kosaku

    2006-08-01

    The apparent inter-lake morphological similarity among East African Great Lakes' cichlid species/genera has left evolutionary biologists asking whether such similarity is due to sharing of common ancestor or mere convergent evolution. In order to answer such question, we first used Geometric Morphometrics, GM, to quantify morphological similarity and then subsequently used Amplified Fragment Length Polymorphism, AFLP, to determine if similar morphologies imply shared ancestry or convergent evolution. GM revealed that not all presumed morphological similar pairs were indeed similar, and the dendrogram generated from AFLP data indicated distinct clusters corresponding to each lake and not inter-lake morphological similar pairs. Such results imply that the morphological similarity is due to convergent evolution and not shared ancestry. The congruency of GM and AFLP generated dendrograms imply that GM is capable of picking up phylogenetic signal, and thus GM can be potential tool in phylogenetic systematics.

  1. Hidden biodiversity in an ancient lake: phylogenetic congruence between Lake Tanganyika tropheine cichlids and their monogenean flatworm parasites

    PubMed Central

    Vanhove, Maarten P. M.; Pariselle, Antoine; Van Steenberge, Maarten; Raeymaekers, Joost A. M.; Hablützel, Pascal I.; Gillardin, Céline; Hellemans, Bart; Breman, Floris C.; Koblmüller, Stephan; Sturmbauer, Christian; Snoeks, Jos; Volckaert, Filip A. M.; Huyse, Tine

    2015-01-01

    The stunning diversity of cichlid fishes has greatly enhanced our understanding of speciation and radiation. Little is known about the evolution of cichlid parasites. Parasites are abundant components of biodiversity, whose diversity typically exceeds that of their hosts. In the first comprehensive phylogenetic parasitological analysis of a vertebrate radiation, we study monogenean parasites infecting tropheine cichlids from Lake Tanganyika. Monogeneans are flatworms usually infecting the body surface and gills of fishes. In contrast to many other parasites, they depend only on a single host species to complete their lifecycle. Our spatially comprehensive combined nuclear-mitochondrial DNA dataset of the parasites covering almost all tropheine host species (N = 18), reveals species-rich parasite assemblages and shows consistent host-specificity. Statistical comparisons of host and parasite phylogenies based on distance and topology-based tests demonstrate significant congruence and suggest that host-switching is rare. Molecular rate evaluation indicates that species of Cichlidogyrus probably diverged synchronically with the initial radiation of the tropheines. They further diversified through within-host speciation into an overlooked species radiation. The unique life history and specialisation of certain parasite groups has profound evolutionary consequences. Hence, evolutionary parasitology adds a new dimension to the study of biodiversity hotspots like Lake Tanganyika. PMID:26335652

  2. Hidden biodiversity in an ancient lake: phylogenetic congruence between Lake Tanganyika tropheine cichlids and their monogenean flatworm parasites.

    PubMed

    Vanhove, Maarten P M; Pariselle, Antoine; Van Steenberge, Maarten; Raeymaekers, Joost A M; Hablützel, Pascal I; Gillardin, Céline; Hellemans, Bart; Breman, Floris C; Koblmüller, Stephan; Sturmbauer, Christian; Snoeks, Jos; Volckaert, Filip A M; Huyse, Tine

    2015-09-03

    The stunning diversity of cichlid fishes has greatly enhanced our understanding of speciation and radiation. Little is known about the evolution of cichlid parasites. Parasites are abundant components of biodiversity, whose diversity typically exceeds that of their hosts. In the first comprehensive phylogenetic parasitological analysis of a vertebrate radiation, we study monogenean parasites infecting tropheine cichlids from Lake Tanganyika. Monogeneans are flatworms usually infecting the body surface and gills of fishes. In contrast to many other parasites, they depend only on a single host species to complete their lifecycle. Our spatially comprehensive combined nuclear-mitochondrial DNA dataset of the parasites covering almost all tropheine host species (N = 18), reveals species-rich parasite assemblages and shows consistent host-specificity. Statistical comparisons of host and parasite phylogenies based on distance and topology-based tests demonstrate significant congruence and suggest that host-switching is rare. Molecular rate evaluation indicates that species of Cichlidogyrus probably diverged synchronically with the initial radiation of the tropheines. They further diversified through within-host speciation into an overlooked species radiation. The unique life history and specialisation of certain parasite groups has profound evolutionary consequences. Hence, evolutionary parasitology adds a new dimension to the study of biodiversity hotspots like Lake Tanganyika.

  3. Phenotypic integration of brain size and head morphology in Lake Tanganyika Cichlids.

    PubMed

    Tsuboi, Masahito; Gonzalez-Voyer, Alejandro; Kolm, Niclas

    2014-03-04

    Phenotypic integration among different anatomical parts of the head is a common phenomenon across vertebrates. Interestingly, despite centuries of research into the factors that contribute to the existing variation in brain size among vertebrates, little is known about the role of phenotypic integration in brain size diversification. Here we used geometric morphometrics on the morphologically diverse Tanganyikan cichlids to investigate phenotypic integration across key morphological aspects of the head. Then, while taking the effect of shared ancestry into account, we tested if head shape was associated with brain size while controlling for the potentially confounding effect of feeding strategy. The shapes of the anterior and posterior parts of the head were strongly correlated, indicating that the head represents an integrated morphological unit in Lake Tanganyika cichlids. After controlling for phylogenetic non-independence, we also found evolutionary associations between head shape, brain size and feeding ecology. Geometric morphometrics and phylogenetic comparative analyses revealed that the anterior and posterior parts of the head are integrated, and that head morphology is associated with brain size and feeding ecology in Tanganyikan cichlid fishes. In light of previous results on mammals, our results suggest that the influence of phenotypic integration on brain diversification is a general process.

  4. Phenotypic integration of brain size and head morphology in Lake Tanganyika Cichlids

    PubMed Central

    2014-01-01

    Background Phenotypic integration among different anatomical parts of the head is a common phenomenon across vertebrates. Interestingly, despite centuries of research into the factors that contribute to the existing variation in brain size among vertebrates, little is known about the role of phenotypic integration in brain size diversification. Here we used geometric morphometrics on the morphologically diverse Tanganyikan cichlids to investigate phenotypic integration across key morphological aspects of the head. Then, while taking the effect of shared ancestry into account, we tested if head shape was associated with brain size while controlling for the potentially confounding effect of feeding strategy. Results The shapes of the anterior and posterior parts of the head were strongly correlated, indicating that the head represents an integrated morphological unit in Lake Tanganyika cichlids. After controlling for phylogenetic non-independence, we also found evolutionary associations between head shape, brain size and feeding ecology. Conclusions Geometric morphometrics and phylogenetic comparative analyses revealed that the anterior and posterior parts of the head are integrated, and that head morphology is associated with brain size and feeding ecology in Tanganyikan cichlid fishes. In light of previous results on mammals, our results suggest that the influence of phenotypic integration on brain diversification is a general process. PMID:24593160

  5. Adaptive divergence between lake and stream populations of an East African cichlid fish.

    PubMed

    Theis, Anya; Ronco, Fabrizia; Indermaur, Adrian; Salzburger, Walter; Egger, Bernd

    2014-11-01

    Divergent natural selection acting in different habitats may build up barriers to gene flow and initiate speciation. This speciation continuum can range from weak or no divergence to strong genetic differentiation between populations. Here, we focus on the early phases of adaptive divergence in the East African cichlid fish Astatotilapia burtoni, which occurs in both Lake Tanganyika (LT) and inflowing rivers. We first assessed the population structure and morphological differences in A. burtoni from southern LT. We then focused on four lake-stream systems and quantified body shape, ecologically relevant traits (gill raker and lower pharyngeal jaw) as well as stomach contents. Our study revealed the presence of several divergent lake-stream populations that rest at different stages of the speciation continuum, but show the same morphological and ecological trajectories along the lake-stream gradient. Lake fish have higher bodies, a more superior mouth position, longer gill rakers and more slender pharyngeal jaws, and they show a plant/algae and zooplankton-biased diet, whereas stream fish feed more on snails, insects and plant seeds. A test for reproductive isolation between closely related lake and stream populations did not detect population-assortative mating. Analyses of F1 offspring reared under common garden conditions indicate that the detected differences in body shape and gill raker length do not constitute pure plastic responses to different environmental conditions, but also have a genetic basis. Taken together, the A. burtoni lake-stream system constitutes a new model to study the factors that enhance and constrain progress towards speciation in cichlid fishes. © 2014 John Wiley & Sons Ltd.

  6. Phylogeography, colonization and population history of the Midas cichlid species complex (Amphilophus spp.) in the Nicaraguan crater lakes

    PubMed Central

    2010-01-01

    Background Elucidation of the mechanisms driving speciation requires detailed knowledge about the phylogenetic relationships and phylogeography of the incipient species within their entire ranges as well as their colonization history. The Midas cichlid species complex Amphilophus spp. has been proven to be a powerful model system for the study of ecological specialization, sexual selection and the mechanisms of sympatric speciation. Here we present a comprehensive and integrative phylogeographic analysis of the complete Midas Cichlid species complex in Nicaragua (> 2000 individuals) covering the entire distributional range, using two types of molecular markers (the mitochondrial DNA control region and 15 microsatellites). We investigated the majority of known lake populations of this species complex and reconstructed their colonization history in order to distinguish between alternative speciation scenarios. Results We found that the large lakes contain older and more diverse Midas Cichlid populations, while all crater lakes hold younger and genetically less variable species assemblages. The large lakes appear to have repeatedly acted as source populations for all crater lakes, and our data indicate that faunal exchange among crater lakes is extremely unlikely. Despite their very recent (often only a few thousand years old) and common origin from the two large Nicaraguan lakes, all crater lake Midas Cichlid radiations underwent independent, but parallel, evolution, and comprise distinct genetic units. Indeed several of these crater lakes contain multiple genetically distinct incipient species that most likely arose through sympatric speciation. Several crater lake radiations can be traced back to a single ancestral line, but some appear to have more than one founding lineage. The timing of the colonization(s) of each crater lake differs, although most of them occurred more (probably much more) recently than 20,000 years ago. Conclusion The genetic differentiation

  7. Malawi.

    PubMed

    1989-02-01

    Malawi is located in southeastern Africa with Mozambique, Tanzania and Zambia as its neighboring countries. The country's climate is subtropical, conducive to the tobacco, tea, coffee and sugar grown there. The population of Malawi is predominantly rural with 90% of the population engaging in subsistence farming. Most of the people are of Bantu origin. There is no visa requirement for those travelling in Malawi, but there are conditions to be aware of for the visitor to Malawi. The government bans the wearing of slacks or shorts by women and hair below the nape of the neck for men. Malaria is endemic and tsetse flies and the risk of encephalitis are present. The water, however, is potable and telecommunications within Malawi are good. The political structure of the country is headed by an elected present and a presidentially appointed cabinet. There are 118 seats in the country's unicameral National Assembly. Although Malawi has traditionally been self-sufficient, it suffered from the world commodity price recession in the 1980s. However, Malawi has continued to grow economically at a slower rate. The United States and Malawi enjoy good diplomatic relations and have an open exchange program. As well, relations with neighboring countries, particularly Mozambique, have improved greatly.

  8. Malawi.

    PubMed

    1985-09-01

    Until the 20th century, migrations and tribal conflicts prevented the formation of a cohesive Malawian society. Malawi is mainly comprised of a rural populace, and primary school education has only become prevalent since Malawi became independent in 1964. Shortly thereafter, Malawi adopted a new constitution and became a republic run by a president. The Malawian government is a substantially modified version of the British system and the members of the presidentially appointed cabinet are either drawn from or become members of Parliament. There are 2 judicial systems in Malawi the magisterial court headed by a 3-member Supreme Court and traditional courts created in 1964 which are based predominantly on the local court system maintained by the British prior to independence. There is only 1 authorized political party. Malawi has grown economically and has relied on expanding agricultural export as the primary vehicle for this growth. Basically, Malawi's economic outlook is favorable despite some problems which have caused a setback in the return of robust growth so apparent in the 1970s. Malawi has been basically pro-Western and has little contact with communist nations. While its political ideology is different from that of its bordering neighbors, Malawi has pursued normal relations with them and with other reighbors in its region. Relations with the US are quite good and their views on the need for economic and political stability in southern Africa are in general agreement. The 2 nations exchange dialogue and visits periodically.

  9. The genomic substrate for adaptive radiation in African cichlid fish

    PubMed Central

    Malinsky, Milan; Keller, Irene; Fan, Shaohua; Simakov, Oleg; Ng, Alvin Y.; Lim, Zhi Wei; Bezault, Etienne; Turner-Maier, Jason; Johnson, Jeremy; Alcazar, Rosa; Noh, Hyun Ji; Russell, Pamela; Aken, Bronwen; Alföldi, Jessica; Amemiya, Chris; Azzouzi, Naoual; Baroiller, Jean-François; Barloy-Hubler, Frederique; Berlin, Aaron; Bloomquist, Ryan; Carleton, Karen L.; Conte, Matthew A.; D'Cotta, Helena; Eshel, Orly; Gaffney, Leslie; Galibert, Francis; Gante, Hugo F.; Gnerre, Sante; Greuter, Lucie; Guyon, Richard; Haddad, Natalie S.; Haerty, Wilfried; Harris, Rayna M.; Hofmann, Hans A.; Hourlier, Thibaut; Hulata, Gideon; Jaffe, David B.; Lara, Marcia; Lee, Alison P.; MacCallum, Iain; Mwaiko, Salome; Nikaido, Masato; Nishihara, Hidenori; Ozouf-Costaz, Catherine; Penman, David J.; Przybylski, Dariusz; Rakotomanga, Michaelle; Renn, Suzy C. P.; Ribeiro, Filipe J.; Ron, Micha; Salzburger, Walter; Sanchez-Pulido, Luis; Santos, M. Emilia; Searle, Steve; Sharpe, Ted; Swofford, Ross; Tan, Frederick J.; Williams, Louise; Young, Sarah; Yin, Shuangye; Okada, Norihiro; Kocher, Thomas D.; Miska, Eric A.; Lander, Eric S.; Venkatesh, Byrappa; Fernald, Russell D.; Meyer, Axel; Ponting, Chris P.; Streelman, J. Todd; Lindblad-Toh, Kerstin; Seehausen, Ole; Di Palma, Federica

    2015-01-01

    Cichlid fishes are famous for large, diverse and replicated adaptive radiations in the Great Lakes of East Africa. To understand the molecular mechanisms underlying cichlid phenotypic diversity, we sequenced the genomes and transcriptomes of five lineages of African cichlids: the Nile tilapia (Oreochromis niloticus), an ancestral lineage with low diversity; and four members of the East African lineage: Neolamprologus brichardi/pulcher (older radiation, Lake Tanganyika), Metriaclima zebra (recent radiation, Lake Malawi), Pundamilia nyererei (very recent radiation, Lake Victoria), and Astatotilapia burtoni (riverine species around Lake Tanganyika). We found an excess of gene duplications in the East African lineage compared to tilapia and other teleosts, an abundance of non-coding element divergence, accelerated coding sequence evolution, expression divergence associated with transposable element insertions, and regulation by novel microRNAs. In addition, we analysed sequence data from sixty individuals representing six closely related species from Lake Victoria, and show genome-wide diversifying selection on coding and regulatory variants, some of which were recruited from ancient polymorphisms. We conclude that a number of molecular mechanisms shaped East African cichlid genomes, and that amassing of standing variation during periods of relaxed purifying selection may have been important in facilitating subsequent evolutionary diversification. PMID:25186727

  10. The genomic substrate for adaptive radiation in African cichlid fish.

    PubMed

    Brawand, David; Wagner, Catherine E; Li, Yang I; Malinsky, Milan; Keller, Irene; Fan, Shaohua; Simakov, Oleg; Ng, Alvin Y; Lim, Zhi Wei; Bezault, Etienne; Turner-Maier, Jason; Johnson, Jeremy; Alcazar, Rosa; Noh, Hyun Ji; Russell, Pamela; Aken, Bronwen; Alföldi, Jessica; Amemiya, Chris; Azzouzi, Naoual; Baroiller, Jean-François; Barloy-Hubler, Frederique; Berlin, Aaron; Bloomquist, Ryan; Carleton, Karen L; Conte, Matthew A; D'Cotta, Helena; Eshel, Orly; Gaffney, Leslie; Galibert, Francis; Gante, Hugo F; Gnerre, Sante; Greuter, Lucie; Guyon, Richard; Haddad, Natalie S; Haerty, Wilfried; Harris, Rayna M; Hofmann, Hans A; Hourlier, Thibaut; Hulata, Gideon; Jaffe, David B; Lara, Marcia; Lee, Alison P; MacCallum, Iain; Mwaiko, Salome; Nikaido, Masato; Nishihara, Hidenori; Ozouf-Costaz, Catherine; Penman, David J; Przybylski, Dariusz; Rakotomanga, Michaelle; Renn, Suzy C P; Ribeiro, Filipe J; Ron, Micha; Salzburger, Walter; Sanchez-Pulido, Luis; Santos, M Emilia; Searle, Steve; Sharpe, Ted; Swofford, Ross; Tan, Frederick J; Williams, Louise; Young, Sarah; Yin, Shuangye; Okada, Norihiro; Kocher, Thomas D; Miska, Eric A; Lander, Eric S; Venkatesh, Byrappa; Fernald, Russell D; Meyer, Axel; Ponting, Chris P; Streelman, J Todd; Lindblad-Toh, Kerstin; Seehausen, Ole; Di Palma, Federica

    2014-09-18

    Cichlid fishes are famous for large, diverse and replicated adaptive radiations in the Great Lakes of East Africa. To understand the molecular mechanisms underlying cichlid phenotypic diversity, we sequenced the genomes and transcriptomes of five lineages of African cichlids: the Nile tilapia (Oreochromis niloticus), an ancestral lineage with low diversity; and four members of the East African lineage: Neolamprologus brichardi/pulcher (older radiation, Lake Tanganyika), Metriaclima zebra (recent radiation, Lake Malawi), Pundamilia nyererei (very recent radiation, Lake Victoria), and Astatotilapia burtoni (riverine species around Lake Tanganyika). We found an excess of gene duplications in the East African lineage compared to tilapia and other teleosts, an abundance of non-coding element divergence, accelerated coding sequence evolution, expression divergence associated with transposable element insertions, and regulation by novel microRNAs. In addition, we analysed sequence data from sixty individuals representing six closely related species from Lake Victoria, and show genome-wide diversifying selection on coding and regulatory variants, some of which were recruited from ancient polymorphisms. We conclude that a number of molecular mechanisms shaped East African cichlid genomes, and that amassing of standing variation during periods of relaxed purifying selection may have been important in facilitating subsequent evolutionary diversification.

  11. Genetic Structure of Pelagic and Littoral Cichlid Fishes from Lake Victoria

    PubMed Central

    Takeda, Miyuki; Kusumi, Junko; Mizoiri, Shinji; Aibara, Mitsuto; Mzighani, Semvua Isa; Sato, Tetsu; Terai, Yohey; Okada, Norihiro; Tachida, Hidenori

    2013-01-01

    The approximately 700 species of cichlids found in Lake Victoria in East Africa are thought to have evolved over a short period of time, and they represent one of the largest known examples of adaptive radiation. To understand the processes that are driving this spectacular radiation, we must determine the present genetic structure of these species and elucidate how this structure relates to the ecological conditions that caused their adaptation. We analyzed the genetic structure of two pelagic and seven littoral species sampled from the southeast area of Lake Victoria using sequences from the mtDNA control region and 12 microsatellite loci as markers. Using a Bayesian model-based clustering method to analyze the microsatellite data, we separated these nine species into four groups: one group composed of pelagic species and another three groups composed mainly of rocky-shore species. Furthermore, we found significant levels of genetic variation between species within each group at both marker loci using analysis of molecular variance (AMOVA), although the nine species often shared mtDNA haplotypes. We also found significant levels of genetic variation between populations within species. These results suggest that initial groupings, some of which appear to have been related to habitat differences, as well as divergence between species within groups took place among the cichlid species of Lake Victoria. PMID:24040175

  12. Genetic structure of pelagic and littoral cichlid fishes from Lake Victoria.

    PubMed

    Takeda, Miyuki; Kusumi, Junko; Mizoiri, Shinji; Aibara, Mitsuto; Mzighani, Semvua Isa; Sato, Tetsu; Terai, Yohey; Okada, Norihiro; Tachida, Hidenori

    2013-01-01

    The approximately 700 species of cichlids found in Lake Victoria in East Africa are thought to have evolved over a short period of time, and they represent one of the largest known examples of adaptive radiation. To understand the processes that are driving this spectacular radiation, we must determine the present genetic structure of these species and elucidate how this structure relates to the ecological conditions that caused their adaptation. We analyzed the genetic structure of two pelagic and seven littoral species sampled from the southeast area of Lake Victoria using sequences from the mtDNA control region and 12 microsatellite loci as markers. Using a Bayesian model-based clustering method to analyze the microsatellite data, we separated these nine species into four groups: one group composed of pelagic species and another three groups composed mainly of rocky-shore species. Furthermore, we found significant levels of genetic variation between species within each group at both marker loci using analysis of molecular variance (AMOVA), although the nine species often shared mtDNA haplotypes. We also found significant levels of genetic variation between populations within species. These results suggest that initial groupings, some of which appear to have been related to habitat differences, as well as divergence between species within groups took place among the cichlid species of Lake Victoria.

  13. Pleistocene desiccation in East Africa bottlenecked but did not extirpate the adaptive radiation of Lake Victoria haplochromine cichlid fishes

    PubMed Central

    Elmer, Kathryn R.; Reggio, Chiara; Wirth, Thierry; Verheyen, Erik; Salzburger, Walter; Meyer, Axel

    2009-01-01

    The Great Lakes region of East Africa, including Lake Victoria, is the center of diversity of the mega-diverse cichlid fishes (Perciformes: Teleostei). Paleolimnological evidence indicates dramatic desiccation of this lake ca. 18,000–15,000 years ago. Consequently, the hundreds of extant endemic haplochromine species in the lake must have either evolved since then or refugia must have existed, within that lake basin or elsewhere, from which Lake Victoria was recolonized. We studied the population history of the Lake Victoria region superflock (LVRS) of haplochromine cichlids based on nuclear genetic analysis (12 microsatellite loci from 400 haplochomines) of populations from Lake Kivu, Lake Victoria, and the connected and surrounding rivers and lakes. Population genetic analyses confirmed that Lake Kivu haplochromines colonized Lake Victoria. Coalescent analyses show a 30- to 50-fold decline in the haplochromine populations of Lake Victoria, Lake Kivu, and the region ca. 18,000–15,000 years ago. We suggest that this coincides with drastic climatic and geological changes in the late Pleistocene. The most recent common ancestor of the Lake Victoria region haplochromines was estimated to have existed about 4.5 million years ago, which corresponds to the first radiation of cichlids in Lake Tanganyika and the origin of the tribe Haplochrominii. This relatively old evolutionary origin may explain the high levels of polymorphism still found in modern haplochromines. This degree of polymorphism might have acted as a “genetic reservoir” that permitted the explosive radiation of hundreds of haplochromines and their array of contemporary adaptive morphologies. PMID:19651614

  14. The Impact of the Geologic History and Paleoclimate on the Diversification of East African Cichlids

    PubMed Central

    Danley, Patrick D.; Husemann, Martin; Ding, Baoqing; DiPietro, Lyndsay M.; Beverly, Emily J.; Peppe, Daniel J.

    2012-01-01

    The cichlid fishes of the East African Great Lakes are the largest extant vertebrate radiation identified to date. These lakes and their surrounding waters support over 2,000 species of cichlid fish, many of which are descended from a single common ancestor within the past 10 Ma. The extraordinary East African cichlid diversity is intricately linked to the highly variable geologic and paleoclimatic history of this region. Greater than 10 Ma, the western arm of the East African rift system began to separate, thereby creating a series of rift basins that would come to contain several water bodies, including the extremely deep Lakes Tanganyika and Malawi. Uplifting associated with this rifting backponded many rivers and created the extremely large, but shallow Lake Victoria. Since their creation, the size, shape, and existence of these lakes have changed dramatically which has, in turn, significantly influenced the evolutionary history of the lakes' cichlids. This paper reviews the geologic history and paleoclimate of the East African Great Lakes and the impact of these forces on the region's endemic cichlid flocks. PMID:22888465

  15. The impact of the geologic history and paleoclimate on the diversification of East african cichlids.

    PubMed

    Danley, Patrick D; Husemann, Martin; Ding, Baoqing; Dipietro, Lyndsay M; Beverly, Emily J; Peppe, Daniel J

    2012-01-01

    The cichlid fishes of the East African Great Lakes are the largest extant vertebrate radiation identified to date. These lakes and their surrounding waters support over 2,000 species of cichlid fish, many of which are descended from a single common ancestor within the past 10 Ma. The extraordinary East African cichlid diversity is intricately linked to the highly variable geologic and paleoclimatic history of this region. Greater than 10 Ma, the western arm of the East African rift system began to separate, thereby creating a series of rift basins that would come to contain several water bodies, including the extremely deep Lakes Tanganyika and Malawi. Uplifting associated with this rifting backponded many rivers and created the extremely large, but shallow Lake Victoria. Since their creation, the size, shape, and existence of these lakes have changed dramatically which has, in turn, significantly influenced the evolutionary history of the lakes' cichlids. This paper reviews the geologic history and paleoclimate of the East African Great Lakes and the impact of these forces on the region's endemic cichlid flocks.

  16. Ancient divergence in bathypelagic lake tanganyika deepwater cichlids: mitochondrial phylogeny of the tribe bathybatini.

    PubMed

    Koblmüller, Stephan; Duftner, Nina; Katongo, Cyprian; Phiri, Harris; Sturmbauer, Christian

    2005-03-01

    The cichlid species flock of Lake Tanganyika represents a polyphyletic assemblage of eight ancestral lineages, which colonized the emerging lake independently. Our study is focused on one of these lineages, the Bathybatini, a tribe of specialized piscivorous cichlids of the deep pelagic zone. By analyzing three mtDNA gene segments of all eight species of the tribe and two species of the closely related Trematocarini, we propose on the basis of a linearized tree analysis that the Bathybatini comprise two distinct lineages, the genera Hemibates and Bathybates, that seeded the primary lacustrine Tanganyika radiation independently. The genus Hemibates is likely to represent a distinct lineage that emerged simultaneously with the tribe Trematocarini and the genus Bathybates and should be therefore treated as a distinct tribe. Within the genus Bathybates, B. minor clearly represents the most ancestral split and is likely to have diverged from the remaining species in the course of the "primary lacustrine Tanganyika radiation" during which also the radiations of the Lamprologini and the H-lineage took place. The remaining "large" Bathybates species also diversified almost simultaneously and in step with the diversification of other Tanganyikan lineages-the Limnochromini and Cyprichromini-with B. graueri occupying the most ancestral branch, suggesting that these were induced by the same environmental changes. The lack of geographic color morphs suggests that competition and resource partitioning, rather than allopatric speciation, promoted speciation within the genus Bathybates.

  17. Crater lake cichlids individually specialize along the benthic–limnetic axis

    PubMed Central

    Kusche, Henrik; Recknagel, Hans; Elmer, Kathryn Rebecca; Meyer, Axel

    2014-01-01

    A common pattern of adaptive diversification in freshwater fishes is the repeated evolution of elongated open water (limnetic) species and high-bodied shore (benthic) species from generalist ancestors. Studies on phenotype-diet correlations have suggested that population-wide individual specialization occurs at an early evolutionary and ecological stage of divergence and niche partitioning. This variable restricted niche use across individuals can provide the raw material for earliest stages of sympatric divergence. We investigated variation in morphology and diet as well as their correlations along the benthic-limnetic axis in an extremely young Midas cichlid species, Amphilophus tolteca, endemic to the Nicaraguan crater lake Asososca Managua. We found that A. tolteca varied continuously in ecologically relevant traits such as body shape and lower pharyngeal jaw morphology. The correlation of these phenotypes with niche suggested that individuals are specialized along the benthic-limnetic axis. No genetic differentiation within the crater lake was detected based on genotypes from 13 microsatellite loci. Overall, we found that individual specialization in this young crater lake species encompasses the limnetic-as well as the benthic macro-habitat. Yet there is no evidence for any diversification within the species, making this a candidate system for studying what might be the early stages preceding sympatric divergence. A common pattern of adaptive diversification in freshwater fishes is the repeated evolution of open water (limnetic) species and of shore (benthic) species. Individual specialization can reflect earliest stages of evolutionary and ecological divergence. We here demonstrate individual specialization along the benthic–limnetic axis in a young adaptive radiation of crater lake cichlid fishes. PMID:24772288

  18. Morphological stasis in an ongoing gastropod radiation from Lake Malawi

    PubMed Central

    Van Bocxlaer, Bert; Hunt, Gene

    2013-01-01

    Evolutionary processes leading to adaptive radiation regularly occur too fast to be accurately recorded in the fossil record but too slowly to be readily observed in living biota. The study of evolutionary radiations is thereby confronted with an epistemological gap between the timescales and approaches used by neontologists and paleontologists. Here we report on an ongoing radiation of extant Bellamya species (n = 4) from the African Rift Lake Malawi that provides an unusual opportunity to bridge this gap. The substantial molecular differentiation in this monophyletic Bellamya clade has arisen since Late Pleistocene megadroughts in the Malawi Basin caused by climate change. Morphological time-series analysis of a high-resolution, radiocarbon-dated sequence of 22 faunas spanning the Holocene documents stasis up to the middle Holocene in all traits studied (shell height, number of whorls, and two variables obtained from geometric morphometrics). Between deposition of the last fossil fauna (∼5 ka) and the present day, a drastic increase in morphological disparity was observed (3.7–5.8 times) associated with an increase in species diversity. Comparison of the rates of morphological evolution obtained from the paleontological time-series with phylogenetic rates indicates that the divergence in two traits could be reconstructed with the slow rates documented in the fossils, that one trait required a rate reduction (stabilizing selection), and the other faster rates (divergent selection). The combined paleontological and comparative approach taken here allows recognition that morphological stasis can be the dominant evolutionary pattern within species lineages, even in very young and radiating clades. PMID:23924610

  19. Genomics of speciation and introgression in Princess cichlid fishes from Lake Tanganyika.

    PubMed

    Gante, Hugo F; Matschiner, Michael; Malmstrøm, Martin; Jakobsen, Kjetill S; Jentoft, Sissel; Salzburger, Walter

    2016-12-01

    How variation in the genome translates into biological diversity and new species originate has endured as the mystery of mysteries in evolutionary biology. African cichlid fishes are prime model systems to address speciation-related questions for their remarkable taxonomic and phenotypic diversity, and the possible role of gene flow in this process. Here, we capitalize on genome sequencing and phylogenomic analyses to address the relative impacts of incomplete lineage sorting, introgression and hybrid speciation in the Neolamprologus savoryi-complex (the 'Princess cichlids') from Lake Tanganyika. We present a time-calibrated species tree based on whole-genome sequences and provide strong evidence for incomplete lineage sorting in the early phases of diversification and multiple introgression events affecting different stages. Importantly, we find that the Neolamprologus chromosomes show centre-to-periphery biases in nucleotide diversity, sequence divergence, GC content, incomplete lineage sorting and rates of introgression, which are likely modulated by recombination density and linked selection. The detection of heterogeneous genomic landscapes has strong implications on the genomic mechanisms involved in speciation. Collinear chromosomal regions can be protected from gene flow and harbour incompatibility genes if they reside in lowly recombining regions, and coupling can evolve between nonphysically linked genomic regions (chromosome centres in particular). Simultaneously, higher recombination towards chromosome peripheries makes these more dynamic, evolvable regions where adaptation polymorphisms have a fertile ground. Hence, differences in genome architecture could explain the levels of taxonomic and phenotypic diversity seen in taxa with collinear genomes and might have contributed to the spectacular cichlid diversity observed today. © 2016 John Wiley & Sons Ltd.

  20. Lacustrine mollusc radiations in the Lake Malawi Basin: experiments in a natural laboratory for evolution

    NASA Astrophysics Data System (ADS)

    Van Damme, D.; Gautier, A.

    2013-09-01

    In terminal Pliocene-early Pleistocene times, part of the Malawi Basin was occupied by paleo-lake Chiwondo. Molluscan biostratigraphy situates this freshwater lake either in the East African wet phase between 2.7-2.4 Ma or that of 2.0-1.8 Ma. In-lake divergent evolution remained restricted to a few molluscan taxa and was very modest. The lacustrine Chiwondo fauna went extinct at the beginning of the Pleistocene. The modern Lake Malawi malacofauna is depauperate and descends from ubiquistic southeast African taxa and some Malawi basin endemics that invaded the present lake after the Late Pleistocene mega-droughts. The Pleistocene aridity crises caused dramatic changes, affecting the malacofauna of all East African lakes. All lacustrine endemic faunas that had evolved in the Pliocene rift lakes, such as paleo-lake Chiwondo, became extinct. In Lake Tanganyika, the freshwater ecosystem did not crash as in other lakes, but the environmental changes were sufficiently important to trigger a vast radiation. All African endemic lacustrine molluscan clades that are the result of in-lake divergence are hence geologically young, including the vast Lavigeria clade in Lake Tanganyika (ca. 43 species).

  1. Contrasting parasite communities among allopatric colour morphs of the Lake Tanganyika cichlid Tropheus

    PubMed Central

    2013-01-01

    Background Adaptation to different ecological environments is thought to drive ecological speciation. This phenomenon culminates in the radiations of cichlid fishes in the African Great Lakes. Multiple characteristic traits of cichlids, targeted by natural or sexual selection, are considered among the driving factors of these radiations. Parasites and pathogens have been suggested to initiate or accelerate speciation by triggering both natural and sexual selection. Three prerequisites for parasite-driven speciation can be inferred from ecological speciation theory. The first prerequisite is that different populations experience divergent infection levels. The second prerequisite is that these infection levels cause divergent selection and facilitate adaptive divergence. The third prerequisite is that parasite-driven adaptive divergence facilitates the evolution of reproductive isolation. Here we investigate the first and the second prerequisite in allopatric chromatically differentiated lineages of the rock-dwelling cichlid Tropheus spp. from southern Lake Tanganyika (Central Africa). Macroparasite communities were screened in eight populations belonging to five different colour morphs. Results Parasite communities were mainly composed of acanthocephalans, nematodes, monogeneans, copepods, branchiurans, and digeneans. In two consecutive years (2011 and 2012), we observed significant variation across populations for infection with acanthocephalans, nematodes, monogeneans of the genera Gyrodactylus and Cichlidogyrus, and the copepod Ergasilus spp. Overall, parasite community composition differed significantly between populations of different colour morphs. Differences in parasite community composition were stable in time. The genetic structure of Tropheus populations was strong and showed a significant isolation-by-distance pattern, confirming that spatial isolation is limiting host dispersal. Correlations between parasite community composition and Tropheus genetic

  2. Contrasting parasite communities among allopatric colour morphs of the Lake Tanganyika cichlid Tropheus.

    PubMed

    Raeymaekers, Joost A M; Hablützel, Pascal I; Grégoir, Arnout F; Bamps, Jolien; Roose, Anna K; Vanhove, Maarten P M; Van Steenberge, Maarten; Pariselle, Antoine; Huyse, Tine; Snoeks, Jos; Volckaert, Filip A M

    2013-02-14

    Adaptation to different ecological environments is thought to drive ecological speciation. This phenomenon culminates in the radiations of cichlid fishes in the African Great Lakes. Multiple characteristic traits of cichlids, targeted by natural or sexual selection, are considered among the driving factors of these radiations. Parasites and pathogens have been suggested to initiate or accelerate speciation by triggering both natural and sexual selection. Three prerequisites for parasite-driven speciation can be inferred from ecological speciation theory. The first prerequisite is that different populations experience divergent infection levels. The second prerequisite is that these infection levels cause divergent selection and facilitate adaptive divergence. The third prerequisite is that parasite-driven adaptive divergence facilitates the evolution of reproductive isolation. Here we investigate the first and the second prerequisite in allopatric chromatically differentiated lineages of the rock-dwelling cichlid Tropheus spp. from southern Lake Tanganyika (Central Africa). Macroparasite communities were screened in eight populations belonging to five different colour morphs. Parasite communities were mainly composed of acanthocephalans, nematodes, monogeneans, copepods, branchiurans, and digeneans. In two consecutive years (2011 and 2012), we observed significant variation across populations for infection with acanthocephalans, nematodes, monogeneans of the genera Gyrodactylus and Cichlidogyrus, and the copepod Ergasilus spp. Overall, parasite community composition differed significantly between populations of different colour morphs. Differences in parasite community composition were stable in time. The genetic structure of Tropheus populations was strong and showed a significant isolation-by-distance pattern, confirming that spatial isolation is limiting host dispersal. Correlations between parasite community composition and Tropheus genetic differentiation were

  3. Additive genetic variance of quantitative traits in natural and pond-bred populations of the Lake Tanganyika cichlid Tropheus moorii.

    PubMed

    Koch, Martin; Wilson, Alastair J; Kerschbaumer, Michaela; Wiedl, Thomas; Sturmbauer, Christian

    Quantitative genetic studies in natural populations are of growing interest to speciation research since divergence is often believed to arise through micro-evolutionary change, caused by natural selection on functional morphological traits. The species flock of cichlid fishes in Africa's oldest lake, Lake Tanganyika, offers a rare opportunity to study this process. Using the cichlid species Tropheus moorii, we assessed the potential for microevolution in a set of morphological traits by estimating their quantitative genetic basis of variation. Two approaches were employed: (1) estimation of trait heritabilities (h(2)) in situ from a sample of wild caught fish, and (2) estimation of h(2) from first generation offspring produced in a semi-natural breeding experiment. In both cases, microsatellite data were used to infer pedigree structure among the sampled individuals and estimates of h(2) were made using an animal model approach. Although power was limited by the pedigree structures estimated (particularly in the wild caught sample), we nonetheless demonstrate the presence of significant additive genetic variance for aspects of morphology that, in the cichlid species Tropheus moorii, are expected to be functionally and ecologically important, and therefore likely targets of natural selection. We hypothesize that traits showing significant additive genetic variance, such as the mouth position have most likely played a key role in the adaptive evolution of the cichlid fish Tropheus moorii.

  4. Influence of Lake Malawi on regional climate from a double-nested regional climate model experiment

    NASA Astrophysics Data System (ADS)

    Diallo, Ismaïla; Giorgi, Filippo; Stordal, Frode

    2017-07-01

    We evaluate the performance of the regional climate model (RCM) RegCM4 coupled to a one dimensional lake model for Lake Malawi (also known as Lake Nyasa in Tanzania and Lago Niassa in Mozambique) in simulating the main characteristics of rainfall and near surface air temperature patterns over the region. We further investigate the impact of the lake on the simulated regional climate. Two RCM simulations, one with and one without Lake Malawi, are performed for the period 1992-2008 at a grid spacing of 10 km by nesting the model within a corresponding 25 km resolution run ("mother domain") encompassing all Southern Africa. The performance of the model in simulating the mean seasonal patterns of near surface air temperature and precipitation is good compared with previous applications of this model. The temperature biases are generally less than 2.5 °C, while the seasonal cycle of precipitation over the region matches observations well. Moreover, the one-dimensional lake model reproduces fairly well the geographical pattern of observed (from satellite measurements) lake surface temperature as well as its mean month-to-month evolution. The Malawi Lake-effects on the moisture and atmospheric circulation of the surrounding region result in an increase of water vapor mixing ratio due to increased evaporation in the presence of the lake, which combines with enhanced rising motions and low-level moisture convergence to yield a significant precipitation increase over the lake and neighboring areas during the whole austral summer rainy season.

  5. Genetic linkage of distinct adaptive traits in sympatrically speciating crater lake cichlid fish

    PubMed Central

    Fruciano, Carmelo; Franchini, Paolo; Kovacova, Viera; Elmer, Kathryn R.; Henning, Frederico; Meyer, Axel

    2016-01-01

    Our understanding of how biological diversity arises is limited, especially in the case of speciation in the face of gene flow. Here we investigate the genomic basis of adaptive traits, focusing on a sympatrically diverging species pair of crater lake cichlid fishes. We identify the main quantitative trait loci (QTL) for two eco-morphological traits: body shape and pharyngeal jaw morphology. These traits diverge in parallel between benthic and limnetic species in the repeated adaptive radiations of this and other fish lineages. Remarkably, a single chromosomal region contains the highest effect size QTL for both traits. Transcriptomic data show that the QTL regions contain genes putatively under selection. Independent population genomic data corroborate QTL regions as areas of high differentiation between the sympatric sister species. Our results provide empirical support for current theoretical models that emphasize the importance of genetic linkage and pleiotropy in facilitating rapid divergence in sympatry. PMID:27597183

  6. Testing the stages model in the adaptive radiation of cichlid fishes in East African Lake Tanganyika

    PubMed Central

    Muschick, Moritz; Nosil, Patrik; Roesti, Marius; Dittmann, Marie Theres; Harmon, Luke; Salzburger, Walter

    2014-01-01

    Adaptive radiation (AR) is a key process in the origin of organismal diversity. However, the evolution of trait disparity in connection with ecological specialization is still poorly understood. Available models for vertebrate ARs predict that diversification occurs in the form of temporal stages driven by different selective forces. Here, we investigate the AR of cichlid fishes in East African Lake Tanganyika and use macroevolutionary model fitting to evaluate whether diversification happened in temporal stages. Six trait complexes, for which we also provide evidence of their adaptiveness, are analysed with comparative methods: body shape, pharyngeal jaw shape, gill raker traits, gut length, brain weight and body coloration. Overall, we do not find strong evidence for the ‘stages model’ of AR. However, our results suggest that trophic traits diversify earlier than traits implicated in macrohabitat adaptation and that sexual communication traits (i.e. coloration) diversify late in the radiation. PMID:25274371

  7. Genetic basis of male colour dimorphism in a Lake Tanganyika cichlid fish.

    PubMed

    Takahashi, T; Sota, T; Hori, M

    2013-06-01

    Phenotypic polymorphisms can be applied to study the micro-evolutionary forces that maintain genetic variation and can mediate speciation, but it can be difficult to determine the genetic basis of polymorphisms. Recently, restriction-site-associated DNA (RAD) sequencing has become popular, which can easily produce multiple single nucleotide polymorphisms from whole genomes. Here, we combined RAD sequencing, allele-specific PCR and Sanger sequencing to determine the genetic basis underlying male colour dimorphism of a Lake Tanganyika cichlid fish, Cyprichromis leptosoma. Our analyses using both a cross-family (two parents and 12 F2 males) and 64 wild individuals do not contradict a hypothesis that two alleles of one-locus control male colour dimorphism. Also, the locus may be located on a genome region that experiences reduced levels of recombination. Although more analyses will be needed to conclude these findings, this study is the first to suggest the genetic basis of a colour polymorphism using RAD sequencing.

  8. Testing the stages model in the adaptive radiation of cichlid fishes in East African Lake Tanganyika.

    PubMed

    Muschick, Moritz; Nosil, Patrik; Roesti, Marius; Dittmann, Marie Theres; Harmon, Luke; Salzburger, Walter

    2014-11-22

    Adaptive radiation (AR) is a key process in the origin of organismal diversity. However, the evolution of trait disparity in connection with ecological specialization is still poorly understood. Available models for vertebrate ARs predict that diversification occurs in the form of temporal stages driven by different selective forces. Here, we investigate the AR of cichlid fishes in East African Lake Tanganyika and use macroevolutionary model fitting to evaluate whether diversification happened in temporal stages. Six trait complexes, for which we also provide evidence of their adaptiveness, are analysed with comparative methods: body shape, pharyngeal jaw shape, gill raker traits, gut length, brain weight and body coloration. Overall, we do not find strong evidence for the 'stages model' of AR. However, our results suggest that trophic traits diversify earlier than traits implicated in macrohabitat adaptation and that sexual communication traits (i.e. coloration) diversify late in the radiation. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  9. Chalinochromis cyanophleps, a new species of cichlid fish (Teleostei: Cichlidae) from Lake Tanganyika.

    PubMed

    Kullander, Sven O; Karlsson, Mikael; Karlsson, Magnus; Norén, Michael

    2014-04-22

    Chalinochromis cyanophleps is described from nine specimens, the largest 129 mm SL, from Namansi. It differs from other species of Chalinochromis in plain trunk colouration, absence of black stripes on the head, relatively narrow lips, presence of tricuspid jaw teeth, and presence of five rather than four dentary lateralis foramina. The blue iridescent stripe below the eye is shared with other lamprologin cichlids, but is broader and more conspicuous in C. cyanophleps. Chalinochromis cyanophleps occurs at depths between 6 and 45 m in rocky habitats along the Tanzanian coast of Lake Tanganyika, from Mvuna Island south to Kalala Island, a stretch of about 90 km. Field observations were made of specimens up to 18 cm total length. The COI DNA barcode sequence differs by 1.8% from that of C. popelini.

  10. Community assembly in Lake Tanganyika cichlid fish: quantifying the contributions of both niche-based and neutral processes.

    PubMed

    Janzen, Thijs; Alzate, Adriana; Muschick, Moritz; Maan, Martine E; van der Plas, Fons; Etienne, Rampal S

    2017-02-01

    The cichlid family features some of the most spectacular examples of adaptive radiation. Evolutionary studies have highlighted the importance of both trophic adaptation and sexual selection in cichlid speciation. However, it is poorly understood what processes drive the composition and diversity of local cichlid species assemblages on relatively short, ecological timescales. Here, we investigate the relative importance of niche-based and neutral processes in determining the composition and diversity of cichlid communities inhabiting various environmental conditions in the littoral zone of Lake Tanganyika, Zambia. We collected data on cichlid abundance, morphometrics, and local environments. We analyzed relationships between mean trait values, community composition, and environmental variation, and used a recently developed modeling technique (STEPCAM) to estimate the contributions of niche-based and neutral processes to community assembly. Contrary to our expectations, our results show that stochastic processes, and not niche-based processes, were responsible for the majority of cichlid community assembly. We also found that the relative importance of niche-based and neutral processes was constant across environments. However, we found significant relationships between environmental variation, community trait means, and community composition. These relationships were caused by niche-based processes, as they disappeared in simulated, purely neutrally assembled communities. Importantly, these results can potentially reconcile seemingly contrasting findings in the literature about the importance of either niche-based or neutral-based processes in community assembly, as we show that significant trait relationships can already be found in nearly (but not completely) neutrally assembled communities; that is, even a small deviation from neutrality can have major effects on community patterns.

  11. Development of remote sensing tools to improve understanding and management of Lake Malawi

    NASA Astrophysics Data System (ADS)

    Chavula, Geoffrey Mudolole

    Degradation of land resources in the drainage basin of Lake Malawi and other lakes of the African Rift Valley has been widespread over the past several decades. Causes for this degradation include inappropriate agricultural practices, indiscriminate disposal of wastes, and increasing population pressure. These factors pose serious threats to water quality in these important lakes. It is difficult and costly to monitor relevant water quality conditions, such as concentrations of chlorophyll-alpha in these large lakes using ground-based methods, and consequently, information on temporal and spatial variations in water quality conditions of these water bodies is quite limited. Methods that use satellite-based remote sensing data to infer lake clarity and chlorophyll levels have been developed in recent years and have potential for alleviating the problem of inadequate water monitoring data in large lakes in poor and developing countries. In addition to providing data on water quality and trophic state conditions of lakes, satellite imagery has potential for determining water circulation patterns in lakes through maps of lake surface temperature (LST). In turn, LST can be used to locate upwelling zones that may enhance commercial fishing in large deep lakes. Satellite imagery also may be used to characterize and map land use and land cover (LULC). Such information can serve as a basis for studies of the relationships between changes in LULC and lake conditions, such as lake level and water quality. This paper describes results of research to develop remote sensing tools to improve the understanding and management of Lake Malawi. It includes three major components, namely: estimating chlorophyll-alpha concentrations in Lake Malawi from MODIS/Terra satellite imagery; assessing the accuracy of existing split-window algorithms to estimate lake surface temperature from AVHRR and MODIS/Terra satellite data; and determining trends in forest cover and other categories of land

  12. Convergent evolution within an adaptive radiation of cichlid fishes.

    PubMed

    Muschick, Moritz; Indermaur, Adrian; Salzburger, Walter

    2012-12-18

    The recurrent evolution of convergent forms is a widespread phenomenon in adaptive radiations (e.g., [1-9]). For example, similar ecotypes of anoles lizards have evolved on different islands of the Caribbean, benthic-limnetic species pairs of stickleback fish emerged repeatedly in postglacial lakes, equivalent sets of spider ecomorphs have arisen on Hawaiian islands, and a whole set of convergent species pairs of cichlid fishes evolved in East African Lakes Malawi and Tanganyika. In all these cases, convergent phenotypes originated in geographic isolation from each other. Recent theoretical models, however, predict that convergence should be common within species-rich communities, such as species assemblages resulting from adaptive radiations. Here, we present the most extensive quantitative analysis to date of an adaptive radiation of cichlid fishes, discovering multiple instances of convergence in body and trophic morphology. Moreover, we show that convergent morphologies are associated with adaptations to specific habitats and resources and that Lake Tanganyika's cichlid communities are characterized by the sympatric occurrence of convergent forms. This prevalent coexistence of distantly related yet ecomorphologically similar species offers an explanation for the greatly elevated species numbers in cichlid species flocks. Copyright © 2012 Elsevier Ltd. All rights reserved.

  13. Estimating the surface temperature of Lake Malawi using AVHRR and MODIS satellite imagery

    NASA Astrophysics Data System (ADS)

    Chavula, Geoffrey; Brezonik, Patrick; Thenkabail, Prasad; Johnson, Thomas; Bauer, Marvin

    This paper discusses the potential offered by both Advanced Very High Resolution Radiometer (AVHRR) and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery in estimating lake surface temperature. The findings from regression analysis show that MODIS/Terra Land Surface Temperature data (MOD11A1) and Ocean Color MODIS/Terra Sea Surface Temperature (SST)-SeaDAS data are closely related to in situ data as evidenced by a relatively high correlation coefficient ( r2 values of 0.7 and 0.74, respectively). In the light of the above, the developed algorithm may be used for estimating lake surface temperature over Lake Malawi from MODIS satellite imagery. Maps of temperature distribution that were generated for the lake from MODIS satellite imagery show that the circulation pattern of Lake Malawi is very complex, with no clear set pattern of temperature distribution over the entire lake. However, the persistence of a cold water zone between Salima and the northern part of Nkhotakota may be indicative of an upwelling region, ideal for the development of fishery industry. Inadequate satellite data made it difficult to assess whether or not the triple window equation previously developed by Wooster et al. [Wooster, M., Patterson, G., Loftie, R., Sear, C., 2001. Derivation and validation of the seasonal thermal structure of Lake Malawi using multi-satellite AVHRR observations. International Journal of Remote Sensing 22(15), 2953-2972] for estimating lake surface temperature using AVHRR was applicable to the entire lake.

  14. Genetic population structure as indirect measure of dispersal ability in a Lake Tanganyika cichlid.

    PubMed

    Koblmüller, Stephan; Sefc, Kristina Maria; Duftner, Nina; Warum, Marko; Sturmbauer, Christian

    2007-06-01

    Diversification and speciation processes are influenced by intrinsic (ecological specialization, dispersal) and extrinsic (habitat structure and instability) factors, but the effect of ecological characteristics on dispersal is difficult to assess. This study uses mitochondrial control region sequences to investigate the population structure and demographic history of the endemic Lake Tanganyika cichlid Neolamprologus caudopunctatus with a preference for the rock-sand interface along two stretches of continuous, rocky shoreline, and across a sandy bay representing a potential dispersal barrier. Populations along uninterrupted habitat were not differentiated; whereas, the sandy bay separated two reciprocally monophyletic clades. The split between the two clades between 170,000 and 260,000 years BP coincides with a period of rising water level following a major lowstand, and indicates that clades remained isolated throughout subsequent lake level fluctuations. Low long-term effective population sizes were inferred from modest genetic diversity estimates, and may be due to recent population expansions starting from small population sizes 45,000-60,000 years BP. Comparisons with available data from specialized rock-dwelling species of the same area suggest that habitat structure and lake level fluctuations determine phylogeographic patterns on large scales, while fine-scale population structure and demography are modulated by species-specific ecologies.

  15. Population genomic tests of models of adaptive radiation in Lake Victoria region cichlid fish.

    PubMed

    Bezault, Etienne; Mwaiko, Salome; Seehausen, Ole

    2011-12-01

    Adaptive radiation is usually thought to be associated with speciation, but the evolution of intraspecific polymorphisms without speciation is also possible. The radiation of cichlid fish in Lake Victoria (LV) is perhaps the most impressive example of a recent rapid adaptive radiation, with 600+ very young species. Key questions about its origin remain poorly characterized, such as the importance of speciation versus polymorphism, whether species persist on evolutionary time scales, and if speciation happens more commonly in small isolated or in large connected populations. We used 320 individuals from 105 putative species from Lakes Victoria, Edward, Kivu, Albert, Nabugabo and Saka, in a radiation-wide amplified fragment length polymorphism (AFLP) genome scan to address some of these questions. We demonstrate pervasive signatures of speciation supporting the classical model of adaptive radiation associated with speciation. A positive relationship between the age of lakes and the average genomic differentiation of their species, and a significant fraction of molecular variance explained by above-species level taxonomy suggest the persistence of species on evolutionary time scales, with radiation through sequential speciation rather than a single starburst. Finally the large gene diversity retained from colonization to individual species in every radiation suggests large effective population sizes and makes speciation in small geographical isolates unlikely.

  16. Organic sedimentation in modern lacustrine systems: A case study from Lake Malawi, East Africa

    USGS Publications Warehouse

    Ellis, Geoffrey S.; Barry J. Katz,; Christopher A. Scholz,; Peter K. Swart,

    2015-01-01

    This study examines the relationship between depositional environment and sedimentary organic geochemistry in Lake Malawi, East Africa, and evaluates the relative significance of the various processes that control sedimentary organic matter (OM) in lacustrine systems. Total organic carbon (TOC) concentrations in recent sediments from Lake Malawi range from 0.01 to 8.80 wt% and average 2.83 wt% for surface sediments and 2.35 wt% for shallow core sediments. Hydrogen index (HI) values as determined by Rock-Eval pyrolysis range from 0 to 756 mg HC g−1 TOC and average 205 mg HC g−1 TOC for surface sediments and 228 mg HC g−1 TOC for shallow core samples. On average, variations in primary productivity throughout the lake may account for ~33% of the TOC content in Lake Malawi sediments (as much as 1 wt% TOC), and have little or no impact on sedimentary HI values. Similarly, ~33% to 66% of the variation in TOC content in Lake Malawi sediments appears to be controlled by anoxic preservation of OM (~1–2 wt% TOC), although some component of the water depth–TOC relationship may be due to physical sediment transport processes. Furthermore, anoxic preservation has a minimal effect on HI values in Lake Malawi sediments. Dilution of OM by inorganic sediment may account for ~16% of variability in TOC content in Lake Malawi sediments (~0.5 wt% TOC). The effect of inputs of terrestrial sediment on the organic character of surface sediments in these lakes is highly variable, and appears to be more closely related to the local depositional environment than the regional flux of terrestrial OM. Total nitrogen and TOC content in surface sediments collected throughout the lake are found to be highly correlated (r2 = 0.95), indicating a well-homogenized source of OM to the lake bottom. The recurring suspension and deposition of terrestrial sediment may account for significant amounts of OM deposited in offshore regions of the lake. This process effectively separates denser

  17. Evolution of the ribosomal RNA internal transcribed spacer one (ITS-1) in cichlid fishes of the Lake Victoria region.

    PubMed

    Booton, G C; Kaufman, L; Chandler, M; Oguto-Ohwayo, R; Duan, W; Fuerst, P A

    1999-03-01

    The nucleotide sequences of the first internal transcribed spacer (ITS-1) of the ribosomal RNA gene cluster have been determined for 11 species of closely related endemic cichlid fishes of the Lake Victoria region (LVR) and 6 related East African cichlids. The ITS-1 sequences confirmed independently derived basal phylogenies, but provide limited insight within this species flock. The line leading to Pseudocrenilabrus multicolor arose early, close to the divergence event that separated the tilapiine and haplochromine tribes of the "African Group" of the family Cichlidae. In this phylogeny, Astatoreochromis alluaudi and the riverine Astatotilapia burtoni are sister taxa, which together are a sister group to a monophyletic assemblage including both Lake Victoria and Lake Edward taxa. The ITS-1 data support the monophyly of haplochromine genera across lakes. Since Lake Victoria is believed to have been dry between 14, 500 and 12,400 BPE, the modern assemblage must have been derived from reinvasion by the products of earlier cladogenesis events. Thus, although the regional superflock is monophyletic, the haplochromines of Lake Victoria itself did not evolve in situ from a single ancestor.

  18. Old fossils–young species: evolutionary history of an endemic gastropod assemblage in Lake Malawi

    PubMed Central

    Schultheiß, Roland; Van Bocxlaer, Bert; Wilke, Thomas; Albrecht, Christian

    2009-01-01

    Studies on environmental changes provide important insights into modes of speciation, into the (adaptive) reoccupation of ecological niches and into species turnover. Against this background, we here examine the history of the gastropod genus Lanistes in the African Rift Lake Malawi, guided by four general evolutionary scenarios, and compare it with patterns reported from other endemic Malawian rift taxa. Based on an integrated approach using a mitochondrial DNA phylogeny and a trait-specific molecular clock in combination with insights from the fossil record and palaeoenvironmental data, we demonstrate that the accumulation of extant molecular diversity in the endemic group did not start before approximately 600 000 years ago from a single lineage. Fossils of the genus from the Malawi Rift, however, are over one million years older. We argue that severe drops in the lake level of Lake Malawi in the Pleistocene offer a potential explanation for this pattern. Our results also challenge previously established phylogenetic relationships within the genus by revealing parallel evolution and providing evidence that the endemic Lanistes species are not restricted to the lake proper but are present throughout the Malawi Rift. PMID:19439440

  19. Old fossils-young species: evolutionary history of an endemic gastropod assemblage in Lake Malawi.

    PubMed

    Schultheiss, Roland; Van Bocxlaer, Bert; Wilke, Thomas; Albrecht, Christian

    2009-08-07

    Studies on environmental changes provide important insights into modes of speciation, into the (adaptive) reoccupation of ecological niches and into species turnover. Against this background, we here examine the history of the gastropod genus Lanistes in the African Rift Lake Malawi, guided by four general evolutionary scenarios, and compare it with patterns reported from other endemic Malawian rift taxa. Based on an integrated approach using a mitochondrial DNA phylogeny and a trait-specific molecular clock in combination with insights from the fossil record and palaeoenvironmental data, we demonstrate that the accumulation of extant molecular diversity in the endemic group did not start before approximately 600,000 years ago from a single lineage. Fossils of the genus from the Malawi Rift, however, are over one million years older. We argue that severe drops in the lake level of Lake Malawi in the Pleistocene offer a potential explanation for this pattern. Our results also challenge previously established phylogenetic relationships within the genus by revealing parallel evolution and providing evidence that the endemic Lanistes species are not restricted to the lake proper but are present throughout the Malawi Rift.

  20. Disentangling Incomplete Lineage Sorting and Introgression to Refine Species-Tree Estimates for Lake Tanganyika Cichlid Fishes.

    PubMed

    Meyer, Britta S; Matschiner, Michael; Salzburger, Walter

    2017-07-01

    Adaptive radiation is thought to be responsible for the evolution of a great portion of the past and present diversity of life. Instances of adaptive radiation, characterized by the rapid emergence of an array of species as a consequence to their adaptation to distinct ecological niches, are important study systems in evolutionary biology. However, because of the rapid lineage formation in these groups, and occasional gene flow between the participating species, it is often difficult to reconstruct the phylogenetic history of species that underwent an adaptive radiation. In this study, we present a novel approach for species-tree estimation in rapidly diversifying lineages, where introgression is known to occur, and apply it to a multimarker data set containing up to 16 specimens per species for a set of 45 species of East African cichlid fishes (522 individuals in total), with a main focus on the cichlid species flock of Lake Tanganyika. We first identified, using age distributions of most recent common ancestors in individual gene trees, those lineages in our data set that show strong signatures of past introgression. This led us to formulate three hypotheses of introgression between different lineages of Tanganyika cichlids: the ancestor of Boulengerochromini (or of Boulengerochromini and Bathybatini) received genomic material from the derived H-lineage; the common ancestor of Cyprichromini and Perissodini experienced, in turn, introgression from Boulengerochromini and/or Bathybatini; and the Lake Tanganyika Haplochromini and closely related riverine lineages received genetic material from Cyphotilapiini. We then applied the multispecies coalescent model to estimate the species tree of Lake Tanganyika cichlids, but excluded the lineages involved in these introgression events, as the multispecies coalescent model does not incorporate introgression. This resulted in a robust species tree, in which the Lamprologini were placed as sister lineage to the H

  1. Evolutionary history of the Lake Tanganyika cichlid tribe Lamprologini (Teleostei: Perciformes) derived from mitochondrial and nuclear DNA data.

    PubMed

    Sturmbauer, Christian; Salzburger, Walter; Duftner, Nina; Schelly, Robert; Koblmüller, Stephan

    2010-10-01

    Lake Tanganyika comprises a cichlid species flock with substrate-breeding and mouthbrooding lineages. While sexual selection via mate choice on male mating color is thought to boost speciation rates in mouthbrooding cichlids, this is not the case in substrate-breeding lamprologines, which mostly form stable pairs and lack sexual dichromatism. We present a comprehensive reconstruction of the evolution of the cichlid tribe Lamprologini, based upon mtDNA sequences and multilocus nuclear DNA (AFLP) markers. Twelve mtDNA clades were identified, seven of which were corroborated by the AFLP tree. The radiation is likely to have started about 5.3 MYA, contemporarily with that of the mouthbrooding C-lineage, and probably triggered by the onset of deep-water conditions in Lake Tanganyika. Neither the Congo- nor the Malagarazi River species form the most ancestral branch. Several conflicts in the mtDNA phylogeny with taxonomic assignments based upon color, eco-morphology and behavior could be resolved and complemented by the AFLP analysis. Introgressive hybridization upon secondary contact seems to be the most likely cause for paraphyly of taxa due to mtDNA capture in species involving brood-care helpers, while accidental hybridization best explains the para- or polyphyly of several gastropod shell breeders. Taxonomic error or paraphyly due to the survival of ancestral lineages appear responsible for inconsistencies in the genera Lamprologus and Neolamprologus. Copyright 2010 Elsevier Inc. All rights reserved.

  2. Evolutionary history of the Lake Tanganyika cichlid tribe Lamprologini (Teleostei: Perciformes) derived from mitochondrial and nuclear DNA data

    PubMed Central

    Sturmbauer, Christian; Salzburger, Walter; Duftner, Nina; Schelly, Robert; Koblmüller, Stephan

    2010-01-01

    Lake Tanganyika comprises a cichlid species flock with substrate-breeding and mouthbrooding lineages. While sexual selection via mate choice on male mating color is thought to boost speciation rates in mouthbrooding cichlids, this is not the case in substrate-breeding lamprologines, which mostly form stable pairs and lack sexual dichromatism. We present a comprehensive reconstruction of the evolution of the cichlid tribe Lamprologini, based upon mtDNA sequences and multilocus nuclear DNA (AFLP) markers. Twelve mtDNA clades were identified, seven of which were corroborated by the AFLP tree. The radiation is likely to have started about 5.3 MYA, contemporarily with that of the mouthbrooding C-lineage, and probably triggered by the onset of deep-water conditions in Lake Tanganyika. Neither the Congo- nor the Malagarazi River species form the most ancestral branch. Several conflicts in the mtDNA phylogeny with taxonomic assignments based upon color, eco-morphology and behavior could be resolved and complemented by the AFLP analysis. Introgressive hybridization upon secondary contact seems to be the most likely cause for paraphyly of taxa due to mtDNA capture in species involving brood-care helpers, while accidental hybridization best explains the para- or polyphyly of several gastropod shell breeders. Taxonomic error or paraphyly due to the survival of ancestral lineages appear responsible for inconsistencies in the genera Lamprologus and Neolamprologus. PMID:20601006

  3. Polygenic sex determination in the cichlid fish Astatotilapia burtoni.

    PubMed

    Roberts, Natalie B; Juntti, Scott A; Coyle, Kaitlin P; Dumont, Bethany L; Stanley, M Kaitlyn; Ryan, Allyson Q; Fernald, Russell D; Roberts, Reade B

    2016-10-26

    The East African riverine cichlid species Astatotilapia burtoni serves as an important laboratory model for sexually dimorphic physiology and behavior, and also serves as an outgroup species for the explosive adaptive radiations of cichlid species in Lake Malawi and Lake Victoria. An astounding diversity of genetic sex determination systems have been revealed within the adaptive radiation of East African cichlids thus far, including polygenic sex determination systems involving the epistatic interaction of multiple, independently segregating sex determination alleles. However, sex determination has remained unmapped in A. burtoni. Here we present mapping results supporting the presence of multiple, novel sex determination alleles, and thus the presence of polygenic sex determination in A. burtoni. Using mapping in small families in conjunction with restriction-site associated DNA sequencing strategies, we identify associations with sex at loci on linkage group 13 and linkage group 5-14. Inheritance patterns support an XY sex determination system on linkage group 5-14 (a chromosome fusion relative to other cichlids studied), and an XYW system on linkage group 13, and these associations are replicated in multiple families. Additionally, combining our genetic data with comparative genomic analysis identifies another fusion that is unassociated with sex, with linkage group 8-24 and linkage group 16-21 fused in A. burtoni relative to other East African cichlid species. We identify genetic signals supporting the presence of three previously unidentified sex determination alleles at two loci in the species A. burtoni, strongly supporting the presence of polygenic sex determination system in the species. These results provide a foundation for future mapping of multiple sex determination genes and their interactions. A better understanding of sex determination in A. burtoni provides important context for their use in behavioral studies, as well as studies of the evolution

  4. Reticulate phylogeny of gastropod-shell-breeding cichlids from Lake Tanganyika--the result of repeated introgressive hybridization.

    PubMed

    Koblmüller, Stephan; Duftner, Nina; Sefc, Kristina M; Aibara, Mitsuto; Stipacek, Martina; Blanc, Michel; Egger, Bernd; Sturmbauer, Christian

    2007-01-25

    The tribe Lamprologini is the major substrate breeding lineage of Lake Tanganyika's cichlid species flock. Among several different life history strategies found in lamprologines, the adaptation to live and breed in empty gastropod shells is probably the most peculiar. Although shell-breeding arose several times in the evolutionary history of the lamprologines, all obligatory and most facultative shell-breeders belong to the so called "ossified group", a monophyletic lineage within the lamprologine cichlids. Since their distinctive life style enables these species to live and breed in closest vicinity, we hypothesized that these cichlids might be particularly prone to accidental hybridization, and that introgression might have affected the evolutionary history of this cichlid lineage. Our analyses revealed discrepancies between phylogenetic hypotheses based on mitochondrial and nuclear (AFLP) data. While the nuclear phylogeny was congruent with morphological, behavioral and ecological characteristics, several species--usually highly specialized shell-breeders--were placed at contradicting positions in the mitochondrial phylogeny. The discordant phylogenies strongly suggest repeated incidents of introgressive hybridization between several distantly related shell-breeding species, which reticulated the phylogeny of this group of cichlids. Long interior branches and high bootstrap support for many interior nodes in the mitochondrial phylogeny argue against a major effect of ancient incomplete lineage sorting on the phylogenetic reconstruction. Moreover, we provide morphological and genetic (mtDNA and microsatellites) evidence for ongoing hybridization among distantly related shell-breeders. In these cases, the territorial males of the inferred paternal species are too large to enter the shells of their mate, such that they have to release their sperm over the entrance of the shell to fertilize the eggs. With sperm dispersal by water currents and wave action, trans

  5. Two new species of zooplanktivorous haplochromine cichlids from Lake Victoria, Tanzania

    PubMed Central

    de Zeeuw, Marnix P.; Westbroek, Irene; van Oijen, Martien J.P.; Witte, Frans

    2013-01-01

    Abstract Two new species of zooplanktivorous haplochromine cichlids from Lake Victoria, Tanzania, are described and illustrated. These species closely resemble each other. Their affinities to other zooplanktivorous haplochromines from Lake Victoria are discussed. Haplochromis argens sp. n., which featured under nicknames (mainly Haplochromis “argens”) in more than 50 papers, was caught both in the Mwanza Gulf and the Emin Pasha Gulf, whereas Haplochromis goldschmidti sp. n. was only found in the Emin Pasha Gulf. Of the latter species only males are available, but it seems unlikely that it represents a case of male colour polymorphism as several presumably unrelated characters differ in sympatry between the two species, suggesting that there is no gene flow. Statistical analysis revealed that the overall difference between the two species is greater than that between the populations from the two locations. Body depth of the two species in sympatry in the Emin Pasha Gulf was more similar than that of Haplochromis goldschmidti sp. n. and the allopatric population of Haplochromis argens sp. n. from the Mwanza Gulf,which mayindicate an overall environmental effect. However, several measurements related to the width of snout and mouth differed more between the populations of the two species in sympatry than between the allopatric populations. In contrast to a group of zooplanktivorous species that recovered successfully after environmental changes in the lake, Haplochromis argens sp. n. is among a group that became extremely rare and probably is in danger of extinction; the conservation status of Haplochromis goldschmidti sp. n. is currently unknown. PMID:23717179

  6. Diet disparity among sympatric herbivorous cichlids in the same ecomorphs in Lake Tanganyika: amplicon pyrosequences on algal farms and stomach contents.

    PubMed

    Hata, Hiroki; Tanabe, Akifumi S; Yamamoto, Satoshi; Toju, Hirokazu; Kohda, Masanori; Hori, Michio

    2014-10-29

    Lake Tanganyika, an ancient lake in the Great Rift Valley, is famous for the adaptive radiation of cichlids. Five tribes of the Cichlidae family have acquired herbivory, with five ecomorphs: grazers, browsers, scrapers, biters and scoopers. Sixteen species of the herbivorous cichlids coexist on a rocky littoral slope in the lake. Seven of them individually defend feeding territories against intruding herbivores to establish algal farms. We collected epiphyton from these territories at various depths and also gathered fish specimens. Algal and cyanobacteria community structures were analysed using the amplicon-metagenomic method. Based on 454-pyrosequencing of SSU rRNA gene sequences, we identified 300 phototrophic taxa, including 197 cyanobacteria, 57 bacillariophytes, and 31 chlorophytes. Algal farms differed significantly in their composition among cichlid species, even in the same ecomorph, due in part to their habitat-depth segregation. The algal species composition of the stomach contents and algal farms of each species differed, suggesting that cichlids selectively harvest their farms. The stomach contents were highly diverse, even between species in the same tribe, in the same feeding ecomorph. In this study, the amplicon-metagenomic approach revealed food niche separation based on habitat-depth segregation among coexisting herbivorous cichlids in the same ecomorphs in Lake Tanganyika.

  7. Ancyrocephalidae (Monogenea) of Lake Tanganyika: III: Cichlidogyrus infecting the world's biggest cichlid and the non-endemic tribes Haplochromini, Oreochromini and Tylochromini (Teleostei, Cichlidae).

    PubMed

    Muterezi Bukinga, Fidel; Vanhove, Maarten P M; Van Steenberge, Maarten; Pariselle, Antoine

    2012-11-01

    Lake Tanganyika is the deepest and oldest African Great Lake and of economic importance. While the diversity of its endemic cichlid radiations yielded scientific interest, a number of cichlid tribes have few representatives in the lake. Some of those, namely Oreochromini (ex-Tilapiini), Haplochromini and Tylochromini, reach higher species numbers in riverine systems. Conversely, the phylogenetic position of the monospecific and endemic Boulengerochromini is unclear. The oreochromines Oreochromis tanganicae and Oreochromis niloticus, the haplochromine Astatotilapia burtoni, the tylochromine Tylochromis polylepis and the boulengerochromine Boulengerochromis microlepis, the largest cichlid species worldwide, were surveyed for ancyrocephalid monogenean gill parasites. Five new species are proposed. Cichlidogyrus gillardinae sp. n. is described from A. burtoni, Cichlidogyrus mbirizei sp. n. from O. tanganicae and Cichlidogyrus nshomboi sp. n. from B. microlepis. T. polylepis harbours Cichlidogyrus mulimbwai sp. n., Cichlidogyrus muzumanii sp. n. and a third, presently undescribed species. Four species known from outside the Tanganyika Basin were retrieved on the oreochromines. The host species are scientific models or important in the sectors of fisheries or ornamental fish trade. Moreover, their phylogenetic positions render them well-suited to help elucidate the historic relationships between riverine and lacustrine African cichlids. In this framework, their Cichlidogyrus fauna is compared to congeners known from African rivers and to the few Tanganyika representatives described. While the parasites of Oreochromis, A. burtoni and T. polylepis are reminiscent of those infecting related hosts throughout Africa, B. microlepis hosts a Cichlidogyrus morphotype typical of Lake Tanganyika. This supports its placement within an endemic cichlid radiation.

  8. Deep-water parasite diversity in Lake Tanganyika: description of two new monogenean species from benthopelagic cichlid fishes.

    PubMed

    Kmentová, Nikol; Gelnar, Milan; Koblmüller, Stephan; Vanhove, Maarten P M

    2016-08-03

    Lake Tanganyika is the world's second deepest lake. Its diverse cichlid assemblage offers a unique opportunity for studying a deep-water host-parasite model in freshwater. Low host specificity and a broad host range including representatives of the Bathybatini tribe in the only monogenean parasite described from this habitat, Cichlidogyrus casuarinus Pariselle, Muterezi Bukinga & Vanhove, 2015 suggest a link between lower specificity and lower host density. Conversely, high host specificity and species richness are reported for monogeneans of the lake's littoral cichlids. We further investigated whether the deep-water environment in Lake Tanganyika is really monogenean species-depauperate by investigating the monogenean fauna of Trematocara unimaculatum (a representative of the tribe Trematocarini, the sister lineage of the Bathybatini) and Benthochromis horii, a member of the tribe Benthochromini, found in the same deep-water habitat as the already known hosts of C. casuarinus. Sclerotised structures of the collected monogenean individuals were characterised morphologically using light microscopy and morphometrics. Both examined cichlid species are infected by a single monogenean species each, which are new to science. They are described as Cichlidogyrus brunnensis n. sp., infecting T. unimaculatum, and Cichlidogyrus attenboroughi n. sp., parasitising on B. horii. Diagnostic characteristics include the distal bifurcation of the accessory piece in C. brunnensis n. sp. and the combination of long auricles and no heel in C. attenboroughi n. sp. In addition C. brunnensis n. sp. does not resemble C. casuarinus, the only species of Cichlidogyrus thus far reported from the Bathybatini. Also Cichlidogyrus attenboroughi n. sp. does not resemble any of the monogenean species documented from the pelagic zone of the lake and is among the few described species of Cichlidogyrus without heel. As two new and non-resembling Cichlidogyrus species are described from T. unimaculatum

  9. Multispecies Outcomes of Sympatric Speciation after Admixture with the Source Population in Two Radiations of Nicaraguan Crater Lake Cichlids

    PubMed Central

    Kautt, Andreas F.; Machado-Schiaffino, Gonzalo; Meyer, Axel

    2016-01-01

    The formation of species in the absence of geographic barriers (i.e. sympatric speciation) remains one of the most controversial topics in evolutionary biology. While theoretical models have shown that this most extreme case of primary divergence-with-gene-flow is possible, only a handful of accepted empirical examples exist. And even for the most convincing examples uncertainties remain; complex histories of isolation and secondary contact can make species falsely appear to have originated by sympatric speciation. This alternative scenario is notoriously difficult to rule out. Midas cichlids inhabiting small and remote crater lakes in Nicaragua are traditionally considered to be one of the best examples of sympatric speciation and lend themselves to test the different evolutionary scenarios that could lead to apparent sympatric speciation since the system is relatively small and the source populations known. Here we reconstruct the evolutionary history of two small-scale radiations of Midas cichlids inhabiting crater lakes Apoyo and Xiloá through a comprehensive genomic data set. We find no signs of differential admixture of any of the sympatric species in the respective radiations. Together with coalescent simulations of different demographic models our results support a scenario of speciation that was initiated in sympatry and does not result from secondary contact of already partly diverged populations. Furthermore, several species seem to have diverged simultaneously, making Midas cichlids an empirical example of multispecies outcomes of sympatric speciation. Importantly, however, the demographic models strongly support an admixture event from the source population into both crater lakes shortly before the onset of the radiations within the lakes. This opens the possibility that the formation of reproductive barriers involved in sympatric speciation was facilitated by genetic variants that evolved in a period of isolation between the initial founding

  10. Multispecies Outcomes of Sympatric Speciation after Admixture with the Source Population in Two Radiations of Nicaraguan Crater Lake Cichlids.

    PubMed

    Kautt, Andreas F; Machado-Schiaffino, Gonzalo; Meyer, Axel

    2016-06-01

    The formation of species in the absence of geographic barriers (i.e. sympatric speciation) remains one of the most controversial topics in evolutionary biology. While theoretical models have shown that this most extreme case of primary divergence-with-gene-flow is possible, only a handful of accepted empirical examples exist. And even for the most convincing examples uncertainties remain; complex histories of isolation and secondary contact can make species falsely appear to have originated by sympatric speciation. This alternative scenario is notoriously difficult to rule out. Midas cichlids inhabiting small and remote crater lakes in Nicaragua are traditionally considered to be one of the best examples of sympatric speciation and lend themselves to test the different evolutionary scenarios that could lead to apparent sympatric speciation since the system is relatively small and the source populations known. Here we reconstruct the evolutionary history of two small-scale radiations of Midas cichlids inhabiting crater lakes Apoyo and Xiloá through a comprehensive genomic data set. We find no signs of differential admixture of any of the sympatric species in the respective radiations. Together with coalescent simulations of different demographic models our results support a scenario of speciation that was initiated in sympatry and does not result from secondary contact of already partly diverged populations. Furthermore, several species seem to have diverged simultaneously, making Midas cichlids an empirical example of multispecies outcomes of sympatric speciation. Importantly, however, the demographic models strongly support an admixture event from the source population into both crater lakes shortly before the onset of the radiations within the lakes. This opens the possibility that the formation of reproductive barriers involved in sympatric speciation was facilitated by genetic variants that evolved in a period of isolation between the initial founding

  11. Body size evolution of a shell-brooding cichlid fish from Lake Tanganyika.

    PubMed

    Takahashi, T; Ota, K

    2016-12-01

    The substrate-brooding cichlid fish Telmatochromis temporalis in Lake Tanganyika demonstrates a simple example of ecological speciation between normal and dwarf morphs through divergent natural selection on body size. The dwarf morph most likely evolved from the ancestral normal morph; therefore, elucidating the evolution of its small body size is a key to understanding this ecological speciation event. Previous studies suggest that the small body size of the dwarf morph is an adaptation to the use of empty snail shells as shelters (males) and spawning sites (females), but this idea has not been fully evaluated. Combining original and previously published information, this study compared likelihood values to determine the primary factor that would be responsible for regulating the body size of the dwarf morph. Male body size is most likely regulated by the ability to turn within shells, which may influence the predation avoidance of adult fish. Females are smaller than males, and their body size is most likely regulated by the ability to lay eggs in the small spaces within shells close to the shell apices where predation risk on eggs is lower. This study provides new evidence supporting the hypothesis that different natural selection factors affected body size of the different sexes of the dwarf morph, which has not been reported in other animal species. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

  12. Reverse evolution in RH1 for adaptation of cichlids to water depth in Lake Tanganyika.

    PubMed

    Nagai, Haruka; Terai, Yohey; Sugawara, Tohru; Imai, Hiroo; Nishihara, Hidenori; Hori, Michio; Okada, Norihiro

    2011-06-01

    Reverse evolution is a widespread phenomenon in biology, but the genetic mechanism for the reversal of a genetic change for adaptation to the ancestral state is not known. Here, we report the first case of complete reverse evolution of two amino acids, serine and alanine, at a single position in RH1 opsin pigment for adaptation to water depth. We determined RH1 sequences of cichlid fishes from four tribes of Lake Tanganyika with different habitat depths. Most of the species were divided into two types: RH1 with 292A for species in shallow water or 292S for species in deep water. Both types were adapted to their ambient light environments as indicated by the absorption spectra of the RH1 pigments. Based on the RH1 locus tree and ecological data, we inferred the ancestral amino acids at position 292 and the distribution of the depth ranges (shallow or deep) of ancestral species of each tribe. According to these estimates, we identified two distinct parallel adaptive evolutions: The replacement A292S occurred at least four times for adaptation from shallow to deep water, and the opposite replacement S292A occurred three times for adaptation from deep to shallow water. The latter parallelism represents the complete reverse evolution from the derived to the ancestral state, following back adaptive mutation with reversal of the RH1 pigment function accompanied by reversal of the species habitat shift.

  13. The genetics of mate preferences in hybrids between two young and sympatric Lake Victoria cichlid species.

    PubMed

    Svensson, Ola; Woodhouse, Katie; van Oosterhout, Cock; Smith, Alan; Turner, George F; Seehausen, Ole

    2017-02-22

    The genetic architecture of mate preferences is likely to affect significant evolutionary processes, including speciation and hybridization. Here, we investigate laboratory hybrids between a pair of sympatric Lake Victoria cichlid fish species that appear to have recently evolved from a hybrid population between similar predecessor species. The species demonstrate strong assortative mating in the laboratory, associated with divergent male breeding coloration (red dorsum versus blue). We show in a common garden experiment, using DNA-based paternity testing, that the strong female mate preferences among males of the two species are fully recovered in a large fraction of their F2 hybrid generation. Individual hybrid females often demonstrated consistent preferences in multiple mate choice trials (more than or equal to five) across a year or more. This result suggests that female mate preference is influenced by relatively few major genes or genomic regions. These preferences were not changed by experience of a successful spawning event with a male of the non-preferred species in a no-choice single-male trial. We found no evidence for imprinting in the F2 hybrids, although the F1 hybrid females may have been imprinted on their mothers. We discuss this nearly Mendelian inheritance of consistent innate mate preferences in the context of speciation theory.

  14. Alternative male mating tactics of the substrate brooding cichlid Telmatochromis temporalis in Lake Tanganyika.

    PubMed

    Katoh, Rei; Munehara, Hiroyuki; Kohda, Masanori

    2005-05-01

    Telmatochromis temporalis is a bi-parental substrate brooding cichlid endemic to Lake Tanganyika. Paired males were always larger than their mates and had territories around nests against conspecific males. However, males smaller than the paired females were found in 18% of the nests. Here we report a reproductive tactic of these small males. The small males had as heavy gonads as paired males, and the gonad somatic index (GSI) of the small males was much higher than that of the latter. The examinations of the paternity and maternity using microsatellite-DNA as a genetic marker revealed that the small males were not genetically related to the pair members, and sired some young in 3 of 5 nests. These small males did not guard the broods, suggesting that they are likely to perform reproductive parasitism as sneakers. Paired males could not enter their spawning nests due to their large size, which made it difficult to chase out sneakers once they entered the nest. Some males as small as the sneakers were found outside the territories of paired males, and their gonads were quite small. Circumstantial evidence suggests that small males have two alternative investment patterns: investing in gonad to be sneakers, and investing in growth to probably be territorial males.

  15. Evolutionary associations between host traits and parasite load: insights from Lake Tanganyika cichlids.

    PubMed

    Hayward, A; Tsuboi, M; Owusu, C; Kotrschal, A; Buechel, S D; Zidar, J; Cornwallis, C K; Løvlie, H; Kolm, N

    2017-02-10

    Parasite diversity and abundance (parasite load) vary greatly among host species. However, the influence of host traits on variation in parasitism remains poorly understood. Comparative studies of parasite load have largely examined measures of parasite species richness and are predominantly based on records obtained from published data. Consequently, little is known about the relationships between host traits and other aspects of parasite load, such as parasite abundance, prevalence and aggregation. Meanwhile, understanding of parasite species richness may be clouded by limitations associated with data collation from multiple independent sources. We conducted a field study of Lake Tanganyika cichlid fishes and their helminth parasites. Using a Bayesian phylogenetic comparative framework, we tested evolutionary associations between five key host traits (body size, gut length, diet breadth, habitat complexity and number of sympatric hosts) predicted to influence parasitism, together with multiple measures of parasite load. We find that the number of host species that a particular host may encounter due to its habitat preferences emerges as a factor of general importance for parasite diversity, abundance and prevalence, but not parasite aggregation. In contrast, body size and gut size are positively related to aspects of parasite load within, but not between species. The influence of host phylogeny varies considerably among measures of parasite load, with the greatest influence exerted on parasite diversity. These results reveal that both host morphology and biotic interactions are key determinants of host-parasite associations and that consideration of multiple aspects of parasite load is required to fully understand patterns in parasitism.

  16. A Japanese view on speciation: "Sumiwake" explosive speciation of the cichlids in Lake Victoria.

    PubMed

    Kawamiya, Nobuo

    2003-01-01

    Imanishi's "mental" (cerebral) view of speciation is presented, in Mizuhata's revision. The key concept here is the "ethological partition" of the species. Members of each species=society (etho-species) share the same mental (brain) software, irrespective of their genetic structure. Cerebral animals perform active programmed selection, not to be confused with passive, non-programmed "natural selection" as in Neo-Darwinism. The program includes mating-choice of peculiar characters, distinct from the Neo-Darwinian sexual selection supposed due to the specific choosy genes. Speciation can occur, as a "partition of species=society", with bifurcation of mate-choosing program in the parent species. A main promoter for this bifurcation is species-specific "passion" for especially significant characters: long necks, ornamental antlers, ocelli feathers, bright nuptial colors etc. The cichlids in Lake Victoria achieved explosive speciation, while retaining their genetic homogeneity completely. Therefore it is illogical to attribute this divergence to extraordinary mutations in "action controlling genes". The origin of species=society (etho-species) can trace along to the Cambrian Period.

  17. Eco-morphological differentiation in Lake Magadi tilapia, an extremophile cichlid fish living in hot, alkaline and hypersaline lakes in East Africa.

    PubMed

    Kavembe, Geraldine D; Kautt, Andreas F; Machado-Schiaffino, Gonzalo; Meyer, Axel

    2016-04-01

    Ecological diversification through divergent selection is thought to be a major force during the process of adaptive radiations. However, the large sizes and complexity of most radiations such as those of the cichlids in the African Great Lakes make it impossible to infer the exact evolutionary history of any population divergence event. The genus Alcolapia, a small cichlid lineage endemic to Lakes Magadi and Natron in East Africa, exhibits phenotypes similar to some of those found in cichlids of the radiations of the African Great Lakes. The simplicity within Alcolapia makes it an excellent model system to investigate ecological diversification and speciation. We used an integrated approach including population genomics based on RAD-seq data, geometric morphometrics and stable isotope analyses to investigate the eco-morphological diversification of tilapia in Lake Magadi and its satellite lake Little Magadi. Additionally, we reconstructed the demographic history of the species using coalescent simulations based on the joint site frequency spectrum. The population in Little Magadi has a characteristically upturned mouth--possibly an adaptation to feeding on prey from the water surface. Eco-morphological differences between populations within Lake Magadi are more subtle, but are consistent with known ecological differences between its lagoons such as high concentrations of nitrogen attributable to extensive guano deposits in Rest of Magadi relative to Fish Springs Lagoon. All populations diverged simultaneously only about 1100 generations ago. Differences in levels of gene flow between populations and the effective population sizes have likely resulted in the inferred heterogeneous patterns of genome-wide differentiation.

  18. Potential Biases in TEX86-Reconstructed Temperatures from Lake Malawi, Africa

    NASA Astrophysics Data System (ADS)

    Kumar, D.; Woltering, M.; Halbur, J.; Schouten, S.; S Sinninghe Damsté, J.; Muñoz-Ucros, J.; Randall, H.; Werne, J. P.

    2016-12-01

    Several plausible paleoclimate reconstructions have been produced from Lake Malawi sedimentary records using the isoGDGT-based paleotemperature proxy TEX86. Current interpretations of these records assume that the distribution of sedimentary isoGDGTs reflects mean annual lake surface temperatures (LST). In lacustrine environments, however, there are a number of factors in addition to LST that may also contribute to variability in TEX86 values (e.g. subsurface temperatures, seasonal bias, etc.). Proper interpretation of TEX86-based temperature records thus requires a thorough understanding of isoGDGT production in the modern water column of Lake Malawi. This study utilized a combination of lipid and genomic analyses to understand the ecology of isoGDGT-producers and to characterize the timing of isoGDGT production in Lake Malawi. Profiles of POM collected from the northern, central, and southern basins provide a snapshot of where isoGDGT-producers reside in the lake's water column and how much they contribute to overall GDGT production. To test for seasonal biases in the proxy, a multi-year time series of isoGDGT production was generated with settling particulate matter (SPM) collected in sediment traps placed in the northern and southern basin. Results of the POM analyses indicate that there are two distinct archaeal communities that produce isoGDGTs in the water column, though maximum GDGT production occurs just below the thermocline. There are two dominant periods of isoGDGT production in the lake: Jan-Apr and Jun-Sept. Despite this, TEX86-reconstructed temperatures from sediment trap samples appear to be biased towards surface water summer temperatures. This bias seems only to have developed over the last couple decades, however, as a comparison of measured lake water temperatures from 1940-2000 and TEX86 temperatures reveals that prior to 1990 TEX86 temperatures closely matched mean annual temperature of the upper 50 m of the water column.

  19. The fish eye view: are cichlids conspicuous?

    PubMed

    Dalton, Brian E; Cronin, Thomas W; Marshall, N Justin; Carleton, Karen L

    2010-07-01

    The extent of animal colouration is determined by an interplay between natural and sexual selection. Both forces probably shape colouration in the speciose, rock-dwelling cichlids of Lake Malawi. Sexual selection is thought to drive male colouration, overcoming natural selection to create conspicuous colour patterns via female mate choice and male-male competition. However, natural selection should make female cichlids cryptic because they mouthbrood their young. We hypothesize that as a result of both sexual and natural selection, males will have colours that are more conspicuous than female colours. Cichlid spectral sensitivity, especially in the ultraviolet, probably influences how colours appear to them. Here we use simple models of the trichromatic colour space of cichlid visual systems to compare the conspicuousness of male and female nuptial colours of nine species. Conspicuousness of colours was evaluated as their Euclidian distance in colour space from environmental backgrounds and from other colours on the same fish. We find in six of the nine species that breeding males have colours that are statistically more conspicuous than female colours. These colours contrast strongly with each other or with the backgrounds, and they fall within a range of spectra best transmitted in the habitat. Female colour distances were sometimes smaller, suggesting that females of some species are more cryptic than males. Therefore, selection can differentially act to generate male colours that are more conspicuous than those in females. However, in two species, females had colours that were more conspicuous than male colours, suggesting that other selective forces and possibly sexual conflicts are acting in this system.

  20. Phylogenetic relationships of the Lake Tanganyika cichlid tribe Lamprologini: the story from mitochondrial DNA.

    PubMed

    Day, Julia J; Santini, Simona; Garcia-Moreno, Jaime

    2007-11-01

    The Lamprologini are the most species-rich and diverse tribe of Lake Tanganyika cichlids, comprising around 90 described species. We reconstruct the most complete ( approximately 70 species) mtDNA phylogeny to date for this tribe, based on NADH dehydrogenase subunit 2 (ND2 approximately 1047 bp) and the non-coding control region ( approximately 874 bp) and examine the degree to which mtDNA trees are good proxies for species trees. Phylogenetic relationships are assessed using Bayesian inference, maximum likelihood and maximum parsimony to determine the robustness of relationships. The resulting topologies are largely congruent and only the tree produced by an unpartitioned BI analysis is rejected using the non-parametric likelihood-based AU test. The trees are remarkably balanced, with two major clades consistently recovered in all analyses and with reasonable support. A smaller clade of deep-water species is also recovered. Overall support is good, when compared to some groups that have undergone adaptive radiation and rapid lineage formation. The much-expanded phylogeny of the group helps resolve the placement of some previously problematic taxa, such as Neolamprologus moori, highlighting the importance of greater taxonomic sampling. The results include a number of divergent placements of closely related species, and the following genera Neolamprologus, Lamprologus, Julidiochromis, Telmatochromis are not monophyletic, with alternative hypotheses consistent with traditional taxonomy providing a significantly worse fit to the data. We find several examples of divergent mtDNA taxa sequences of presumed closely related species. This could be due to incorrect taxonomy or to the failure of the mtDNA to reflect species relationships and may support the hypothesis that speciation within this group has been facilitated by introgressive hybridisation.

  1. Developmental effects of visual environment on species-assortative mating preferences in Lake Victoria cichlid fish.

    PubMed

    Wright, D S; Demandt, N; Alkema, J T; Seehausen, O; Groothuis, T G G; Maan, M E

    2017-02-01

    Local adaptation can be a potent force in speciation, with environmental heterogeneity leading to niche specialization and population divergence. However, local adaption often requires nonrandom mating to generate reproductive isolation. Population divergence in sensory properties can be particularly consequential in speciation, affecting both ecological adaptation and sexual communication. Pundamilia pundamila and Pundamilia nyererei are two closely related African cichlid species that differ in male coloration, blue vs. red. They co-occur at rocky islands in southern Lake Victoria, but inhabit different depth ranges with different light environments. The species differ in colour vision properties, and females exert species-specific preferences for blue vs. red males. Here, we investigated the mechanistic link between colour vision and preference, which could provide a rapid route to reproductive isolation. We tested the behavioural components of this link by experimentally manipulating colour perception - we raised both species and their hybrids under light conditions mimicking shallow and deep habitats - and tested female preference for blue and red males under both conditions. We found that rearing light significantly affected female preference: shallow-reared females responded more strongly to P. pundamilia males and deep-reared females favoured P. nyererei males - implying that visual development causally affects mate choice. These results are consistent with sensory drive predictions, suggesting that the visual environment is key to behavioural isolation of these species. However, the observed plasticity could also make the species barrier vulnerable to environmental change: species-assortative preferences were weaker in females that were reared in the other species' light condition.

  2. A ~1.3Ma paleoecological record from scientific drilling at Lake Malawi, East Africa

    NASA Astrophysics Data System (ADS)

    Cohen, Andrew S.; Blome, Margaret; Ivory, Sarah; King, John; Cole, Julie; McGlue, Michael

    2016-04-01

    Long records of Quaternary ecological and climatic change are critical to understanding the range of potential responses of ecosystems to environmental forcing. Here we present an integrated lake and watershed paleoecological analysis from drill core records obtained by the Lake Malawi Drilling Project, documenting extraordinary fluctuations in climate, hydrology and ecosystem response for the southern tropics of Africa. High resolution lacustrine and terrestrial paleoecology and sedimentology data sets from these Early Pleistocene-Holocene drill cores provide the most complete record of this duration currently available from Africa. Time series analyses of these records demonstrate strong orbital forcing of regional hydroclimate that drives high-amplitude changes in Malawi ecosystems. Prior to ~600ka we also observe a secondary overprint of watershed processes involving river capture or diversion that may have a tectonic origin. We observe shifts between more arid conditions (shallow alkaline and well mixed lake, with discontinuous desert vegetation) and more humid environments (deep, stratified, freshwater lake with dense forest). These broadly synchronous changes in lake paleoecology, lake sedimentology, and watershed vegetation demonstrate the major role of climate in regulating this system. Transitions between these lake/watershed state extremes is often very abrupt, suggesting that the combined lake/watershed repeatedly passed through hydroclimate thresholds, with important implications for the evolution of the lake's endemic biodiversity and ecosystem. The tempo of lake/watershed state fluctuations changes at the Mid-Pleistocene Transition, altering from one of higher frequency/lower amplitude variability prior to 900ka to lower frequency/higher amplitude variability after that time.

  3. Genetic and developmental basis for fin shape variation in African cichlid fishes.

    PubMed

    Navon, Dina; Olearczyk, Nathan; Albertson, R Craig

    2017-01-01

    Adaptive radiations are often characterized by the rapid evolution of traits associated with divergent feeding modes. For example, the evolutionary history of African cichlids is marked by repeated and coordinated shifts in skull, trophic, fin and body shape. Here, we seek to explore the molecular basis for fin shape variation in Lake Malawi cichlids. We first described variation within an F2 mapping population derived by crossing two cichlid species with divergent morphologies including fin shape. We then used this population to genetically map loci that influence variation in this trait. We found that the genotype-phenotype map for fin shape is largely distinct from other morphological characters including body and craniofacial shape. These data suggest that key aspects of fin, body and jaw shape are genetically modular and that the coordinated evolution of these traits in cichlids is more likely due to common selective pressures than to pleiotropy or linkage. We next combined genetic mapping data with population-level genome scans to identify wnt7aa and col1a1 as candidate genes underlying variation in the number of pectoral fin ray elements. Gene expression patterns across species with different fin morphologies and small molecule manipulation of the Wnt pathway during fin development further support the hypothesis that variation at these loci underlies divergence in fin shape between cichlid species. In all, our data provide additional insights into the genetic and molecular mechanisms associated with morphological divergence in this important adaptive radiation.

  4. Genetic architecture sets limits on transgressive segregation in hybrid cichlid fishes.

    PubMed

    Albertson, R Craig; Kocher, Thomas D

    2005-03-01

    The role of hybridization in the evolution of animal species is poorly understood. Transgressive segregation is a mechanism through which hybridization can generate diversity and ultimately lead to speciation. In this report we investigated the capacity of hybridization to generate novel (transgressive) phenotypes in the taxonomically diverse cichlid fishes. We generated a large F2 hybrid population by crossing two closely related cichlid species from Lake Malawi in Africa with differently shaped heads. Our morphometric analysis focused on two traits with different selective histories. The cichlid lower jaw (mandible) has evolved in response to strong directional selection, and does not segregate beyond the parental phenotype. The cichlid neurocranium (skull) has likely diverged in response to forces other than consistent directional selection (e.g., stabilizing selection), and exhibits marked transgressive segregation in our F2 population. We show that the genetic architecture of the cichlid jaw limits transgression, whereas the genetic basis of skull shape is permissive of transgressive segregation. These data suggest that natural selection, acting through the genome, will limit the degree of diversity that may be achieved via hybridization. Results are discussed in the context of the broader question of how phenotypic diversity may be achieved in rapidly evolving systems.

  5. Patterns in fish radiation are compatible with Pleistocene desiccation of Lake Victoria and 14,600 year history for its cichlid species flock.

    PubMed Central

    Seehausen, Ole

    2002-01-01

    Geophysical data are currently being interpreted as evidence for a late Pleistocene desiccation of Lake Victoria and its refilling 14,600 years ago. This implies that between 500 and 1000 endemic cichlid fish species must have evolved in 14,600 years, the fastest large-scale species radiation known. A recent review concludes that biological evidence clearly rejects the postulated Pleistocene desiccation of the lake: a 14,600 year history would imply exceptionally high speciation rates across a range of unrelated fish taxa. To test this suggestion, I calculated speciation rates for all 41 phylogenetic lineages of fish in the lake. Except for one cichlid lineage, accepting a 14 600 year history does not require any speciation rates that fall outside the range observed in fishes in other young lakes around the world. The exceptional taxon is a lineage of haplochromine cichlids that is also known for its rapid speciation elsewhere. Moreover, since it is unknown how many founding species it has, it is not certain that its speciation rates are really outside the range observed in fishes in other young lakes. Fish speciation rates are generally faster in younger than in older lakes, and those in Lake Victoria, by far the largest of the young lakes of the world, are no exception. From the speciation rates and from biogeographical observations that Lake Victoria endemics, which lack close relatives within the lake basin, have such relatives in adjacent drainage systems that may have had Holocene connections to Lake Victoria, I conclude that the composition of the fish assemblage does not provide biological evidence against Pleistocene desiccation. It supports a hypothesis of recent colonization from outside the lake basin rather than survival of a diverse assemblage within the basin. PMID:11886641

  6. Altering an extended phenotype reduces intraspecific male aggression and can maintain diversity in cichlid fish

    PubMed Central

    Croft, Guy E.; Joyce, Domino A.

    2013-01-01

    Reduced male aggression towards different phenotypes generating negative frequency-dependent intrasexual selection has been suggested as a mechanism to facilitate the invasion and maintenance of novel phenotypes in a population. To date, the best empirical evidence for the phenomenon has been provided by laboratory studies on cichlid fish with different colour polymorphisms. Here we experimentally tested the hypothesis in a natural population of Lake Malawi cichlid fish, in which males build sand-castles (bowers) to attract females during seasonal leks. We predicted that if bower shape plays an important role in male aggressive interactions, aggression among conspecific males should decrease when their bower shape is altered. Accordingly, we allocated randomly chosen bowers in a Nyassachromis cf. microcephalus lek into three treatments: control, manipulated to a different shape, and simulated manipulation. We then measured male behaviours and bower shape before and after these treatments. We found that once bower shape was altered, males were involved in significantly fewer aggressive interactions with conspecific males than before manipulation. Mating success was not affected. Our results support the idea that an extended phenotype, such as bower shape, can be important in maintaining polymorphic populations. Specifically, reduced male conspecific aggression towards males with different extended phenotypes (here, bower shapes) may cause negative frequency-dependent selection, allowing the invasion and establishment of a new phenotype (bower builder). This could help our understanding of mechanisms of diversification within populations, and in particular, the overall diversification of bower shapes within Lake Malawi cichlids. PMID:24349896

  7. Repeated parallel evolution of parental care strategies within Xenotilapia, a genus of cichlid fishes from Lake Tanganyika.

    PubMed

    Kidd, Michael R; Duftner, Nina; Koblmüller, Stephan; Sturmbauer, Christian; Hofmann, Hans A

    2012-01-01

    The factors promoting the evolution of parental care strategies have been extensively studied in experiment and theory. However, most attempts to examine parental care in an evolutionary context have evaluated broad taxonomic categories. The explosive and recent diversifications of East African cichlid fishes offer exceptional opportunities to study the evolution of various life history traits based on species-level phylogenies. The Xenotilapia lineage within the endemic Lake Tanganyika cichlid tribe Ectodini comprises species that display either biparental or maternal only brood care and hence offers a unique opportunity to study the evolution of distinct parental care strategies in a phylogenetic framework. In order to reconstruct the evolutionary relationships among 16 species of this lineage we scored 2,478 Amplified Fragment Length Polymorphisms (AFLPs) across the genome. We find that the Ectodini genus Enantiopus is embedded within the genus Xenotilapia and that during 2.5 to 3 million years of evolution within the Xenotilapia clade there have been 3-5 transitions from maternal only to biparental care. While most previous models suggest that uniparental care (maternal or paternal) arose from biparental care, we conclude from our species-level analysis that the evolution of parental care strategies is not only remarkably fast, but much more labile than previously expected.

  8. Repeated Parallel Evolution of Parental Care Strategies within Xenotilapia, a Genus of Cichlid Fishes from Lake Tanganyika

    PubMed Central

    Kidd, Michael R.; Duftner, Nina; Koblmüller, Stephan; Sturmbauer, Christian; Hofmann, Hans A.

    2012-01-01

    The factors promoting the evolution of parental care strategies have been extensively studied in experiment and theory. However, most attempts to examine parental care in an evolutionary context have evaluated broad taxonomic categories. The explosive and recent diversifications of East African cichlid fishes offer exceptional opportunities to study the evolution of various life history traits based on species-level phylogenies. The Xenotilapia lineage within the endemic Lake Tanganyika cichlid tribe Ectodini comprises species that display either biparental or maternal only brood care and hence offers a unique opportunity to study the evolution of distinct parental care strategies in a phylogenetic framework. In order to reconstruct the evolutionary relationships among 16 species of this lineage we scored 2,478 Amplified Fragment Length Polymorphisms (AFLPs) across the genome. We find that the Ectodini genus Enantiopus is embedded within the genus Xenotilapia and that during 2.5 to 3 million years of evolution within the Xenotilapia clade there have been 3–5 transitions from maternal only to biparental care. While most previous models suggest that uniparental care (maternal or paternal) arose from biparental care, we conclude from our species-level analysis that the evolution of parental care strategies is not only remarkably fast, but much more labile than previously expected. PMID:22347454

  9. Complex histories of repeated gene flow in Cameroon crater lake cichlids cast doubt on one of the clearest examples of sympatric speciation.

    PubMed

    Martin, Christopher H; Cutler, Joseph S; Friel, John P; Dening Touokong, Cyrille; Coop, Graham; Wainwright, Peter C

    2015-06-01

    One of the most celebrated examples of sympatric speciation in nature are monophyletic radiations of cichlid fishes endemic to Cameroon crater lakes. However, phylogenetic inference of monophyly may not detect complex colonization histories involving some allopatric isolation, such as double invasions obscured by genome-wide gene flow. Population genomic approaches are better suited to test hypotheses of sympatric speciation in these cases. Here, we use comprehensive sampling from all four sympatric crater lake cichlid radiations in Cameroon and outgroups across Africa combined with next-generation sequencing to genotype tens of thousands of SNPs. We find considerable evidence of gene flow between all four radiations and neighboring riverine populations after initial colonization. In a few cases, some sympatric species are more closely related to outgroups than others, consistent with secondary gene flow facilitating their speciation. Our results do not rule out sympatric speciation in Cameroon cichlids, but rather reveal a complex history of speciation with gene flow, including allopatric and sympatric phases, resulting in both reproductively isolated species and incipient species complexes. The best remaining non-cichlid examples of sympatric speciation all involve assortative mating within microhabitats. We speculate that this feature may be necessary to complete the process of sympatric speciation in nature.

  10. Genome-wide RAD sequence data provide unprecedented resolution of species boundaries and relationships in the Lake Victoria cichlid adaptive radiation.

    PubMed

    Wagner, Catherine E; Keller, Irene; Wittwer, Samuel; Selz, Oliver M; Mwaiko, Salome; Greuter, Lucie; Sivasundar, Arjun; Seehausen, Ole

    2013-02-01

    Although population genomic studies using next generation sequencing (NGS) data are becoming increasingly common, studies focusing on phylogenetic inference using these data are in their infancy. Here, we use NGS data generated from reduced representation genomic libraries of restriction-site-associated DNA (RAD) markers to infer phylogenetic relationships among 16 species of cichlid fishes from a single rocky island community within Lake Victoria's cichlid adaptive radiation. Previous attempts at sequence-based phylogenetic analyses in Victoria cichlids have shown extensive sharing of genetic variation among species and no resolution of species or higher-level relationships. These patterns have generally been attributed to the very recent origin (<15,000 years) of the radiation, and ongoing hybridization between species. We show that as we increase the amount of sequence data used in phylogenetic analyses, we produce phylogenetic trees with unprecedented resolution for this group. In trees derived from our largest data supermatrices (3 to >5.8 million base pairs in width), species are reciprocally monophyletic with high bootstrap support, and the majority of internal branches on the tree have high support. Given the difficulty of the phylogenetic problem that the Lake Victoria cichlid adaptive radiation represents, these results are striking. The strict interpretation of the topologies we present here warrants caution because many questions remain about phylogenetic inference with very large genomic data set and because we can with the current analysis not distinguish between effects of shared ancestry and post-speciation gene flow. However, these results provide the first conclusive evidence for the monophyly of species in the Lake Victoria cichlid radiation and demonstrate the power that NGS data sets hold to resolve even the most difficult of phylogenetic challenges. © 2012 Blackwell Publishing Ltd.

  11. Low Genetic and Morphometric Intraspecific Divergence in Peripheral Copadichromis Populations (Perciformes: Cichlidae) in the Lake Malawi Basin

    PubMed Central

    Anseeuw, Dieter; Raeymaekers, Joost A. M.; Busselen, Paul; Verheyen, Erik; Snoeks, Jos

    2011-01-01

    Peripheral isolated populations may undergo rapid divergence from the main population due to various factors such as a bottleneck or a founder effect followed by genetic drift or local selection pressures. Recent populations of two economically important Copadichromis species in Lake Malombe, a satellite lake of Lake Malawi, were neither genetically nor morphometrically distinct from their source populations in the main lake. Evidence was found for a founder effect which had a different impact on the genetic composition of the two species. In addition, the increased fishing pressure in Lake Malombe may have led to a reduction of the body sizes of both species. PMID:21716858

  12. Evolutionary relationships of the limnochromini, a tribe of benthic deepwater cichlid fish endemic to Lake Tanganyika, East Africa.

    PubMed

    Duftner, Nina; Koblmüller, Stephan; Sturmbauer, Christian

    2005-03-01

    Lake Tanganyika harbors an enormous diversity of cichlid fish that stem from eight distinct ancestral lineages, which colonized the lake after its formation 9 to 12 million years ago. Six of twelve currently described tribes are assigned to the "H-lineage," an assemblage of exclusively mouthbrood-ing cichlids, all of which evolved during a short period of time during the course of the primary radiation of lacustrine species. Our study focuses on the deepwater tribe Limnochromini, comprising bi-parental mouthbrooders, and is based on phylogenetic analysis of two mitochondrial gene segments. We confirm the polyphyletic origin of the Limnochromini as they are defined to date, in that Gnathochromis pfefferi is placed among the Tropheini, whereas the genus Benthochromis is presented as an independent lineage. The remaining nine species were unambiguously resolved as monophyletic and should be redefined as the tribe Limnochromini. Concerning generic assignments, the genus Greenwoodochromis appeared as monophyletic, Limnochromis as paraphyletic, and the genera Reganochromis and Baileychromis as monophyletic sister genera. The linearized tree analysis and the comparison of average sequence divergences to that of the remaining tribes of the H-lineage revealed a relatively recent but simultaneous proliferation of the Limnochromini, suggesting that the same environmental changes triggered the radiation of particular deepwater, benthic, pelagic, and littoral lineages. By using a preliminary calibration of a molecular clock based on gamma-corrected amino acid distances of the NADH2 gene, the diversification of the Limnochromini could tentatively be dated to 2.9-3.5 MYA, coinciding with a period of aridification in East Africa between 2.5 and 3 MYA. The lack of geographic color morphs and the structural uniformity and resource scarcity of deepwater habitats suggest that competition and resource partitioning leading to differential trophic specialization promoted speciation

  13. Management implications of the response of two tilapiine cichlids to long-term changes in lake level, allodiversity and exploitation in an equatorial lake.

    PubMed

    Oyugi, Dalmas Oyugi; Harper, David Matthew; Ntiba, Japheth Michemi; Kisia, Seth Marande; Britton, John Robert

    2011-07-01

    The tilapiine cichlids Oreochromis leucostictus and Tilapia zillii were introduced into Lake Naivasha, Kenya, in 1956. Previous studies on data collected to 1987 revealed they were persistent following establishment, despite environmental variability and exploitation. Recent data, however, suggest this persistence is under threat as data indicate some significant declines in aspects of their abundance since 1999. The influence of changes in lake level, allodiversity and fishing effort on this decline was tested and showed that a decline in lake level was a significant causal factor. The recent change in allodiversity, with the establishment and dominance of Cyprinus carpio in the fishery, was not significant on the catch per unit effort of O. leucostictus but was on T. zillii. Since 1999, catches of tilapiines in the fishery have been independent of fishing effort, contrary to between 1975 and 1987, suggesting their management through application of fishery models may no longer be applicable. As it was anthropogenic-mediated lake level changes that were mainly responsible for their decline, then lake management should focus on sustainable water utilization that maximizes lake levels in accordance with the basin-wide water balance.

  14. Active-source seismic imaging below Lake Malawi (Nyasa) from the SEGMeNT project

    NASA Astrophysics Data System (ADS)

    Shillington, D. J.; Scholz, C. A.; Gaherty, J. B.; Accardo, N. J.; McCartney, T.; Chindandali, P. R. N.; Kamihanda, G.; Trinhammer, P.; Wood, D. A.; Khalfan, M.; Ebinger, C. J.; Nyblade, A.; Mbogoni, G. J.; Mruma, A. H.; Salima, J.; Ferdinand-Wambura, R.

    2015-12-01

    Little is known about the controls on the initiation and development of magmatism and segmentation in young rift systems. The northern Lake Malawi (Nyasa) rift in the East African Rift System is an early stage rift exhibiting pronounced tectonic segmentation, which is defined in the upper crust by ~100-km-long border faults. Very little volcanism is associated with rifting; the only surface expression of magmatism occurs in an accommodation zone between segments to the north of the lake in the Rungwe Volcanic Province. The SEGMeNT (Study of Extension and maGmatism in Malawi aNd Tanzania) project is a multidisciplinary, multinational study that is acquiring a suite of geophysical, geological and geochemical data to characterize deformation and magmatism in the crust and mantle lithosphere along 2-3 segments of this rift. As a part of the SEGMeNT project, we acquired seismic reflection and refraction data in Lake Malawi (Nyasa) in March-April 2015. Over 2000 km of seismic reflection data were acquired with a 500 to 2580 cu in air gun array from GEUS/Aarhus and a 500- to 1500-m-long seismic streamer from Syracuse University over a grid of lines across and along the northern and central basins. Air gun shots from MCS profiles and 1000 km of additional shooting with large shot intervals were also recorded on 27 short-period and 6 broadband lake bottom seismometers from Scripps Oceanographic Institute as a part of the Ocean Bottom Seismic Instrument Pool (OBSIP) as well as the 55-station onshore seismic array. The OBS were deployed along one long strike line and two dip lines. We will present preliminary data and results from seismic reflection and refraction data acquired in the lake and their implications for crustal deformation within and between rift segments. Seismic reflection data image structures up to ~5-6 km below the lake bottom, including syntectonic sediments, intrabasinal faults and other complex horsts. Some intrabasinal faults in both the northern and

  15. A new cichlid fish in the Sahara: The Ounianga Serir lakes (Chad), a biodiversity hotspot in the desert.

    PubMed

    Trape, Sébastien

    In the rare perennial bodies of water of the Sahara desert, only a few fish species have survived to increasing aridification since the end of the last humid period at the Holocene, approximately 5000 years BP. Here, I report the occurrence of an undescribed haplochomine cichlid fish in Lake Boukou, one of the seven Ounianga Serir lakes (Chad). These lakes are located in one of the most arid areas of the Sahara desert, but they persist by virtue of subsurface inflow of fresh groundwater from a large fossil aquifer. Astatotilapia tchadensis sp. nov. is characterized by a black bar between eye and corner of mouth, rounded orange spots on anal fin, scales ctenoid, lower limb of first gill arch with 7-8 gill rackers, dorsal fin with 13-14 spines and 9-11 soft rays, anal fin with 3 spines and 8-9 soft rays, 29 or 30 lateral line scales, and lower pharyngeal dentition with enlarged molariform teeth. The new species is easily distinguished from A. desfontainii and A. flaviijosephii, the northernmost haplochromine species currently isolated from its other group members, and appears close to an unnamed species of Lake Chad basin. Ounianga Serir lakes and especially Lake Boukou present a remarkable diversity of fish, the highest known in the Sahara desert with a total of at least six fish species belonging to six genera and three families. They also constitute an exceptional natural landscape inscribed on the UNESCO world heritage list in 2012 and a biodiversity hotspot for desert vertebrate species.

  16. Out of Tanganyika: Genesis, explosive speciation, key-innovations and phylogeography of the haplochromine cichlid fishes

    PubMed Central

    Salzburger, Walter; Mack, Tanja; Verheyen, Erik; Meyer, Axel

    2005-01-01

    Background The adaptive radiations of cichlid fishes in East Africa are well known for their spectacular diversity and their astonishingly fast rates of speciation. About 80% of all 2,500 cichlid species in East Africa, and virtually all cichlid species from Lakes Victoria (~500 species) and Malawi (~1,000 species) are haplochromines. Here, we present the most extensive phylogenetic and phylogeographic analysis so far that includes about 100 species and is based on about 2,000 bp of the mitochondrial DNA. Results Our analyses revealed that all haplochromine lineages are ultimately derived from Lake Tanganyika endemics. We find that the three most ancestral lineages of the haplochromines sensu lato are relatively species poor, albeit widely distributed in Africa, whereas a fourth newly defined lineage – the 'modern haplochromines' – contains an unparalleled diversity that makes up more than 7% of the worlds' ~25,000 teleost species. The modern haplochromines' ancestor, most likely a riverine generalist, repeatedly gave rise to similar ecomorphs now found in several of the species flocks. Also, the Tanganyikan Tropheini are derived from that riverine ancestor suggesting that they successfully re-colonized Lake Tanganyika and speciated in parallel to an already established cichlid adaptive radiation. In contrast to most other known examples of adaptive radiations, these generalist ancestors were derived from highly diverse and specialized endemics from Lake Tanganyika. A reconstruction of life-history traits revealed that in an ancestral lineage leading to the modern haplochromines the characteristic egg-spots on anal fins of male individuals evolved. Conclusion We conclude that Lake Tanganyika is the geographic and genetic cradle of all haplochromine lineages. In the ancestors of the replicate adaptive radiations of the 'modern haplochromines', behavioral (maternal mouthbrooding), morphological (egg-spots) and sexually selected (color polymorphism) key

  17. Population genomic signatures of divergent adaptation, gene flow and hybrid speciation in the rapid radiation of Lake Victoria cichlid fishes.

    PubMed

    Keller, I; Wagner, C E; Greuter, L; Mwaiko, S; Selz, O M; Sivasundar, A; Wittwer, S; Seehausen, O

    2013-06-01

    Adaptive radiations are an important source of biodiversity and are often characterized by many speciation events in very short succession. It has been proposed that the high speciation rates in these radiations may be fuelled by novel genetic combinations produced in episodes of hybridization among the young species. The role of such hybridization events in the evolutionary history of a group can be investigated by comparing the genealogical relationships inferred from different subsets of loci, but such studies have thus far often been hampered by shallow genetic divergences, especially in young adaptive radiations, and the lack of genome-scale molecular data. Here, we use a genome-wide sampling of SNPs identified within restriction site-associated DNA (RAD) tags to investigate the genomic consistency of patterns of shared ancestry and adaptive divergence among five sympatric cichlid species of two genera, Pundamilia and Mbipia, which form part of the massive adaptive radiation of cichlids in the East African Lake Victoria. Species pairs differ along several axes: male nuptial colouration, feeding ecology, depth distribution, as well as the morphological traits that distinguish the two genera and more subtle morphological differences. Using outlier scan approaches, we identify signals of divergent selection between all species pairs with a number of loci showing parallel patterns in replicated contrasts either between genera or between male colour types. We then create SNP subsets that we expect to be characterized to different extents by selection history and neutral processes and describe phylogenetic and population genetic patterns across these subsets. These analyses reveal very different evolutionary histories for different regions of the genome. To explain these results, we propose at least two intergeneric hybridization events (between Mbipia spp. and Pundamilia spp.) in the evolutionary history of these five species that would have lead to the evolution

  18. Weak disruptive selection and incomplete phenotypic divergence in two classic examples of sympatric speciation: cameroon crater lake cichlids.

    PubMed

    Martin, Christopher H

    2012-10-01

    Recent documentation of a few compelling examples of sympatric speciation led to a proliferation of theoretical models. Unfortunately, plausible examples from nature have rarely been used to test model predictions, such as the initial presence of strong disruptive selection. Here I estimated the form and strength of selection in two classic examples of sympatric speciation: radiations of Cameroon cichlids restricted to Lakes Barombi Mbo and Ejagham. I measured five functional traits and relative growth rates in over 500 individuals within incipient species complexes from each lake. Disruptive selection was prevalent in both groups on single and multivariate trait axes but weak relative to stabilizing selection on other traits and most published estimates of disruptive selection. Furthermore, despite genetic structure, assortative mating, and bimodal species-diagnostic coloration, trait distributions were unimodal in both species complexes, indicating the earliest stages of speciation. Long waiting times or incomplete sympatric speciation may result when disruptive selection is initially weak. Alternatively, I present evidence of additional constraints in both species complexes, including weak linkage between coloration and morphology, reduced morphological variance aligned with nonlinear selection surfaces, and minimal ecological divergence. While other species within these radiations show complete phenotypic separation, morphological and ecological divergence in these species complexes may be slow or incomplete outside optimal parameter ranges, in contrast to rapid divergence of their sexual coloration.

  19. Modularity of the Oral Jaws Is Linked to Repeated Changes in the Craniofacial Shape of African Cichlids

    PubMed Central

    Parsons, Kevin J.; Cooper, W. James; Albertson, R. Craig

    2011-01-01

    The African cichlids of the East-African rift-lakes provide one of the most dramatic examples of adaptive radiation known. It has long been thought that functional decoupling of the oral and pharyngeal jaws in cichlids has facilitated their explosive evolution. Recent research has also shown that craniofacial evolution from radiations in lakes Victoria, Malawi, and Tanganyika has occurred along a shared primary axis of shape divergence, whereby the preorbital region of the skull changes in a manner that is, relatively independent from other head regions. We predicted that the preorbital region would comprise a variational module and used an extensive dataset from each lake that allowed us to test this prediction using a model selection approach. Our findings supported the presence of a preorbital module across all lakes, within each lake, and for Malawi, within sand and rock-dwelling clades. However, while a preorbital module was consistently present, notable differences were also observed among groups. Of particular interest, a negative association between patterns of variational modularity was observed between the sand and rock-dwelling clades, a patter consistent with character displacement. These findings provide the basis for further experimental research involving the determination of the developmental and genetic bases of these patterns of modularity. PMID:21716745

  20. Genomic signatures of divergent selection and speciation patterns in a 'natural experiment', the young parallel radiations of Nicaraguan crater lake cichlid fishes.

    PubMed

    Kautt, Andreas F; Elmer, Kathryn R; Meyer, Axel

    2012-10-01

    Divergent selection is the main driving force in sympatric ecological speciation and may also play a strong role in divergence between allopatric populations. Characterizing the genome-wide impact of divergent selection often constitutes a first step in unravelling the genetic bases underlying adaptation and ecological speciation. The Midas cichlid fish (Amphilophus citrinellus) species complex in Nicaragua is a powerful system for studying evolutionary processes. Independent colonizations of isolated young crater lakes by Midas cichlid populations from the older and great lakes of Nicaragua resulted in the repeated evolution of adaptive radiations by intralacustrine sympatric speciation. In this study we performed genome scans on two repeated radiations of crater lake species and their great lake source populations (1030 polymorphic AFLPs, n ∼ 30 individuals per species). We detected regions under divergent selection (0.3% in the crater lake Xiloá flock and 1.7% in the older crater lake Apoyo radiation) that might be responsible for the sympatric diversifications. We find no evidence that the same genomic regions have been involved in the repeated evolution of parallel adaptations across crater lake flocks. However, there is some genetic parallelism apparent (seven out of 51 crater lake to great lake outlier loci are shared; 13.7%) that is associated with the allopatric divergence of both crater lake flocks. Interestingly, our results suggest that the number of outlier loci involved in sympatric and allopatric divergence increases over time. A phylogeny based on the AFLP data clearly supports the monophyly of both crater lake species flocks and indicates a parallel branching order with a primary split along the limnetic-benthic axis in both radiations. © 2012 Blackwell Publishing Ltd.

  1. The cusp of evolution and development: a model of cichlid tooth shape diversity.

    PubMed

    Streelman, J T; Webb, J F; Albertson, R C; Kocher, T D

    2003-01-01

    Tooth shape is a hallmark of repeated evolutionary radiations among cichlid fishes from East Africa. Cusp shape and number vary both within populations and among closely related species with different feeding behaviors and ecologies. Here, we use histology and scanning electron microscopy to chart the developmental trajectory of tooth shape differences in fishes from Lake Malawi. We demonstrate that species with bi- or tricuspid adult (replacement) teeth initially possess a first-generation unicuspid dentition. Notably, the timing of turnover from first-generation to replacement teeth differs among species and is correlated with feeding ecology. Next, we use field data for cichlid species with adult unicuspid, bicuspid, and tricuspid teeth to demonstrate a strong and positive relationship between the number of teeth in a row and tooth shape. We discuss cichlid tooth ontogeny in the context of morphogenetic models designed to explain the developmental basis of tooth shape variation in mammals. We suggest that the dramatic differences in cichlid dentitions can be explained by variation in the expression of common activators and inhibitors acting at multiple stages of odontogenesis.

  2. Lateralized kinematics of predation behavior in a Lake Tanganyika scale-eating cichlid fish.

    PubMed

    Takeuchi, Yuichi; Hori, Michio; Oda, Yoichi

    2012-01-01

    Behavioral lateralization has been documented in many vertebrates. The scale-eating cichlid fish Perissodus microlepis is well known for exhibiting lateral dimorphism in its mouth morphology and lateralized behavior in robbing scales from prey fish. A previous field study indicated that this mouth asymmetry closely correlates with the side on which prey is attacked, but details of this species' predation behavior have not been previously analyzed because of the rapidity of the movements. Here, we studied scale-eating behavior in cichlids in a tank through high-speed video monitoring and quantitative assessment of behavioral laterality and kinematics. The fish observed showed a clear bias toward striking on one side, which closely correlated with their asymmetric mouth morphologies. Furthermore, the maximum angular velocity and amplitude of body flexion were significantly larger during attacks on the preferred side compared to those on the nonpreferred side, permitting increased predation success. In contrast, no such lateral difference in movement elements was observed in acoustically evoked flexion during the escape response, which is similar to flexion during scale eating and suggests that they share a common motor control pathway. Thus the neuronal circuits controlling body flexion during scale eating may be functionally lateralized upstream of this common motor pathway.

  3. Lateralized Kinematics of Predation Behavior in a Lake Tanganyika Scale-Eating Cichlid Fish

    PubMed Central

    Takeuchi, Yuichi; Hori, Michio; Oda, Yoichi

    2012-01-01

    Behavioral lateralization has been documented in many vertebrates. The scale-eating cichlid fish Perissodus microlepis is well known for exhibiting lateral dimorphism in its mouth morphology and lateralized behavior in robbing scales from prey fish. A previous field study indicated that this mouth asymmetry closely correlates with the side on which prey is attacked, but details of this species' predation behavior have not been previously analyzed because of the rapidity of the movements. Here, we studied scale-eating behavior in cichlids in a tank through high-speed video monitoring and quantitative assessment of behavioral laterality and kinematics. The fish observed showed a clear bias toward striking on one side, which closely correlated with their asymmetric mouth morphologies. Furthermore, the maximum angular velocity and amplitude of body flexion were significantly larger during attacks on the preferred side compared to those on the nonpreferred side, permitting increased predation success. In contrast, no such lateral difference in movement elements was observed in acoustically evoked flexion during the escape response, which is similar to flexion during scale eating and suggests that they share a common motor control pathway. Thus the neuronal circuits controlling body flexion during scale eating may be functionally lateralized upstream of this common motor pathway. PMID:22238598

  4. Active intra-basin faulting in the Northern Basin of Lake Malawi from seismic reflection data

    NASA Astrophysics Data System (ADS)

    Shillington, D. J.; Chindandali, P. R. N.; Scholz, C. A.; Ebinger, C. J.; Onyango, E. A.; Peterson, K.; Gaherty, J. B.; Nyblade, A.; Accardo, N. J.; McCartney, T.; Oliva, S. J.; Kamihanda, G.; Ferdinand, R.; Salima, J.; Mruma, A. H.

    2016-12-01

    Many questions remain about the development and evolution of fault systems in weakly extended rifts, including the relative roles of border faults and intra-basin faults, and segmentation at various scales. The northern Lake Malawi (Nyasa) rift in the East African Rift System is an early stage rift exhibiting pronounced tectonic segmentation, which is defined by 100-km-long border faults. The basins also contain a series of intrabasinal faults and associated synrift sediments. The occurrence of the 2009 Karonga Earthquake Sequence on one of these intrabasinal faults indicates that some of them are active. Here we present new multichannel seismic reflection data from the Northern Basin of the Malawi Rift collected in 2015 as a part of the SEGMeNT (Study of Extension and maGmatism in Malawi aNd Tanzania) project. This rift basin is bound on its east side by the west-dipping Livingstone border fault. Over 650 km of seismic reflection profiles were acquired in the Northern Basin using a 500 to 1540 cu in air gun array and a 1200- to 1500-m seismic streamer. Dip lines image a series of north-south oriented west-dipping intra-basin faults and basement reflections up to 5 s twtt near the border fault. Cumulative offsets on intra-basin faults decrease to the west. The largest intra-basin fault has a vertical displacement of >2 s two-way travel time, indicating that it has accommodated significant total extension. Some of these intra-basin faults offset the lake bottom and the youngest sediments by up to 50 s twtt ( 37 m), demonstrating they are still active. The two largest intra-basin faults exhibit the largest offsets of young sediments and also correspond to the area of highest seismicity based on analysis of seismic data from the 89-station SEGMeNT onshore/offshore network (see Peterson et al, this session). Fault patterns in MCS profiles vary along the basin, suggesting a smaller scale of segmentation of faults within the basin; these variations in fault patterns

  5. Evolution of a unique predatory feeding apparatus: functional anatomy, development and a genetic locus for jaw laterality in Lake Tanganyika scale-eating cichlids

    PubMed Central

    2010-01-01

    Background While bilaterality is a defining characteristic of triploblastic animals, several assemblages have managed to break this symmetry in order to exploit the adaptive peaks garnered through the lateralization of behaviour or morphology. One striking example of an evolved asymmetry in vertebrates comes from a group of scale-eating cichlid fishes from Lake Tanganyika. Members of the Perissodini tribe of cichlid fishes have evolved dental and craniofacial asymmetries in order to more effectively remove scales from the left or right flanks of prey. Here we examine the evolution and development of craniofacial morphology and laterality among Lake Tanganyika scale-eating cichlids. Results Using both geometric and traditional morphometric methods we found that the craniofacial evolution in the Perissodini involved discrete shifts in skeletal anatomy that reflect differences in habitat preference and predation strategies. Further, we show that the evolutionary history of the Perissodini is characterized by an accentuation of craniofacial laterality such that certain taxa show elaborate sided differences in craniofacial shape consistent with the sub-partitioning of function between sides of the head during attacks. Craniofacial laterality in the scale-eating specialist Perissodus microlepis was found to be evident early in development and exhibited a unimodal distribution, which is contrary to the adult condition where jaw laterality has been described as a discrete, bimodal antisymmetry. Finally, using linkage and association analyses we identified a conserved locus for jaw handedness that segregates among East African cichlids. Conclusions We suggest that, during the evolution of the Perissodini, selection has accentuated a latent, genetically determined handedness of the craniofacial skeleton, enabling the evolution of jaw asymmetries in order to increase predation success. Continued work on the developmental genetic basis of laterality in the Perissodini will

  6. Tropical African climate variability during the last glacial/interglacial transition: the molecular record from Lake Malawi

    NASA Astrophysics Data System (ADS)

    Castañeda, I. S.; Werne, J. P.; Johnson, T. C.

    2003-12-01

    In general, information regarding tropical African climate variability is relatively limited, especially in comparison with high-latitude studies. Unlike the high-latitudes where climate change is often expressed by fluctuations in temperature, low-latitude climate change is often expressed as variability in zonal circulation, which can result in hydrological fluctuations. Lake Malawi, situated in low-latitude tropical Africa (9-14° S), contains a continuous and high-resolution sedimentary record of the past 22ka BP and is anoxic below 250m, which enhances preservation of organic matter (OM). For these reasons, L. Malawi is an excellent location to examine the response of low-latitude African climate to global climate change. The climate of Malawi is strongly influenced by the position and seasonal migration of the ITCZ. During the rainy season from November to March, the ITCZ is positioned over L. Malawi (12-13° S) and the dominant winds are weak and northerly. Between April and May the ITCZ moves northward towards the equator and strong southerly winds prevail (Jury & Mwafulirwa, 2002). Previous studies of L. Malawi have shown responses to global climatic events, such as the Younger Dryas. Additionally, studies have demonstrated the response of L. Malawi to local or regional events, such as variability in the ITCZ. Based on BSi MAR, diatom, phosphorus, and trace metal data, Johnson et al. (2002) proposed that at times more frequent or stronger northerly winds promoted upwelling in the northern basin of L. Malawi, and suggested more southerly migrations of the ITCZ (reaching latitudes of >13\\deg S) as the cause of these increased winds. Additionally, a recent study of L. Malawi based on multiple bulk geochemical proxies provides evidence for both southward and northward displacements of the ITCZ during the past 23ka BP (Filippi and Talbot, submitted). In this study the molecular biomarker record of L. Malawi is examined. Previous studies of Lake Malawi have

  7. Waxing and Waning of Forests: Late Quaternary Biogeography of Lake Malawi, Southeast Africa

    NASA Astrophysics Data System (ADS)

    Ivory, S.; Lézine, A. M.; Vincens, A.; Cohen, A. S.

    2014-12-01

    African ecosystems are at great risk due to climate and land-use change. Despite the status of several of these regions as biodiversity hotspots, long-standing ideas about African ecology and biogeography have been unable to be tested until now due to lack of sufficiently long records. Here, we present the first long, continuous terrestrial record of vegetation from Lake Malawi, East Africa which goes back to the early Late Quaternary, permitting us to investigate changes in physiognomy and forest composition over many transitions. In this record, we observe eight phases of forest expansion and collapse. Although diversity is much greater during forest phases, composition varies little from phase to phase. Very high abundances of afromontane taxa suggest frequent widespread colonization of the lowlands by modern high elevation trees. Although there are clear successional stages within each forest such that turnover is great within a single phase, among forest samples between phases, there is little dissimilarity. Each forest phase is interrupted by rapid decline of arboreal taxa and expansion of semi-arid grasslands or woodlands whose composition varies greatly from phase to phase. The variable composition of the more open phases, all occurring during arid periods, is likely dynamically linked to thresholds in regional hydrology associated with lake level and moisture recycling within the watershed. This vegetation is unlike any found at Malawi today, with assemblages suggesting strong Somali-Masai affinities. Furthermore, nearly all semi-arid assemblages contain small abundances of forest taxa typically growing in areas with wetter edaphic conditions, suggesting that moist lowland gallery forests were present but restricted to waterways during exceptionally arid times. The waxing and waning of forests throughout this interval has important implications for early human biogeography across Africa as well as disturbance regimes that are crucial for the maintenance of

  8. Divergent Selection on Opsins Drives Incipient Speciation in Lake Victoria Cichlids

    PubMed Central

    Terai, Yohey; Seehausen, Ole; Sasaki, Takeshi; Takahashi, Kazuhiko; Mizoiri, Shinji; Sugawara, Tohru; Sato, Tetsu; Watanabe, Masakatsu; Konijnendijk, Nellie; Mrosso, Hillary D. J; Tachida, Hidenori; Imai, Hiroo; Shichida, Yoshinori; Okada, Norihiro

    2006-01-01

    Divergent natural selection acting on ecological traits, which also affect mate choice, is a key element of ecological speciation theory, but has not previously been demonstrated at the molecular gene level to our knowledge. Here we demonstrate parallel evolution in two cichlid genera under strong divergent selection in a gene that affects both. Strong divergent natural selection fixed opsin proteins with different predicted light absorbance properties at opposite ends of an environmental gradient. By expressing them and measuring absorbance, we show that the reciprocal fixation adapts populations to divergent light environments. The divergent evolution of the visual system coincides with divergence in male breeding coloration, consistent with incipient ecological by-product speciation. PMID:17147472

  9. Deltas of the Lake Malawi rift, east Africa: Seismic expression and exploration implications

    SciTech Connect

    Scholz, C.A.

    1995-11-01

    High-resolution, air-gun-sourced seismic reflection surveys over the offshore regions of five river deltas in Lake Malawi in the East African rift system reveal considerable variability in acoustic facies and stratigraphic architecture. This variability can largely be attributed to the influences of different structural settings, and to a lesser degree to high-amplitude (100-400 m) and high-frequency (1000 to 100,000 yr) fluctuations in lake level. Deltas on flexural and axial margins in the rift lake show well-developed progradational geometries. In contrast, a delta on a steep, accommodation zone margin distributes coarse sediments over a broad depositional apron, rather than concentrating sediment in discrete progradational lobes as on the other deltas. A large border fault margin river delta displays the most complex tectonic and stratigraphic architecture of all the deltas studied. It contains several delta-associated facies, including prograding clinoform packages, fan deltas stacked against a boundary fault, and extensive subaqueous fans. Flexural margin lowstand deltas may be the most prospective for hydrocarbon exploration due to their large, internally well-organized, progradational lobes and their close proximity to deep-water, high total organic carbon lacustrine source facies.

  10. Species-Specific Relationships between Water Transparency and Male Coloration within and between Two Closely Related Lake Victoria Cichlid Species

    PubMed Central

    Castillo Cajas, Ruth F.; Selz, Oliver M.; Ripmeester, Erwin A. P.; Seehausen, Ole; Maan, Martine E.

    2012-01-01

    Environmental variation in signalling conditions affects animal communication traits, with possible consequences for sexual selection and reproductive isolation. Using spectrophotometry, we studied how male coloration within and between populations of two closely related Lake Victoria cichlid species (Pundamilia pundamilia and P. nyererei) covaries with water transparency. Focusing on coloration patches implicated in sexual selection, we predicted that in clear waters, with broad-spectrum light, (1) colours should become more saturated and (2) shift in hue away from the dominant ambient wavelengths, compared to more turbid waters. We found support for these predictions for the red and yellow coloration of P. nyererei but not the blue coloration of P. pundamilia. This may be explained by the species difference in depth distribution, which generates a steeper gradient in visual conditions for P. nyererei compared to P. pundamilia. Alternatively, the importance of male coloration in intraspecific sexual selection may differ between the species. We also found that anal fin spots, that is, the orange spots on male haplochromine anal fins that presumably mimic eggs, covaried with water transparency in a similar way for both species. This is in contrast to the other body regions studied and suggests that, while indeed functioning as signals, these spots may not play a role in species differentiation. PMID:22888462

  11. Social status-dependent nest choice of territorial males under reproductive parasitism in a Lake Tanganyika cichlid Telmatochromis vittatus.

    PubMed

    Ota, K; Kohda, M

    2011-03-01

    Field and laboratory studies were conducted to examine how territorial males of a Lake Tanganyika cichlid Telmatochromis vittatus balance the conflicting demands on nest choice between occupying large nests with more females and avoiding reproductive parasitism (nest piracy, which is adopted by the largest males in the population). Pirates less frequently intruded the nests farther from neighbours, perhaps due to the costs associated with travelling between nests. The field experiment showed that territorial male T. vittatus sacrificed the fitness benefits that large nests offer and instead prioritized occupying the nests farther from neighbours on which fewer pirates intruded. The field observations suggested that they adopt different strategies for nest choice according to their relative competitive ability to pirates; the large territorial males, who are size-matched to pirates and can defend their nests against them, compete for larger nests among the more-isolated nests, whereas subordinate territorial males, which are smaller than pirates and thus inferior to them, compete for the more-isolated nests among the less-isolated nests. These findings suggest that the territorial male T. vittatus chooses the more-isolated nests to avoid pirate males at the expense of occupying large nests.

  12. Species-Specific Relationships between Water Transparency and Male Coloration within and between Two Closely Related Lake Victoria Cichlid Species.

    PubMed

    Castillo Cajas, Ruth F; Selz, Oliver M; Ripmeester, Erwin A P; Seehausen, Ole; Maan, Martine E

    2012-01-01

    Environmental variation in signalling conditions affects animal communication traits, with possible consequences for sexual selection and reproductive isolation. Using spectrophotometry, we studied how male coloration within and between populations of two closely related Lake Victoria cichlid species (Pundamilia pundamilia and P. nyererei) covaries with water transparency. Focusing on coloration patches implicated in sexual selection, we predicted that in clear waters, with broad-spectrum light, (1) colours should become more saturated and (2) shift in hue away from the dominant ambient wavelengths, compared to more turbid waters. We found support for these predictions for the red and yellow coloration of P. nyererei but not the blue coloration of P. pundamilia. This may be explained by the species difference in depth distribution, which generates a steeper gradient in visual conditions for P. nyererei compared to P. pundamilia. Alternatively, the importance of male coloration in intraspecific sexual selection may differ between the species. We also found that anal fin spots, that is, the orange spots on male haplochromine anal fins that presumably mimic eggs, covaried with water transparency in a similar way for both species. This is in contrast to the other body regions studied and suggests that, while indeed functioning as signals, these spots may not play a role in species differentiation.

  13. Acquisition of Lateralized Predation Behavior Associated with Development of Mouth Asymmetry in a Lake Tanganyika Scale-Eating Cichlid Fish.

    PubMed

    Takeuchi, Yuichi; Hori, Michio; Tada, Shinya; Oda, Yoichi

    2016-01-01

    The scale-eating cichlid Perissodus microlepis with asymmetric mouth is an attractive model of behavioral laterality: each adult tears off scales from prey fishes' left or right flanks according to the direction in which its mouth is skewed. To investigate the development of behavioral laterality and mouth asymmetry, we analyzed stomach contents and lower jaw-bone asymmetry of various-sized P. microlepis (22 ≤ SL<115 mm) sampled in Lake Tanganyika. The shapes of the pored scales found in each specimen's stomach indicated its attack side preference. Early-juvenile specimens (SL<45 mm) feeding mainly on zooplankton exhibited slight but significant mouth asymmetry. As the fish acquired scale-eating (45 mm ≤ SL), attack side preference was gradually strengthened, as was mouth asymmetry. Among size-matched individuals, those with more skewed mouths ate more scales. These findings show that behavioral laterality in scale-eating P. microlepis is established in association with development of mouth asymmetry which precedes the behavioral acquisition, and that this synergistic interaction between physical and behavioral literalities may contribute to efficient scale-eating.

  14. Acquisition of Lateralized Predation Behavior Associated with Development of Mouth Asymmetry in a Lake Tanganyika Scale-Eating Cichlid Fish

    PubMed Central

    Takeuchi, Yuichi; Hori, Michio; Tada, Shinya; Oda, Yoichi

    2016-01-01

    The scale-eating cichlid Perissodus microlepis with asymmetric mouth is an attractive model of behavioral laterality: each adult tears off scales from prey fishes’ left or right flanks according to the direction in which its mouth is skewed. To investigate the development of behavioral laterality and mouth asymmetry, we analyzed stomach contents and lower jaw-bone asymmetry of various-sized P. microlepis (22≤SL<115mm) sampled in Lake Tanganyika. The shapes of the pored scales found in each specimen’s stomach indicated its attack side preference. Early-juvenile specimens (SL<45mm) feeding mainly on zooplankton exhibited slight but significant mouth asymmetry. As the fish acquired scale-eating (45mm≤SL), attack side preference was gradually strengthened, as was mouth asymmetry. Among size-matched individuals, those with more skewed mouths ate more scales. These findings show that behavioral laterality in scale-eating P. microlepis is established in association with development of mouth asymmetry which precedes the behavioral acquisition, and that this synergistic interaction between physical and behavioral literalities may contribute to efficient scale-eating. PMID:26808293

  15. Correlation between nuptial colors and visual sensitivities tuned by opsins leads to species richness in sympatric Lake Victoria cichlid fishes.

    PubMed

    Miyagi, Ryutaro; Terai, Yohey; Aibara, Mitsuto; Sugawara, Tohru; Imai, Hiroo; Tachida, Hidenori; Mzighani, Semvua Isa; Okitsu, Takashi; Wada, Akimori; Okada, Norihiro

    2012-11-01

    Reproductive isolation that prevents interspecific hybridization between closely related coexisting species maintains sympatric species diversity. One of the reproductive isolations is mate choice based on color signals (breeding color perceived by color vision). This is well known in several animal taxa, yet little is known about its genetic and molecular mechanism. Lake Victoria cichlid fishes are thought to be an example of sympatric species diversity. In the species inhabiting different light environments in rocky shore, speciation by sensory drive through color signals has been proposed by analyses of the long wavelength-sensitive (LWS) opsin gene and the male nuptial coloration. However, the genetic and molecular mechanism of how diversity of sympatric species occurring in the same habitat is maintained remains unknown. To address this issue, we determined nucleotide sequences of eight opsins of six sympatric species collected from a sandy-muddy shore--an ideal model system for studying sympatric species. Among eight opsins, the LWS and RH1 alleles were diversified and one particular allele is dominant or fixed in each species, and we propose that this is due to natural selection. The functions of their LWS alleles were also diversified as shown by absorption measurements of reconstituted visual pigments. To analyze the relationship between nuptial coloration and the absorption of LWS pigments, we systematically evaluated and defined nuptial coloration. We showed that the coloration was species specific with respect to hue and significantly differentiated by the index values of hue (dominant wavelength: λ(d)). The λ(d) value of the male nuptial coloration correlated with the absorption of LWS pigments from all the species, suggesting that reproductive isolation through mate choice using color signals may prevent sympatric interspecific hybridization, thereby maintaining the species diversity in sympatric species in Lake Victoria.

  16. Ash from the Toba supereruption in Lake Malawi shows no volcanic winter in East Africa at 75 ka.

    PubMed

    Lane, Christine S; Chorn, Ben T; Johnson, Thomas C

    2013-05-14

    The most explosive volcanic event of the Quaternary was the eruption of Mt. Toba, Sumatra, 75,000 y ago, which produced voluminous ash deposits found across much of the Indian Ocean, Indian Peninsula, and South China Sea. A major climatic downturn observed within the Greenland ice cores has been attributed to the cooling effects of the ash and aerosols ejected during the eruption of the Youngest Toba Tuff (YTT). These events coincided roughly with a hypothesized human genetic bottleneck, when the number of our species in Africa may have been reduced to near extinction. Some have speculated that the demise of early modern humans at that time was due in part to a dramatic climate shift triggered by the supereruption. Others have argued that environmental conditions would not have been so severe to have such an impact on our ancestors, and furthermore, that modern humans may have already expanded beyond Africa by this time. We report an observation of the YTT in Africa, recovered as a cryptotephra layer in Lake Malawi sediments, >7,000 km west of the source volcano. The YTT isochron provides an accurate and precise age estimate for the Lake Malawi paleoclimate record, which revises the chronology of past climatic events in East Africa. The YTT in Lake Malawi is not accompanied by a major change in sediment composition or evidence for substantial temperature change, implying that the eruption did not significantly impact the climate of East Africa and was not the cause of a human genetic bottleneck at that time.

  17. Testing the potential of DNA barcoding in vertebrate radiations: the case of the littoral cichlids (Pisces, Perciformes, Cichlidae) from Lake Tanganyika.

    PubMed

    Breman, Floris C; Loix, Sara; Jordaens, Kurt; Snoeks, Jos; Van Steenberge, Maarten

    2016-11-01

    We obtained 398 cytochrome c oxidase subunit I barcodes of 96 morphospecies of Lake Tanganyika (LT) cichlids from the littoral zone. The potential of DNA barcoding in these fishes was tested using both species identification and species delineation methods. The best match (BM) and best close match (BCM) methods were used to evaluate the overall identification success. For this, three libraries were analysed in which the specimens were categorized into Operational Taxonomic Units (OTU) in three alternative ways: (A) morphologically distinct, including undescribed, species, (B) valid species and (C) complexes of morphologically similar or closely related species. For libraries A, B and C, 73, 73 and 96% (BM) and 72, 70 and 94% (BCM) of the specimens were correctly identified. Additionally, the potential of two species delineation methods was tested. The General Mixed Yule Coalescent (GMYC) analysis suggested 70 hypothetical species, while the Automatic Barcode Gap Discovery (ABGD) method revealed 115 putative species. Although the ABGD method had a tendency to oversplit, it outperformed the GMYC analysis in retrieving the species. In most cases where ABGD suggested oversplitting, this was due to intraspecific geographical variation. The failure of the GMYC method to retrieve many species could be attributed to discrepancies between mitochondrial gene trees and the evolutionary histories of LT cichlid species. Littoral LT cichlids have complex evolutionary histories that include instances of hybridization, introgression and rapid speciation. Nevertheless, although the utility of DNA barcoding in identification is restricted to the level of complexes, it has potential for species discovery in cichlid radiations. © 2016 John Wiley & Sons Ltd.

  18. Linking the North Atlantic Oscillation to Rainfall Over Northern Lake Malawi

    NASA Astrophysics Data System (ADS)

    Johnson, T. C.; Powers, L. A.; Werne, J. P.; Brown, E. T.; Castaneda, I.; Schouten, S.; Sinninghe-Damste, J.

    2005-12-01

    Piston and multi-cores recovered from the north basin of Lake Malawi in 1998 by the International Decade for the East African Lakes (IDEAL) have provided a rich history of climate variability spanning the past 25,000 years. As we now begin to analyze the cores recovered by the Malawi Drilling Project in early 2005, we are considering the relationships among sedimentary signals of temperature (TEX86), northerly winds associated with a southward excursion of the Inter-Tropical Convergence Zone (per cent biogenic silica), and rainfall (terrigenous mass accumulation rate) in the well dated 1998 cores. A high-resolution record of the past 800 years suggests that rainfall in this region (10 - 12° S, 30 - 35° E) was relatively low during the Little Ice Age, when northerly winds were more prevalent, attributed to a more southerly position of the ITCZ during austral summers. The TEX86 signal of lake (surface?) temperature ranged mostly between 24 and 26°C during this period, with the coldest temperature of about 22°C around AD1680 and the warmest temperature, exceeding 27°C, in the youngest sediment sample. The cooler water temperatures coincide with periods of highest diatom productivity, consistent with the latter being due to relatively intense upwelling associated with the northerly winds. Our observation of low rainfall during periods of more southerly migration of the ITCZ is consistent with the results of McHugh and Rogers (2001), who linked rainfall in southeastern Africa to the North Atlantic Oscillation (NAO). During years of weak NAO, equatorial westerly transport of Atlantic moisture across Africa during austral summer is relatively intense, causing high rainfall in the East African Rift between the equator and 16° S. Conversely, when the NAO is positive, rainfall is higher south of 15° S than north of this latitude, which is consistent with a southward migration of the ITCZ. McHugh, M. J. and J. C. Rogers (2001). "North Atlantic Oscillation influence on

  19. Genetic and morphological population differentiation in the rock-dwelling and specialized shrimp-feeding cichlid fish species Altolamprologus compressiceps from Lake Tanganyika, East Africa.

    PubMed

    Spreitzer, Maria Luise; Mautner, Selma; Makasa, Lawrence; Sturmbauer, Christian

    With about 250 endemic species, Lake Tanganyika contains an extraordinarily diverse cichlid fish fauna, and thus represents an ideal model system for the study of pathways and processes of speciation. The Lamprologini form the most species-rich tribe in Lake Tanganyika comprising about 100 species in seven genera, most of which are endemic to the lake. They are territorial substrate-breeders and represent a monophyletic tribe. By combined analysis of population genetics and geometric morphometric markers, we assessed gene flow among three populations of the highly specialized shrimp-feeding rock-dweller Altolamprologus compressiceps, separated by geographic distance and ecological barriers. Five highly polymorphic microsatellite markers were analyzed in conjunction with 17 landmarks in order to compare genetic differences to body shape differences among populations. Both genetic and morphological analyses revealed significant differentiation among the three studied populations. A significant, but overall relatively low degree of genetic differentiation supports a very recent divergence. Phenotypic differentiation was primarily found in the head region of A. compressiceps. In agreement with findings in other cichlid species, similar adaptations to specialized feeding mechanisms can consequently lead to marginal shape changes in the trophic apparatus.

  20. Reduced host-specificity in a parasite infecting non-littoral Lake Tanganyika cichlids evidenced by intraspecific morphological and genetic diversity.

    PubMed

    Kmentová, Nikol; Gelnar, Milan; Mendlová, Monika; Van Steenberge, Maarten; Koblmüller, Stephan; Vanhove, Maarten P M

    2016-12-22

    Lake Tanganyika is well-known for its high species-richness and rapid radiation processes. Its assemblage of cichlid fishes recently gained momentum as a framework to study parasite ecology and evolution. It offers a rare chance to investigate the influence of a deepwater lifestyle in a freshwater fish-parasite system. Our study represents the first investigation of parasite intraspecific genetic structure related to host specificity in the lake. It focused on the monogenean flatworm Cichlidogyrus casuarinus infecting deepwater cichlids belonging to Bathybates and Hemibates. Morphological examination of C. casuarinus had previously suggested a broad host range, while the lake's other Cichlidogyrus species are usually host specific. However, ongoing speciation or cryptic diversity could not be excluded. To distinguish between these hypotheses, we analysed intraspecific diversity of C. casuarinus. Monogeneans from nearly all representatives of the host genera were examined using morphometrics, geomorphometrics and genetics. We confirmed the low host-specificity of C. casuarinus based on morphology and nuclear DNA. Yet, intraspecific variation of sclerotized structures was observed. Nevertheless, the highly variable mitochondrial DNA indicated recent population expansion, but no ongoing parasite speciation, confirming, for the first time in freshwater, reduced parasite host specificity in the deepwater realm, probably an adaptation to low host availability.

  1. Divergence in cis-regulatory sequences surrounding the opsin gene arrays of African cichlid fishes

    PubMed Central

    2011-01-01

    Background Divergence within cis-regulatory sequences may contribute to the adaptive evolution of gene expression, but functional alleles in these regions are difficult to identify without abundant genomic resources. Among African cichlid fishes, the differential expression of seven opsin genes has produced adaptive differences in visual sensitivity. Quantitative genetic analysis suggests that cis-regulatory alleles near the SWS2-LWS opsins may contribute to this variation. Here, we sequence BACs containing the opsin genes of two cichlids, Oreochromis niloticus and Metriaclima zebra. We use phylogenetic footprinting and shadowing to examine divergence in conserved non-coding elements, promoter sequences, and 3'-UTRs surrounding each opsin in search of candidate cis-regulatory sequences that influence cichlid opsin expression. Results We identified 20 conserved non-coding elements surrounding the opsins of cichlids and other teleosts, including one known enhancer and a retinal microRNA. Most conserved elements contained computationally-predicted binding sites that correspond to transcription factors that function in vertebrate opsin expression; O. niloticus and M. zebra were significantly divergent in two of these. Similarly, we found a large number of relevant transcription factor binding sites within each opsin's proximal promoter, and identified five opsins that were considerably divergent in both expression and the number of transcription factor binding sites shared between O. niloticus and M. zebra. We also found several microRNA target sites within the 3'-UTR of each opsin, including two 3'-UTRs that differ significantly between O. niloticus and M. zebra. Finally, we examined interspecific divergence among 18 phenotypically diverse cichlids from Lake Malawi for one conserved non-coding element, two 3'-UTRs, and five opsin proximal promoters. We found that all regions were highly conserved with some evidence of CRX transcription factor binding site turnover. We

  2. Divergence in cis-regulatory sequences surrounding the opsin gene arrays of African cichlid fishes.

    PubMed

    O'Quin, Kelly E; Smith, Daniel; Naseer, Zan; Schulte, Jane; Engel, Samuel D; Loh, Yong-Hwee E; Streelman, J Todd; Boore, Jeffrey L; Carleton, Karen L

    2011-05-09

    Divergence within cis-regulatory sequences may contribute to the adaptive evolution of gene expression, but functional alleles in these regions are difficult to identify without abundant genomic resources. Among African cichlid fishes, the differential expression of seven opsin genes has produced adaptive differences in visual sensitivity. Quantitative genetic analysis suggests that cis-regulatory alleles near the SWS2-LWS opsins may contribute to this variation. Here, we sequence BACs containing the opsin genes of two cichlids, Oreochromis niloticus and Metriaclima zebra. We use phylogenetic footprinting and shadowing to examine divergence in conserved non-coding elements, promoter sequences, and 3'-UTRs surrounding each opsin in search of candidate cis-regulatory sequences that influence cichlid opsin expression. We identified 20 conserved non-coding elements surrounding the opsins of cichlids and other teleosts, including one known enhancer and a retinal microRNA. Most conserved elements contained computationally-predicted binding sites that correspond to transcription factors that function in vertebrate opsin expression; O. niloticus and M. zebra were significantly divergent in two of these. Similarly, we found a large number of relevant transcription factor binding sites within each opsin's proximal promoter, and identified five opsins that were considerably divergent in both expression and the number of transcription factor binding sites shared between O. niloticus and M. zebra. We also found several microRNA target sites within the 3'-UTR of each opsin, including two 3'-UTRs that differ significantly between O. niloticus and M. zebra. Finally, we examined interspecific divergence among 18 phenotypically diverse cichlids from Lake Malawi for one conserved non-coding element, two 3'-UTRs, and five opsin proximal promoters. We found that all regions were highly conserved with some evidence of CRX transcription factor binding site turnover. We also found three

  3. A Tropical Template for D-O Events During MIS 3? Results From the Lake Malawi Drilling Project

    NASA Astrophysics Data System (ADS)

    Brown, E. T.; Johnson, T. C.; Scholz, C. A.; King, J. W.; Cohen, A. S.

    2007-12-01

    As part of the Lake Malawi Drilling Project we have undertaken a 1 cm-scale resolution (ca. 20 yr) XRF scanning study of core from site 2A in the Northern Basin of the lake. We have focused on certain parameters, including Fe, Zr:Ti, and Si:Ti; these may be interpreted to represent changing input of terrigenous sediments (delivered to the lake by rivers), soils developed from weathered volcanic ash (delivered more effectively under drier windier conditions), and biogenic silica, respectively. We present here a record of East African climate since 55 ka that indicates rapid shifts between discrete climate modes that appear to be related to abrupt warming (Dansgaard- Oeschger) and cooling (Heinrich) events observed in Greenland. The events in Malawi appear to correspond to episodes of dry conditions and increased northerly winds. Such conditions may occur at times that southward excursion of the Intertropical Convergence Zone brings the tropical rain belt to the south of the study area. Although the timing of the Malawi events cannot be determined exactly, our independent age model, based on 25 radiocarbon dates and stratigraphic correlations to events dated in a nearby at 63 and 75 ka, implies that they occur prior to their Greenland counterparts, consistent with southward excursions of the ITCZ during Greenland stadials. The magnitude and form of each of the events recorded in Malawi sediments corresponds to the scale of the subsequent Greenland warming. This suggests that a tropical component of climate sets a template for abrupt high northern latitude climate fluctuations associated with the bipolar seesaw.

  4. Orbital- versus glacial-mode forcing of tropical African climate: Results of scientific drilling in Lake Malawi, East Africa

    NASA Astrophysics Data System (ADS)

    Scholz, C. A.; Cohen, A. S.; Johnson, T. C.; King, J. W.; Brown, E. T.; Lyons, R. P.; Stone, J. R.; Beuning, K. R.

    2007-12-01

    Lake Malawi extends from 9-14 degrees S within the East African Rift Valley, and at 700 m deep, contains more than 20 percent of the surface water on the African continent. In 2005 the Lake Malawi Scientific Drilling Project drilled 7 holes at two sites in the lake, recovering a continuous sediment record that samples much of the Quaternary. Detailed studies completed to date on sediments deposited during the past 145 ka indicate periods of severe aridity at precessional frequency between 135 and 75 ka, when the lake's water volume was periodically reduced by at least 95 percent. These dramatic drops in lake level (more than 550 m), signifying markedly arid conditions in the catchment, are documented in sediment lithology (decreased organic carbon content and increased authigenic carbonate content during severe lowstands), aquatic microfossils (appearance of a littoral ostracode fauna, and saline/alkaline lake diatom flora during extreme low lake stages), as well as in dramatic reductions in catchment pollen production. These intervals of pronounced tropical African aridity in the early late-Pleistocene were much more severe than the Last Glacial Maximum, and are consistent with sediment records from Lakes Tanganyika (East Africa) and Bosumtwi (West Africa). In all three lakes a major rise in water levels and a shift to more humid conditions is observed after ~70 ka. The transition to wetter, more stable conditions coincides with the relaxation of orbital eccentricity and a reduction in the amplitude of precession. The observed climate mode switch to decreased environmental variability is consistent with terrestrial and marine records from in and around tropical Africa, but these new drill cores provide evidence for dramatically drier conditions prior to 70 ka that have not as yet been detected in marine sediment records. Such climate change may have stimulated the expansion and migrations of early modern human populations.

  5. The Central Lake Malawi (Nyasa) Rift: single or multiple rift segments?

    NASA Astrophysics Data System (ADS)

    McCartney, T.; Scholz, C. A.; Shillington, D. J.; Accardo, N. J.; Chindandali, P. R. N.; Kamihanda, G.

    2015-12-01

    Accommodation zones connect rift segments, which are fundamental elements of continental rift architecture. The sedimentary record aids our assessment of the evolution of this linkage. The central basin of Lake Malawi is one of the most structurally complex regions of the Malawi Rift. Border fault margins have been interpreted on both shorelines; three structures within the basin have been interpreted as segments of a corresponding accommodation zone. We investigate these structures by integrating single- and multi-channel reflection seismic data, including new MCS acquired in 2015 for the SEGMeNT project. The stratigraphic record in the central basin, inferred from seismic reflection profiles, provides compelling evidence that most fault-related subsidence is accommodated by the western border fault. Strata on both sides of all three structures dip to the west. The pre-rift basement in the sub-basin west of the central structure is considerably deeper (~ 4 s TWTT sub-bottom) than that in the broader eastern sub-basin (~ 2.5 s TWTT sub-bottom). A syncline in the eastern sub-basin shows little variation in seismic facies, particularly over the last 1.3 m.y. In contrast, the western sub-basin exhibits seismic facies indicative of fluvial input from two major rivers, siliciclastic input from the border fault footwall rising > 1000 m above lake level, and mud diapirs in the deepest part of the sub-basin. Horizons pierced by these diapirs onlap the central structure, suggesting diapir rise postdates relative uplift of the structure. Correlations with the age model from a 2005 scientific drilling project will better constrain this timing. The structural high helps focus siliciclastic sediments into the sub-basin, resulting in the overpressure conditions required for mud diapirism. We hypothesize that the diapirs are the result of sediment loading in the deep main depocenter of the central basin rather than fault mechanisms. The basement highs in the central basin control

  6. The role of rare morph advantage and conspicuousness in the stable gold-dark colour polymorphism of a crater lake Midas cichlid fish.

    PubMed

    Torres-Dowdall, Julián; Golcher-Benavides, Jimena; Machado-Schiaffino, Gonzalo; Meyer, Axel

    2017-09-01

    Genetically based stable colour polymorphisms provide a unique opportunity to study the evolutionary processes that preserve genetic variability in the wild. Different mechanisms are proposed to promote the stability of polymorphisms, but only few empirical examples have been documented, resulting in an incomplete understanding of these mechanisms. A remarkable genetically determined stable colour polymorphism is found in the Nicaraguan Midas cichlid species complex (Amphilophus cf. citrinellus). All Midas cichlids start their life with a dark-grey coloration (dark morph), but individuals carrying the dominant "gold" allele (c. 10%) lose their melanophores later in life, revealing the underlying orange coloration (gold morph). How this polymorphism is maintained remains unclear. Two main hypotheses have been proposed, both suggesting differential predation upon colour morphs as the proximate mechanism. One predicts that the conspicuous gold morph is more likely to be preyed upon, but this disadvantage is balanced by their competitive dominance over the dark morph. The second hypothesis suggests a rare morph advantage where the rarer gold morph experiences less predation. Empirical evidence for either of these mechanisms is still circumstantial and inconclusive. We conducted two field experiments in a Nicaraguan crater lake using wax models simulating both morphs to determine predation pressure upon Midas cichlid colour morphs. First, we tested the interaction of coloration and depth on attack rate. Second, we tested the interaction of fish size and coloration. We contrasted the pattern of attacks from these experiments to the predicted predation patterns from the hypotheses proposed to explain the colour polymorphism's stability. Large models imitating colour morphs were attacked at similar rates irrespectively of their position in the water column. Yet, attacks upon small models resembling juveniles were directed mainly towards dark models. This resulted in a

  7. First description of monogenean parasites in Lake Tanganyika: the cichlid Simochromis diagramma (Teleostei, Cichlidae) harbours a high diversity of Gyrodactylus species (Platyhelminthes, Monogenea).

    PubMed

    Vanhove, Maarten P M; Snoeks, Jos; Volckaert, Filip A M; Huyse, Tine

    2011-03-01

    Lake Tanganyika harbours the most diverse endemic cichlid fish assemblage of Africa, but its monogenean fish parasites have not been investigated. Here we report, for the first time, on the Gyrodactylus parasites in this hotspot of fish biodiversity. Haptor morphometrics and nuclear ribosomal DNA sequences revealed 3 new species on Zambian Simochromis diagramma: Gyrodactylus sturmbaueri n. sp., G. thysi n. sp. and G. zimbae n. sp. Their distinct morphology and strong genetic differentiation suggest that they belong to distant lineages within the genus Gyrodactylus, and phylogenetic reconstructions suggest affinities with other genera of gyrodactylids. Additional U-shaped haptoral plates in G. thysi n. sp. and a second large spine-like structure in the male copulatory organ of G. zimbae seem to represent new features for the genus. Such large diversity on a single host species can probably be explained by host-switching events during the course of evolution, in agreement with the generally accepted concept that ecological transfer is an important aspect of gyrodactylid speciation. Additional parasitological surveys on other host species, covering a broader phylogenetic and geographical range, should clarify the evolutionary history of Gyrodactylidae on cichlids in the African Great Lake and other parts of Africa.

  8. Reduced host-specificity in a parasite infecting non-littoral Lake Tanganyika cichlids evidenced by intraspecific morphological and genetic diversity

    PubMed Central

    Kmentová, Nikol; Gelnar, Milan; Mendlová, Monika; Van Steenberge, Maarten; Koblmüller, Stephan; Vanhove, Maarten P. M.

    2016-01-01

    Lake Tanganyika is well-known for its high species-richness and rapid radiation processes. Its assemblage of cichlid fishes recently gained momentum as a framework to study parasite ecology and evolution. It offers a rare chance to investigate the influence of a deepwater lifestyle in a freshwater fish-parasite system. Our study represents the first investigation of parasite intraspecific genetic structure related to host specificity in the lake. It focused on the monogenean flatworm Cichlidogyrus casuarinus infecting deepwater cichlids belonging to Bathybates and Hemibates. Morphological examination of C. casuarinus had previously suggested a broad host range, while the lake’s other Cichlidogyrus species are usually host specific. However, ongoing speciation or cryptic diversity could not be excluded. To distinguish between these hypotheses, we analysed intraspecific diversity of C. casuarinus. Monogeneans from nearly all representatives of the host genera were examined using morphometrics, geomorphometrics and genetics. We confirmed the low host-specificity of C. casuarinus based on morphology and nuclear DNA. Yet, intraspecific variation of sclerotized structures was observed. Nevertheless, the highly variable mitochondrial DNA indicated recent population expansion, but no ongoing parasite speciation, confirming, for the first time in freshwater, reduced parasite host specificity in the deepwater realm, probably an adaptation to low host availability. PMID:28004766

  9. From Lake Malawi Drilling: East African Climate May Have Caused Major Evolutionary Turnover in Mammalian Species During MIS 14

    NASA Astrophysics Data System (ADS)

    Johnson, Thomas; Werne, Josef

    2016-04-01

    Hominin evolution underwent important changes in the last 1.3 million years, including the extinction of Paranthropus at about 1.2 Ma, leaving Homo as the sole hominin genus. Our genus experienced a major increase in cranial capacity at about 500 ka, and our species, H. sapiens, first appeared at ~200 ka. There was a major turnover in mammalian species in East Africa between 540 and 400 ka, favoring descendants of smaller size and less specialized diet. An understanding of what drove evolution in these directions is fundamental to understanding the development of modern H. sapiens. Climate certainly played a role, for it is the principal factor that influences the distribution of vegetation and habitability on the landscape. We present a 1.3 million year record of temperature and hydroclimate in the basin of Lake Malawi, the second deepest lake in Africa, derived from a 380 m sediment sequence taken from a water depth of 590 m by the Lake Malawi Drilling Project. Seismic reflection profiles used to select the site portray an undisturbed sedimentary section that was not impacted by erosion, turbidity currents or mass wasting events. Sediment samples were analyzed to produce records of temperature (TEX86) and aridity (Ca content and leaf wax δ13C). The temperature record displays progressively larger amplitude glacial-interglacial variations from MIS 13 (~500 ka) to MIS 5 (~125 ka). Intervals of low Ca abundance, which reflect lake high stands, correlate with times of depleted δ13Cwax and relatively warm temperatures. The Malawi basin experienced warm, wet interglacials and cooler (by about 2 - 4°C), dry glacial periods, with roughly a 100 ky periodicity since the Mid-Pleistocene Transition (MPT), about 900 ka. The paleoclimate record from Lake Malawi sediments portrays a transition from a highly variable and predominantly arid climate prior to 900 ka to a progressively more humid environment after the MPT dominated by 100 ky cycles consisting of warm, wet

  10. Ash from the Toba supereruption in Lake Malawi shows no volcanic winter in East Africa at 75 ka

    PubMed Central

    Lane, Christine S.; Chorn, Ben T.; Johnson, Thomas C.

    2013-01-01

    The most explosive volcanic event of the Quaternary was the eruption of Mt. Toba, Sumatra, 75,000 y ago, which produced voluminous ash deposits found across much of the Indian Ocean, Indian Peninsula, and South China Sea. A major climatic downturn observed within the Greenland ice cores has been attributed to the cooling effects of the ash and aerosols ejected during the eruption of the Youngest Toba Tuff (YTT). These events coincided roughly with a hypothesized human genetic bottleneck, when the number of our species in Africa may have been reduced to near extinction. Some have speculated that the demise of early modern humans at that time was due in part to a dramatic climate shift triggered by the supereruption. Others have argued that environmental conditions would not have been so severe to have such an impact on our ancestors, and furthermore, that modern humans may have already expanded beyond Africa by this time. We report an observation of the YTT in Africa, recovered as a cryptotephra layer in Lake Malawi sediments, >7,000 km west of the source volcano. The YTT isochron provides an accurate and precise age estimate for the Lake Malawi paleoclimate record, which revises the chronology of past climatic events in East Africa. The YTT in Lake Malawi is not accompanied by a major change in sediment composition or evidence for substantial temperature change, implying that the eruption did not significantly impact the climate of East Africa and was not the cause of a human genetic bottleneck at that time. PMID:23630269

  11. Examining the Response of Tropical Terrestrial Vegetation to Paleoenvironmental Variability: an Organic and Isotopic Geochemical Record from Lake Malawi, East Africa

    NASA Astrophysics Data System (ADS)

    Castaneda, I. S.; Werne, J. P.; Johnson, T. C.; Filley, T. R.

    2005-12-01

    In this study, molecular biomarkers and compound-specific carbon isotopes are used to investigate terrestrial vegetation change in East Africa since the Last Glacial Maximum (LGM). Lake Malawi, located in the southern hemisphere between 9° S and 14° S, provides a particularly interesting and sensitive location to examine the response of terrestrial vegetation to climatic change as the lake is presently situated within a C{3} dominated vegetation zone (tree savannah) but C{4} dominated vegetation zones (grass savannah) are present to both the north and south of the lake. Additionally, Lake Malawi has been shown to respond to both southern and northern hemisphere climatic forcings, including the Antarctic Cold Reversal, the Younger Dryas, and the 8.2 cal ka cold event (Powers et al., 2005; Filippi and Talbot, 2005; Johnson et al., 2002). Climatic variability in East Africa is often expressed as hydrological fluctuations (Gasse, 2000), which typically lead to changes in the primary productivity of both terrestrial and aquatic ecosystems. It is hypothesized that during colder and more arid intervals, grass savannah vegetation zones expanded while tree savannah vegetation zones contracted, resulting in increased inputs of C{4} biomass to Lake Malawi. The ratio of cinnamyl to vanillyl lignin phenols (C/V ratio), indicative of non-woody vs. woody tissue input (Goñi, 1997), correlates closely with bulk δ 13C{org} values in Lake Malawi and suggests a terrestrial influence on bulk carbon isotopic values. Combined C/V ratios and bulk δ 13C values suggest a greater contribution of C{4} grasses to Lake Malawi during the LGM followed by a gradual shift to more C{3} vegetation until approximately 13 cal ka, and a shift back to greater contributions of C{4} grasses between 4 cal ka and the present.

  12. Visual adaptation in Lake Victoria cichlid fishes: depth-related variation of color and scotopic opsins in species from sand/mud bottoms.

    PubMed

    Terai, Yohey; Miyagi, Ryutaro; Aibara, Mitsuto; Mizoiri, Shinji; Imai, Hiroo; Okitsu, Takashi; Wada, Akimori; Takahashi-Kariyazono, Shiho; Sato, Akie; Tichy, Herbert; Mrosso, Hillary D J; Mzighani, Semvua I; Okada, Norihiro

    2017-08-22

    For Lake Victoria cichlid species inhabiting rocky substrates with differing light regimes, it has been proposed that adaptation of the long-wavelength-sensitive (LWS) opsin gene triggered speciation by sensory drive through color signal divergence. The extensive and continuous sand/mud substrates are also species-rich, and a correlation between male nuptial coloration and the absorption of LWS pigments has been reported. However, the factors driving genetic and functional diversity of LWS pigments in sand/mud habitats are still unresolved. To address this issue, nucleotide sequences of eight opsin genes were compared in ten Lake Victoria cichlid species collected from sand/mud bottoms. Among eight opsins, the LWS and rod-opsin (RH1) alleles were diversified and one particular allele was dominant or fixed in each species. Natural selection has acted on and fixed LWS alleles in each species. The functions of LWS and RH1 alleles were measured by absorption of reconstituted A1- and A2-derived visual pigments. The absorption of pigments from RH1 alleles most common in deep water were largely shifted toward red, whereas those of LWS alleles were largely shifted toward blue in both A1 and A2 pigments. In both RH1 and LWS pigments, A2-derived pigments were closer to the dominant light in deep water, suggesting the possibility of the adaptation of A2-derived pigments to depth-dependent light regimes. The RH1 and LWS sequences may be diversified for adaptation of A2-derived pigments to different light environments in sand/mud substrates. Diversification of the LWS alleles may have originally taken place in riverine environments, with a new mutation occurring subsequently in Lake Victoria.

  13. Lake Malawi sediment and pore water chemistry: Proposition of a conceptual model for stratification intensification since the end of the Little Ice Age

    NASA Astrophysics Data System (ADS)

    Branchu, Philippe; Bergonzini, Laurent; Pons-branchu, Edwige; Violier, Eric; Dittrich, Maria; Massault, Marc; Ghaleb, Bassam

    2010-07-01

    Sedimentary records of salinity indicators are largely used to reconstruct past climatic changes in lacustrine systems where chemistry is sensitive to hydroclimatic conditions. In large fresh lakes of the East African Rift such as Lakes Tanganyika and Malawi, salinity is often considered constant and other paleoclimatological proxy data are used. However, a relation between lake surface chloride concentration and hydroclimatic regime was previously demonstrated at the century scale in Lake Tanganyika. This relation is transposed to Lake Malawi on the base of similarity between hydrochemical budgets of both lakes that are computed for the whole lake and epilimnion. Whereas numerous physico-chemical difficulties make generally debatable use of lake pore water chemistry, as illustrated here by diffusion modelling, the dissolved chloride concentration profile from a core sampled in northern Lake Malawi is considered as a potential indicator of limnological-hydroclimatic condition changes for the last 200 years. A decrease in pore water chloride concentration between 1840 AD and present situation is directly associated to a metalimnetic water salinity decrease. The chronology of this event is synchronous with diatom productivity change demonstrated by Johnson et al. (2001) at the end of the Little Ice Age (LIA). A conceptual model of Lake Malawi, based on salinity, organic carbon and its "dead" watershed contribution, lake-level and productivity changes since the mid 19th century is presented. A new scenario is proposed, based on thermal stratification reinforcement at the end of the LIA. Lake productivity and chemistry depend on stratification strength, water column mixing rate and on climatic variability. During the LIA, nutrient distribution profiles were more homogeneous with depth due to the climatically (colder and drier climatic conditions than today) induced destabilisation of the mixing barrier. The productive system is then auto-supplied and does not require

  14. Constraints on Faulting and Basin Architecture in the North Basin of Lake Malawi from Active-Source Seismic Data

    NASA Astrophysics Data System (ADS)

    Onyango, E. A.; Shillington, D. J.; Accardo, N. J.; Scholz, C. A.; Ebinger, C. J.; Gaherty, J. B.; McCartney, T.; Nyblade, A.; Chindandali, P. R. N.; Kamihanda, G.; Ferdinand, R.; Salima, J.; Mruma, A. H.

    2016-12-01

    The East African Rift System (EARS) is actively extending as evidenced by seismicity and volcanic activity, and it is a great example of continental rifting. The western branch of the EARS consists of a series of rift basins bound by 100-km-long border faults, with Lake Malawi being the southernmost. Previous studies on Lake Malawi suggest that the border faults accommodate most of the crustal extension and account for most of the seismicity. However, the 2009 Karonga earthquake sequence and other seismicity on intrabasinal faults suggest that they may also be important for crustal extension and hazards. This study uses seismic reflection and wide-angle refraction data from the Study of Extension and maGmatism in Malawi and Tanzania (SEGMeNT) experiment to constrain detailed basin architecture, shallow velocities, and fault structures of the North Basin of the Malawi Rift. We present results from the main reflection/refraction dip line across the North Basin. Seven lake bottom seismometers (LBS) were spaced at 7 km and recorded shots from a 2580 cu in air gun array fired every 250 m. We recorded multichannel seismic data (MCS) along the same line with a 1500-m-long streamer and a source of 1540 cu in fired every 37.5 m. The LBS also recorded the small volume shots along this line. We picked sedimentary and crustal refractions and reflections using recordings from both shot volumes. We used the First Arrival Seismic Tomography (FAST) code to obtain a smooth velocity model using the first arrivals, and iterative forward modeling was done using the RAYINVR code to produce layered model using both first and later arrivals. Concurrently, the coincident seismic reflection profile was processed using the SeisSpace software package. Preliminary results show sediments in the North basin are thickening Eastward, reaching a thickness of over 4 km adjacent to the Livingstone border fault. Sediments have velocities of 2-3 km/s. The largest intra-basin fault has a substantial

  15. Prevalence and distribution of Schistosoma haematobium infection among school children living in southwestern shores of Lake Malawi.

    PubMed

    Kayuni, Sekeleghe; Peeling, Rosanna; Makaula, Peter

    2017-03-01

    The prevalence of Schistosoma haematobium infection has been shown to be about 23.7% among children living in the lakeshore areas of Malawi, with reinfection rates of about 30% to 40%. This study aimed to determine the current prevalence and distribution of S. haematobium infection in school children along the southwestern shores of Lake Malawi and examine the control interventions present in the area. This prospective cross-sectional study was conducted in primary schools. School children were enrolled, demographic data were collected, and urine samples were submitted for analysis on macrohaematuria, microhaematuria, and S. haematobium eggs. A questionnaire was administered to 3 health facilities on diagnosis and treatment of schistosomiasis, as well as the control interventions against it. Four hundred children (174 males and 226 females) were enrolled from 7 primary schools. Mean participant age was 9.57 years (range 7 to 12 years). Fifty children (12.5%) had S. haematobium eggs detected in their urine, with the mean egg count being 15/10 mL. The highest infection intensity category (≥ 50 eggs/10mL) was seen in 10 children (2.5%). Prevalence varied significantly between the schools, with rates ranging from 0% to 20%. Schools with higher prevalence rates were located farther away from the nearest public hospital that provides treatment free of charge. Prevalence correlated with previous history of mass chemotherapy in schools. Mass chemotherapy, health education, and improved water supply and sanitation were some of the interventions that contributed to lower prevalence rates in some areas. Schistosomiasis prevalence around southwestern Lake Malawi was lower than previously reported, owing to control interventions focusing on health education, improved water supply, sanitation, and mass chemotherapy. Consistent and uniform interventions can reduce prevalence further and sustain control. As prevalence falls, diagnostics can identify high transmission areas

  16. Use of qualitative environmental and phenotypic variables in the context of allele distribution models: detecting signatures of selection in the genome of Lake Victoria cichlids.

    PubMed

    Joost, Stéphane; Kalbermatten, Michael; Bezault, Etienne; Seehausen, Ole

    2012-01-01

    When searching for loci possibly under selection in the genome, an alternative to population genetics theoretical models is to establish allele distribution models (ADM) for each locus to directly correlate allelic frequencies and environmental variables such as precipitation, temperature, or sun radiation. Such an approach implementing multiple logistic regression models in parallel was implemented within a computing program named MATSAM: . Recently, this application was improved in order to support qualitative environmental predictors as well as to permit the identification of associations between genomic variation and individual phenotypes, allowing the detection of loci involved in the genetic architecture of polymorphic characters. Here, we present the corresponding methodological developments and compare the results produced by software implementing population genetics theoretical models (DFDIST: and BAYESCAN: ) and ADM (MATSAM: ) in an empirical context to detect signatures of genomic divergence associated with speciation in Lake Victoria cichlid fishes.

  17. Surface wave imaging of the weakly extended Malawi Rift from ambient-noise and teleseismic Rayleigh waves from onshore and lake-bottom seismometers

    NASA Astrophysics Data System (ADS)

    Accardo, N. J.; Gaherty, J. B.; Shillington, D. J.; Ebinger, C. J.; Nyblade, A. A.; Mbogoni, G. J.; Chindandali, P. R. N.; Ferdinand, R. W.; Mulibo, G. D.; Kamihanda, G.; Keir, D.; Scholz, C.; Selway, K.; O'Donnell, J. P.; Tepp, G.; Gallacher, R.; Mtelela, K.; Salima, J.; Mruma, A.

    2017-06-01

    Located at the southernmost sector of the Western Branch of the East African Rift System, the Malawi Rift exemplifies an active, magma-poor, weakly extended continental rift. To investigate the controls on rifting, we image crustal and uppermost mantle structure beneath the region using ambient-noise and teleseismic Rayleigh-wave phase velocities between 9 and 100 s period. Our study includes six lake-bottom seismometers located in Lake Malawi (Nyasa), the first time seismometers have been deployed in any of the African rift lakes. Noise levels in the lake are lower than that of shallow oceanic environments and allow successful application of compliance corrections and instrument orientation determination. Resulting phase-velocity maps reveal slow velocities primarily confined to Lake Malawi at short periods (T <= 12 s), indicating thick sediments in the border-fault bounded rift basin. The slowest velocities occur within the Central Basin where Malawi Rift sedimentary strata may overlie older (Permo-Triassic) Karoo group sediments. At longer periods (T > 25 s), a prominent low-velocity anomaly exists beneath the Rungwe Volcanic Province at the northern terminus of the rift basin. Estimates of phase-velocity sensitivity indicates these low velocities occur within the lithospheric mantle and potentially uppermost asthenosphere, suggesting that mantle processes may control the association of volcanic centres and the localization of magmatism. Beneath the main portion of the Malawi Rift, a modest reduction in velocity is also observed at periods sensitive to the crust and upper mantle, but these velocities are much higher than those observed beneath Rungwe.

  18. Constraint and diversification of developmental trajectories in cichlid facial morphologies.

    PubMed

    Powder, Kara E; Milch, Kayla; Asselin, Garrett; Albertson, R Craig

    2015-01-01

    A major goal of evolutionary biology is to understand the origins of phenotypic diversity. Changes in development, for instance heterochrony, can be a potent source of phenotypic variation. On the other hand, development can also constrain the spectrum of phenotypes that can be produced. In order to understand these dual roles of development in evolution, we examined the developmental trajectory of a trait central to the extensive adaptive radiation of East African cichlid fishes: craniofacial adaptations that allow optimal exploitation of ecological niches. Specifically, we use geometric morphometric analysis to compare morphological ontogenies among six species of Lake Malawi cichlids (n > 500 individuals) that span a major ecomorphological axis. We further evaluate how modulation of Wnt signaling impacts the long-term developmental trajectory of facial development. We find that, despite drastic differences in adult craniofacial morphologies, there are general similarities in the path of craniofacial ontogeny among species, suggesting that natural selection is working within a conserved developmental program. However, we also detect species-specific differences in the timing, direction, and/or duration of particular developmental trajectories, including evidence of heterochrony. Previous work in cichlids and other systems suggests that species-specific differences in adult morphology are due to changes in molecular signaling pathways that regulate early craniofacial development. In support of this, we demonstrate that modulation of Wnt signaling at early stages can shift a developmental trajectory into morphospace normally occupied by another species. However, without sustained modulation, craniofacial shape can recover by juvenile stages. This underscores the idea that craniofacial development is robust and that adult head shapes are the product of many molecular changes acting over extended periods of development. Our results are consistent with the

  19. Fine Resolution Analysis of Lake Malawi Sediment Record Shows No Significant Climatic Impacts from the Mount Toba Super-Eruption of ~75ky

    NASA Astrophysics Data System (ADS)

    Jackson, L. J.; Stone, J.; Cohen, A. S.

    2014-12-01

    Debate over long, and short-term climatic impacts of the Mt. Toba super-eruption circa 75ky is often focused on East Africa. A severe drop in anatomically modern human populations has been hypothesized to be synchronous with a volcanic winter caused by the Toba super-eruption. If the Toba eruption caused a volcanic winter in East Africa, climatologically-sensitive ecosystems, such as Lake Malawi and its immediate watershed should show a direct and observable response in the sediment record. Cooler temperatures would cause a reduction of density contrast between epilimnion and hypolimnion waters, allowing for increased mixing and oxygenation of normally anoxic bottom waters. Enhanced mixing would cause noticeable changes in lake fly and algal communities. Cooler temperatures might also affect precipitation and the fire regime in the surrounding watershed. We analyzed two Lake Malawi cores at the finest practical resolution. Core 2A-10H-2 was analyzed in less than 6-year intervals and core 1C-8H-1 in 7-year intervals surrounding the Youngest Toba Tephra (YTT) for microfaunal abundance and variability, sediment composition, and evidence of changes in the occurrence of fires or watershed precipitation. Our analysis included point counts of diatoms and other algae, lake flies, charcoal, and siliciclastics. Changes in microfossil assemblage, variability, and abundance, as well as sediment composition around the YTT in Core 2A and 1C do not indicate that increased mixing or cooler temperatures occurred in either the central or northern basins of Lake Malawi. Similarly, charcoal counts do not suggest a change in fire regime. Our results indicate that at a subdecadal scale there was no substantial response in Lake Malawi or its immediate watershed to the Mt. Toba super-eruption, in contrast to predictions from the volcanic winter hypothesis.

  20. Early-stage rifting in the southwest East African Rift: Insights from new reflection seismic data from Lakes Tanganyika and Malawi (Nyasa)

    NASA Astrophysics Data System (ADS)

    Scholz, C. A.; Wood, D. A.; Shillington, D. J.; McCartney, T.; Accardo, N. J.

    2015-12-01

    The western branch of the East African Rift is characterized by modest amounts of mainly amagmatic extension; deeply-subsided, fault-controlled basins; and large-magnitude, deep seismicity. Lakes Tanganyika and Malawi are two of the world's largest lakes, with maximum water depths of 1450 and 700 m respectively. Newly acquired seismic reflection data, along with newly reprocessed legacy data reveal thick sedimentary sections, in excess of 5 km in some localities. The 1980's vintage legacy data from Project PROBE have been reprocessed through pre-stack depth migration in Lake Tanganyika, and similar reprocessing of legacy data from Lake Malawi is forthcoming. New high-fold and large-source commercial and academic data have recently been collected in southern Lake Tanganyika, and in the northern and central basins of Lake Malawi as part of the 2015 SEGMeNT project. In the case of Lake Tanganyika, new data indicate the presence of older sediment packages that underlie previously identified "pre-rift" basement (the "Nyanja Event"). These episodes of sedimentation and extension may substantially predate the modern lake. These deep stratal reflections are absent in many localites, possibly on account of attenuation of the acoustic signal. However in one area of southern Lake Tanganyika, the newly-observed deep strata extend axially for ~70 km, likely representing deposits from a discrete paleolake. The high-amplitude Nyanja Event is interpreted as the onset of late-Cenozoic rifting, and the changing character of the overlying depositional sequences reflects increasing relief in the rift valley, as well as the variability of fluvial inputs, and the intermittent connectivity of upstream lake catchments. Earlier Tanganyika sequences are dominated by shallow lake and fluvial-lacustrine facies, whereas later sequences are characterized by extensive gravity flow deposition in deep water, and pronounced erosion and incision in shallow water depths and on littoral platforms. The

  1. Strong assortative mating by diet, color, size, and morphology but limited progress toward sympatric speciation in a classic example: Cameroon crater lake cichlids.

    PubMed

    Martin, Christopher H

    2013-07-01

    Models predict that sympatric speciation depends on restrictive parameter ranges, such as sufficiently strong disruptive selection and assortative mating, but compelling examples in nature have rarely been used to test these predictions. I measured the strength of assortative mating within a species complex of Tilapia in Lake Ejagham, Cameroon, a celebrated example of incipient sympatric adaptive radiation. This species complex is in the earliest stages of speciation: morphological and ecological divergence are incomplete, species differ primarily in breeding coloration, and introgression is common. I captured 27 mated pairs in situ and measured the diet, color, size, and morphology of each individual. I found strong assortative mating by color, size, head depth, and dietary source of benthic or pelagic prey along two independent dimensions of assortment. Thus, Ejagham Tilapia showed strong assortative mating most conducive to sympatric speciation. Nonetheless, in contrast to a morphologically bimodal Sarotherodon cichlid species pair in the lake, Ejagham Tilapia show more limited progress toward speciation, likely due to insufficient strength of disruptive selection on morphology estimated in a previous study (γ = 0.16). This supports the predicted dependence of sympatric speciation on strong assortment and strong disruptive selection by examining a potentially stalled example in nature.

  2. Evolution of opercle shape in cichlid fishes from Lake Tanganyika - adaptive trait interactions in extant and extinct species flocks

    PubMed Central

    Wilson, Laura A. B.; Colombo, Marco; Sánchez-Villagra, Marcelo R.; Salzburger, Walter

    2015-01-01

    Phenotype-environment correlations and the evolution of trait interactions in adaptive radiations have been widely studied to gain insight into the dynamics underpinning rapid species diversification. In this study we explore the phenotype-environment correlation and evolution of operculum shape in cichlid fishes using an outline-based geometric morphometric approach combined with stable isotope indicators of macrohabitat and trophic niche. We then apply our method to a sample of extinct saurichthyid fishes, a highly diverse and near globally distributed group of actinopterygians occurring throughout the Triassic, to assess the utility of extant data to inform our understanding of ecomorphological evolution in extinct species flocks. A series of comparative methods were used to analyze shape data for 54 extant species of cichlids (N = 416), and 6 extinct species of saurichthyids (N = 44). Results provide evidence for a relationship between operculum shape and feeding ecology, a concentration in shape evolution towards present along with evidence for convergence in form, and significant correlation between the major axes of shape change and measures of gut length and body elongation. The operculum is one of few features that can be compared in extant and extinct groups, enabling reconstruction of phenotype-environment interactions and modes of evolutionary diversification in deep time. PMID:26584885

  3. Evolution of opercle shape in cichlid fishes from Lake Tanganyika - adaptive trait interactions in extant and extinct species flocks.

    PubMed

    Wilson, Laura A B; Colombo, Marco; Sánchez-Villagra, Marcelo R; Salzburger, Walter

    2015-11-20

    Phenotype-environment correlations and the evolution of trait interactions in adaptive radiations have been widely studied to gain insight into the dynamics underpinning rapid species diversification. In this study we explore the phenotype-environment correlation and evolution of operculum shape in cichlid fishes using an outline-based geometric morphometric approach combined with stable isotope indicators of macrohabitat and trophic niche. We then apply our method to a sample of extinct saurichthyid fishes, a highly diverse and near globally distributed group of actinopterygians occurring throughout the Triassic, to assess the utility of extant data to inform our understanding of ecomorphological evolution in extinct species flocks. A series of comparative methods were used to analyze shape data for 54 extant species of cichlids (N = 416), and 6 extinct species of saurichthyids (N = 44). Results provide evidence for a relationship between operculum shape and feeding ecology, a concentration in shape evolution towards present along with evidence for convergence in form, and significant correlation between the major axes of shape change and measures of gut length and body elongation. The operculum is one of few features that can be compared in extant and extinct groups, enabling reconstruction of phenotype-environment interactions and modes of evolutionary diversification in deep time.

  4. Diatom-inferred climate changes in the southern tropics of East Africa (Lake Malawi) during the past millenium

    NASA Astrophysics Data System (ADS)

    Gasse, F.; Pailles, C.; Brown, E. T.; Johnson, T. C.

    2003-04-01

    Laminated sediment cores from the north basin of Lake Malawi (ca. 10^oN, 34^oE) have provided an excellent chronology for the past millenium, based on varve countings and 210Pb dating (Barry et al., 2002, in The East African Great lakes: Limnology, Palaeolimnology and Biodiversity, E.A. Odada, D.O. Olago, Eds., Kluwer Academic Pub., Dordrecht, the Netherlands, pp. 369-391.). The combined biogenic silica (Bsi) profile from 6 cores suggested that primary production was higher in the north basin from about 1570 to 1850 AD, an interval coinciding with the Little Ice Age (LIA) when lake level was about 120 m lower than today (Johnson et al., 2001, Geology 29, 83, 2001). Here, a detailed diatom analysis (species percentage frequency, concentration and biovolume per weight unit, biodivesrsity) of two laminated cores complement these results. The diatom study suggests a decrease in lake level starting around 1400 AD, and periods of enhanced productivity and burial rate between ca. 1400 and 1800 AD. The 1400-1800 interval is complex, with episodes of maximum Si-input and maximum mixing centred around 1600-1650 and 1750-1780 AD. During the last two centuries, the waterbody was better stratified and possibly shallower than prior to 1400 AD. The diatom-inferred palaeoproductivity record correlates well with the Bsi profile, and with the Ni/Ti profile which reflects wind-transport of volcanic ash from the North. Periods of high productivity and high Ni/Ti ratio during the LIA reflect enhanced northerly winds which promoted upwelling in the north basin, while southerly winds predominate today. Our diatom record is then compared with the few high-resolution climate records from tropical Africa spanning the last millenium (speleothems, lake, and ice core records). Interhemispheric differences and potential causes (e;g. insolation changes, Dansgaard-Oeschger events...) are discussed.

  5. Adaptive sequence evolution in a color gene involved in the formation of the characteristic egg-dummies of male haplochromine cichlid fishes.

    PubMed

    Salzburger, Walter; Braasch, Ingo; Meyer, Axel

    2007-11-15

    The exceptionally diverse species flocks of cichlid fishes in East Africa are prime examples of parallel adaptive radiations. About 80% of East Africa's more than 1 800 endemic cichlid species, and all species of the flocks of Lakes Victoria and Malawi, belong to a particularly rapidly evolving lineage, the haplochromines. One characteristic feature of the haplochromines is their possession of egg-dummies on the males' anal fins. These egg-spots mimic real eggs and play an important role in the mating system of these maternal mouthbrooding fish. Here, we show that the egg-spots of haplochromines are made up of yellow pigment cells, xanthophores, and that a gene coding for a type III receptor tyrosine kinase, colony-stimulating factor 1 receptor a (csf1ra), is expressed in egg-spot tissue. Molecular evolutionary analyses reveal that the extracellular ligand-binding and receptor-interacting domain of csf1ra underwent adaptive sequence evolution in the ancestral lineage of the haplochromines, coinciding with the emergence of egg-dummies. We also find that csf1ra is expressed in the egg-dummies of a distantly related cichlid species, the ectodine cichlid Ophthalmotilapia ventralis, in which markings with similar functions evolved on the pelvic fin in convergence to those of the haplochromines. We conclude that modifications of existing signal transduction mechanisms might have evolved in the haplochromine lineage in association with the origination of anal fin egg-dummies. That positive selection has acted during the evolution of a color gene that seems to be involved in the morphogenesis of a sexually selected trait, the egg-dummies, highlights the importance of further investigations of the comparative genomic basis of the phenotypic diversification of cichlid fishes.

  6. Adaptive sequence evolution in a color gene involved in the formation of the characteristic egg-dummies of male haplochromine cichlid fishes

    PubMed Central

    Salzburger, Walter; Braasch, Ingo; Meyer, Axel

    2007-01-01

    Background The exceptionally diverse species flocks of cichlid fishes in East Africa are prime examples of parallel adaptive radiations. About 80% of East Africa's more than 1 800 endemic cichlid species, and all species of the flocks of Lakes Victoria and Malawi, belong to a particularly rapidly evolving lineage, the haplochromines. One characteristic feature of the haplochromines is their possession of egg-dummies on the males' anal fins. These egg-spots mimic real eggs and play an important role in the mating system of these maternal mouthbrooding fish. Results Here, we show that the egg-spots of haplochromines are made up of yellow pigment cells, xanthophores, and that a gene coding for a type III receptor tyrosine kinase, colony-stimulating factor 1 receptor a (csf1ra), is expressed in egg-spot tissue. Molecular evolutionary analyses reveal that the extracellular ligand-binding and receptor-interacting domain of csf1ra underwent adaptive sequence evolution in the ancestral lineage of the haplochromines, coinciding with the emergence of egg-dummies. We also find that csf1ra is expressed in the egg-dummies of a distantly related cichlid species, the ectodine cichlid Ophthalmotilapia ventralis, in which markings with similar functions evolved on the pelvic fin in convergence to those of the haplochromines. Conclusion We conclude that modifications of existing signal transduction mechanisms might have evolved in the haplochromine lineage in association with the origination of anal fin egg-dummies. That positive selection has acted during the evolution of a color gene that seems to be involved in the morphogenesis of a sexually selected trait, the egg-dummies, highlights the importance of further investigations of the comparative genomic basis of the phenotypic diversification of cichlid fishes. PMID:18005399

  7. D-O Events in the Southern Tropics of East Africa? Initial XRF Results From the Lake Malawi Drilling Project

    NASA Astrophysics Data System (ADS)

    Brown, E. T.; Johnson, T. C.; Scholz, C. A.; King, J.; Cohen, A. S.

    2006-12-01

    As part of the Lake Malawi Drilling Project we have undertaken a 1 cm-scale resolution XRF scanning study of core from site 2A in the Northern Basin of the lake (ca. 10 South latitude). This 38-m core provides an essentially continuous record of regional climate over the past 70,000 years, so our XRF analyses correspond to an average temporal resolution of approximately 20 years. We have focused our initial study on certain parameters, including Fe, Zr:Ti, and Si:Ti. These may be interpreted to represent changing input of terrigenous sediments (delivered to the lake rivers), soils developed from weathered volcanic ash (delivered more effectively under drier windier conditions), and biogenic silica, respectively. Our initial analyses of the XRF results indicate abrupt and strong, millennial-scale variability in regional climate throughout the past 70,000 years. The series of events consists of rapid (~100-year) increases in Zr:Ti and Si:Ti followed by slower decreases toward background values. These events are strikingly similar in form and in timing to Dansgaard- Oeschger events of high northern latitudes. The Younger Dryas and the Holocene "cold" periods in the Northern Hemisphere were times of enhanced input of wind-blown volcanic ash-derived materials and of diatom productivity, probably stimulated by northerly winds and upwelling in the north of the lake. Interestingly, in contrast to the Late Glacial and Holocene, times of higher productivity and enhanced input of volcanic-ash derived material in the earlier part of the record coincide with episodes of warming as recorded in Greenland ice. This suggests that a significant change in the tropical response to climate forcing occurred at the time of waning of Northern Hemisphere glaciation.

  8. Hedgehog signaling mediates adaptive variation in a dynamic functional system in the cichlid feeding apparatus

    PubMed Central

    Hu, Yinan; Albertson, R. Craig

    2014-01-01

    Adaptive variation in the craniofacial skeleton is a key component of resource specialization and habitat divergence in vertebrates, but the proximate genetic mechanisms that underlie complex patterns of craniofacial variation are largely unknown. Here we demonstrate that the Hedgehog (Hh) signaling pathway mediates widespread variation across a complex functional system that affects the kinematics of lower jaw depression—the opercular four-bar linkage apparatus—among Lake Malawi cichlids. By using a combined quantitative trait locus mapping and population genetics approach, we show that allelic variation in the Hh receptor, ptch1, affects the development of distinct bony elements in the head that represent two of three movable links in this functional system. The evolutionarily derived allele is found in species that feed from the water column, and is associated with shifts in anatomy that translate to a four-bar system capable of faster jaw rotation. Alternatively, the ancestral allele is found in species that feed on attached algae, and is associated with the development of a four-bar system that predicts slower jaw movement. Experimental manipulation of the Hh pathway during cichlid development recapitulates functionally salient natural variation in craniofacial geometry. In all, these results significantly extend our understanding of the mechanisms that fine-tune the craniofacial skeletal complex during adaptation to new foraging niches. PMID:24912175

  9. Hedgehog signaling mediates adaptive variation in a dynamic functional system in the cichlid feeding apparatus.

    PubMed

    Hu, Yinan; Albertson, R Craig

    2014-06-10

    Adaptive variation in the craniofacial skeleton is a key component of resource specialization and habitat divergence in vertebrates, but the proximate genetic mechanisms that underlie complex patterns of craniofacial variation are largely unknown. Here we demonstrate that the Hedgehog (Hh) signaling pathway mediates widespread variation across a complex functional system that affects the kinematics of lower jaw depression--the opercular four-bar linkage apparatus--among Lake Malawi cichlids. By using a combined quantitative trait locus mapping and population genetics approach, we show that allelic variation in the Hh receptor, ptch1, affects the development of distinct bony elements in the head that represent two of three movable links in this functional system. The evolutionarily derived allele is found in species that feed from the water column, and is associated with shifts in anatomy that translate to a four-bar system capable of faster jaw rotation. Alternatively, the ancestral allele is found in species that feed on attached algae, and is associated with the development of a four-bar system that predicts slower jaw movement. Experimental manipulation of the Hh pathway during cichlid development recapitulates functionally salient natural variation in craniofacial geometry. In all, these results significantly extend our understanding of the mechanisms that fine-tune the craniofacial skeletal complex during adaptation to new foraging niches.

  10. Induced cytochrome P450 1A activity in cichlid fishes from Guandu River and Jacarepaguá Lake, Rio de Janeiro, Brazil.

    PubMed

    Parente, Thiago E M; De-Oliveira, Ana C A X; Paumgartten, Francisco J R

    2008-03-01

    The induction of cytochrome P4501A-mediated activity (e.g. ethoxyresorufin-O-deethylation, EROD) has been used as a biomarker for monitoring fish exposure to AhR-receptor ligands such as polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB) and polychlorinated dibenzo-dioxins/furans (PCDD/Fs). In this study we found that hepatic EROD is induced in fish ("Nile tilapia", Oreochromis niloticus and "acará", Geophagus brasiliensis) from the Guandu River (7-17-fold) and Jacarepaguá Lake (7-fold), Rio de Janeiro, Brazil. Since both cichlid fish are consumed by the local population and the Guandu River is the main source of the drinking water supply for the greater Rio de Janeiro metropolitan area, pollution by cytochrome P4501A-inducing chemicals is a cause for concern and should be further investigated in sediments, water and biota. We additionally showed that EROD activity in the fish liver post-mitochondrial supernatant-simpler, cheaper and less time consuming to prepare than the microsomal fraction-is sufficiently sensitive for monitoring purposes.

  11. Comparative support for the expensive tissue hypothesis: Big brains are correlated with smaller gut and greater parental investment in Lake Tanganyika cichlids.

    PubMed

    Tsuboi, Masahito; Husby, Arild; Kotrschal, Alexander; Hayward, Alexander; Buechel, Séverine D; Zidar, Josefina; Løvlie, Hanne; Kolm, Niclas

    2015-01-01

    The brain is one of the most energetically expensive organs in the vertebrate body. Consequently, the energetic requirements of encephalization are suggested to impose considerable constraints on brain size evolution. Three main hypotheses concerning how energetic constraints might affect brain evolution predict covariation between brain investment and (1) investment into other costly tissues, (2) overall metabolic rate, and (3) reproductive investment. To date, these hypotheses have mainly been tested in homeothermic animals and the existing data are inconclusive. However, there are good reasons to believe that energetic limitations might play a role in large-scale patterns of brain size evolution also in ectothermic vertebrates. Here, we test these hypotheses in a group of ectothermic vertebrates, the Lake Tanganyika cichlid fishes. After controlling for the effect of shared ancestry and confounding ecological variables, we find a negative association between brain size and gut size. Furthermore, we find that the evolution of a larger brain is accompanied by increased reproductive investment into egg size and parental care. Our results indicate that the energetic costs of encephalization may be an important general factor involved in the evolution of brain size also in ectothermic vertebrates. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

  12. Foraging environment determines the genetic architecture and evolutionary potential of trophic morphology in cichlid fishes.

    PubMed

    Parsons, Kevin J; Concannon, Moira; Navon, Dina; Wang, Jason; Ea, Ilene; Groveas, Kiran; Campbell, Calum; Albertson, R Craig

    2016-12-01

    Phenotypic plasticity allows organisms to change their phenotype in response to shifts in the environment. While a central topic in current discussions of evolutionary potential, a comprehensive understanding of the genetic underpinnings of plasticity is lacking in systems undergoing adaptive diversification. Here, we investigate the genetic basis of phenotypic plasticity in a textbook adaptive radiation, Lake Malawi cichlid fishes. Specifically, we crossed two divergent species to generate an F3 hybrid mapping population. At early juvenile stages, hybrid families were split and reared in alternate foraging environments that mimicked benthic/scraping or limnetic/sucking modes of feeding. These alternate treatments produced a variation in morphology that was broadly similar to the major axis of divergence among Malawi cichlids, providing support for the flexible stem theory of adaptive radiation. Next, we found that the genetic architecture of several morphological traits was highly sensitive to the environment. In particular, of 22 significant quantitative trait loci (QTL), only one was shared between the environments. In addition, we identified QTL acting across environments with alternate alleles being differentially sensitive to the environment. Thus, our data suggest that while plasticity is largely determined by loci specific to a given environment, it may also be influenced by loci operating across environments. Finally, our mapping data provide evidence for the evolution of plasticity via genetic assimilation at an important regulatory locus, ptch1. In all, our data address long-standing discussions about the genetic basis and evolution of plasticity. They also underscore the importance of the environment in affecting developmental outcomes, genetic architectures, morphological diversity and evolutionary potential.

  13. Phytoliths Used to Investigate the Effects of the Indonesian Mount Toba Super-Eruption (~75 kyr) in East Africa: A Subdecadal Record from Lake Malawi

    NASA Astrophysics Data System (ADS)

    Yost, C. L.; Cohen, A. S.

    2014-12-01

    The recent discovery of cryptotephra visually and chemically matched to the Youngest Toba Tuff (YTT, 75.0 ± 0.9 kyr) in Lake Malawi drill core sediments has spurred renewed interest in this period of time in East Africa. The YTT is the most recent and largest of the four Mount Toba eruptions, and is the only super-eruption to have taken place during the Quaternary. The timing of the YTT approximately coincides with a hypothesized human genetic bottleneck. Several climate models have proposed an episode of global cooling following the YTT; however, the magnitude and duration of the cooling is much debated, ranging from just a few degrees of cooling to a state of volcanic winter. Cored sediments from Lake Malawi provide an excellent record of local variability in the lake's watershed that may be linked to specific climatic events. To investigate the possible effects of the YTT in East Africa, we continuously sampled Lake Malawi drill core 2A-10H-2 at 2-4 mm (~6 yr) intervals above and below the first occurrence of the YTT. Poaceae phytoliths were grouped into plant functional types (C3, C4, xerophytic, mesophytic, arboreal, etc.), revealing mostly subtle changes in terrestrial vegetation over the ~400 yr time period examined. Abrupt increases in concentration values for phytoliths derived from riverine Podostemaceae plants appear to signal increased discharge from rivers draining the surrounding uplands. Perhaps most significant is the increasing trend in burned phytoliths and decreasing trend in tree phytoliths post-YTT. Although there appears to be a very weak cooling signal synchronous with the YTT, the most abrupt terrestrial vegetation changes appear to be better correlated with the deposition of a slightly older cryptotephra horizon derived from the local Rungwe Volcanic Province. A potential complication with this record is the existence of a turbidite pre-YTT that encompasses the Rungwe horizon.

  14. Ecological and Lineage-Specific Factors Drive the Molecular Evolution of Rhodopsin in Cichlid Fishes.

    PubMed

    Torres-Dowdall, Julián; Henning, Frederico; Elmer, Kathryn R; Meyer, Axel

    2015-11-01

    The visual system in the colorful cichlid fishes from the African great lakes is believed to be important for their adaptive radiations. However, few studies have attempted to compare the visual system of radiating cichlid lineages with that of cichlids that have not undergone recent radiations. One such study published in this journal (Schott RK, Refvik SP, Hauser FE, López-Fernández H, Chang BSW. 2014. Divergent positive selection in rhodopsin from lake and riverine cichlid fishes. Mol Biol Evol. 31:1149-1165) found divergent selection on rhodopsin between African lacustrine and riverine cichlid species and riverine Neotropical cichlids, concluding that ecology drives the molecular evolution of this opsin. Here, we expand this analysis by incorporating rhodopsin sequences from Neotropical lacustrine cichlids and show that both ecology and phylogeny are important drivers of the molecular evolution of rhodopsin in cichlids. We found little overlap of sites under selection between African and Neotropical lineages and a faster rate of molecular evolution in African compared with Neotropical cichlids. These results support the notion that genetic or population genetic features particular to African cichlids contributed to their radiations. © The Author 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  15. Genetic evidence for prevalence of alloparental care in a socially monogamous biparental cichlid fish, Perissodus microlepis, from Lake Tanganyika supports the "selfish shepherd effect" hypothesis.

    PubMed

    Lee, Hyuk Je; Heim, Valentin; Meyer, Axel

    2016-05-01

    Alloparental care - care for unrelated young - is rare in animals, and its ecological or evolutionary advantages or, alternative maladaptive nature, remain unclear. We investigate alloparental care in the socially monogamous cichlid fish Perissodus microlepis from Lake Tanganyika that exhibits bi-parental care. In a genetic parentage analysis, we discovered a surprisingly high percentage of alloparental care represented by brood mixing, extra-pair paternity and extra-pair maternity in all broods that we investigated. The percentage of nondescendant juveniles of other parents, i.e., brood mixing, ranged from 5% to 57% (mean = 28%). The distribution of genetic parentage also suggests that this socially monogamous species has, in fact, polygamous mating system. The prevalence of genetically mixed broods can be best explained by two, not mutually exclusive hypotheses on farming-out and fostering behaviors. In the majority of broods, the sizes of the parents' own (descendant) offspring were significantly larger than those of the adopted (nondescendant) juveniles, supporting the 'selfish shepherd effect' hypothesis, i.e., that foster parents preferentially accept unrelated "smaller or not larger" young since this would tend to lower the predation risks for their own larger offspring. There was also a tendency for larger parents particularly mothers, more so than smaller parents, to care predominantly for their own offspring. Larger parents might be better at defending against cuckoldry and having foreign young dumped into their broods through farming-out behavior. This result might argue for maladaptive effects of allopatric care for the foster parents that only larger and possibly more experienced pairs can guard against. It needs to be determined why, apparently, the ability to recognize one's own young has not evolved in this species.

  16. Uncovering human social networks in coping with Lake Chilwa recessions in Malawi.

    PubMed

    Nagoli, Joseph; Chiwona-Karltun, Linley

    2017-05-01

    This paper provides an in-depth understanding of social dynamics in the form of kinship ties in matrilineal societies. It unpacks gender roles and relationships at the community level to understand how social structures, created by the pattern of relations, enhance or hinder coping initiatives during lake recessions in the Lake Chilwa socio-ecological system. Using qualitative and quantitative methods including in-depth interviews, Focus Group Discussions (FGD) and household questionnaires, this paper provides insights into how people in the Lake Chilwa social-ecological system prepare for and cope with Lake Chilwa water recessions by capitalising on their social networks. The findings have shown that during lake recessions poor households in the Lake Chilwa socio-ecological system are cushioned by fellow households through lineage networks. There is strong tradition secured through kinship ties where the generic term 'mwambo wathu' (our tradition) embraces a group of formative norms enforced via a series of rules and rituals. Based in a matrilineal system, women have strong rights over land allocation and use in which the female sorority group 'mbumba' is very stable. There is a great deal of reciprocity and food redistribution among the households. This self-organization provides deeper meaning about how people assimilate the dynamics affecting their social and natural environments. Specifically the findings provide evidence on how households, communities and their livelihoods in Africa are reconstructed as natural resources fluctuate.

  17. Riparian ecosystem resilience and livelihood strategies under test: lessons from Lake Chilwa in Malawi and other lakes in Africa.

    PubMed

    Kafumbata, Dalitso; Jamu, Daniel; Chiotha, Sosten

    2014-04-05

    This paper reviews the importance of African lakes and their management challenges. African inland lakes contribute significantly to food security, livelihoods and national economies through direct exploitation of fisheries, water resources for irrigation and hydropower generation. Because of these key contributions, the ecosystem services provided are under significant stress mainly owing to high demand by increasing populations, negative anthropogenic impacts on lake catchments and high levels of poverty which result in unsustainable use. Climate variability exacerbates the stress on these ecosystems. Current research findings show that the lakes cannot sustain further development activities on the scale seen over the past few decades. Millions of people are at risk of losing livelihoods through impacts on livestock and wildlife. The review further shows that the problems facing these lakes are beyond the purview of current management practices. A much better understanding of the interactions and feedbacks between different components of the lake socio-ecological systems is needed to address the complex challenges of managing these ecosystem services. This review suggests that the three small wetlands of Chad, Chilwa and Naivasha provide an opportunity for testing novel ideas that integrate sustainability of natural resource management with livelihoods in order to inform policy on how future land use and climatic variability will affect both food security and the ecosystem services associated with it.

  18. Riparian ecosystem resilience and livelihood strategies under test: lessons from Lake Chilwa in Malawi and other lakes in Africa

    PubMed Central

    Kafumbata, Dalitso; Jamu, Daniel; Chiotha, Sosten

    2014-01-01

    This paper reviews the importance of African lakes and their management challenges. African inland lakes contribute significantly to food security, livelihoods and national economies through direct exploitation of fisheries, water resources for irrigation and hydropower generation. Because of these key contributions, the ecosystem services provided are under significant stress mainly owing to high demand by increasing populations, negative anthropogenic impacts on lake catchments and high levels of poverty which result in unsustainable use. Climate variability exacerbates the stress on these ecosystems. Current research findings show that the lakes cannot sustain further development activities on the scale seen over the past few decades. Millions of people are at risk of losing livelihoods through impacts on livestock and wildlife. The review further shows that the problems facing these lakes are beyond the purview of current management practices. A much better understanding of the interactions and feedbacks between different components of the lake socio-ecological systems is needed to address the complex challenges of managing these ecosystem services. This review suggests that the three small wetlands of Chad, Chilwa and Naivasha provide an opportunity for testing novel ideas that integrate sustainability of natural resource management with livelihoods in order to inform policy on how future land use and climatic variability will affect both food security and the ecosystem services associated with it. PMID:24535395

  19. Niche divergence facilitated by fine‐scale ecological partitioning in a recent cichlid fish adaptive radiation

    PubMed Central

    Ford, Antonia G. P.; Rüber, Lukas; Newton, Jason; Dasmahapatra, Kanchon K.; Balarin, John D.; Bruun, Kristoffer; Day, Julia J.

    2016-01-01

    Ecomorphological differentiation is a key feature of adaptive radiations, with a general trend for specialization and niche expansion following divergence. Ecological opportunity afforded by invasion of a new habitat is thought to act as an ecological release, facilitating divergence, and speciation. Here, we investigate trophic adaptive morphology and ecology of an endemic clade of oreochromine cichlid fishes (Alcolapia) that radiated along a herbivorous trophic axis following colonization of an isolated lacustrine environment, and demonstrate phenotype‐environment correlation. Ecological and morphological divergence of the Alcolapia species flock are examined in a phylogenomic context, to infer ecological niche occupation within the radiation. Species divergence is observed in both ecology and morphology, supporting the importance of ecological speciation within the radiation. Comparison with an outgroup taxon reveals large‐scale ecomorphological divergence but shallow genomic differentiation within the Alcolapia adaptive radiation. Ancestral morphological reconstruction suggests lake colonization by a generalist oreochromine phenotype that diverged in Lake Natron to varied herbivorous morphologies akin to specialist herbivores in Lakes Tanganyika and Malawi. PMID:27659769

  20. Sensory drive in cichlid speciation.

    PubMed

    Maan, Martine E; Hofker, Kees D; van Alphen, Jacques J M; Seehausen, Ole

    2006-06-01

    The role of selection in speciation is a central yet poorly understood problem in evolutionary biology. The rapid radiations of extremely colorful cichlid fish in African lakes have fueled the hypothesis that sexual selection can drive species divergence without geographical isolation. Here we present experimental evidence for a mechanism by which sexual selection becomes divergent: in two sibling species from Lake Victoria, female mating preferences for red and blue male nuptial coloration coincide with their context-independent sensitivities to red and blue light, which in turn correspond to a difference in ambient light in the natural habitat of the species. These results suggest that natural selection on visual performance, favoring different visual properties in different spectral environments, may lead to divergent sexual selection on male nuptial coloration. This interplay of ecological and sexual selection along a light gradient may provide a mechanism of rapid speciation through divergent sensory drive.

  1. The effect of selection on a long wavelength-sensitive (LWS) opsin gene of Lake Victoria cichlid fishes

    PubMed Central

    Terai, Yohey; Mayer, Werner E.; Klein, Jan; Tichy, Herbert; Okada, Norihiro

    2002-01-01

    In East African Lake Victoria >200 endemic species of haplochromine fishes have been described on the basis of morphological and behavioral differences. Yet molecular analysis has failed to reveal any species-specific differences among these fishes in either mitochondrial or nuclear genes. Although the genes could be shown to vary, the variations represent trans-species polymorphisms not yet assorted along species lines. Nevertheless, fixed genetic differences must exist between the species at loci responsible for the adaptive characters distinguishing the various forms from one another. Here we describe variation and fixation at the long wavelength-sensitive (LWS) opsin locus, which is selection-driven, adaptive, and if not species- then at least population-specific. Because color is one of the characters distinguishing species of haplochromine fishes and color perception plays an important part in food acquisition and mate choice, we suggest that the observed variation and fixation at the LWS opsin locus may have been involved in the process that has led to the spectacular species divergence of haplochromine fishes in Lake Victoria. PMID:12438648

  2. The Eyes Have It: Regulatory and Structural Changes Both Underlie Cichlid Visual Pigment Diversity

    PubMed Central

    Marshall, N. Justin; Cronin, Thomas W.; Seehausen, Ole; Carleton, Karen L.

    2009-01-01

    A major goal of evolutionary biology is to unravel the molecular genetic mechanisms that underlie functional diversification and adaptation. We investigated how changes in gene regulation and coding sequence contribute to sensory diversification in two replicate radiations of cichlid fishes. In the clear waters of Lake Malawi, differential opsin expression generates diverse visual systems, with sensitivities extending from the ultraviolet to the red regions of the spectrum. These sensitivities fall into three distinct clusters and are correlated with foraging habits. In the turbid waters of Lake Victoria, visual sensitivity is constrained to longer wavelengths, and opsin expression is correlated with ambient light. In addition to regulatory changes, we found that the opsins coding for the shortest- and longest-wavelength visual pigments have elevated numbers of potentially functional substitutions. Thus, we present a model of sensory evolution in which both molecular genetic mechanisms work in concert. Changes in gene expression generate large shifts in visual pigment sensitivity across the collective opsin spectral range, but changes in coding sequence appear to fine-tune visual pigment sensitivity at the short- and long-wavelength ends of this range, where differential opsin expression can no longer extend visual pigment sensitivity. PMID:20027211

  3. The eyes have it: regulatory and structural changes both underlie cichlid visual pigment diversity.

    PubMed

    Hofmann, Christopher M; O'Quin, Kelly E; Marshall, N Justin; Cronin, Thomas W; Seehausen, Ole; Carleton, Karen L

    2009-12-01

    A major goal of evolutionary biology is to unravel the molecular genetic mechanisms that underlie functional diversification and adaptation. We investigated how changes in gene regulation and coding sequence contribute to sensory diversification in two replicate radiations of cichlid fishes. In the clear waters of Lake Malawi, differential opsin expression generates diverse visual systems, with sensitivities extending from the ultraviolet to the red regions of the spectrum. These sensitivities fall into three distinct clusters and are correlated with foraging habits. In the turbid waters of Lake Victoria, visual sensitivity is constrained to longer wavelengths, and opsin expression is correlated with ambient light. In addition to regulatory changes, we found that the opsins coding for the shortest- and longest-wavelength visual pigments have elevated numbers of potentially functional substitutions. Thus, we present a model of sensory evolution in which both molecular genetic mechanisms work in concert. Changes in gene expression generate large shifts in visual pigment sensitivity across the collective opsin spectral range, but changes in coding sequence appear to fine-tune visual pigment sensitivity at the short- and long-wavelength ends of this range, where differential opsin expression can no longer extend visual pigment sensitivity.

  4. Relaxed trait covariance in interspecific cichlid hybrids predicts morphological diversity in adaptive radiations.

    PubMed

    Selz, O M; Lucek, K; Young, K A; Seehausen, O

    2014-01-01

    The process of adaptive radiation involves multiple events of speciation in short succession, associated with ecological diversification. Understanding this process requires identifying the origins of heritable phenotypic variation that allows adaptive radiation to progress. Hybridization is one source of genetic and morphological variation that may spur adaptive radiation. We experimentally explored the potential role of hybridization in facilitating the onset of adaptive radiation. We generated first- and second-generation hybrids of four species of African cichlid fish, extant relatives of the putative ancestors of the adaptive radiations of Lakes Victoria and Malawi. We compared patterns in hybrid morphological variation with the variation in the lake radiations. We show that significant fractions of the interspecific morphological variation and the major trajectories in morphospace that characterize whole radiations can be generated in second-generation hybrids. Furthermore, we show that covariation between traits is relaxed in second-generation hybrids, which may facilitate adaptive diversification. These results support the idea that hybridization can provide the heritable phenotypic diversity necessary to initiate adaptive radiation. © 2013 The Authors. Journal of Evolutionary Biology © 2013 European Society For Evolutionary Biology.

  5. 3D Variations in Sediment Architecture in the Central Basin of Lake Malawi from the SEGMeNT Active-Source Experiment

    NASA Astrophysics Data System (ADS)

    Eatmon, A.; Accardo, N. J.; Shillington, D. J.; Onyango, E. A.; Scholz, C. A.; McCartney, T.; Ebinger, C. J.; Gaherty, J. B.; Nyblade, A.; Chindandali, P. R. N.; Kamihanda, G.; Ferdinand, R.; Salima, J.; Mruma, A. H.

    2016-12-01

    A fundamental question in geophysics is how continental rifts evolve from initiation to breakup. Our study aims to elucidate the controls on early-stage rifting utilizing recently collected active-source wide-angle refraction data from the weakly extended Malawi Rift, which is composed of a series of border-fault bound basins whose polarity reverses along strike. Our study focuses on the Central Basin of Lake Malawi. The Central Basin is bounded to the west by the 1,000 m high Central Basin border fault and contains a series of enigmatic structures within the basin. To constrain the thickness of synrift and pre-rift sediments and upper crustal structure associated with intrabasinal structure, we have undertaken 3D velocity modeling of the Central Basin using new active-source data acquired in Lake Malawi (Nyasa) as a part of the SEGMeNT project. We picked first arrivals on shots recorded on 12 "lake" bottom seismometers resulting in over 38,000 unique picks with maximum offsets of 90 km. We then inverted these picks using the First Arrival Seismic Tomography (FAST) package for the 3D structure. The resulting model spans 80 km north to south, 50 km east to west, and 10 km in depth. We also apply strict quality control measures to ensure only robust picks are utilized in the inversion. Starting models are built from smoothed inversion of picks at close offsets to ensure that shallow structure is not mapped to depth. Our results indicate a marked transition in the character of sedimentary basins within the Central Basin. Sediments thicken to the west at the southern end of the Central Basin reaching a maximum thickness of 4.5 km and in contrast, sediments thicken to the east at the northern end near Manda, Tanzania and reach a maximum thickness of 4.0 km. This may indicate that the west dipping border fault that bounds the eastern side of the basin to the north influences the Central Basin at its northern end. We image a linear, high-velocity feature that extends from

  6. Full-vector paleomagnetic secular variation records from latest quaternary sediments of Lake Malawi (10.0°S, 34.3°E)

    NASA Astrophysics Data System (ADS)

    Lund, Steve; Platzman, Ellen; Johnson, Tom

    2016-07-01

    We have conducted a paleomagnetic study of Late Quaternary sediments from Lake Malawi, East Africa, in order to develop a high-resolution record of paleomagnetic secular variation (PSV). This study has recovered PSV records from two cores (3P, 6P) in northern Lake Malawi (10.0°S, 34.3°E). The PSV appears to be recorded in fine-grained detrital magnetite/titanomagnetite grains. Detailed af demagnetization of the natural remanence (NRM) shows that a distinctive characteristic remanence (ChRM) is demagnetized from ∼20 to 80 mT, which decreases simply toward the origin. The resulting directional PSV records for 3P and 6P are easily correlatable with 29 distinct inclination features and 29 declination features. The statistical character of the PSV in both cores is consistent with Holocene PSV noted at other Holocene equatorial sites. Radiocarbon dating of the cores is based on 18 independent radiocarbon dates and four dated stratigraphic horizons that can be correlated into each core. The final directional PSV time series cover the last 24,000 years with an average sediment accumulation rate of ∼30 cm/kyr. We have also developed a relative paleointensity estimate for these PSV records based on normalizing the NRM (after 20 mT af demagnetization) by the SIRM (after 20 mT af demagnetization). Changing sedimentation patterns complicate any attempt to develop a single paleointensity record for the entire core lengths. We have developed a relative paleointensity record for the last 6000 years that has 14 correlatable features including 5 notable peaks in intensity. Three of these peaks are synchronous with paleointensity highs farther north in SE Europe/SW Asia/Egypt but two of the peaks are at times of low paleointensity farther north. We interpret this to indicate that Lake Malawi (10°S) is at least partly under the influence of a different flux-regeneration region of the outer-core dynamo. A relative paleointensity record was also developed for ∼11,000-24,000 YBP

  7. Quantifying mating success of territorial males and sneakers in a bower-building cichlid fish

    PubMed Central

    Magalhaes, I. S.; Smith, A. M.; Joyce, D. A.

    2017-01-01

    The strategies and traits males evolve to mate with females are incredible in their diversity. Theory on the evolution of secondary sexual characters suggests that evolving any costly trait or strategy will pay off and stabilise in the population if it is advantageous compared to the alternative less costly strategy, but quantifying the relative success of the two can be difficult. In Lake Malawi, Africa, there are >200 species of cichlid fish in which the males form leks and spend several weeks per year building sand-castle “bowers” several times their size. We tested the idea that a less costly “sneaking” strategy could be successful by quantifying the mating success of bower-holding versus non-bower-holding males. We PIT-tagged every fish in a semi-natural experimental set-up and placed tag-readers on the side of bowers to determine which fish held a bower. We then genotyped the eggs removed from females’ mouths to assign paternity of each egg. Broods were fathered by up to 3 different males. Although paternity was mostly assigned to males that held a bower, a small number of males who did not own a bower were more successful than some of those that did, indicating a role for an alternative strategy in these bower builders. PMID:28128313

  8. Quantifying mating success of territorial males and sneakers in a bower-building cichlid fish.

    PubMed

    Magalhaes, I S; Smith, A M; Joyce, D A

    2017-01-27

    The strategies and traits males evolve to mate with females are incredible in their diversity. Theory on the evolution of secondary sexual characters suggests that evolving any costly trait or strategy will pay off and stabilise in the population if it is advantageous compared to the alternative less costly strategy, but quantifying the relative success of the two can be difficult. In Lake Malawi, Africa, there are >200 species of cichlid fish in which the males form leks and spend several weeks per year building sand-castle "bowers" several times their size. We tested the idea that a less costly "sneaking" strategy could be successful by quantifying the mating success of bower-holding versus non-bower-holding males. We PIT-tagged every fish in a semi-natural experimental set-up and placed tag-readers on the side of bowers to determine which fish held a bower. We then genotyped the eggs removed from females' mouths to assign paternity of each egg. Broods were fathered by up to 3 different males. Although paternity was mostly assigned to males that held a bower, a small number of males who did not own a bower were more successful than some of those that did, indicating a role for an alternative strategy in these bower builders.

  9. Feeding in the dark: lateral-line-mediated prey detection in the peacock cichlid Aulonocara stuartgranti.

    PubMed

    Schwalbe, Margot A B; Bassett, Daniel K; Webb, Jacqueline F

    2012-06-15

    The cranial lateral line canal system of teleost fishes is morphologically diverse and is characterized by four patterns. One of these, widened lateral line canals, has evolved convergently in a wide range of teleosts, including the Lake Malawi peacock cichlids (Aulonocara), and has been attributed to its role in prey detection. The ability to study Aulonocara in the laboratory provides an opportunity to test the hypothesis that their reported ability to feed on invertebrate prey living in sandy substrates in their natural habitat is the result of lateral-line-mediated prey detection. The goal of this study was to determine whether Aulonocara stuartgranti could detect hydrodynamic stimuli generated by tethered brine shrimp (visualized using digital particle image velocimetry) under light and dark conditions, with and without treatment with cobalt chloride, which is known to temporarily inactivate the lateral line system. Fish were presented with six pairs of tethered live and dead adult brine shrimp and feeding behavior was recorded with HD digital video. Results demonstrate that A. stuartgranti: (1) uses the same swimming/feeding strategy as they do in the field; (2) detects and consumes invertebrate prey in the dark using its lateral line system; (3) alters prey detection behavior when feeding on the same prey under light and dark conditions, suggesting the involvement of multiple sensory modalities; and (4) after treatment with cobalt chloride, exhibits a reduction in their ability to detect hydrodynamic stimuli produced by prey, especially in the dark, thus demonstrating the role of the lateral line system in prey detection.

  10. Genetic mapping of horizontal stripes in Lake Victoria cichlid fishes: benefits and pitfalls of using RAD markers for dense linkage mapping.

    PubMed

    Henning, Frederico; Lee, Hyuk Je; Franchini, Paolo; Meyer, Axel

    2014-11-01

    The genetic dissection of naturally occurring phenotypes sheds light on many fundamental and longstanding questions in speciation and adaptation and is a central research topic in evolutionary biology. Until recently, forward-genetic approaches were virtually impossible to apply to nonmodel organisms, but the development of next-generation sequencing techniques eases this difficulty. Here, we use the ddRAD-seq method to map a colour trait with a known adaptive function in cichlid fishes, well-known textbook examples for rapid rates of speciation and astonishing phenotypic diversification. A suite of phenotypic key innovations is related to speciation and adaptation in cichlids, among which body coloration features prominently. The focal trait of this study, horizontal stripes, evolved in parallel in several cichlid radiations and is associated with piscivorous foraging behaviour. We conducted interspecific crosses between Haplochromis sauvagei and H. nyererei and constructed a linkage map with 867 SNP markers distributed on 22 linkage groups and total size of 1130.63 cM. Lateral stripes are inherited as a Mendelian trait and map to a single genomic interval that harbours a paralog of a gene with known function in stripe patterning. Dorsolateral and mid-lateral stripes were always coinherited and are thus under the same genetic control. Additionally, we directly quantify the genotyping error rates in RAD markers and offer guidelines for identifying and dealing with errors. Uncritical marker selection was found to severely impact linkage map construction. Fortunately, by applying appropriate quality control steps, a genotyping accuracy of >99.9% can be reached, thus allowing for efficient linkage mapping of evolutionarily relevant traits.

  11. The oldest fossil cichlids (Teleostei: Perciformes): indication of a 45 million-year-old species flock.

    PubMed Central

    Murray, A. M.

    2001-01-01

    Five closely related species of fossil cichlids collected from an Eocene site in Tanzania, East Africa, represent the oldest known cichlids. The specimens are whole-body, articulated fishes that are extremely well preserved and, therefore, have the potential to add to our knowledge of the history of this family. Modern cichlids are particularly well known for the numerous species flocks of the East African Great Lakes. A great deal of research is ongoing regarding all aspects of the fishes in these flocks, including their evolutionary history The new collection of fossils reported here is interpreted as representing a species flock that arose in a small crater lake. These fossils indicate that cichlids' ability to form species flocks evolved early in the history of this family. PMID:11321055

  12. Temporal patterns of diversification across global cichlid biodiversity (Acanthomorpha: Cichlidae).

    PubMed

    McMahan, Caleb D; Chakrabarty, Prosanta; Sparks, John S; Smith, W M Leo; Davis, Matthew P

    2013-01-01

    The contrasting distribution of species diversity across the major lineages of cichlids makes them an ideal group for investigating macroevolutionary processes. In this study, we investigate whether different rates of diversification may explain the disparity in species richness across cichlid lineages globally. We present the most taxonomically robust time-calibrated hypothesis of cichlid evolutionary relationships to date. We then utilize this temporal framework to investigate whether both species-rich and depauperate lineages are associated with rapid shifts in diversification rates and if exceptional species richness can be explained by clade age alone. A single significant rapid rate shift increase is detected within the evolutionary history of the African subfamily Pseudocrenilabrinae, which includes the haplochromins of the East African Great Lakes. Several lineages from the subfamilies Pseudocrenilabrinae (Australotilapiini, Oreochromini) and Cichlinae (Heroini) exhibit exceptional species richness given their clade age, a net rate of diversification, and relative rates of extinction, indicating that clade age alone is not a sufficient explanation for their increased diversity. Our results indicate that the Neotropical Cichlinae includes lineages that have not experienced a significant rapid burst in diversification when compared to certain African lineages (rift lake). Neotropical cichlids have remained comparatively understudied with regard to macroevolutionary patterns relative to African lineages, and our results indicate that of Neotropical lineages, the tribe Heroini may have an elevated rate of diversification in contrast to other Neotropical cichlids. These findings provide insight into our understanding of the diversification patterns across taxonomically disparate lineages in this diverse clade of freshwater fishes and one of the most species-rich families of vertebrates.

  13. Lilongwe, Malawi

    NASA Image and Video Library

    2016-08-10

    Lilongwe is the capital city of Malawi. Like many cities in Africa, it has seen phenomenal growth in the last 50 years. In 1966 the population was about 19,000; in 1987 the census counted 223,000 inhabitants; and in 2015 1,080,000 residents called Lilongwe home. . The Landsat image was acquired 27 August 1984, and the ASTER image on 31 July 2015. The images cover an area of 20 by 33 km, and are located at 14 degrees south, 33.8 degrees east. http://photojournal.jpl.nasa.gov/catalog/?IDNumber=pia20804

  14. Embryonic and larval development in the Midas cichlid fish species flock (Amphilophus spp.): a new evo-devo model for the investigation of adaptive novelties and species differences.

    PubMed

    Kratochwil, Claudius F; Sefton, Maggie M; Meyer, Axel

    2015-02-26

    Central American crater lake cichlid fish of the Midas species complex (Amphilophus spp.) are a model system for sympatric speciation and fast ecological diversification and specialization. Midas cichlids have been intensively analyzed from an ecological and morphological perspective. Genomic resources such as transcriptomic and genomic data sets, and a high-quality draft genome are available now. Many ecologically relevant species-specific traits and differences such as pigmentation and cranial morphology arise during development. Detailed descriptions of the early development of the Midas cichlid in particular, will help to investigate the ontogeny of species differences and adaptations. We describe the embryonic and larval development of the crater lake cichlid, Amphilophus xiloaensis, until seven days after fertilization. Similar to previous studies on teleost development, we describe six periods of embryogenesis - the zygote, cleavage, blastula, gastrula, segmentation, and post-hatching period. Furthermore, we define homologous stages to well-described teleost models such as medaka and zebrafish, as well as other cichlid species such as the Nile tilapia and the South American cichlid Cichlasoma dimerus. Key morphological differences between the embryos of Midas cichlids and other teleosts are highlighted and discussed, including the presence of adhesive glands and different early chromatophore patterns, as well as variation in developmental timing. The developmental staging of the Midas cichlid will aid researchers in the comparative investigation of teleost ontogenies. It will facilitate comparative developmental biological studies of Neotropical and African cichlid fish in particular. In the past, the species flocks of the African Great Lakes have received the most attention from researchers, but some lineages of the 300-400 species of Central American lakes are fascinating model systems for adaptive radiation and rapid phenotypic evolution. The availability

  15. Childbearing in Malawi, Africa.

    PubMed

    Gennaro, S; Kamwendo, L A; Mbweza, E; Kershbaumer, R

    1998-01-01

    Malawi is a small, landlocked country in South Eastern Africa that faces many challenges in providing health care to childbearing women. Through a partnership between the faculty of the University of Pennsylvania, School of Nursing, faculty of the Kamuzu College of Nursing in Malawi, and the Malawi Ministry of Health and Population, an ongoing collaboration has led to research and demonstration projects designed to improve the health of women and children in Malawi. To underscore the cultural context within which childbearing occurs, care of the childbearing family in Malawi is described, as is research that has documented some of the similarities and differences between childbearing in Malawi and the United States.

  16. Complete Mitochondrial DNA Sequences of the Threadfin Cichlid (Petrochromis trewavasae) and the Blunthead Cichlid (Tropheus moorii) and Patterns of Mitochondrial Genome Evolution in Cichlid Fishes

    PubMed Central

    Fischer, Christoph; Koblmüller, Stephan; Gülly, Christian; Schlötterer, Christian; Sturmbauer, Christian; Thallinger, Gerhard G.

    2013-01-01

    The cichlid fishes of the East African Great Lakes represent a model especially suited to study adaptive radiation and speciation. With several African cichlid genome projects being in progress, a promising set of closely related genomes is emerging, which is expected to serve as a valuable data base to solve questions on genotype-phenotype relations. The mitochondrial (mt) genomes presented here are the first results of the assembly and annotation process for two closely related but eco-morphologically highly distinct Lake Tanganyika cichlids, Petrochromis trewavasae and Tropheus moorii. The genomic sequences comprise 16,588 bp (P. trewavasae) and 16,590 bp (T. moorii), and exhibit the typical mitochondrial structure, with 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, and a non-coding control region. Analyses confirmed that the two species are very closely related with an overall sequence similarity of 96%. We analyzed the newly generated sequences in the phylogenetic context of 21 published labroid fish mitochondrial genomes. Consistent with other vertebrates, the D-loop region was found to evolve faster than protein-coding genes, which in turn are followed by the rRNAs; the tRNAs vary greatly in the rate of sequence evolution, but on average evolve the slowest. Within the group of coding genes, ND6 evolves most rapidly. Codon usage is similar among examined cichlid tribes and labroid families; although a slight shift in usage patterns down the gene tree could be observed. Despite having a clearly different nucleotide composition, ND6 showed a similar codon usage. C-terminal ends of Cox1 exhibit variations, where the varying number of amino acids is related to the structure of the obtained phylogenetic tree. This variation may be of functional relevance for Cox1 synthesis. PMID:23826193

  17. Detection of artificial water flows by the lateral line system of a benthic feeding cichlid fish.

    PubMed

    Schwalbe, Margot A B; Sevey, Benjamin J; Webb, Jacqueline F

    2016-04-01

    The mechanosensory lateral line system of fishes detects water motions within a few body lengths of the source. Several types of artificial stimuli have been used to probe lateral line function in the laboratory, but few studies have investigated the role of flow sensing in benthic feeding teleosts. In this study, we used artificial flows emerging from a sandy substrate to assess the contribution of flow sensing to prey detection in the peacock cichlid, Aulonocara stuartgranti, which feeds on benthic invertebrates in Lake Malawi. Using a positive reinforcement protocol, we trained fish to respond to flows lacking the visual and chemical cues generated by tethered prey in prior studies with A. stuartgranti Fish successfully responded to artificial flows at all five rates presented (characterized using digital particle image velocimetry), and showed a range of flow-sensing behaviors, including an unconditioned bite response. Immediately after lateral line inactivation, fish rarely responded to flows and the loss of vital fluorescent staining of hair cells (with 4-di-2-ASP) verified lateral line inactivation. Within 2 days post-treatment, some aspects of flow-sensing behavior returned and after 7 days, flow-sensing behavior and hair cell fluorescence both returned to pre-treatment levels, which is consistent with the reported timing of hair cell regeneration in other vertebrates. The presentation of ecologically relevant water flows to assess flow-sensing behaviors and the use of a positive reinforcement protocol are methods that present new opportunities to study the role of flow sensing in the feeding ecology of benthic feeding fishes.

  18. Mapping of pigmentation QTL on an anchored genome assembly of the cichlid fish, Metriaclima zebra.

    PubMed

    O'Quin, Claire T; Drilea, Alexi C; Conte, Matthew A; Kocher, Thomas D

    2013-04-27

    Pigmentation patterns are one of the most recognizable phenotypes across the animal kingdom. They play an important role in camouflage, communication, mate recognition and mate choice. Most progress on understanding the genetics of pigmentation has been achieved via mutational analysis, with relatively little work done to understand variation in natural populations. Pigment patterns vary dramatically among species of cichlid fish from Lake Malawi, and are thought to be important in speciation. In this study, we crossed two species, Metriaclima zebra and M. mbenjii, that differ in several aspects of their body and fin color. We genotyped 798 SNPs in 160 F2 male individuals to construct a linkage map that was used to identify quantitative trait loci (QTL) associated with the pigmentation traits of interest. We also used the linkage map to anchor portions of the M. zebra genome assembly. We constructed a linkage map consisting of 834 markers in 22 linkage groups that spanned over 1,933 cM. QTL analysis detected one QTL each for dorsal fin xanthophores, caudal fin xanthophores, and pelvic fin melanophores. Dorsal fin and caudal fin xanthophores share a QTL on LG12, while pelvic fin melanophores have a QTL on LG11. We used the mapped markers to anchor 66.5% of the M. zebra genome assembly. Within each QTL interval we identified several candidate genes that might play a role in pigment cell development. This is one of a few studies to identify QTL for natural variation in fish pigmentation. The QTL intervals we identified did not contain any pigmentation genes previously identified by mutagenesis studies in other species. We expect that further work on these intervals will identify new genes involved in pigment cell development in natural populations.

  19. Convergence of gut microbiotas in the adaptive radiations of African cichlid fishes.

    PubMed

    Baldo, Laura; Pretus, Joan Lluís; Riera, Joan Lluís; Musilova, Zuzana; Bitja Nyom, Arnold Roger; Salzburger, Walter

    2017-09-01

    Ecoevolutionary dynamics of the gut microbiota at the macroscale level, that is, in across-species comparisons, are largely driven by ecological variables and host genotype. The repeated explosive radiations of African cichlid fishes in distinct lakes, following a dietary diversification in a context of reduced genetic diversity, provide a natural setup to explore convergence, divergence and repeatability in patterns of microbiota dynamics as a function of the host diet, phylogeny and environment. Here we characterized by 16S rRNA amplicon sequencing the gut microbiota of 29 cichlid species from two distinct lakes/radiations (Tanganyika and Barombi Mbo) and across a broad dietary and phylogenetic range. Within each lake, a significant deviation between a carnivorous and herbivorous lifestyle was found. Herbivore species were characterized by an increased bacterial taxonomic and functional diversity and converged in key compositional and functional community aspects. Despite a significant lake effect on the microbiota structure, this process has occurred with remarkable parallels in the two lakes. A metabolic signature most likely explains this trend, as indicated by a significant enrichment in herbivores/omnivores of bacterial taxa and functions associated with fiber degradation and detoxification of plant chemical compounds. Overall, compositional and functional aspects of the gut microbiota individually and altogether validate and predict main cichlid dietary habits, suggesting a fundamental role of gut bacteria in cichlid niche expansion and adaptation.

  20. Rapid and parallel adaptive evolution of the visual system of Neotropical Midas cichlid fishes.

    PubMed

    Torres-Dowdall, Julián; Pierotti, Michele E R; Härer, Andreas; Karagic, Nidal; Woltering, Joost M; Henning, Frederico; Elmer, Kathryn R; Meyer, Axel

    2017-04-21

    Midas cichlid fish are a Central American species flock containing 13 described species that has been dated to only few thousand years old, a historical timescale infrequently associated with speciation. Their radiation involved the colonization of several clear water crater lakes from two turbid great lakes. Therefore, Midas cichlids have been subjected to widely varying photic conditions during their radiation. Being a primary signal relay for information from the environment to the organism, the visual system is under continuing selective pressure and a prime organ system for accumulating adaptive changes during speciation, particularly in the case of dramatic shifts in photic conditions. Here, we characterize the full visual system of Midas cichlids at organismal and genetic levels, to determine what types of adaptive changes evolved within the short time span of their radiation. We show that Midas cichlids have a diverse visual system with unexpectedly high intra- and interspecific variation in color vision sensitivity and lens transmittance. Midas cichlid populations in the clear crater lakes have convergently evolved visual sensitivities shifted towards shorter wavelengths compared to the ancestral populations from the turbid great lakes. This divergence in sensitivity is driven by changes in chromophore usage, differential opsin expression, opsin coexpression, and to a lesser degree by opsin coding sequence variation. The visual system of Midas cichlids has the evolutionary capacity to rapidly integrate multiple adaptations to changing light environments. Our data may indicate that, in early stages of divergence, changes in opsin regulation could precede changes in opsin coding sequence evolution. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  1. English Teaching Profile: Malawi.

    ERIC Educational Resources Information Center

    British Council, London (England). English Language and Literature Div.

    The role and status of English instruction in Malawi is outlined. The role of English in Malawi as a whole, English instruction within the educational system, language teacher supply and training, and British support for English instruction in Malawi are reported. English is taught as a subject in primary school and is the language of instruction…

  2. Rapid adaptation to a novel light environment: The importance of ontogeny and phenotypic plasticity in shaping the visual system of Nicaraguan Midas cichlid fish (Amphilophus citrinellus spp.).

    PubMed

    Härer, Andreas; Torres-Dowdall, Julián; Meyer, Axel

    2017-08-09

    Colonization of novel habitats is typically challenging to organisms. In the initial stage after colonization, approximation to fitness optima in the new environment can occur by selection acting on standing genetic variation, modification of developmental patterns or phenotypic plasticity. Midas cichlids have recently colonized crater Lake Apoyo from great Lake Nicaragua. The photic environment of crater Lake Apoyo is shifted towards shorter wavelengths compared to great Lake Nicaragua and Midas cichlids from both lakes differ in visual sensitivity. We investigated the contribution of ontogeny and phenotypic plasticity in shaping the visual system of Midas cichlids after colonizing this novel photic environment. To this end, we measured cone opsin expression both during development and after experimental exposure to different light treatments. Midas cichlids from both lakes undergo ontogenetic changes in cone opsin expression, but visual sensitivity is consistently shifted towards shorter wavelengths in crater lake fish, which leads to a paedomorphic retention of their visual phenotype. This shift might be mediated by lower levels of thyroid hormone in crater lake Midas cichlids (measured indirectly as dio2 and dio3 gene expression). Exposing fish to different light treatments revealed that cone opsin expression is phenotypically plastic in both species during early development, with short and long wavelength light slowing or accelerating ontogenetic changes, respectively. Notably, this plastic response was maintained into adulthood only in the derived crater lake Midas cichlids. We conclude that the rapid evolution of Midas cichlids' visual system after colonizing crater Lake Apoyo was mediated by a shift in visual sensitivity during ontogeny and was further aided by phenotypic plasticity during development. © 2017 John Wiley & Sons Ltd.

  3. Incipient speciation driven by hypertrophied lips in Midas cichlid fishes?

    PubMed

    Machado-Schiaffino, Gonzalo; Kautt, Andreas F; Torres-Dowdall, Julian; Baumgarten, Lukas; Henning, Frederico; Meyer, Axel

    2017-01-30

    Sympatric speciation has been debated in evolutionary biology for decades. Although it has gained in acceptance recently, still only a handful of empirical examples are seen as valid (e.g. crater lake cichlids). In this study, we disentangle the role of hypertrophied lips in the repeated adaptive radiations of Nicaraguan crater lake cichlid fish. We assessed the role of disruptive selection and assortative mating during the early stages of divergence and found a functional trade-off in feeding behaviour between thick- and thin-lipped ecotypes, suggesting that this trait is a target of disruptive selection. Thick-lipped fish perform better on nonevasive prey at the cost of a poorer performance on evasive prey. Using enclosures in the wild, we found that thick-lipped fish perform significantly better in rocky than in sandy habitats. We found almost no mixed pairs during two breeding seasons and hence significant assortative mating. Genetic differentiation between ecotypes seems to be related to the time since colonization, being subtle in L. Masaya (1600 generations ago) and absent in the younger L. Apoyeque (<600 generations ago). Genome-wide differentiation between ecotypes was higher in the old source lakes than in the young crater lakes. Our results suggest that hypertrophied lips might be promoting incipient sympatric speciation through divergent selection (ecological divergence in feeding performance) and nonrandom mating (assortative mating) in the young Nicaraguan crater lakes. Nonetheless, further manipulative experiments are needed in order to confirm the role of hypertrophied lips as the main cue for assortative mating.

  4. Multiple episodic evolution events in V1R receptor genes of East-African cichlids.

    PubMed

    Nikaido, Masato; Ota, Tomoki; Hirata, Tadashi; Suzuki, Hikoyu; Satta, Yoko; Aibara, Mitsuto; Mzighani, Semvua I; Sturmbauer, Christian; Hagino-Yamagishi, Kimiko; Okada, Norihiro

    2014-05-06

    Fish use olfaction to detect a variety of nonvolatile chemical signals, and thus, this sense is key to survival and communication. However, the contribution of the olfactory sense to social-especially reproductive-interactions in cichlids is still controversial. To obtain insights into this issue, we investigated the genes encoding V1Rs-possible candidates for reproductive pheromone receptors-among East-African cichlids. Interestingly, we found an excess of nonsynonymous over synonymous substitutions in four of six V1R genes in multiple cichlid lineages. First, we found that highly dimorphic V1R2 allele groups were shared among the cichlids inhabiting all East-African Great Lakes emerged through the episodic accumulation of the nonsynonymous substitutions prior to the radiation of the Lake Tanganyika species flock. We further detected such episodic events in V1R1 of the tribe Tropheini, and in V1R3 and V1R6 of the tribe Trematocarini. The excess of nonsynonymous substitutions in these examples were indicated as dN/dS > 1, which were all statistically significant by Fisher's exact test. Furthermore, we speculate that the amino acid changes in these episodic events are likely functional switch because they occurred in the putative ligand-binding pocket. Our finding of the occurrence of multiple episodic events and the unexpected gene diversity in one unique gene family is suggestive of the contribution of the V1R to the species diversification and the social interaction in cichlids.

  5. The Role of microRNAs in the Repeated Parallel Diversification of Lineages of Midas Cichlid Fish from Nicaragua

    PubMed Central

    Franchini, Paolo; Xiong, Peiwen; Fruciano, Carmelo; Meyer, Axel

    2016-01-01

    Cichlid fishes are an ideal model system for studying biological diversification because they provide textbook examples of rapid speciation. To date, there has been little focus on the role of gene regulation during cichlid speciation. However, in recent years, gene regulation has been recognized as a powerful force linking diversification in gene function to speciation. Here, we investigated the potential role of miRNA regulation in the diversification of six cichlid species of the Midas cichlid lineage (Amphilophus spp.) inhabiting the Nicaraguan crater lakes. Using several genomic resources, we inferred 236 Midas miRNA genes that were used to predict the miRNA target sites on 8,232 Midas 3′-UTRs. Using population genomic calculations of SNP diversity, we found the miRNA genes to be more conserved than protein coding genes. In contrast to what has been observed in other cichlid fish, but similar to what has been typically found in other groups, we observed genomic signatures of purifying selection on the miRNA targets by comparing these sites with the less conserved nontarget portion of the 3′-UTRs. However, in one species pair that has putatively speciated sympatrically in crater Lake Apoyo, we recovered a different pattern of relaxed purifying selection and high genetic divergence at miRNA targets. Our results suggest that sequence evolution at miRNA binding sites could be a critical genomic mechanism contributing to the rapid phenotypic evolution of Midas cichlids. PMID:27189980

  6. Adaptive phenotypic plasticity in the Midas cichlid fish pharyngeal jaw and its relevance in adaptive radiation

    PubMed Central

    2011-01-01

    Background Phenotypic evolution and its role in the diversification of organisms is a central topic in evolutionary biology. A neglected factor during the modern evolutionary synthesis, adaptive phenotypic plasticity, more recently attracted the attention of many evolutionary biologists and is now recognized as an important ingredient in both population persistence and diversification. The traits and directions in which an ancestral source population displays phenotypic plasticity might partly determine the trajectories in morphospace, which are accessible for an adaptive radiation, starting from the colonization of a novel environment. In the case of repeated colonizations of similar environments from the same source population this "flexible stem" hypothesis predicts similar phenotypes to arise in repeated subsequent radiations. The Midas Cichlid (Amphilophus spp.) in Nicaragua has radiated in parallel in several crater-lakes seeded by populations originating from the Nicaraguan Great Lakes. Here, we tested phenotypic plasticity in the pharyngeal jaw of Midas Cichlids. The pharyngeal jaw apparatus of cichlids, a second set of jaws functionally decoupled from the oral ones, is known to mediate ecological specialization and often differs strongly between sister-species. Results We performed a common garden experiment raising three groups of Midas cichlids on food differing in hardness and calcium content. Analyzing the lower pharyngeal jaw-bones we find significant differences between diet groups qualitatively resembling the differences found between specialized species. Observed differences in pharyngeal jaw expression between groups were attributable to the diet's mechanical resistance, whereas surplus calcium in the diet was not found to be of importance. Conclusions The pharyngeal jaw apparatus of Midas Cichlids can be expressed plastically if stimulated mechanically during feeding. Since this trait is commonly differentiated - among other traits - between

  7. Intersex and alterations in reproductive development of a cichlid, Tilapia guineensis, from a municipal domestic water supply lake (Eleyele) in Southwestern Nigeria.

    PubMed

    Adeogun, Aina O; Ibor, Oju R; Adeduntan, Sherifat D; Arukwe, Augustine

    2016-01-15

    The objectives of this study were to develop and validate biomarker techniques for aquatic environmental monitoring of endocrine disrupting chemicals (EDCs) in Nigeria aquatic ecosystems, using the Eleyele Lake, which is a major source of domestic water supply to Ibadan and its surrounding towns, as a model aquatic environment and Tilapia guineensis, as a model organism. A total of 55 male and 28 female fish were used for this study. No significant difference in condition factor was observed between the sexes. Evaluation of gross gonadal morphology of the sampled fish showed 33% intersex prevalence in the sampled population, of which respective 71 and 29% were males and females, with visible testis and ovary developing alongside phenotypic females and males. Plasma concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), 11-ketotestosterone (11-KT) and 17β-estradiol (E2) were performed, showing that male fish had significantly higher plasma LH and E2 concentrations, compared to females. Vitellogenin (Vtg) and zona radiata proteins (Zrp) mRNA levels were significantly higher in males, compared to female fish. Contaminant analysis revealed that PCB 81, 123, 138 and 196 were the only PCB congeners detected in sediment and fish muscle (PCB153 in sediment), while dieldrin was the only organochlorine compound (OC) detected in Eleyele sediment. These responses were used in a multivariate analysis, showing that two principal components were extracted and accounted for 74% of total variation in the dataset. The principal component analysis (PCA) showed that male fish variables were positively correlated with PCB congeners 18 and 123, while female fish showed positive correlations with congener 81, 138, 189, 196, indicating sex-specific pattern of association between PCBs concentrations and biomarker expression. In addition, strong positive correlation between male fish and LH, E2, FSH and Vtg was observed, while female fish positively correlated with

  8. A complex mode of aggressive mimicry in a scale-eating cichlid fish.

    PubMed

    Boileau, Nicolas; Cortesi, Fabio; Egger, Bernd; Muschick, Moritz; Indermaur, Adrian; Theis, Anya; Büscher, Heinz H; Salzburger, Walter

    2015-09-01

    Aggressive mimicry is an adaptive tactic of parasitic or predatory species that closely resemble inoffensive models in order to increase fitness via predatory gains. Although similarity of distantly related species is often intuitively implicated with mimicry, the exact mechanisms and evolutionary causes remain elusive in many cases. Here, we report a complex aggressive mimicry strategy in Plecodus straeleni, a scale-eating cichlid fish from Lake Tanganyika, which imitates two other cichlid species. Employing targeted sequencing on ingested scales, we show that P. straeleni does not preferentially parasitize its models but—contrary to prevailing assumptions—targets a variety of co-occurring dissimilar looking fish species. Combined with tests for visual resemblance and visual modelling from a prey perspective, our results suggest that complex interactions among different cichlid species are involved in this mimicry system.

  9. A complex mode of aggressive mimicry in a scale-eating cichlid fish

    PubMed Central

    Boileau, Nicolas; Cortesi, Fabio; Egger, Bernd; Muschick, Moritz; Indermaur, Adrian; Theis, Anya; Büscher, Heinz H.; Salzburger, Walter

    2015-01-01

    Aggressive mimicry is an adaptive tactic of parasitic or predatory species that closely resemble inoffensive models in order to increase fitness via predatory gains. Although similarity of distantly related species is often intuitively implicated with mimicry, the exact mechanisms and evolutionary causes remain elusive in many cases. Here, we report a complex aggressive mimicry strategy in Plecodus straeleni, a scale-eating cichlid fish from Lake Tanganyika, which imitates two other cichlid species. Employing targeted sequencing on ingested scales, we show that P. straeleni does not preferentially parasitize its models but—contrary to prevailing assumptions—targets a variety of co-occurring dissimilar looking fish species. Combined with tests for visual resemblance and visual modelling from a prey perspective, our results suggest that complex interactions among different cichlid species are involved in this mimicry system. PMID:26399975

  10. The species flocks of East African cichlid fishes: recent advances in molecular phylogenetics and population genetics

    NASA Astrophysics Data System (ADS)

    Salzburger, Walter; Meyer, Axel

    With more than 3,000 species, the fish family Cichlidae is one of the most species-rich families of vertebrates. Cichlids occur in southern and central America, Africa, Madagascar, and India. The hotspot of their biodiversity is East Africa, where they form adaptive radiations composed of hundreds of endemic species in several lakes of various sizes and ages. The unparalleled species richness of East African cichlids has been something of a conundrum for evolutionary biologists and ecologists, since it has been in doubt whether these hundreds of species arose by allopatric speciation or whether it is necessary to invoke somewhat less traditional models of speciation, such as micro-allopatric, peripatric, or even sympatric speciation or evolution through sexual selection mediated by female choice. Ernst Mayr's analyses of these evolutionary uniquely diverse species assemblages have contributed to a more direct approach to this problem and have led to a deeper understanding of the patterns and processes that caused the formation of these huge groups of species. We review here recent molecular data on population differentiation and phylogenetics, which have helped to unravel, to some extent, the patterns and processes that led to the formation and ecological maintenance of cichlid species flocks. It is becoming apparent that sexually selected traits do play an important role in speciation in micro-allopatric or even sympatric settings. Species richness seems to be roughly correlated with the surface area, but not the age, of the lakes. We observe that the oldest lineages of a species flock of cichlids are often less species-rich and live in the open water or deepwater habitats. While the species flocks of the Lake Malawai and the Lake Victoria areas were shown to be monophyletic, the cichlid assemblage of Lake Tanganyika seems to consist of several independent species flocks. Cichlids emerge as an evolutionary model system in which many fundamental questions in

  11. Using Cichlids for Illustrating Mendel's Laws

    ERIC Educational Resources Information Center

    Gennaro, Eugene D.; Winters, Charlotte M.

    1978-01-01

    A classroom experiment is proposed in which students can mate a banded or spotted convict cichlid with a pink convict cichlid and observe the markings of their "children" and "grandchildren" as a way of illustrating Mendel's Laws of Dominance and Segregation. (MN)

  12. Using Cichlids for Illustrating Mendel's Laws

    ERIC Educational Resources Information Center

    Gennaro, Eugene D.; Winters, Charlotte M.

    1978-01-01

    A classroom experiment is proposed in which students can mate a banded or spotted convict cichlid with a pink convict cichlid and observe the markings of their "children" and "grandchildren" as a way of illustrating Mendel's Laws of Dominance and Segregation. (MN)

  13. Hybrid Breakdown in Cichlid Fish

    PubMed Central

    Stelkens, Rike Bahati; Schmid, Corinne; Seehausen, Ole

    2015-01-01

    Studies from a wide diversity of taxa have shown a negative relationship between genetic compatibility and the divergence time of hybridizing genomes. Theory predicts the main breakdown of fitness to happen after the F1 hybrid generation, when heterosis subsides and recessive allelic (Dobzhansky-Muller) incompatibilities are increasingly unmasked. We measured the fitness of F2 hybrids of African haplochromine cichlid fish bred from species pairs spanning several thousand to several million years divergence time. F2 hybrids consistently showed the lowest viability compared to F1 hybrids and non-hybrid crosses (crosses within the grandparental species), in agreement with hybrid breakdown. Especially the short- and long-term survival (2 weeks to 6 months) of F2 hybrids was significantly reduced. Overall, F2 hybrids showed a fitness reduction of 21% compared to F1 hybrids, and a reduction of 43% compared to the grandparental, non-hybrid crosses. We further observed a decrease of F2 hybrid viability with the genetic distance between grandparental lineages, suggesting an important role for negative epistatic interactions in cichlid fish postzygotic isolation. The estimated time window for successful production of F2 hybrids resulting from our data is consistent with the estimated divergence time between the multiple ancestral lineages that presumably hybridized in three major adaptive radiations of African cichlids. PMID:25996870

  14. Ancient hybridization fuels rapid cichlid fish adaptive radiations

    PubMed Central

    Meier, Joana I.; Marques, David A.; Mwaiko, Salome; Wagner, Catherine E.; Excoffier, Laurent; Seehausen, Ole

    2017-01-01

    Understanding why some evolutionary lineages generate exceptionally high species diversity is an important goal in evolutionary biology. Haplochromine cichlid fishes of Africa's Lake Victoria region encompass >700 diverse species that all evolved in the last 150,000 years. How this ‘Lake Victoria Region Superflock' could evolve on such rapid timescales is an enduring question. Here, we demonstrate that hybridization between two divergent lineages facilitated this process by providing genetic variation that subsequently became recombined and sorted into many new species. Notably, the hybridization event generated exceptional allelic variation at an opsin gene known to be involved in adaptation and speciation. More generally, differentiation between new species is accentuated around variants that were fixed differences between the parental lineages, and that now appear in many new combinations in the radiation species. We conclude that hybridization between divergent lineages, when coincident with ecological opportunity, may facilitate rapid and extensive adaptive radiation. PMID:28186104

  15. Multiple Episodic Evolution Events in V1R Receptor Genes of East-African Cichlids

    PubMed Central

    Nikaido, Masato; Ota, Tomoki; Hirata, Tadashi; Suzuki, Hikoyu; Satta, Yoko; Aibara, Mitsuto; Mzighani, Semvua I.; Sturmbauer, Christian; Hagino-Yamagishi, Kimiko; Okada, Norihiro

    2014-01-01

    Fish use olfaction to detect a variety of nonvolatile chemical signals, and thus, this sense is key to survival and communication. However, the contribution of the olfactory sense to social—especially reproductive—interactions in cichlids is still controversial. To obtain insights into this issue, we investigated the genes encoding V1Rs—possible candidates for reproductive pheromone receptors—among East-African cichlids. Interestingly, we found an excess of nonsynonymous over synonymous substitutions in four of six V1R genes in multiple cichlid lineages. First, we found that highly dimorphic V1R2 allele groups were shared among the cichlids inhabiting all East-African Great Lakes emerged through the episodic accumulation of the nonsynonymous substitutions prior to the radiation of the Lake Tanganyika species flock. We further detected such episodic events in V1R1 of the tribe Tropheini, and in V1R3 and V1R6 of the tribe Trematocarini. The excess of nonsynonymous substitutions in these examples were indicated as dN/dS > 1, which were all statistically significant by Fisher’s exact test. Furthermore, we speculate that the amino acid changes in these episodic events are likely functional switch because they occurred in the putative ligand-binding pocket. Our finding of the occurrence of multiple episodic events and the unexpected gene diversity in one unique gene family is suggestive of the contribution of the V1R to the species diversification and the social interaction in cichlids. PMID:24803573

  16. Human Melioidosis, Malawi, 2011

    PubMed Central

    Katangwe, Thembi; Purcell, Janet; Bar-Zeev, Naor; Denis, Brigitte; Montgomery, Jacqui; Alaerts, Maaike; Heyderman, Robert Simon; Dance, David A.B.; Kennedy, Neil; Feasey, Nicholas

    2013-01-01

    A case of human melioidosis caused by a novel sequence type of Burkholderia pseudomallei occurred in a child in Malawi, southern Africa. A literature review showed that human cases reported from the continent have been increasing. PMID:23735189

  17. Evolution of egg dummies in Tanganyikan cichlid fishes: the roles of parental care and sexual selection.

    PubMed

    Amcoff, M; Gonzalez-Voyer, A; Kolm, N

    2013-11-01

    Sexual selection has been suggested to be an important driver of speciation in cichlid fishes of the Great Lakes of Africa, and the presence of male egg dummies is proposed to have played a key role. Here, we investigate how mouthbrooding and egg dummies have evolved in Tanganyikan cichlids, the lineage which seeded the other African radiations, with a special emphasis on the egg dummies. Using modern phylogenetic comparative analyses and a phylogeny including 86% of the 200 described species, we provide formal evidence demonstrating correlated evolution between mouthbrooding and egg dummies in Tanganyikan cichlids. These results concur with existing evidence, suggesting that egg dummies have evolved through sensory exploitation. We also demonstrate that there is a strong evolutionary correlation between the presence of egg dummies and both pre- and post-copulatory sexual selection. Moreover, egg dummy evolution was contingent on the intensity of pre- and post-copulatory sexual selection in Tanganyikan cichlids. In sum, our results provide evidence supporting the hypothesis of egg dummies evolving through sensory exploitation and highlight the role of sexual selection in favouring the evolution and maintenance of this trait. © 2013 The Authors. Journal of Evolutionary Biology © 2013 European Society For Evolutionary Biology.

  18. Time and origin of cichlid colonization of the lower Congo rapids.

    PubMed

    Schwarzer, Julia; Misof, Bernhard; Ifuta, Seraphin N; Schliewen, Ulrich K

    2011-01-01

    Most freshwater diversity is arguably located in networks of rivers and streams, but, in contrast to lacustrine systems riverine radiations, are largely understudied. The extensive rapids of the lower Congo River is one of the few river stretches inhabited by a locally endemic cichlid species flock as well as several species pairs, for which we provide evidence that they have radiated in situ. We use more that 2,000 AFLP markers as well as multilocus sequence datasets to reconstruct their origin, phylogenetic history, as well as the timing of colonization and speciation of two Lower Congo cichlid genera, Steatocranus and Nanochromis. Based on a representative taxon sampling and well resolved phylogenetic hypotheses we demonstrate that a high level of riverine diversity originated in the lower Congo within about 5 mya, which is concordant with age estimates for the hydrological origin of the modern lower Congo River. A spatial genetic structure is present in all widely distributed lineages corresponding to a trisection of the lower Congo River into major biogeographic areas, each with locally endemic species assemblages. With the present study, we provide a phylogenetic framework for a complex system that may serve as a link between African riverine cichlid diversity and the megadiverse cichlid radiations of the East African lakes. Beyond this we give for the first time a biologically estimated age for the origin of the lower Congo River rapids, one of the most extreme freshwater habitats on earth.

  19. Risk Communication of Groundwater Quality in Northern Malawi, Africa

    NASA Astrophysics Data System (ADS)

    Holm, R.

    2011-12-01

    Malawi lies in Africa's Great Rift Valley. Its western border is defined by Lake Malawi, the third largest lake in Africa. Over 80% of Malawians live in rural areas and 90% of the labor force is associated with agriculture. More than half of the population lives below the poverty line. Area characteristics indicate a high likelihood of nitrate and total coliform in community drinking water. Infants exposed to high nitrate are at risk of developing methemoglobinemia. In addition, diarrheal diseases from unsafe drinking water are one of the top causes of mortality in children under five. Without sufficient and sustainable supplies of clean water, these challenges will continue to threaten Malawi's ability to overcome the devastating impact of diarrheal diseases on its population. Therefore, Malawi remains highly dependent on outside assistance and influence to reduce or eliminate the threat posed by unsafe drinking water. This research presents a literature review of nitrate and total coliform groundwater quality and a proposed risk communication plan for drinking water in northern Malawi.

  20. A Hybrid Genetic Linkage Map of Two Ecologically and Morphologically Divergent Midas Cichlid Fishes (Amphilophus spp.) Obtained by Massively Parallel DNA Sequencing (ddRADSeq)

    PubMed Central

    Recknagel, Hans; Elmer, Kathryn R.; Meyer, Axel

    2013-01-01

    Cichlid fishes are an excellent model system for studying speciation and the formation of adaptive radiations because of their tremendous species richness and astonishing phenotypic diversity. Most research has focused on African rift lake fishes, although Neotropical cichlid species display much variability as well. Almost one dozen species of the Midas cichlid species complex (Amphilophus spp.) have been described so far and have formed repeated adaptive radiations in several Nicaraguan crater lakes. Here we apply double-digest restriction-site associated DNA sequencing to obtain a high-density linkage map of an interspecific cross between the benthic Amphilophus astorquii and the limnetic Amphilophus zaliosus, which are sympatric species endemic to Crater Lake Apoyo, Nicaragua. A total of 755 RAD markers were genotyped in 343 F2 hybrids. The map resolved 25 linkage groups and spans a total distance of 1427 cM with an average marker spacing distance of 1.95 cM, almost matching the total number of chromosomes (n = 24) in these species. Regions of segregation distortion were identified in five linkage groups. Based on the pedigree of parents to F2 offspring, we calculated a genome-wide mutation rate of 6.6 × 10−8 mutations per nucleotide per generation. This genetic map will facilitate the mapping of ecomorphologically relevant adaptive traits in the repeated phenotypes that evolved within the Midas cichlid lineage and, as the first linkage map of a Neotropical cichlid, facilitate comparative genomic analyses between African cichlids, Neotropical cichlids and other teleost fishes. PMID:23316439

  1. Strategic growth decisions in helper cichlids.

    PubMed Central

    Heg, Dik; Bender, Nicole; Hamilton, Ian

    2004-01-01

    Recently, it has been shown that group-living subordinate clownfish Amphiprion percula increase their growth rate after acquiring the dominant breeder male position in the group. Evidence was found for strategic growth adjustments of subordinate fishes depending on the threat of eviction, i.e. subordinates adjust their growth rates so they remain smaller than the dominant fish and thereby limit the threat of being expelled from the territory. However, it is impossible to exclude several alternative factors that potentially could have influenced the observed changes in growth, owing to the nature of that experiment (removing the second-ranking fish--the breeder male--caused the third-ranking fish to change sex to become breeder male and change rank). We studied strategic growth decisions in the group-living Lake Tanganyika cichlid Neolamprologus pulcher under controlled laboratory conditions with ad libitum food availability. First, we show that male breeders grow faster than subordinate male helpers of the same initial size and confirm that N. pulcher shows status-dependent growth. Second, we improved on the experimental design by not removing the dominant breeder male in the group; instead we replaced the breeder male with a new breeder male in a full factorial design and measured growth of the subordinate male helpers is a function of the size difference with the old and the new breeder male. As predicted, male helpers showed strategic growth adjustments, i.e. growing faster when the size difference with the breeder male is large. Strategic growth adjustments were less pronounced than status-dependent growth adjustments. PMID:15801617

  2. Remarkable rates of lightning strike mortality in Malawi.

    PubMed

    Mulder, Monique Borgerhoff; Msalu, Lameck; Caro, Tim; Salerno, Jonathan

    2012-01-01

    Livingstone's second mission site on the shore of Lake Malawi suffers very high rates of consequential lightning strikes. Comprehensive interviewing of victims and their relatives in seven Traditional Authorities in Nkhata Bay District, Malawi revealed that the annual rate of consequential strikes was 419/million, more than six times higher than that in other developing countries; the rate of deaths from lightning was 84/million/year, 5.4 times greater than the highest ever recorded. These remarkable figures reveal that lightning constitutes a significant stochastic source of mortality with potential life history consequences, but it should not deflect attention away from the more prominent causes of mortality in this rural area.

  3. Vulnerability to climate change and adaptation strategies of local communities in Malawi: experiences of women fish-processing groups in the Lake Chilwa Basin

    NASA Astrophysics Data System (ADS)

    Jørstad, Hanne; Webersik, Christian

    2016-12-01

    In recent years, research on climate change and human security has received much attention among policy makers and academia alike. Communities in the Global South that rely on an intact resource base and struggle with poverty, existing inequalities and historical injustices will especially be affected by predicted changes in temperature and precipitation. The objective of this article is to better understand under what conditions local communities can adapt to anticipated impacts of climate change. The empirical part of the paper answers the question as to what extent local women engaged in fish processing in the Chilwa Basin in Malawi have experienced climate change and how they are affected by it. The article assesses an adaptation project designed to make those women more resilient to a warmer and more variable climate. The research results show that marketing and improving fish processing as strategies to adapt to climate change have their limitations. The study concludes that livelihood diversification can be a more effective strategy for Malawian women to adapt to a more variable and unpredictable climate rather than exclusively relying on a resource base that is threatened by climate change.

  4. The geographical distribution of lymphatic filariasis infection in Malawi

    PubMed Central

    Ngwira, Bagrey MM; Tambala, Phillimon; Perez, A Maria; Bowie, Cameron; Molyneux, David H

    2007-01-01

    Mapping distribution of lymphatic filariasis (LF) is a prerequisite for planning national elimination programmes. Results from a nation wide mapping survey for lymphatic filariasis (LF) in Malawi are presented. Thirty-five villages were sampled from 23 districts excluding three districts (Karonga, Chikwawa and Nsanje) that had already been mapped and Likoma, an Island, where access was not possible in the time frame of the survey. Antigenaemia prevalence [based on immunochromatographic card tests (ICT)] ranged from 0% to 35.9%. Villages from the western side of the country and distant from the lake tended to be of lower prevalence. The exception was a village in Mchinji district on the Malawi-Zambia border where a prevalence of 18.2% was found. In contrast villages from lake shore districts [Salima, Mangochi, Balaka and Ntcheu (Bwanje valley)] and Phalombe had prevalences of over 20%. A national map is developed which incorporates data from surveys in Karonga, Chikwawa and Nsanje districts, carried out in 2000. There is a marked decline in prevalence with increasing altitude. Further analysis revealed a strong negative correlation (R2 = 0.7 p < 0.001) between altitude and prevalence. These results suggest that the lake shore, Phalombe plain and the lower Shire valley will be priority areas for the Malawi LF elimination programme. Implications of these findings as regards implementing a national LF elimination programme in Malawi are discussed. PMID:18047646

  5. Tol2-Mediated Generation of a Transgenic Haplochromine Cichlid, Astatotilapia burtoni

    PubMed Central

    Fernald, Russell D.

    2013-01-01

    Cichlid fishes represent one of the most species-rich and rapid radiations of a vertebrate family. These ∼2200 species, predominantly found in the East African Great Lakes, exhibit dramatic differences in anatomy, physiology, and behavior. However, the genetic bases for this radiation, and for the control of their divergent traits, are unknown. A flood of genomic and transcriptomic data promises to suggest mechanisms underlying the diversity, but transgenic technology will be needed to rigorously test the hypotheses generated. Here we demonstrate the successful use of the Tol2 transposon system to generate transgenic Astatotilapia burtoni, a haplochromine cichlid from Lake Tanganyika, carrying the GFP transgene under the control of the ubiquitous EF1α promoter. The transgene integrates into the genome, is successfully passed through the germline, and the widespread GFP expression pattern is stable across siblings and multiple generations. The stable inheritance and expression patterns indicate that the Tol2 system can be applied to generate A. burtoni transgenic lines. Transgenesis has proven to be a powerful technology for manipulating genes and cells in other model organisms and we anticipate that transgenic A. burtoni and other cichlids will be used to test the mechanisms underlying behavior and speciation. PMID:24204902

  6. Genetic isolation and morphological divergence mediated by high-energy rapids in two cichlid genera from the lower Congo rapids.

    PubMed

    Markert, Jeffrey A; Schelly, Robert C; Stiassny, Melanie Lj

    2010-05-19

    It is hypothesized that one of the mechanisms promoting diversification in cichlid fishes in the African Great Lakes has been the well-documented pattern of philopatry along shoreline habitats leading to high levels of genetic isolation among populations. However lake habitats are not the only centers of cichlid biodiversity - certain African rivers also contain large numbers of narrowly endemic species. Patterns of isolation and divergence in these systems have tended to be overlooked and are not well understood. We examined genetic and morphological divergence among populations of two narrowly endemic cichlid species, Teleogramma depressum and Lamprologus tigripictilis, from a 100 km stretch of the lower Congo River using both nDNA microsatellites and mtDNA markers along with coordinate-based morphological techniques. In L. tigripictilis, the strongest genetic break was concordant with measurable phenotypic divergence but no morphological disjunction was detected for T. depressum despite significant differentiation at mtDNA and nDNA microsatellite markers. The genetic markers revealed patterns of philopatry and estimates of genetic isolation that are among the highest reported for any African cichlid species over a comparable geographic scale. We hypothesize that the high levels of philopatry observed are generated and maintained by the extreme hydrology of the lower Congo River.

  7. Plume-induced continental break-up from Red Sea to Lake Malawi: 3D numerical models of the East African Rift System

    NASA Astrophysics Data System (ADS)

    Koptev, Alexander; Burov, Evgueni; Calais, Eric; Leroy, Sylvie; Gerya, Taras; Cloetingh, Sierd; Guillou-Frottier, Laurent

    2017-04-01

    We use numerical thermo-mechanical experiments in order to analyze the role of active mantle plume, far-field tectonic stresses and pre-existing lithospheric heterogeneities in structural development of the East African Rift system (EARS). It is commonly assumed that the Cenozoic rifts have avoided the cratons and follow the mobile belts which serve as the weakest pathways within the non-uniform material structured during pre-rift stages. Structural control of the pre-existing heterogeneities within the Proterozoic belts at the scale of individual faults or rifts has been demonstrated as well. However, the results of our numerical experiments show that the formation of two rift zones on opposite sides of a thick lithosphere segment can be explained without appealing to pre-imposed heterogeneities at the crustal level. These models have provided a unified physical framework to understand the development of the Eastern branch, the Western branch and its southern prolongation by the Malawi rift around thicker lithosphere of the Tanzanian and Bangweulu cratons as a result of the interaction between pre-stressed continental lithosphere and single mantle plume anomaly corresponding to the Kenyan plume. The second series of experiments has been designed in order to investigate northern segment of the EARS where Afro-Arabian plate separation is supposed to be related with the impact of Afar mantle plume. We demonstrate that whereas relatively simple linear rift structures are preferred in case of uni-directional extension, more complex rifting patterns combining one or several ridge-ridge-ridge triple junctions can form in response to bi-directional extensional far-field stresses. In particular, our models suggest that Afar triple junction represents an end-member mode of plume-induced bi-directional rifting combining asymmetrical northward traction and symmetrical EW extension of similar magnitudes. The presence of pre-existing linear weak zones appears to be not

  8. Lacustrine mollusc radiations in the Malawi Basin: experiments in a natural laboratory for evolution

    NASA Astrophysics Data System (ADS)

    Van Damme, D.; Gautier, A.

    2012-12-01

    In Terminal Pliocene-Early Pleistocene times, part of the Malawi Basin was occupied by palaeo-lake Chiwondo. Molluscan biostratigraphy situates this freshwater lake either in the East African wet phase between 2.7-2.4 Ma or that of 2.0-1.8 Ma. In-lake divergent evolution remained restricted to a few molluscan taxa and was very modest. The lacustrine Chiwondo fauna went extinct at the beginning of the Pleistocene. The Modern Lake Malawi malacofauna is poor and descends from ubiquistic South-East African taxa and some Malawi Basin endemics that invaded the present lake after the Late Pleistocene mega-droughts. The Pleistocene aridity crises caused dramatic changes, affecting the malacofauna of all East African lakes. All lacustrine endemic faunas that had evolved in the Pliocene rift lakes, such as palaeo-lake Chiwondo, became extinct. In Lake Tanganyika, the freshwater ecosystem did not crash as in other lakes, but the environmental changes were sufficiently important to trigger a vast radiation. All African endemic lacustrine molluscan clades that are the result of in-lake divergence are hence geologically young, including the vast Lavigeria clade in Lake Tanganyika (ca. 43 species).

  9. Temporal diversification of Central American cichlids

    PubMed Central

    2010-01-01

    Background Cichlid fishes are classic examples of adaptive radiation because of their putative tendency to explosively diversify after invading novel environments. To examine whether ecological opportunity increased diversification (speciation minus extinction) early in a species-rich cichlid radiation, we determined if Heroine cichlids experienced a burst of diversification following their invasion of Central America. Results We first reconstructed the Heroine phylogeny and determined the basal node to use as the root of Central American Heroine diversification. We then examined the influence of incomplete taxon sampling on this group's diversification patterns. First, we added missing species randomly to the phylogeny and assessed deviations from a constant rate of lineage accumulation. Using a range of species numbers, we failed to recover significant deviations from a pure-birth process and found little support for an early burst of diversification. Then, we examined patterns of lineage accumulation as nodes were increasingly truncated. We assumed that as we removed more recently diverged lineages that sampling would become more complete thereby increasing the power to detect deviations from a pure-birth model. However, truncation of nodes provided even less support for an early burst of diversification. Conclusions Contrary to expectations, our analyses suggest Heroine cichlids did not undergo a burst of diversification when they invaded from South America. Throughout their history in Central America, Heroine cichlids appear to have diversified at a constant rate. PMID:20840768

  10. Convict cichlids benefit from close proximity to another species of cichlid fish.

    PubMed

    Lehtonen, Topi K

    2008-12-23

    The coexistence of species with overlapping resource use is often thought to involve only negative fitness effects as a consequence of interspecific competition. Furthermore, the scarce empirical research on positive species interactions has predominantly focused on sessile organisms. Here, I experimentally assessed the effect of close proximity of a potential brood predator and competitor on reproductive success of a neotropical cichlid fish. I demonstrate that convict cichlid (Archocentrus nigrofasciatus) broods have a higher survival rate near territories of the Nicaragua cichlid (Hypsophrys nicaraguensis), and that escape from predation and nest takeovers is the most likely explanation for the decreased offspring mortality.

  11. Morphology, Molecules, and Monogenean Parasites: An Example of an Integrative Approach to Cichlid Biodiversity

    PubMed Central

    Van Steenberge, Maarten; Pariselle, Antoine; Huyse, Tine; Volckaert, Filip A. M.; Snoeks, Jos; Vanhove, Maarten P. M.

    2015-01-01

    The unparalleled biodiversity of Lake Tanganyika (Africa) has fascinated biologists for over a century; its unique cichlid communities are a preferred model for evolutionary research. Although species delineation is, in most cases, relatively straightforward, higher-order classifications were shown not to agree with monophyletic groups. Here, traditional morphological methods meet their limitations. A typical example are the tropheine cichlids currently belonging to Simochromis and Pseudosimochromis. The affiliations of these widespread and abundant cichlids are poorly understood. Molecular work suggested that genus and species boundaries should be revised. Moreover, previous morphological results indicated that intraspecific variation should be considered to delineate species in Lake Tanganyika cichlids. We review the genera Simochromis and Pseudosimochromis using an integrative approach. Besides a morphometric study and a barcoding approach, monogenean Cichlidogyrus (Platyhelminthes: Ancyrocephalidae) gill parasites, often highly species-specific, are used as complementary markers. Six new species are described. Cichlidogyrus raeymaekersi sp. nov., C. muterezii sp. nov. and C. banyankimbonai sp. nov. infect S. diagramma. Cichlidogyrus georgesmertensi sp. nov. was found on S. babaulti and S. pleurospilus, C. franswittei sp. nov. on both S. marginatus and P. curvifrons and C. frankwillemsi sp. nov. only on P. curvifrons. As relatedness between Cichlidogyrus species usually reflects relatedness between hosts, we considered Simochromis monotypic because the three Cichlidogyrus species found on S. diagramma belonged to a different morphotype than those found on the other Simochromis. The transfer of S. babaulti, S. marginatus, S. pleurospilus and S. margaretae to Pseudosimochromis was justified by the similarity of their Cichlidogyrus fauna and the intermediate morphology of S. margaretae. Finally parasite data also supported the synonymy between S. pleurospilus and S

  12. Morphology, molecules, and monogenean parasites: an example of an integrative approach to cichlid biodiversity.

    PubMed

    Van Steenberge, Maarten; Pariselle, Antoine; Huyse, Tine; Volckaert, Filip A M; Snoeks, Jos; Vanhove, Maarten P M

    2015-01-01

    The unparalleled biodiversity of Lake Tanganyika (Africa) has fascinated biologists for over a century; its unique cichlid communities are a preferred model for evolutionary research. Although species delineation is, in most cases, relatively straightforward, higher-order classifications were shown not to agree with monophyletic groups. Here, traditional morphological methods meet their limitations. A typical example are the tropheine cichlids currently belonging to Simochromis and Pseudosimochromis. The affiliations of these widespread and abundant cichlids are poorly understood. Molecular work suggested that genus and species boundaries should be revised. Moreover, previous morphological results indicated that intraspecific variation should be considered to delineate species in Lake Tanganyika cichlids. We review the genera Simochromis and Pseudosimochromis using an integrative approach. Besides a morphometric study and a barcoding approach, monogenean Cichlidogyrus (Platyhelminthes: Ancyrocephalidae) gill parasites, often highly species-specific, are used as complementary markers. Six new species are described. Cichlidogyrus raeymaekersi sp. nov., C. muterezii sp. nov. and C. banyankimbonai sp. nov. infect S. diagramma. Cichlidogyrus georgesmertensi sp. nov. was found on S. babaulti and S. pleurospilus, C. franswittei sp. nov. on both S. marginatus and P. curvifrons and C. frankwillemsi sp. nov. only on P. curvifrons. As relatedness between Cichlidogyrus species usually reflects relatedness between hosts, we considered Simochromis monotypic because the three Cichlidogyrus species found on S. diagramma belonged to a different morphotype than those found on the other Simochromis. The transfer of S. babaulti, S. marginatus, S. pleurospilus and S. margaretae to Pseudosimochromis was justified by the similarity of their Cichlidogyrus fauna and the intermediate morphology of S. margaretae. Finally parasite data also supported the synonymy between S. pleurospilus and S

  13. Holocene Full-Vector Secular Variation from African Lakes

    NASA Astrophysics Data System (ADS)

    Lund, S.; Platzman, E. S.; Johnson, T. C.; Scholz, C. A.; Cohen, A. S.; Russell, J. M.

    2014-12-01

    We are developing a regional pattern of Holocene paleomagnetic secular variation (PSV) from four lakes in East Africa - Lake Turkana (3°N), Lake Victoria (1°S), Lake Tanganyika (5°S), and Lake Malawi (10°S). Detailed paleomagnetic and rock magnetic measurements have been made on two cores from Lake Malawi (9m meters in depth, last ~10,000 years), two cores from Lake Victoria (8 m, last ~8,000 years), 11 cores from Lake Turkana (2-9 m, last ~10,000 years), and one core from Lake Tanganyika (5 m, last ~5,000 years). Our rock magnetic studies identify significant intervals of magnetic mineral dissolution in Lakes Victoria and Tanganyika making parts of these cores unsuitable for relative paleointensity studies. On the other hand, rock magnetic variability in the Lake Malawi and Lake Turkana cores are stable and correlatable among cores. We have recovered directional secular variation records from Lakes Malawi, Victoria, and Turkana. Millennial-scale inclination and declination features can be correlated among cores at each lake and between lakes. We have also recovered relative paleointensity records from Lakes Malawi and Turkana. More than 20 radiocarbon dates and detailed seismic stratigraphy (Turkana) provide critical added information for correlating and dating the paleomagnetic records.

  14. Chromosome differentiation patterns during cichlid fish evolution

    PubMed Central

    2010-01-01

    Background Cichlid fishes have been the subject of increasing scientific interest because of their rapid adaptive radiation which has led to an extensive ecological diversity and their enormous importance to tropical and subtropical aquaculture. To increase our understanding of chromosome evolution among cichlid species, karyotypes of one Asian, 22 African, and 30 South American cichlid species were investigated, and chromosomal data of the family was reviewed. Results Although there is extensive variation in the karyotypes of cichlid fishes (from 2n = 32 to 2n = 60 chromosomes), the modal chromosome number for South American species was 2n = 48 and the modal number for the African ones was 2n = 44. The only Asian species analyzed, Etroplus maculatus, was observed to have 46 chromosomes. The presence of one or two macro B chromosomes was detected in two African species. The cytogenetic mapping of 18S ribosomal RNA (18S rRNA) gene revealed a variable number of clusters among species varying from two to six. Conclusions The karyotype diversification of cichlids seems to have occurred through several chromosomal rearrangements involving fissions, fusions and inversions. It was possible to identify karyotype markers for the subfamilies Pseudocrenilabrinae (African) and Cichlinae (American). The karyotype analyses did not clarify the phylogenetic relationship among the Cichlinae tribes. On the other hand, the two major groups of Pseudocrenilabrinae (tilapiine and haplochromine) were clearly discriminated based on the characteristics of their karyotypes. The cytogenetic mapping of 18S ribosomal RNA (18S rRNA) gene did not follow the chromosome diversification in the family. The dynamic evolution of the repeated units of rRNA genes generates patterns of chromosomal distribution that do not help follows the phylogenetic relationships among taxa. The presence of B chromosomes in cichlids is of particular interest because they may not be represented in the reference genome

  15. Carotenoid-based coloration in cichlid fishes

    PubMed Central

    Sefc, Kristina M.; Brown, Alexandria C.; Clotfelter, Ethan D.

    2014-01-01

    Animal colors play important roles in communication, ecological interactions and speciation. Carotenoid pigments are responsible for many yellow, orange and red hues in animals. Whereas extensive knowledge on the proximate mechanisms underlying carotenoid coloration in birds has led to testable hypotheses on avian color evolution and signaling, much less is known about the expression of carotenoid coloration in fishes. Here, we promote cichlid fishes (Perciformes: Cichlidae) as a system in which to study the physiological and evolutionary significance of carotenoids. Cichlids include some of the best examples of adaptive radiation and color pattern diversification in vertebrates. In this paper, we examine fitness correlates of carotenoid pigmentation in cichlids and review hypotheses regarding the signal content of carotenoid-based ornaments. Carotenoid-based coloration is influenced by diet and body condition and is positively related to mating success and social dominance. Gaps in our knowledge are discussed in the last part of this review, particularly in the understanding of carotenoid metabolism pathways and the genetics of carotenoid coloration. We suggest that carotenoid metabolism and transport are important proximate mechanisms responsible for individual and population-differences in cichlid coloration that may ultimately contribute to diversification and speciation. PMID:24667558

  16. Cichlid genomics and phenotypic diversity in a comparative context.

    PubMed

    Hulsey, C Darrin

    2009-12-01

    Cichlid fishes provide an excellent natural system for integrating studies of genomics and adaptive radiation. Cichlids are unique in comprising a substantial fraction of all vertebrate species, possessing unique jaw structures, displaying an exceptional range of breeding systems, and exhibiting rampant phenotypic convergence. The rate of divergence in cichlid jaws, teeth, color patterns, visual systems, reproductive biology, and mating behaviors is unparalleled among vertebrates. I discuss ways rapid divergence in cichlids and other adaptive radiations make understanding the genomic basis of adaptive divergence more tractable. Then, I briefly overview some major findings and insights into vertebrate adaptation that have been gained through cichlid genetic studies. Finally, I discuss the extensive evolutionary replication provided by cichlid adaptive radiations and their potential for studies of genotype-to-phenotype mapping.

  17. Gut Microbiota Dynamics during Dietary Shift in Eastern African Cichlid Fishes

    PubMed Central

    Baldo, Laura; Riera, Joan Lluís; Tooming-Klunderud, Ave; Albà, M. Mar; Salzburger, Walter

    2015-01-01

    The gut microbiota structure reflects both a host phylogenetic history and a signature of adaptation to the host ecological, mainly trophic niches. African cichlid fishes, with their array of closely related species that underwent a rapid dietary niche radiation, offer a particularly interesting system to explore the relative contribution of these two factors in nature. Here we surveyed the host intra- and interspecific natural variation of the gut microbiota of five cichlid species from the monophyletic tribe Perissodini of lake Tanganyika, whose members transitioned from being zooplanktivorous to feeding primarily on fish scales. The outgroup riverine species Astatotilapia burtoni, largely omnivorous, was also included in the study. Fusobacteria, Firmicutes and Proteobacteria represented the dominant components in the gut microbiota of all 30 specimens analysed according to two distinct 16S rRNA markers. All members of the Perissodini tribe showed a homogenous pattern of microbial alpha and beta diversities, with no significant qualitative differences, despite changes in diet. The recent diet shift between zooplantkon- and scale-eaters simply reflects on a significant enrichment of Clostridium taxa in scale-eaters where they might be involved in the scale metabolism. Comparison with the omnivorous species A. burtoni suggests that, with increased host phylogenetic distance and/or increasing herbivory, the gut microbiota begins differentiating also at qualitative level. The cichlids show presence of a large conserved core of taxa and a small set of core OTUs (average 13–15%), remarkably stable also in captivity, and putatively favoured by both restricted microbial transmission among related hosts (putatively enhanced by mouthbrooding behavior) and common host constraints. This study sets the basis for a future large-scale investigation of the gut microbiota of cichlids and its adaptation in the process of the host adaptive radiation. PMID:25978452

  18. Evolution of genomic structural variation and genomic architecture in the adaptive radiations of African cichlid fishes

    PubMed Central

    Fan, Shaohua; Meyer, Axel

    2014-01-01

    African cichlid fishes are an ideal system for studying explosive rates of speciation and the origin of diversity in adaptive radiation. Within the last few million years, more than 2000 species have evolved in the Great Lakes of East Africa, the largest adaptive radiation in vertebrates. These young species show spectacular diversity in their coloration, morphology and behavior. However, little is known about the genomic basis of this astonishing diversity. Recently, five African cichlid genomes were sequenced, including that of the Nile Tilapia (Oreochromis niloticus), a basal and only relatively moderately diversified lineage, and the genomes of four representative endemic species of the adaptive radiations, Neolamprologus brichardi, Astatotilapia burtoni, Metriaclima zebra, and Pundamila nyererei. Using the Tilapia genome as a reference genome, we generated a high-resolution genomic variation map, consisting of single nucleotide polymorphisms (SNPs), short insertions and deletions (indels), inversions and deletions. In total, around 18.8, 17.7, 17.0, and 17.0 million SNPs, 2.3, 2.2, 1.4, and 1.9 million indels, 262, 306, 162, and 154 inversions, and 3509, 2705, 2710, and 2634 deletions were inferred to have evolved in N. brichardi, A. burtoni, P. nyererei, and M. zebra, respectively. Many of these variations affected the annotated gene regions in the genome. Different patterns of genetic variation were detected during the adaptive radiation of African cichlid fishes. For SNPs, the highest rate of evolution was detected in the common ancestor of N. brichardi, A. burtoni, P. nyererei, and M. zebra. However, for the evolution of inversions and deletions, we found that the rates at the terminal taxa are substantially higher than the rates at the ancestral lineages. The high-resolution map provides an ideal opportunity to understand the genomic bases of the adaptive radiation of African cichlid fishes. PMID:24917883

  19. Lake

    ERIC Educational Resources Information Center

    Wien, Carol Anne

    2008-01-01

    The lake is blue black and deep. It is a glaciated finger lake, clawed out of rock when ice retracted across Nova Scotia in a northerly direction during the last ice age. The lake is narrow, a little over a mile long, and deep, 90 to 190 feet in places according to local lore, off the charts in others. The author loves to swim there, with a sense…

  20. Ancient lakes as evolutionary reservoirs: evidence from the thalassoid gastropods of Lake Tanganyika.

    PubMed

    Wilson, Anthony B; Glaubrecht, Matthias; Meyer, Axel

    2004-03-07

    Ancient lakes are often collectively viewed as evolutionary hot spots of diversification. East Africa's Lake Tanganyika has long been the subject of scientific interest owing to dramatic levels of endemism in species as diverse as cichlid fishes, paludomid gastropods, decapod and ostracod crustaceans and poriferans. It is the largest and deepest of the African rift lakes, and its endemic fauna has been presented with a stable inland environment for over 10 Myr, offering unique opportunities for within-lake diversification. Although astonishing diversification has been documented in the endemic cichlid fauna of the lake, similar patterns of rapid diversification have long been assumed for other groups. In contrast to this hypothesis of rapid speciation, we show here that there has been no acceleration in the rate of speciation in the thalassoid gastropods of the lake following lake colonization. While limited within-lake speciation has occurred, the dramatic conchological diversity of gastropods presently found within the lake has evolved from at least four major lineages that pre-date its formation by as much as 40 Myr. At the same time, a widespread group of African gastropods appears to have evolved from taxa presently found in the lake. While Lake Tanganyika has been a cradle of speciation for cichlid fishes, it has also been an important evolutionary reservoir of gastropod lineages that have been extirpated outside the basin.

  1. The Gut Microbial Community of Midas Cichlid Fish in Repeatedly Evolved Limnetic-Benthic Species Pairs

    PubMed Central

    Frickey, Tancred; Jones, Julia C.; Meyer, Axel

    2014-01-01

    Gut bacterial communities are now known to influence a range of fitness related aspects of organisms. But how different the microbial community is in closely related species, and if these differences can be interpreted as adaptive is still unclear. In this study we compared microbial communities in two sets of closely related sympatric crater lake cichlid fish species pairs that show similar adaptations along the limnetic-benthic axis. The gut microbial community composition differs in the species pair inhabiting the older of two crater lakes. One major difference, relative to other fish, is that in these cichlids that live in hypersaline crater lakes, the microbial community is largely made up of Oceanospirillales (52.28%) which are halotolerant or halophilic bacteria. This analysis opens up further avenues to identify candidate symbiotic or co-evolved bacteria playing a role in adaptation to similar diets and life-styles or even have a role in speciation. Future functional and phylosymbiotic analyses might help to address these issues. PMID:24733403

  2. The gut microbial community of Midas cichlid fish in repeatedly evolved limnetic-benthic species pairs.

    PubMed

    Franchini, Paolo; Fruciano, Carmelo; Frickey, Tancred; Jones, Julia C; Meyer, Axel

    2014-01-01

    Gut bacterial communities are now known to influence a range of fitness related aspects of organisms. But how different the microbial community is in closely related species, and if these differences can be interpreted as adaptive is still unclear. In this study we compared microbial communities in two sets of closely related sympatric crater lake cichlid fish species pairs that show similar adaptations along the limnetic-benthic axis. The gut microbial community composition differs in the species pair inhabiting the older of two crater lakes. One major difference, relative to other fish, is that in these cichlids that live in hypersaline crater lakes, the microbial community is largely made up of Oceanospirillales (52.28%) which are halotolerant or halophilic bacteria. This analysis opens up further avenues to identify candidate symbiotic or co-evolved bacteria playing a role in adaptation to similar diets and life-styles or even have a role in speciation. Future functional and phylosymbiotic analyses might help to address these issues.

  3. Country watch. Malawi.

    PubMed

    Singogo, P P; Chintengo, S

    1994-01-01

    Traditional health practitioners (THP) far outnumber biomedical staff in Malawi. They are generally well-known, accepted, and trusted by villagers, and are respected guardians of sociocultural values and opinion leaders concerning health. Many treat 5-6 sexually transmitted disease patients per day. The National AIDS Program therefore enlisted the collaboration of the Herbalist Association of Malawi in a special AIDS project. Objectives were to train THPs as peer educators, increase biomedical practitioners' awareness of traditional healing practices, and promote greater communication and cooperation between THPs and the biomedical sector. Although many THPs are illiterate, their generally literate secretaries help facilitate use of the manual and the dissemination of information. The first training course was organized for THPs from two districts in 1992 with seven more following to train a total 234 THPs. Biomedical practitioners from the district provide support. A participatory approach is used to engage THPs in exercises and group discussions. Follow-up has shown success with THPs understanding that AIDS is incurable and that is has a big impact upon the community. 91% were conducting AIDS education sessions, several have trained other healers in their districts, and some actively distribute condoms in their communities. The project now wants to train traditional birth attendants and involve biomedical health staff in record keeping for the THPs on condom distribution.

  4. Complex patterns of divergence among green-sensitive (RH2a) African cichlid opsins revealed by Clade model analyses

    PubMed Central

    2012-01-01

    Background Gene duplications play an important role in the evolution of functional protein diversity. Some models of duplicate gene evolution predict complex forms of paralog divergence; orthologous proteins may diverge as well, further complicating patterns of divergence among and within gene families. Consequently, studying the link between protein sequence evolution and duplication requires the use of flexible substitution models that can accommodate multiple shifts in selection across a phylogeny. Here, we employed a variety of codon substitution models, primarily Clade models, to explore how selective constraint evolved following the duplication of a green-sensitive (RH2a) visual pigment protein (opsin) in African cichlids. Past studies have linked opsin divergence to ecological and sexual divergence within the African cichlid adaptive radiation. Furthermore, biochemical and regulatory differences between the RH2aα and RH2aβ paralogs have been documented. It thus seems likely that selection varies in complex ways throughout this gene family. Results Clade model analysis of African cichlid RH2a opsins revealed a large increase in the nonsynonymous-to-synonymous substitution rate ratio (ω) following the duplication, as well as an even larger increase, one consistent with positive selection, for Lake Tanganyikan cichlid RH2aβ opsins. Analysis using the popular Branch-site models, by contrast, revealed no such alteration of constraint. Several amino acid sites known to influence spectral and non-spectral aspects of opsin biochemistry were found to be evolving divergently, suggesting that orthologous RH2a opsins may vary in terms of spectral sensitivity and response kinetics. Divergence appears to be occurring despite intronic gene conversion among the tandemly-arranged duplicates. Conclusions Our findings indicate that variation in selective constraint is associated with both gene duplication and divergence among orthologs in African cichlid RH2a opsins. At

  5. Complex patterns of divergence among green-sensitive (RH2a) African cichlid opsins revealed by Clade model analyses.

    PubMed

    Weadick, Cameron J; Chang, Belinda S W

    2012-10-18

    Gene duplications play an important role in the evolution of functional protein diversity. Some models of duplicate gene evolution predict complex forms of paralog divergence; orthologous proteins may diverge as well, further complicating patterns of divergence among and within gene families. Consequently, studying the link between protein sequence evolution and duplication requires the use of flexible substitution models that can accommodate multiple shifts in selection across a phylogeny. Here, we employed a variety of codon substitution models, primarily Clade models, to explore how selective constraint evolved following the duplication of a green-sensitive (RH2a) visual pigment protein (opsin) in African cichlids. Past studies have linked opsin divergence to ecological and sexual divergence within the African cichlid adaptive radiation. Furthermore, biochemical and regulatory differences between the RH2aα and RH2aβ paralogs have been documented. It thus seems likely that selection varies in complex ways throughout this gene family. Clade model analysis of African cichlid RH2a opsins revealed a large increase in the nonsynonymous-to-synonymous substitution rate ratio (ω) following the duplication, as well as an even larger increase, one consistent with positive selection, for Lake Tanganyikan cichlid RH2aβ opsins. Analysis using the popular Branch-site models, by contrast, revealed no such alteration of constraint. Several amino acid sites known to influence spectral and non-spectral aspects of opsin biochemistry were found to be evolving divergently, suggesting that orthologous RH2a opsins may vary in terms of spectral sensitivity and response kinetics. Divergence appears to be occurring despite intronic gene conversion among the tandemly-arranged duplicates. Our findings indicate that variation in selective constraint is associated with both gene duplication and divergence among orthologs in African cichlid RH2a opsins. At least some of this variation may

  6. IMMUNISATION TRAINING NEEDS IN MALAWI.

    PubMed

    Tsega, A Y; Hausi, H T; Steinglass, R; Chirwa, G Z

    2014-09-01

    The Malawi Ministry of Health (MOH) and its immunisation partners conducted a training needs assessment in May 2013 to assess the current status of immunisation training programmemes in health training institutions, to identify unmet training needs, and to recommend possible solutions for training of health workers on a regular basis. A cross-sectional, descriptive study. Health training institutions in Malawi, a developing country that does not regularly update its curricula to include new vaccines and management tools, nor train healthcare workers on a regular basis. Researchers interviewed Malawi's central immunisation manager, three zonal immunisation officers, six district officers, 12 health facility immunisation coordinators, and eight principals of training institutions. All health training institutions in Malawi include immunisation in their preservice training curricula. However, the curriculum is not regularly updated; thus, the graduates are not well equipped to provide quality services. In addition, the duration of the training curriculum is inadequate, and in-service training sessions for managers and service providers are conducted only on an ad hoc basis. All levels of Malawi's health system have not met sufficient training needs for providing immunisations, and the health training institutions teach their students with outdated materials. It is recommended that the training institutions update their training curricula regularly and the service providers are trained on a regular basis.

  7. Evolutionary Fate of the Androgen Receptor−Signaling Pathway in Ray-Finned Fishes with a Special Focus on Cichlids

    PubMed Central

    Lorin, Thibault; Salzburger, Walter; Böhne, Astrid

    2015-01-01

    The emergence of the steroid system is coupled to the evolution of multicellular animals. In vertebrates in particular, the steroid receptor repertoire has been shaped by genome duplications characteristic to this lineage. Here, we investigate for the first time the composition of the androgen receptor–signaling pathway in ray-finned fish genomes by focusing in particular on duplicates that emerged from the teleost-specific whole-genome duplication. We trace lineage- and species-specific duplications and gene losses for the genomic and nongenomic pathway of androgen signaling and subsequently investigate the sequence evolution of these genes. In one particular fish lineage, the cichlids, we find evidence for differing selection pressures acting on teleost-specific whole-genome duplication paralogs at a derived evolutionary stage. We then look into the expression of these duplicated genes in four cichlid species from Lake Tanganyika indicating, once more, rapid changes in expression patterns in closely related fish species. We focus on a particular case, the cichlid specific duplication of the rac1 GTPase, which shows possible signs of a neofunctionalization event. PMID:26333839

  8. Complementary description of Ergasilus arthrosis Roberts, 1969 (Copepoda: Poecilostomatoida: Ergasilidae), a new parasite of cichlid teleosts in southeast Mexico.

    PubMed

    Jiménez-García, María Isabel; Suárez-Morales, Eduardo

    2017-01-01

    During a parasitological survey of the ichthyofauna of Lake Catemaco, a freshwater system in the Mexican State of Veracruz, the widespread copepod Ergasilus arthrosis Roberts, 1969 was recovered from two cichlid teleosts, Mayaheros urophthalmus (Günther) and Oreochromis sp. This is the first confirmed record of this copepod species outside of the United States and from Mexico; its finding as a parasite of cichlids represents an expansion of the known host range for this copepod. The local prevalence and intensity of infection of E. arthrosis was highest in M. urophthalmus. The infection prevalence of E. arthrosis on M. urophthalmus (60%) was higher than that known for other ergasilids on cichlids. Ergasilus arthrosis can be distinguished from its closest congener E. lizae Krøyer, 1863 by the morphometry of the antennary segments, the ventral ornamentation of the thoracic sclerites and by details of the antennulary setation, but also by its habitat and host preferences. Taxonomic illustrations and morphological details of the specimens examined are also provided together with comments on the variability of this species.

  9. Lineage-Specific Expansion of Vomeronasal Type 2 Receptor-Like (OlfC) Genes in Cichlids May Contribute to Diversification of Amino Acid Detection Systems

    PubMed Central

    Nikaido, Masato; Suzuki, Hikoyu; Toyoda, Atsushi; Fujiyama, Asao; Hagino-Yamagishi, Kimiko; Kocher, Thomas D.; Carleton, Karen; Okada, Norihiro

    2013-01-01

    Fish use olfaction to sense a variety of nonvolatile chemical signals in water. However, the evolutionary importance of olfaction in species-rich cichlids is controversial. Here, we determined an almost complete sequence of the vomeronasal type 2 receptor-like (OlfC: putative amino acids receptor in teleosts) gene cluster using the bacterial artificial chromosome library of the Lake Victoria cichlid, Haplochromis chilotes. In the cluster region, we found 61 intact OlfC genes, which is the largest number of OlfC genes identified among the seven teleost fish investigated to date. Data mining of the Oreochromis niloticus (Nile tilapia) draft genome sequence, and genomic Southern hybridization analysis revealed that the ancestor of all modern cichlids had already developed almost the same OlfC gene repertoire, which was accomplished by lineage-specific gene expansions. Furthermore, comparison of receptor sequences showed that recently duplicated paralogs are more variable than orthologs of different species at particular sites that were predicted to be involved in amino acid selectivity. Thus, the increase of paralogs through gene expansion may lead to functional diversification in detection of amino acids. This study implies that cichlids have developed a potent capacity to detect a variety of amino acids (and their derivatives) through OlfCs, which may have contributed to the extraordinary diversity of their feeding habitats. PMID:23501830

  10. Introduced Predator Elicits Deficient Brood Defence Behaviour in a Crater Lake Fish

    PubMed Central

    Lehtonen, Topi K.; McCrary, Jeffrey K.; Meyer, Axel

    2012-01-01

    Introduced species represent one of the most serious global threats to biodiversity. In this field-based study, we assessed behavioural responses of brood tending cichlid fish to an invasive predator of their offspring. This was achieved by comparing parental defence responses of the endangered arrow cichlid (Amphilophus zaliosus), a fish species endemic to the crater lake Apoyo in Nicaragua, towards the bigmouth sleeper (Gobiomorus dormitor), a formidable predator of cichlid fry, and all other potential fish predators of offspring. The bigmouth sleeper was recently introduced into Apoyo but naturally co-exists with cichlids in a few other Nicaraguan lakes. Arrow cichlid parents allowed bigmouth sleepers to advance much closer to their fry than other predators before initiating aggressive brood defence behaviours. Interestingly, parents of a very closely related species, A. sagittae, which has coevolved with bigmouth sleepers in crater lake Xiloá, reacted to approaching bigmouth sleepers at comparable distances as to other predators of cichlid fry. These results provide a novel demonstration of the specific mechanism (i.e. naive parental behaviour) by which invasive predators may negatively affect species that lack the adequate behavioural repertoire. PMID:22253881

  11. Parsing parallel evolution: ecological divergence and differential gene expression in the adaptive radiations of thick-lipped Midas cichlid fishes from Nicaragua.

    PubMed

    Manousaki, Tereza; Hull, Pincelli M; Kusche, Henrik; Machado-Schiaffino, Gonzalo; Franchini, Paolo; Harrod, Chris; Elmer, Kathryn R; Meyer, Axel

    2013-02-01

    The study of parallel evolution facilitates the discovery of common rules of diversification. Here, we examine the repeated evolution of thick lips in Midas cichlid fishes (the Amphilophus citrinellus species complex)-from two Great Lakes and two crater lakes in Nicaragua-to assess whether similar changes in ecology, phenotypic trophic traits and gene expression accompany parallel trait evolution. Using next-generation sequencing technology, we characterize transcriptome-wide differential gene expression in the lips of wild-caught sympatric thick- and thin-lipped cichlids from all four instances of repeated thick-lip evolution. Six genes (apolipoprotein D, myelin-associated glycoprotein precursor, four-and-a-half LIM domain protein 2, calpain-9, GTPase IMAP family member 8-like and one hypothetical protein) are significantly underexpressed in the thick-lipped morph across all four lakes. However, other aspects of lips' gene expression in sympatric morphs differ in a lake-specific pattern, including the magnitude of differentially expressed genes (97-510). Generally, fewer genes are differentially expressed among morphs in the younger crater lakes than in those from the older Great Lakes. Body shape, lower pharyngeal jaw size and shape, and stable isotopes (δ(13)C and δ(15)N) differ between all sympatric morphs, with the greatest differentiation in the Great Lake Nicaragua. Some ecological traits evolve in parallel (those related to foraging ecology; e.g. lip size, body and head shape) but others, somewhat surprisingly, do not (those related to diet and food processing; e.g. jaw size and shape, stable isotopes). Taken together, this case of parallelism among thick- and thin-lipped cichlids shows a mosaic pattern of parallel and nonparallel evolution.

  12. Phenotypic plasticity is maintained despite geographical isolation in an African cichlid fish, Pseudocrenilabrus multicolor.

    PubMed

    Wiens, Kirsten E; Crispo, Erika; Chapman, Lauren J

    2014-01-01

    Gene flow among populations in different selective environments should favor the evolution of phenotypic plasticity over local adaptation. Plasticity in development is a common response to long-term hypoxia in some widespread African fishes, including Pseudocrenilabrus multicolor, a cichlid that exploits both normoxic (high oxygen) rivers/lakes and hypoxic (low oxygen) swamps. Previous studies have shown that fish from normoxic and hypoxic sites differ in many traits, including gill size, brain size and body shape, and that much of this variation reflects developmental plasticity. However, these earlier studies focused on areas in Uganda where gene flow between swamp and river or lake populations is high. In this study we tested the hypothesis that P. multicolor from a relatively isolated lake population (Lake Saka, Uganda) exhibit low levels of plasticity in traits related to oxygen uptake. Multiple broods of P. multicolor from Lake Saka were reared under low and high dissolved oxygen, and traits related to gill size, brain mass and body shape were quantified. Surprisingly, both gill size and brain mass showed high levels of developmental plasticity. We suggest that high levels of plasticity, particularly in the gill size of P. multicolor, reflects low costs of maintaining the plastic response, even in relatively isolated populations. © 2012 Wiley Publishing Asia Pty Ltd, ISZS and IOZ/CAS.

  13. Introgressive hybridization in a trophically polymorphic cichlid.

    PubMed

    Hulsey, C Darrin; García-de-León, Francisco J

    2013-11-01

    Trophically polymorphic species could represent lineages that are rapidly diverging along an ecological axis or could phenotypically mark the collapse of species through introgressive hybridization. We investigated patterns of introgression between the trophically polymorphic cichlid fish Herichthys minckleyi and its relative H. cyanoguttatus using a combination of population genetics and species tree analyses. We first examined the distribution of mitochondrial haplotypes within the alternative H. minckleyi pharyngeal jaw morphotypes that are endemic to the small desert valley of Cuatro Ciénegas. We recovered two clusters of mitochondrial haplotypes. The first contained a number of slightly differentiated cytochrome b (cytb) haplotypes that showed some phylogeographic signal and were present in both jaw morphotypes. The other haplotype was monomorphic, highly differentiated from the other cluster, present in equal frequencies in the morphotypes, and identical to H. cyanoguttatus haplotypes found outside Cuatro Ciénegas. Then, we investigated whether H. minckleyi individuals with the H. cyanoguttatus cytb were more evolutionarily similar to H. cyanoguttatus or other H. minckleyi using a species tree analysis of 84 nuclear loci. Both H. minckleyi pharyngeal morphotypes, regardless of their cytb haplotype, were quite distinct from H. cyanoguttatus. However, hybridization could be blurring subdivision within H. minckleyi as the alternative jaw morphotypes were not genetically distinct from one another. Accounting for introgression from H. cyanoguttatus will be essential to understand the evolution of the trophically polymorphic cichlid H. minckleyi.

  14. Introgressive hybridization in a trophically polymorphic cichlid

    PubMed Central

    Hulsey, C Darrin; García-de-León, Francisco J

    2013-01-01

    Trophically polymorphic species could represent lineages that are rapidly diverging along an ecological axis or could phenotypically mark the collapse of species through introgressive hybridization. We investigated patterns of introgression between the trophically polymorphic cichlid fish Herichthys minckleyi and its relative H. cyanoguttatus using a combination of population genetics and species tree analyses. We first examined the distribution of mitochondrial haplotypes within the alternative H. minckleyi pharyngeal jaw morphotypes that are endemic to the small desert valley of Cuatro Ciénegas. We recovered two clusters of mitochondrial haplotypes. The first contained a number of slightly differentiated cytochrome b (cytb) haplotypes that showed some phylogeographic signal and were present in both jaw morphotypes. The other haplotype was monomorphic, highly differentiated from the other cluster, present in equal frequencies in the morphotypes, and identical to H. cyanoguttatus haplotypes found outside Cuatro Ciénegas. Then, we investigated whether H. minckleyi individuals with the H. cyanoguttatus cytb were more evolutionarily similar to H. cyanoguttatus or other H. minckleyi using a species tree analysis of 84 nuclear loci. Both H. minckleyi pharyngeal morphotypes, regardless of their cytb haplotype, were quite distinct from H. cyanoguttatus. However, hybridization could be blurring subdivision within H. minckleyi as the alternative jaw morphotypes were not genetically distinct from one another. Accounting for introgression from H. cyanoguttatus will be essential to understand the evolution of the trophically polymorphic cichlid H. minckleyi. PMID:24340193

  15. Mapping Malaria Transmission Intensity in Malawi, 2000–2010

    PubMed Central

    Bennett, Adam; Kazembe, Lawrence; Mathanga, Don P.; Kinyoki, Damaris; Ali, Doreen; Snow, Robert W.; Noor, Abdisalan M.

    2013-01-01

    Substantial development assistance has been directed towards reducing the high malaria burden in Malawi over the past decade. We assessed changes in transmission over this period of malaria control scale-up by compiling community Plasmodium falciparum rate (PfPR) data during 2000–2011 and used model-based geostatistical methods to predict mean PfPR2–10 in 2000, 2005, and 2010. In addition, we calculated population-adjusted prevalences and populations at risk by district to inform malaria control program priority setting. The national population-adjusted PfPR2–10 was 37% in 2010, and we found no evidence of change over this period of scale-up. The entire population of Malawi is under meso-endemic transmission risk, with those in districts along the shore of Lake Malawi and Shire River Valley under highest risk. The lack of change in prevalence confirms modeling predictions that when compared with lower transmission, prevalence reductions in high transmission settings require greater investment and longer time scales. PMID:24062477

  16. The experience of irrigation management transfer in two irrigation schemes in Malawi, 1960s 2002

    NASA Astrophysics Data System (ADS)

    Nkhoma, Bryson G.; Mulwafu, Wapulumuka O.

    This study examines the process of irrigation management transfer (IMT) in Malawi using the case studies of Likangala and Domasi irrigation schemes in the lake Chilwa basin. It observes that the concept of irrigation management transfer has been adopted against the background of poor performance of irrigation schemes in Malawi and the desire of the state to conform to global trends and approaches in the management of irrigation schemes. In the context of Malawi, the process of IMT involves rehabilitation of schemes and training of farmers before handing them over. The paper notes that so far the handover process has been fraught with many challenges, not least of which includes lack of adequate funds, delays, lack of public awareness and farmers’ conflicting perceptions on the handover of irrigation schemes. These problems militate against the success of IMT in the Domasi and Likangala irrigation schemes in particular and other schemes in the country as a whole.

  17. Non-random brood mixing suggests adoption in a colonial cichlid.

    PubMed

    Schaedelin, Franziska C; van Dongen, Wouter F D; Wagner, Richard H

    2013-03-01

    Parental care of unrelated offspring is widespread but not well understood. We used 11 polymorphic microsatellite loci to investigate the relatedness of fry and parentally caring adults in a 118-nest colony of the socially and genetically monogamous cichlid fish Neolamprologus caudopunctatus in Lake Tanganyika. There was a high proportion of brood mixing, with 59% of 32 broods containing fry unrelated to both parents, and 18% of all 291 sampled fry being unrelated to the breeding pair. There was no evidence of kin selection for adoption because the genetic and foster parents were not more related than expected by chance. Parentage was assigned to 12 adopted fry from 10 broods. Distances traversed by fry varied markedly, from less than one to over 40 meters. The larger distances suggest that at least some brood mixing was instigated by parents transporting portions of their broods in their mouths, as occurs in some cichlids. Further evidence of non-random brood mixing was that foreign fry did not differ in size from their foster siblings within broods, even though they were significantly larger than fry produced by the tending pairs within the colony. These findings suggest that at least some foreign fry had dispersed non-randomly and were adopted by their foster parents. Enlarged broods are known to provide reduced per capita predation, making it potentially adaptive for breeders to adopt unrelated offspring.

  18. Social motivation and conflict resolution tactics as potential building blocks of sociality in cichlid fishes.

    PubMed

    Balshine, Sigal; Wong, Marian Y L; Reddon, Adam R

    2017-01-03

    Even closely related and ecologically similar cichlid species of Lake Tanganyika exhibit an impressive diversity of social systems, and therefore these fishes offer an excellent opportunity to examine the evolution of social behaviour. Sophisticated social relationships are thought to have evolved via a building block design where more fundamental social behaviours and cognitive processes have been combined, incrementally modified, and elaborated over time. Here, we studied two of these putative social building blocks in two closely related species of cichlids: Neolamprologus pulcher, a group-living species, and Telmatochromis temporalis, a non-grouping species. Otherwise well matched in ecology, this pair of species provide an excellent comparison point to understand how behavioural processes may have been modified in relation to the evolution of sociality. Using social assays in both the laboratory and in the field, we explored each species' motivation to interact with conspecifics, and each species' conflict resolution tactics. We found that individuals of the group living species, N. pulcher, displayed higher social motivation and were more likely to produce submission displays than were individuals of the non-grouping species, T. temporalis. We argue that the motivation to interact with conspecifics is a necessary prerequisite for the emergence of group living, and that the use of submission reduces the costs of conflict and facilitates the maintenance of close social proximity. These results suggest that social motivation and conflict resolution tactics are associated with social complexity, and that these behavioural traits may be functionally significant in the evolution and maintenance of sociality.

  19. Handed Foraging Behavior in Scale-Eating Cichlid Fish: Its Potential Role in Shaping Morphological Asymmetry

    PubMed Central

    Meyer, Axel

    2012-01-01

    Scale-eating cichlid fish, Perissodus microlepis, from Lake Tanganyika display handed (lateralized) foraging behavior, where an asymmetric ‘left’ mouth morph preferentially feeds on the scales of the right side of its victim fish and a ‘right’ morph bites the scales of the left side. This species has therefore become a textbook example of the astonishing degree of ecological specialization and negative frequency-dependent selection. We investigated the strength of handedness of foraging behavior as well as its interaction with morphological mouth laterality in P. microlepis. In wild-caught adult fish we found that mouth laterality is, as expected, a strong predictor of their preferred attack orientation. Also laboratory-reared juvenile fish exhibited a strong laterality in behavioral preference to feed on scales, even at an early age, although the initial level of mouth asymmetry appeared to be small. This suggests that pronounced mouth asymmetry is not a prerequisite for handed foraging behavior in juvenile scale-eating cichlid fish and might suggest that behavioral preference to attack a particular side of the prey plays a role in facilitating morphological asymmetry of this species. PMID:22970282

  20. Water-level fluctuations and metapopulation dynamics as drivers of genetic diversity in populations of three Tanganyikan cichlid fish species

    PubMed Central

    Nevado, B; Mautner, S; Sturmbauer, C; Verheyen, E

    2013-01-01

    Understanding how genetic variation is generated and maintained in natural populations, and how this process unfolds in a changing environment, remains a central issue in biological research. In this work, we analysed patterns of genetic diversity from several populations of three cichlid species from Lake Tanganyika in parallel, using the mitochondrial DNA control region. We sampled populations inhabiting the littoral rocky habitats in both very deep and very shallow areas of the lake. We hypothesized that the former would constitute relatively older, more stable and genetically more diverse populations, because they should have been less severely affected by the well-documented episodes of dramatic water-level fluctuations. In agreement with our predictions, populations of all three species sampled in very shallow shorelines showed traces of stronger population growth than populations of the same species inhabiting deep shorelines. However, contrary to our working hypothesis, we found a significant trend towards increased genetic diversity in the younger, demographically less stable populations inhabiting shallow areas, in comparison with the older and more stable populations inhabiting the deep shorelines. We interpret this finding as the result of the establishment of metapopulation dynamics in the former shorelines, by the frequent perturbation and reshuffling of individuals between populations due to the lake-level fluctuations. The repeated succession of periods of allopatric separation and secondary contact is likely to have further increased the rapid pace of speciation in lacustrine cichlids. PMID:23837841

  1. Country watch: Malawi.

    PubMed

    Knox, G

    1995-01-01

    The Drought Network for information sharing eventually led to the establishment of the more formal Southern Region AIDS Network (SORAN) where representatives from government and nongovernmental organizations (NGOs) focused on awareness raising, lobbying, and advocacy. As an initial step towards networking on HIV/AIDS issues, a festival was organized in Blantyre on December 4, 1993, by NGOs, private companies, church groups, school children, and volunteers to bring about behavior change. About 2000 people gathered to listen to music, learn about HIV transmission through drama group presentations, watch videos with HIV/STD prevention messages, and learn about proper condom use. The participants officially established SORAN in February 1994 to act as a coordinating body for organizations working in prevention and care for HIV/STD-infected persons and their families. Network activities endeavored: to assist organizations interested in developing HIV/AIDS programs and activities; to encourage the business communities to participate in multisectoral coordination and to help channel funds from them to HIV/AIDS programs; to act as a resource center for information about HIV/AIDS; and to lobby among politicians as well as traditional local and religious leaders. When the first multi-party parliamentary election approached in May 1994, SORAN challenged representatives of 7 political parties and a women's organization to speak out publicly on what they envisioned doing about HIV/AIDS. The Grand Walk was also organized by SORAN members representing the Catholic Episcopal Conference of Malawi, the Protestant Blantyre Synod, a local brewery, and UNICEF. About 500 walkers received support from passersby. 70% were school children 10-18 years old who sang AIDS awareness songs and passed out flyers. Three months later the National AIDS Program's Big Walk for AIDS, following a National AIDS Crisis Conference, signaled the government's public recognition of the need for a

  2. Functional coupling constrains craniofacial diversification in Lake Tanganyika cichlids

    PubMed Central

    Tsuboi, Masahito; Gonzalez-Voyer, Alejandro; Kolm, Niclas

    2015-01-01

    Functional coupling, where a single morphological trait performs multiple functions, is a universal feature of organismal design. Theory suggests that functional coupling may constrain the rate of phenotypic evolution, yet empirical tests of this hypothesis are rare. In fish, the evolutionary transition from guarding the eggs on a sandy/rocky substrate (i.e. substrate guarding) to mouthbrooding introduces a novel function to the craniofacial system and offers an ideal opportunity to test the functional coupling hypothesis. Using a combination of geometric morphometrics and a recently developed phylogenetic comparative method, we found that head morphology evolution was 43% faster in substrate guarding species than in mouthbrooding species. Furthermore, for species in which females were solely responsible for mouthbrooding the males had a higher rate of head morphology evolution than in those with bi-parental mouthbrooding. Our results support the hypothesis that adaptations resulting in functional coupling constrain phenotypic evolution. PMID:25948565

  3. Functional coupling constrains craniofacial diversification in Lake Tanganyika cichlids.

    PubMed

    Tsuboi, Masahito; Gonzalez-Voyer, Alejandro; Kolm, Niclas

    2015-05-01

    Functional coupling, where a single morphological trait performs multiple functions, is a universal feature of organismal design. Theory suggests that functional coupling may constrain the rate of phenotypic evolution, yet empirical tests of this hypothesis are rare. In fish, the evolutionary transition from guarding the eggs on a sandy/rocky substrate (i.e. substrate guarding) to mouthbrooding introduces a novel function to the craniofacial system and offers an ideal opportunity to test the functional coupling hypothesis. Using a combination of geometric morphometrics and a recently developed phylogenetic comparative method, we found that head morphology evolution was 43% faster in substrate guarding species than in mouthbrooding species. Furthermore, for species in which females were solely responsible for mouthbrooding the males had a higher rate of head morphology evolution than in those with bi-parental mouthbrooding. Our results support the hypothesis that adaptations resulting in functional coupling constrain phenotypic evolution.

  4. Molecular and fossil evidence place the origin of cichlid fishes long after Gondwanan rifting.

    PubMed

    Friedman, Matt; Keck, Benjamin P; Dornburg, Alex; Eytan, Ron I; Martin, Christopher H; Hulsey, C Darrin; Wainwright, Peter C; Near, Thomas J

    2013-11-07

    Cichlid fishes are a key model system in the study of adaptive radiation, speciation and evolutionary developmental biology. More than 1600 cichlid species inhabit freshwater and marginal marine environments across several southern landmasses. This distributional pattern, combined with parallels between cichlid phylogeny and sequences of Mesozoic continental rifting, has led to the widely accepted hypothesis that cichlids are an ancient group whose major biogeographic patterns arose from Gondwanan vicariance. Although the Early Cretaceous (ca 135 Ma) divergence of living cichlids demanded by the vicariance model now represents a key calibration for teleost molecular clocks, this putative split pre-dates the oldest cichlid fossils by nearly 90 Myr. Here, we provide independent palaeontological and relaxed-molecular-clock estimates for the time of cichlid origin that collectively reject the antiquity of the group required by the Gondwanan vicariance scenario. The distribution of cichlid fossil horizons, the age of stratigraphically consistent outgroup lineages to cichlids and relaxed-clock analysis of a DNA sequence dataset consisting of 10 nuclear genes all deliver overlapping estimates for crown cichlid origin centred on the Palaeocene (ca 65-57 Ma), substantially post-dating the tectonic fragmentation of Gondwana. Our results provide a revised macroevolutionary time scale for cichlids, imply a role for dispersal in generating the observed geographical distribution of this important model clade and add to a growing debate that questions the dominance of the vicariance paradigm of historical biogeography.

  5. Molecular and fossil evidence place the origin of cichlid fishes long after Gondwanan rifting

    PubMed Central

    Friedman, Matt; Keck, Benjamin P.; Dornburg, Alex; Eytan, Ron I.; Martin, Christopher H.; Hulsey, C. Darrin; Wainwright, Peter C.; Near, Thomas J.

    2013-01-01

    Cichlid fishes are a key model system in the study of adaptive radiation, speciation and evolutionary developmental biology. More than 1600 cichlid species inhabit freshwater and marginal marine environments across several southern landmasses. This distributional pattern, combined with parallels between cichlid phylogeny and sequences of Mesozoic continental rifting, has led to the widely accepted hypothesis that cichlids are an ancient group whose major biogeographic patterns arose from Gondwanan vicariance. Although the Early Cretaceous (ca 135 Ma) divergence of living cichlids demanded by the vicariance model now represents a key calibration for teleost molecular clocks, this putative split pre-dates the oldest cichlid fossils by nearly 90 Myr. Here, we provide independent palaeontological and relaxed-molecular-clock estimates for the time of cichlid origin that collectively reject the antiquity of the group required by the Gondwanan vicariance scenario. The distribution of cichlid fossil horizons, the age of stratigraphically consistent outgroup lineages to cichlids and relaxed-clock analysis of a DNA sequence dataset consisting of 10 nuclear genes all deliver overlapping estimates for crown cichlid origin centred on the Palaeocene (ca 65–57 Ma), substantially post-dating the tectonic fragmentation of Gondwana. Our results provide a revised macroevolutionary time scale for cichlids, imply a role for dispersal in generating the observed geographical distribution of this important model clade and add to a growing debate that questions the dominance of the vicariance paradigm of historical biogeography. PMID:24048155

  6. Microsatellites Cross-Species Amplification across Some African Cichlids.

    PubMed

    Bezault, Etienne; Rognon, Xavier; Gharbi, Karim; Baroiller, Jean-Francois; Chevassus, Bernard

    2012-01-01

    The transfer of the genomic resources developed in the Nile tilapia, Oreochromis niloticus, to other Tilapiines sensu lato and African cichlid would provide new possibilities to study this amazing group from genetics, ecology, evolution, aquaculture, and conservation point of view. We tested the cross-species amplification of 32 O. niloticus microsatellite markers in a panel of 15 species from 5 different African cichlid tribes: Oreochromines (Oreochromis, Sarotherodon), Boreotilapiines (Tilapia), Chromidotilapines, Hemichromines, and Haplochromines. Amplification was successfully observed for 29 markers (91%), with a frequency of polymorphic (P(95)) loci per species around 70%. The mean number of alleles per locus and species was 3.2 but varied from 3.7 within Oreochromis species to 1.6 within the nontilapia species. The high level of cross-species amplification and polymorphism of the microsatellite markers tested in this study provides powerful tools for a wide range of molecular genetic studies within tilapia species as well as for other African cichlids.

  7. Hearing in Cichlid Fishes under Noise Conditions

    PubMed Central

    Ladich, Friedrich; Schulz-Mirbach, Tanja

    2013-01-01

    Background Hearing thresholds of fishes are typically acquired under laboratory conditions. This does not reflect the situation in natural habitats, where ambient noise may mask their hearing sensitivities. In the current study we investigate hearing in terms of sound pressure (SPL) and particle acceleration levels (PAL) of two cichlid species within the naturally occurring range of noise levels. This enabled us to determine whether species with and without hearing specializations are differently affected by noise. Methodology/Principal Findings We investigated auditory sensitivities in the orange chromide Etroplus maculatus, which possesses anterior swim bladder extensions, and the slender lionhead cichlid Steatocranus tinanti, in which the swim bladder is much smaller and lacks extensions. E. maculatus was tested between 0.2 and 3kHz and S. tinanti between 0.1 and 0.5 kHz using the auditory evoked potential (AEP) recording technique. In both species, SPL and PAL audiograms were determined in the presence of quiet laboratory conditions (baseline) and continuous white noise of 110 and 130 dB RMS. Baseline thresholds showed greatest hearing sensitivity around 0.5 kHz (SPL) and 0.2 kHz (PAL) in E. maculatus and 0.2 kHz in S. tinanti. White noise of 110 dB elevated the thresholds by 0–11 dB (SPL) and 7–11 dB (PAL) in E. maculatus and by 1–2 dB (SPL) and by 1–4 dB (PAL) in S. tinanti. White noise of 130 dB elevated hearing thresholds by 13–29 dB (SPL) and 26–32 dB (PAL) in E. maculatus and 6–16 dB (SPL) and 6–19 dB (PAL) in S. tinanti. Conclusions Our data showed for the first time for SPL and PAL thresholds that the specialized species was masked by different noise regimes at almost all frequencies, whereas the non-specialized species was much less affected. This indicates that noise can limit sound detection and acoustic orientation differently within a single fish family. PMID:23469032

  8. Perspectives on Theological Education in Malawi

    ERIC Educational Resources Information Center

    Matemba, Yonah Hisbon

    2011-01-01

    This article gives an overview of (Christian) Theological Education (CTE) in Malawi. To place the discussion in its appropriate context, information about Malawi is given including the impact of Christianity on the country. The article then describes historical aspects of CTE and highlights some of its inherent shortcomings, before shifting to…

  9. Perspectives on Theological Education in Malawi

    ERIC Educational Resources Information Center

    Matemba, Yonah Hisbon

    2011-01-01

    This article gives an overview of (Christian) Theological Education (CTE) in Malawi. To place the discussion in its appropriate context, information about Malawi is given including the impact of Christianity on the country. The article then describes historical aspects of CTE and highlights some of its inherent shortcomings, before shifting to…

  10. Specialized morphology for a generalist diet: evidence for Liem's Paradox in a cichlid fish.

    PubMed

    Binning, S A; Chapman, L J; Cosandey-Godin, A

    2009-11-01

    The stable isotope ratio and seasonal changes in diet of Alluaud's haplo Astatoreochromis alluaudi, a cichlid fish with massive pharyngeal jaws well known for its ability to process hard-bodied prey, are described. The diet of A. alluaudi was quantified in Lake Saka, Uganda, over a period of 30 months. Variation in physico-chemical variables (mean monthly rainfall, water temperature, turbidity and dissolved oxygen), as well as potential competitor density and food abundance, was measured throughout the second half of the study (14 months). Stomach contents and isotope analysis revealed a diet comprised mainly of fishes and insects, with a low contribution of molluscs (0-33%) in any given month. No correlation was detected between diet and either macroinvertebrate abundance or competitor abundance. The running average rainfall was positively related to the percentage of fish consumed per month. Although A. alluaudi exhibits an apparent molluscivorous trophic morphology in Lake Saka, molluscs did not appear to compose a major portion of its diet. Gradients of rainfall seemed to be the most important environmental predictor of diet choice in Lake Saka. These results are discussed with reference to Liem's Paradox that apparently morphologically specialized fishes often function as generalist feeders in the wild.

  11. Sedimentary deposits in response to rift geometry in Malawi, Africa

    SciTech Connect

    Bishop, M.G. )

    1991-03-01

    Sedimentary deposits of the Malawi continental rift basin are a direct result of topography and tectonics unique to rift structure. Recent models describe rifts as asymmetric half-graben connected in series by transfer of accommodation zones. Half-graben consist of roughly parallel, tilted fault blocks stepping up from the bounding fault zone where maximum subsidence occurs. The rift becomes a local baselevel and depocenter as regional drainage is shed away by the rift shoulders. Most of the sediments are derived locally due to internal drainage of connected basins, individual basins, and individual fault blocks. The patterns of sedimentation and facies associations depend on structural position at both fault block and half-graben scales. Drainage is directed and dammed by tilted fault blocks. Forward-tilted fault blocks form basinward-thickening sediment wedges filled with facies of axial fluvial systems, alluvial fault-scarp fans, and ponded swamp and lake deposits. These deposits are asymmetrically shifted toward the controlling fault and onlap the upthrown side of the block, ordinarily the site of erosion or nondeposition. Rivers entering the lake on back tilted fault blocks form large deltas resulting in basinward fining and thinning sediment wedges. Lacustrine, nearshore, shoreline, and lake shore plain deposits over multiple fault blocks record lake levels, water chemistry, and tectonic episodes. Tectonic movement periodically changes the basin depth, configuration, and baselevel. This movement results in widespread unconformities deposition and reworking of sediments within the rift.

  12. Cholera outbreaks in Malawi in 1998-2012: social and cultural challenges in prevention and control.

    PubMed

    Msyamboza, Kelias Phiri; Kagoli, Mathew; M'bang'ombe, Maurice; Chipeta, Sikhona; Masuku, Humphrey Dzanjo

    2014-06-11

    Cholera still remains a significant cause of morbidity and mortality in developing countries, although comprehensive surveillance data to inform policy and strategies are scarce. A desk review of the national cholera database and zonal and districts reports was conducted. Interviews were conducted with district health management teams, health workers, and participants in communities in six districts affected by cholera in 2011/2012 to obtain data on water, sanitation, and sociocultural issues. From 1998 to 2012, cholera outbreaks occurred every year in Malawi, with the highest number of cases and deaths reported in 2001/2002 (33,546 cases, 968 deaths; case fatality rate [CFR] 2.3%). In 2011/2012, cholera outbreak was widespread in the southern region, affecting 10 out of 13 districts, where 1,806 cases and 38 deaths (CFR 2.1%) were reported. Unsafe water sources, lack of maintenance of broken boreholes, frequent breakdown of piped water supply, low coverage of pit latrines (range 40%-60%), lack of hand washing facilities (< 5%), salty borehole water, fishermen staying on Lake Chilwa, cross-border Malawi-Mozambique disease spread, and sociocultural issues were some of the causes of the persistent cholera outbreaks in Malawi. Despite improvements in safe drinking water and sanitation, cholera is still a major public health problem. Introduction of a community-led total sanitation approach, use of social and cultural information in community mobilization strategies, and introduction of an oral cholera vaccine could help to eliminate cholera in Malawi.

  13. Linkage relationships and haplotype polymorphism among cichlid Mhc class II B loci.

    PubMed Central

    Málaga-Trillo, E; Zaleska-Rutczynska, Z; McAndrew, B; Vincek, V; Figueroa, F; Sültmann, H; Klein, J

    1998-01-01

    The species flocks of cichlid fishes in the Great East African Lakes are paradigms of adaptive radiation and hence, of great interest to evolutionary biologists. Phylogenetic studies of these fishes have, however, been hampered by the lack of suitable polymorphic markers. The genes of the major histocompatibility complex hold the promise to provide, through their extensive polymorphism, a large number of such markers, but their use has been hampered by the complexity of the genetic system and the lack of definition of the individual loci. In this study we take the first substantial step to alleviate this problem. Using a combination of methods, including the typing of single sperm cells, gyno- or androgenetic individuals, and haploid embryos, as well as sequencing of class II B restriction fragments isolated from gels for Southern blots, we identify the previously characterized homology groups as distinct loci. At least 17 polymorphic class II B loci, all of which are presumably transcribed, have been found among the different species studied. Most of these loci are shared across the various cichlid species and genera. The number of loci per haplotype varies from individual to individual, ranging from 1 to 13. A total of 21 distinct haplotypes differing in the number of loci they carry has thus far been identified. All the polymorphic loci are part of the same cluster in which, however, distances between at least some of the loci (as indicated by recombination frequencies) are relatively large. Both the individual loci and the haplotypes can now be used to study phylogenetic relationships among the members of the species flocks and the mode in which speciation occurs during adaptive radiation. PMID:9649539

  14. Incidence of induced abortion in Malawi, 2015.

    PubMed

    Polis, Chelsea B; Mhango, Chisale; Philbin, Jesse; Chimwaza, Wanangwa; Chipeta, Effie; Msusa, Ausbert

    2017-01-01

    In Malawi, abortion is legal only if performed to save a woman's life; other attempts to procure an abortion are punishable by 7-14 years imprisonment. Most induced abortions in Malawi are performed under unsafe conditions, contributing to Malawi's high maternal mortality ratio. Malawians are currently debating whether to provide additional exceptions under which an abortion may be legally obtained. An estimated 67,300 induced abortions occurred in Malawi in 2009 (equivalent to 23 abortions per 1,000 women aged 15-44), but changes since 2009, including dramatic increases in contraceptive prevalence, may have impacted abortion rates. We conducted a nationally representative survey of health facilities to estimate the number of cases of post-abortion care, as well as a survey of knowledgeable informants to estimate the probability of needing and obtaining post-abortion care following induced abortion. These data were combined with national population and fertility data to determine current estimates of induced abortion and unintended pregnancy in Malawi using the Abortion Incidence Complications Methodology. We estimate that approximately 141,044 (95% CI: 121,161-160,928) induced abortions occurred in Malawi in 2015, translating to a national rate of 38 abortions per 1,000 women aged 15-49 (95% CI: 32 to 43); which varied by geographical zone (range: 28-61). We estimate that 53% of pregnancies in Malawi are unintended, and that 30% of unintended pregnancies end in abortion. Given the challenges of estimating induced abortion, and the assumptions required for calculation, results should be viewed as approximate estimates, rather than exact measures. The estimated abortion rate in 2015 is higher than in 2009 (potentially due to methodological differences), but similar to recent estimates from nearby countries including Tanzania (36), Uganda (39), and regional estimates in Eastern and Southern Africa (34-35). Over half of pregnancies in Malawi are unintended. Our

  15. Function of a key morphological innovation: fusion of the cichlid pharyngeal jaw

    PubMed Central

    Darrin Hulsey, C

    2005-01-01

    The pharyngeal jaw of cichlids may represent a key innovation that facilitated their unparalleled trophic divergence. In cichlids, ‘fusion’ of the lower pharyngeal jaw (LPJ) results from suturing between the two lower ceratobranchials. To examine, what novel abilities a more extensively fused pharyngeal jaw may confer, the function of LPJ suturing was examined in Heroine cichlids. Greater LPJ suturing, pharyngeal jaw splitting under compression and the forces used to crush molluscs in the wild suggest increased LPJ fusion in the trophically polymorphic Herichthys minckleyi operates to strengthen the pharyngeal jaw. Among Heroine cichlid species, the presence of an external LPJ suture and feeding specialization on molluscs was evolutionarily quite variable, but greater LPJ fusion estimated from the amount of external suturing was highly correlated with molluscivory. Throughout cichlid diversification, increased pharyngeal jaw fusion via suturing has likely helped to reinforce the LPJ during pharyngeal processing thereby facilitating the ability of cichlids to exploit durable prey. PMID:16608685

  16. quaddRAD: a new high-multiplexing and PCR duplicate removal ddRAD protocol produces novel evolutionary insights in a nonradiating cichlid lineage.

    PubMed

    Franchini, Paolo; Monné Parera, Daniel; Kautt, Andreas F; Meyer, Axel

    2017-03-01

    The identification of thousands of variants across the genomes and their accurate genotyping are crucial for estimating the genetic parameters needed to address a host of molecular ecological and evolutionary questions. With rapid advances of massively parallel high-throughput sequencing technologies, several methods have recently been developed to access genomewide data on population variation. One of the most successful and widely used techniques relies on the combination of restriction enzymes and sequencing-by-synthesis: restriction-site-associated DNA sequencing (RADSeq). We developed a new, more time- and cost-efficient double-digest RAD paired-end protocol (quaddRAD) that simplifies and speeds up the identification of PCR duplicates and permits large-scale multiplexing. Assessing its performance on a technical data set, we also applied the quaddRAD method on population samples of a Neotropical cichlid fish lineage (Archocentrus centrarchus) to assess its genetic structure and demographic history. While we identified allopatric interlake genetic divergence, most likely driven by drift, no signature of sympatric divergence was detected. This differs from what has been observed in the clade of Midas cichlids (Amphilophus citrinellus spp.), another cichlid lineage that inhabits the same lakes and shares a similar demographic history, but has evolved into small-scale adaptive radiations via sympatric speciation. We demonstrate that quaddRAD is a robust and efficient method for genotyping a massive number and widely overlapping set of loci with high accuracy. Furthermore, the results on A. centrarchus open new research avenues providing an ideal system to investigate genome-level mechanisms that could alter the speciation potential of different but closely related cichlid lineages.

  17. Process and pattern in cichlid radiations - inferences for understanding unusually high rates of evolutionary diversification.

    PubMed

    Seehausen, Ole

    2015-07-01

    The cichlid fish radiations in the African Great Lakes differ from all other known cases of rapid speciation in vertebrates by their spectacular trophic diversity and richness of sympatric species, comparable to the most rapid angiosperm radiations. I review factors that may have facilitated these radiations and compare these with insights from recent work on plant radiations. Work to date suggests that it was a coincidence of ecological opportunity, intrinsic ecological versatility and genomic flexibility, rapidly evolving behavioral mate choice and large amounts of standing genetic variation that permitted these spectacular fish radiations. I propose that spatially orthogonal gradients in the fit of phenotypes to the environment facilitate speciation because they allow colonization of alternative fitness peaks during clinal speciation despite local disruptive selection. Such gradients are manifold in lakes because of the interaction of water depth as an omnipresent third spatial dimension with other fitness-relevant variables. I introduce a conceptual model of adaptive radiation that integrates these elements and discuss its applicability to, and predictions for, plant radiations. © 2015 The Author. New Phytologist © 2015 New Phytologist Trust.

  18. Allometric shape change of the lower pharyngeal jaw correlates with a dietary shift to piscivory in a cichlid fish

    NASA Astrophysics Data System (ADS)

    Hellig, Christoph J.; Kerschbaumer, Michaela; Sefc, Kristina M.; Koblmüller, Stephan

    2010-07-01

    The morphological versatility of the pharyngeal jaw of cichlid fishes is assumed to represent a key factor facilitating their unparalleled trophic diversification and explosive radiation. It is generally believed that the functional design of an organism relates to its ecology, and thus, specializations to different diets are typically associated with distinct morphological designs, especially manifested in the cichlids’ pharyngeal jaw apparatus. Thereby, the lower pharyngeal jaw (LPJ) incorporates some of the most predictive features for distinct diet-related morphotypes. Thus, considering that piscivorous cichlids experience an ontogenetic dietary shift from typically various kinds of invertebrates to fish, concomitant morphological changes in the LPJ are expected. Using Lepidiolamprologus elongatus, a top predator in the shallow rocky habitat of Lake Tanganyika, as model, and applying geometric and traditional morphometric techniques, we demonstrate an allometric change in ontogenetic LPJ shape development coinciding with the completion of the dietary shift toward piscivory. The piscivorous LPJ morphotype is initiated in juvenile fish by increasing elongation and narrowing of the LPJ and—when the fish reach a size of 80-90 mm standard length—further refined by the elongation of the posterior muscular processes, which serve as insertion for the fourth musculus levator externus. The enlarged muscular processes of the fully mature piscivorous morphotype provide for the construction of a powerful lever system, which allows the large individuals to process large prey fish and rely on exclusive piscivory.

  19. Malawi: the Peace Corps challenges.

    PubMed

    Roth, R L

    1996-12-01

    An acquired immunodeficiency syndrome (AIDS) prevention project was begun in Malawi in January 1993 by Peace Corps Malawi. 23 workers strive: 1) to offer health education and counseling with regard to human immunodeficiency virus (HIV) infection and AIDS in district hospitals, health centers, and health clinics; 2) to encourage the participation of community groups in AIDS prevention, education, and counseling support activities; and 3) to implement AIDS education in primary and secondary schools. Volunteer activities include health education, home-based care, school programs (drama groups, peer counseling), income-generating activities, condom distribution, and formation of district committees and sub-committees. Target groups include women and youth. Sexual health is promoted. Malawian counterparts are being trained by the volunteers to ensure sustainability; local volunteers are becoming important as resources become scarce. The program is becoming decentralized as it moves into the villages, and community groups are increasing in number. Obstacles include: 1) the lack of resources; 2) the fact that the District AIDS Coordinators are also clinical officers and medical assistants and so can serve only part time; 3) the cultural taboos that make discussion of certain topics difficult; 4) the political system; 5) illiteracy among women; 6) drug abuse among youth; and 7) the difficulty of remaining separated from one's work when one is surrounded by clients, including coworkers, who are HIV positive.

  20. Traditional birth attendants in Malawi.

    PubMed

    Smit, J J

    1994-06-01

    Traditional Birth Attendants (TBAs) and traditional healers form an important link in the chain of health personnel providing primary health care in Malawi. In spite of the establishment of hospitals and health centres, it is to these traditional healers and TBAs that the majority of people turn in times of sickness and child-birth. Approximately 60 per cent of all deliveries in Malawi occur in the villages. It is therefore important that due regard be paid to the activities of these traditional practitioners in order to ensure the achievement of the goal--"Health for all by the year 2000". The training of TBAs is seen as part of the Maternal and Child Health Services in the country. The Ministry of Health is responsible for the training and control of Traditional Birth Attendants and in 1976 opened a register in order to list all those trained. In early 1978 a training course for selected TBAs was conducted at the Kamuzu Central Hospital, Lilongwe and from 1982 the training programme evolved into a national training programme for TBAs. By February 1987, a total of 841 Traditional birth Attendants had been trained and the programme is still continuing.

  1. Persistent C3 vegetation accompanied Plio-Pleistocene hominin evolution in the Malawi Rift (Chiwondo Beds, Malawi).

    PubMed

    Lüdecke, Tina; Schrenk, Friedemann; Thiemeyer, Heinrich; Kullmer, Ottmar; Bromage, Timothy G; Sandrock, Oliver; Fiebig, Jens; Mulch, Andreas

    2016-01-01

    The development of East African savannas is crucial for the origin and evolution of early hominins. These ecosystems, however, vary widely in their fraction of woody cover and today range from closed woodland to open grassland savanna. Here, we present the first Plio-Pleistocene long-term carbon isotope (δ(13)C) record from pedogenic carbonate and Suidae teeth in the southern East African Rift (EAR). These δ(13)C data from the Chiwondo and Chitimwe Beds (Karonga Basin, Northern Malawi) represent a southern hemisphere record in the EAR, a key region for reconstructing vegetation patterns in today's Zambezian Savanna, and permit correlation with data on the evolution and migration of early hominins in today's Somali-Masai Endemic Zone. The sediments along the northwestern shore of Lake Malawi contain fossils attributed to Homo rudolfensis and Paranthropus boisei. The associated hominin localities (Uraha, Malema) are situated between the well-known hominin bearing sites of the Somali-Masai Endemic Zone in the Eastern Rift and the Highveld Grassland in southern Africa, and fill an important geographical gap for hominin research. Persistent δ(13)C values around -9‰ from pedogenic carbonate and suid enamel covering the last ∼4.3 Ma indicate a C3-dominated closed environment with regional patches of C4-grasslands in the Karonga Basin. The overall fraction of woody cover of 60-70% reflects significantly higher canopy density in the Malawi Rift than the Eastern Rift through time. The discrepancy between the two savanna types originated in the Late Pliocene, when the Somali-Masai ecosystem started to show increasing evidence for open, C4-dominated landscapes. Based on the Malawi δ(13)C data, the evolution of savanna ecosystems in Eastern Africa followed different patterns along the north-south extent of the EAR. The appearance of C4-grasses is considered a driver of evolutionary faunal shifts, but despite the difference of ecosystem evolution in the north, similar

  2. Schistosomiasis in U.S. Peace Corps volunteers--Malawi, 1992.

    PubMed

    1993-07-30

    Schistosomiasis (i.e., "snail fever" or "bilharzia") is a parasitic infection caused by trematodes (flukes) and is endemic in 74 countries in Africa, South America, the Caribbean, and Asia. U.S. residents who work or travel in these countries may be at risk for schistosomiasis. During 1992, two U.S. Peace Corps volunteers (PCVs) were evacuated from Africa because of Schistosoma hematobium infection of the central nervous system (CNS). Both were exposed to fresh water while vacationing at Cape Maclear, a popular resort area on Lake Malawi (Figure 1), in December 1991. This report summarizes the investigation of these two cases and a follow-up investigation of expatriates residing in Malawi.

  3. Lakes, Lagerstaetten, and Evolution

    NASA Astrophysics Data System (ADS)

    Kordesch, E. G.; Park, L. E.

    2001-12-01

    The diversity of terrestrial systems is estimated to be greater than in the marine realm. However no hard data yet exists to substantiate this claim. Ancient lacustrine deposits may preserve an exceptionally diverse fossil fauna and aid in determining continental faunal diversities. Fossils preserved in lake deposits, especially those with exceptional preservation (i.e. Konservat Lagerstaetten), may represent a dependable method for determining species diversity changes in the terrestrial environment because of their faunal completeness. Important Konservat Lagerstaetten, such as the Green River Formation (US) and Messel (Germany), both Eocene in age, are found in lake sediments and show a remarkable faunal diversity for both vertebrates and invertebrates. To date information from nearly 25 lake lagerstaetten derived from different types of lake basins from the Carboniferous to the Miocene have been collected and described. Carboniferous sites derive from the cyclothems of Midcontinent of the US while many Cenozoic sites have been described from North and South America as well as Europe and Australia. Asian sites contain fossils from the Mesozoic and Cenozoic. With this data, insight into the evolutionary processes associated with lake systems can be examined. Do lakes act as unique evolutionary crucibles in contrast to marine systems? The speciation of cichlid fishes in present-day African lakes appears to be very high and is attributed to the diversity of environments found in large rift lakes. Is this true of all ancient lakes or just large rift lakes? The longevity of a lake system may be an important factor in allowing speciation and evolutionary processes to occur; marine systems are limited only in the existence of environments as controlled by tectonics and sea level changes, on the order of tens of millions of years. Rift lakes are normally the longest lived in the millions of years. Perhaps there are only certain types of lakes in which speciation of

  4. Institutional Challenges to Viable Civil-Military Relations in Malawi

    DTIC Science & Technology

    2008-03-01

    thesis are entirely those of the author, and do not represent the official position of the Malawi Defense Force ( MDF ) or Malawi Government...and the long-standing tensions between them, the MYP and MDF erupted into open conflict. On December 3, the MDF attacked MYP headquarters and the... MDF blocked a political rally of UDF. See also Nyasa Times, “Ex-President and Former Malawi Defense Force Commander Urges Malawi Army to Uphold

  5. Computer animation as a tool to study preferences in the cichlid Pelvicachromis taeniatus.

    PubMed

    Baldauf, S A; Kullmann, H; Thünken, T; Winter, S; Bakker, T C M

    2009-08-01

    Four choice experiments were conducted with both sexes of the cichlid Pelvicachromis taeniatus using computer-manipulated stimuli of digital images differing in movement, body shape or colouration. The results show that computer animations can be useful and flexible tools in studying preferences of a cichlid with complex and variable preferences for different visual cues.

  6. Malawi uses games to educate the young.

    PubMed

    Dodd, R

    1995-10-01

    Recent figures suggest that Malawi has the highest rates of HIV infection in the world, with at least 12% of the sexually active population estimated to be HIV-seropositive. In urban areas, 30% of women attending antenatal clinics are infected with HIV. By March 1995, more than 37,000 AIDS cases had been reported. Adolescents and children about to enter adolescence in Malawi are at particular risk of contracting HIV. Attempting to avoid exposure to HIV, many men have spurned mature female prostitutes in favor of young girls. In exchange for school fees and other gifts, girls as young as eight years old have sexual intercourse with mature Malawian men. These men are often infected with HIV. It therefore follows that five out of six youngsters with HIV in Malawi are female. Since their female peers are involved with older men, boys are increasingly having sex with the older women rejected by mature men. Studies suggest that 55% of school pupils have experienced sexual intercourse, 76% of whom first had sex when they were younger than age 15. "AIDS Challenge" is a board game developed for distribution to all secondary schools in Malawi with the purpose of educating students about AIDS. It is played on a modified snakes-and-ladders board, using a pack of 100 cards, each with some true or false statements about AIDS. 36 boys and 35 girls aged 13-20 years from a government secondary school participated in the first trial. Four weeks of playing the game had a significant effect upon pupils' knowledge of HIV. While some of the statements on the cards are specific to Malawi, the game can easily be adapted for use in other African countries. The game is available from UNICEF Malawi at Box 30375, Capital City, Lilongwe 3, Malawi.

  7. Microsatellites Cross-Species Amplification across Some African Cichlids

    PubMed Central

    Bezault, Etienne; Rognon, Xavier; Gharbi, Karim; Baroiller, Jean-Francois; Chevassus, Bernard

    2012-01-01

    The transfer of the genomic resources developed in the Nile tilapia, Oreochromis niloticus, to other Tilapiines sensu lato and African cichlid would provide new possibilities to study this amazing group from genetics, ecology, evolution, aquaculture, and conservation point of view. We tested the cross-species amplification of 32 O. niloticus microsatellite markers in a panel of 15 species from 5 different African cichlid tribes: Oreochromines (Oreochromis, Sarotherodon), Boreotilapiines (Tilapia), Chromidotilapines, Hemichromines, and Haplochromines. Amplification was successfully observed for 29 markers (91%), with a frequency of polymorphic (P95) loci per species around 70%. The mean number of alleles per locus and species was 3.2 but varied from 3.7 within Oreochromis species to 1.6 within the nontilapia species. The high level of cross-species amplification and polymorphism of the microsatellite markers tested in this study provides powerful tools for a wide range of molecular genetic studies within tilapia species as well as for other African cichlids. PMID:22701809

  8. National and Local Sources of Power: Important Considerations for Teacher Education Reforms in Rural Malawi

    ERIC Educational Resources Information Center

    Chazema, Jacqueline; O'Meara, James

    2011-01-01

    The establishment of formal teacher training systems is a relatively new innovation in some parts of Africa. Formal training of secondary teachers in Malawi commenced when the government of Malawi opened the University of Malawi in 1965. The contribution of Malawi's ruling parties to the development of teacher education in Malawi since then is an…

  9. National and Local Sources of Power: Important Considerations for Teacher Education Reforms in Rural Malawi

    ERIC Educational Resources Information Center

    Chazema, Jacqueline; O'Meara, James

    2011-01-01

    The establishment of formal teacher training systems is a relatively new innovation in some parts of Africa. Formal training of secondary teachers in Malawi commenced when the government of Malawi opened the University of Malawi in 1965. The contribution of Malawi's ruling parties to the development of teacher education in Malawi since then is an…

  10. Isolation and sequencing of cDNA clones coding for the catalytic unit of glucose-6-phosphatase from two haplochromine cichlid fishes.

    PubMed

    Nagl, S; Mayer, W E; Klein, J

    1999-01-01

    Complementary DNA clones coding for the catalytic unit of the enzyme glucose-6-phosphatase (G6Pase) were obtained from Haplochromis nubilus and Haplochromis xenognathus, two cichlid fish species from Lake Victoria. The translated sequence of these two cDNAs identifies a polypeptide consisting of 352 amino acid residues and showing a 54.4% similarity to the human form of G6Pase. The amino acid sequences of the two fish species are identical. The comparison of the fish amino acid sequence with the corresponding sequences of rat, mouse, and human G6Pase revealed that the amino acid residues, which are involved in G6Pase catalysis in humans, are also conserved in fish G6Pase. Northern blot analysis showed that G6Pase is expressed at the same level in 6- and 10-day-old fish. A three base pair insertion/deletion polymorphism was found in the 3'-untranslated region of the fish G6Pase gene. The polymorphism will be a useful marker in a phylogenetic study of Lake Victoria cichlids.

  11. Sampling genetic diversity in the sympatrically and allopatrically speciating Midas cichlid species complex over a 16 year time series

    PubMed Central

    Bunje, Paul ME; Barluenga, Marta; Meyer, Axel

    2007-01-01

    Background Speciation often occurs in complex or uncertain temporal and spatial contexts. Processes such as reinforcement, allopatric divergence, and assortative mating can proceed at different rates and with different strengths as populations diverge. The Central American Midas cichlid fish species complex is an important case study for understanding the processes of speciation. Previous analyses have demonstrated that allopatric processes led to species formation among the lakes of Nicaragua as well as sympatric speciation that is occurring within at least one crater lake. However, since speciation is an ongoing process and sampling genetic diversity of such lineages can be biased by collection scheme or random factors, it is important to evaluate the robustness of conclusions drawn on individual time samples. Results In order to assess the validity and reliability of inferences based on different genetic samples, we have analyzed fish from several lakes in Nicaragua sampled at three different times over 16 years. In addition, this time series allows us to analyze the population genetic changes that have occurred between lakes, where allopatric speciation has operated, as well as between different species within lakes, some of which have originated by sympatric speciation. Focusing on commonly used genetic markers, we have analyzed both DNA sequences from the complete mitochondrial control region as well as nuclear DNA variation at ten microsatellite loci from these populations, sampled thrice in a 16 year time period, to develop a robust estimate of the population genetic history of these diversifying lineages. Conclusion The conclusions from previous work are well supported by our comprehensive analysis. In particular, we find that the genetic diversity of derived crater lake populations is lower than that of the source population regardless of when and how each population was sampled. Furthermore, changes in various estimates of genetic diversity within lakes

  12. Predation risk is an ecological constraint for helper dispersal in a cooperatively breeding cichlid.

    PubMed Central

    Heg, Dik; Bachar, Zina; Brouwer, Lyanne; Taborsky, Michael

    2004-01-01

    Environmental conditions are thought to be responsible for the extent and benefits of cooperative breeding in many animal societies, but experimental tests are scarce. We manipulated predator pressure in the cooperatively breeding cichlid Neolamprologus pulcher in Lake Tanganyika, where predators have been suggested to influence helper and breeder survival, helper dispersal and group reproductive success. We varied the type and intensity of predation by releasing medium, large, or no predators inside large underwater cages enclosing two or three group territories. Helper and breeder survival, helper dispersal and group reproductive success decreased from the control, to the medium- and large-predator treatments. These effects were modified by helper body size and the number of adults protecting the group from predators, supporting the 'group augmentation hypothesis'. Predators forced helpers to stay closer to, and spend more time inside, protective shelters. The results demonstrate the importance of predators for group living in this species, and support the 'ecological constraints hypothesis' of cooperative breeding, in the sense that subordinates stay at home rather than leave and breed independently under the risk of predation. PMID:15556889

  13. Frequency-dependent social dominance in a color polymorphic cichlid fish.

    PubMed

    Dijkstra, Peter D; Lindström, Jan; Metcalfe, Neil B; Hemelrijk, Charlotte K; Brendel, Mischa; Seehausen, Ole; Groothuis, Ton G G

    2010-10-01

    A mechanism commonly suggested to explain the persistence of color polymorphisms in animals is negative frequency-dependent selection. It could result from a social dominance advantage to rare morphs. We tested for this in males of red and blue color morphs of the Lake Victoria cichlid, Pundamilia. Earlier work has shown that males preferentially attack the males of their own morph, while red males are more likely to win dyadic contests with blue males. In order to study the potential contribution of both factors to the morph co-existence, we manipulated the proportion of red and blue males in experimental assemblages and studied its effect on social dominance. We then tried to disentangle the effects of the own-morph attack bias and social dominance of red using simulations. In the experiment, we found that red males were indeed socially dominant to the blue ones, but only when rare. However, blue males were not socially dominant when rare. The simulation results suggest that an own-morph attack bias reduces the social dominance of red males when they are more abundant. Thus, there is no evidence of symmetric negative frequency-dependent selection acting on social dominance, suggesting that additional fitness costs to the red morph must explain their co-existence.

  14. Territorial males can sire more offspring in nests with smaller doors in the cichlid Lamprologus lemairii.

    PubMed

    Ota, Kazutaka; Awata, Satoshi; Morita, Masaya; Yokoyama, Ryota; Kohda, Masanori

    2014-01-01

    To examine how territorial males counter reproductive parasites, we examined the paternity of broods guarded by territorial males using 5 microsatellite loci and factors that determine siring success in a wild population of the Lake Tanganyika cichlid Lamprologus lemairii. Females enter rock holes (nests) and spawn inside, and territorial males release milt over the nest openings. Sneakers attempt to dart into the nests, but territorial males often interrupt the attempt. The body size of territorial males (territorial defense ability) and the size of nest opening (the ability to prevent sneakers from nest intrusions) are predicted to be factors that affect paternity at the premating stage, whereas milt quality traits are factors that affect paternity at the postmating stage. Parentage analyses of 477 offspring revealed that most clutches have few or no cuckolders, and territorial males sired >80% of eggs in 7 of the 10 analyzed clutches. Larger territorial males that spawned in nests with narrower openings had greater siring success. In contrast, none of the milt traits affected the siring success. These suggest that territorial male L. lemairii adopt premating strategies whereby they effectively prevent reproductive parasitism.

  15. Female promiscuity promotes the evolution of faster sperm in cichlid fishes.

    PubMed

    Fitzpatrick, John L; Montgomerie, Robert; Desjardins, Julie K; Stiver, Kelly A; Kolm, Niclas; Balshine, Sigal

    2009-01-27

    Sperm competition, the contest among ejaculates from rival males to fertilize ova of a female, is a common and powerful evolutionary force influencing ejaculate traits. During competitive interactions between ejaculates, longer and faster spermatozoa are expected to have an edge; however, to date, there has been mixed support for this key prediction from sperm competition theory. Here, we use the spectacular radiation of cichlid fishes from Lake Tanganyika to examine sperm characteristics in 29 closely related species. We provide phylogenetically robust evidence that species experiencing greater levels of sperm competition have faster-swimming sperm. We also show that sperm competition selects for increases in the number, size, and longevity of spermatozoa in the ejaculate of a male, and, contrary to expectations from theory, we find no evidence of trade-offs among sperm traits in an interspecific analysis. Also, sperm swimming speed is positively correlated with sperm length among, but not within, species. These different responses to sperm competition at intra- and interspecific levels provide a simple, powerful explanation for equivocal results from previous studies. Using phylogenetic analyses, we also reconstructed the probable evolutionary route of trait evolution in this taxon, and show that, in response to increases in the magnitude of sperm competition, the evolution of sperm traits in this clade began with the evolution of faster (thus, more competitive) sperm.

  16. Reproductive-tactic-specific variation in sperm swimming speeds in a shell-brooding cichlid.

    PubMed

    Fitzpatrick, J L; Desjardins, J K; Milligan, N; Montgomerie, R; Balshine, S

    2007-08-01

    Theory predicts that males experiencing elevated levels of sperm competition will invest more in gonads and produce faster-swimming sperm. Although there is ample evidence in support of the first prediction, few studies have examined sperm swimming speed in relation to sperm competition. In this study, we tested these predictions from sperm competition theory by examining sperm characteristics in Telmatochromis vittatus, a small shell-brooding cichlid fish endemic to Lake Tanganyika. Males exhibit four different reproductive tactics: pirate, territorial, satellite, and sneaker. Pirate males temporarily displace all other competing males from a shell nest, whereas sneaker males always release sperm in the presence of territorial and satellite males. Due to the fact that sneakers spawn in the presence of another male, sneakers face the highest levels of sperm competition and pirates the lowest, whereas satellites and territorials experience intermediate levels. In accordance with predictions, sperm from sneakers swam faster than sperm from males adopting the other reproductive tactics, whereas sperm from pirates was slowest. Interestingly, we were unable to detect any variation in sperm tail length among these reproductive tactics. Thus, sperm competition appears to have influenced sperm energetics in this species without having any influence on sperm size.

  17. Predation risk is an ecological constraint for helper dispersal in a cooperatively breeding cichlid.

    PubMed

    Heg, Dik; Bachar, Zina; Brouwer, Lyanne; Taborsky, Michael

    2004-11-22

    Environmental conditions are thought to be responsible for the extent and benefits of cooperative breeding in many animal societies, but experimental tests are scarce. We manipulated predator pressure in the cooperatively breeding cichlid Neolamprologus pulcher in Lake Tanganyika, where predators have been suggested to influence helper and breeder survival, helper dispersal and group reproductive success. We varied the type and intensity of predation by releasing medium, large, or no predators inside large underwater cages enclosing two or three group territories. Helper and breeder survival, helper dispersal and group reproductive success decreased from the control, to the medium- and large-predator treatments. These effects were modified by helper body size and the number of adults protecting the group from predators, supporting the 'group augmentation hypothesis'. Predators forced helpers to stay closer to, and spend more time inside, protective shelters. The results demonstrate the importance of predators for group living in this species, and support the 'ecological constraints hypothesis' of cooperative breeding, in the sense that subordinates stay at home rather than leave and breed independently under the risk of predation.

  18. Genetic dissection of adaptive form and function in rapidly-speciating cichlid fishes.

    PubMed

    Henning, Frederico; Machado-Schiaffino, Gonzalo; Baumgarten, Lukas; Meyer, Axel

    2017-02-17

    Genes of major phenotypic effects and strong genetic correlations can facilitate adaptation, direct selective responses and potentially lead to phenotypic convergence. However, the preponderance of this type of genetic architecture in repeatedly-evolved adaptations remains unknown. Using hybrids between Haplochromis chilotes (thick-lipped) and H. nyererei (thin-lipped) we investigated the genetics underlying hypertrophied lips and elongated heads, traits that evolved repeatedly in cichlids. At least 25 loci of small-to-moderate and mainly additive effects were detected. Phenotypic variation in lip and head morphology was largely independent. Although several QTL overlapped for lip and head morphology traits, they were often of opposite effects. The distribution of effect signs suggests strong selection on lips. The fitness implications of several detected loci were demonstrated using a laboratory assay testing for the association between genotype and variation in foraging performance. The persistence of low fitness alleles in head morphology appears to be maintained through antagonistic pleiotropy/close linkage with positive-effect lip morphology alleles. Rather than being based on few major loci with strong positive genetic correlations, our results indicate that the evolution of the Lake Victoria thick-lipped ecomorph is the result of selection on numerous loci distributed throughout the genome. This article is protected by copyright. All rights reserved.

  19. Female promiscuity promotes the evolution of faster sperm in cichlid fishes

    PubMed Central

    Fitzpatrick, John L.; Montgomerie, Robert; Desjardins, Julie K.; Stiver, Kelly A.; Kolm, Niclas; Balshine, Sigal

    2009-01-01

    Sperm competition, the contest among ejaculates from rival males to fertilize ova of a female, is a common and powerful evolutionary force influencing ejaculate traits. During competitive interactions between ejaculates, longer and faster spermatozoa are expected to have an edge; however, to date, there has been mixed support for this key prediction from sperm competition theory. Here, we use the spectacular radiation of cichlid fishes from Lake Tanganyika to examine sperm characteristics in 29 closely related species. We provide phylogenetically robust evidence that species experiencing greater levels of sperm competition have faster-swimming sperm. We also show that sperm competition selects for increases in the number, size, and longevity of spermatozoa in the ejaculate of a male, and, contrary to expectations from theory, we find no evidence of trade-offs among sperm traits in an interspecific analysis. Also, sperm swimming speed is positively correlated with sperm length among, but not within, species. These different responses to sperm competition at intra- and interspecific levels provide a simple, powerful explanation for equivocal results from previous studies. Using phylogenetic analyses, we also reconstructed the probable evolutionary route of trait evolution in this taxon, and show that, in response to increases in the magnitude of sperm competition, the evolution of sperm traits in this clade began with the evolution of faster (thus, more competitive) sperm. PMID:19164576

  20. Clubfoot in Malawi: local theories of causation.

    PubMed

    Bedford, K Juliet A; Chidothi, Paul; Sakala, Harris; Cashman, John; Lavy, Chris

    2011-04-01

    This paper examines local theories of the causation of clubfoot expressed by the guardians of children undergoing treatment at clinics run by the Malawi National Clubfoot Programme (MNCP). Core data was collected and analysed using qualitative methodologies of critical medical anthropology. Sixty detailed case studies were completed, each based on an extended open-ended interview with patient guardians. Five main theories of causation were put forward: God; the devil; witchcraft or curses; biological reasons; and inherited condition. Each was elaborated in a variety of ways. There is growing international recognition of the importance of examining the relationship between culture and disability. This study is the first attempt to do so for clubfoot in Malawi. It provides a platform on which to build future qualitative research that can be harnessed by the MNCP and similar initiatives to develop their knowledge base and service provision, both in Malawi and the wider African context.

  1. Maternal mortality in Malawi, 1977–2012

    PubMed Central

    Colbourn, Tim; Lewycka, Sonia; Nambiar, Bejoy; Anwar, Iqbal; Phoya, Ann; Mhango, Chisale

    2013-01-01

    Background Millennium Development Goal 5 (MDG 5) targets a 75% reduction in maternal mortality from 1990 to 2015, yet accurate information on trends in maternal mortality and what drives them is sparse. We aimed to fill this gap for Malawi, a country in sub-Saharan Africa with high maternal mortality. Methods We reviewed the literature for population-based studies that provide estimates of the maternal mortality ratio (MMR) in Malawi, and for studies that list and justify variables potentially associated with trends in MMR. We used all population-based estimates of MMR representative of the whole of Malawi to construct a best-fit trend-line for the range of years with available data, calculated the proportion attributable to HIV and qualitatively analysed trends and evidence related to other covariates to logically assess likely candidate drivers of the observed trend in MMR. Results 14 suitable estimates of MMR were found, covering the years 1977–2010. The resulting best-fit line predicted MMR in Malawi to have increased from 317 maternal deaths/100 000 live-births in 1980 to 748 in 1990, before peaking at 971 in 1999, and falling to 846 in 2005 and 484 in 2010. Concurrent deteriorations and improvements in HIV and health system investment and provisions are the most plausible explanations for the trend. Female literacy and education, family planning and poverty reduction could play more of a role if thresholds are passed in the coming years. Conclusions The decrease in MMR in Malawi is encouraging as it appears that recent efforts to control HIV and improve the health system are bearing fruit. Sustained efforts to prevent and treat maternal complications are required if Malawi is to attain the MDG 5 target and save the lives of more of its mothers in years to come. PMID:24353257

  2. Incidence of induced abortion in Malawi, 2015

    PubMed Central

    Mhango, Chisale; Philbin, Jesse; Chimwaza, Wanangwa; Chipeta, Effie; Msusa, Ausbert

    2017-01-01

    Background In Malawi, abortion is legal only if performed to save a woman’s life; other attempts to procure an abortion are punishable by 7–14 years imprisonment. Most induced abortions in Malawi are performed under unsafe conditions, contributing to Malawi’s high maternal mortality ratio. Malawians are currently debating whether to provide additional exceptions under which an abortion may be legally obtained. An estimated 67,300 induced abortions occurred in Malawi in 2009 (equivalent to 23 abortions per 1,000 women aged 15–44), but changes since 2009, including dramatic increases in contraceptive prevalence, may have impacted abortion rates. Methods We conducted a nationally representative survey of health facilities to estimate the number of cases of post-abortion care, as well as a survey of knowledgeable informants to estimate the probability of needing and obtaining post-abortion care following induced abortion. These data were combined with national population and fertility data to determine current estimates of induced abortion and unintended pregnancy in Malawi using the Abortion Incidence Complications Methodology. Results We estimate that approximately 141,044 (95% CI: 121,161–160,928) induced abortions occurred in Malawi in 2015, translating to a national rate of 38 abortions per 1,000 women aged 15–49 (95% CI: 32 to 43); which varied by geographical zone (range: 28–61). We estimate that 53% of pregnancies in Malawi are unintended, and that 30% of unintended pregnancies end in abortion. Given the challenges of estimating induced abortion, and the assumptions required for calculation, results should be viewed as approximate estimates, rather than exact measures. Conclusions The estimated abortion rate in 2015 is higher than in 2009 (potentially due to methodological differences), but similar to recent estimates from nearby countries including Tanzania (36), Uganda (39), and regional estimates in Eastern and Southern Africa (34–35). Over

  3. Positively essential: traditional birth attendants in Malawi.

    PubMed

    Stronge, Shirley

    2011-06-01

    One of the biggest challenges for healthcare professionals working in developing countries is the lack of trained personnel to carry out much needed health care provision. Shirley Stronge worked as a nurse/midwife tutor in a rural area in the north of Malawi. Millennium Development Goals four and five have focused our attention on the care required by mothers and newborns. Shirley has chosen to reflect on the role of Traditional Birth Attendants in the north of Malawi and their positive impact on maternity services in this area.

  4. Tackling Malawi's human resources crisis.

    PubMed

    Palmer, Debbie

    2006-05-01

    In sub-Saharan Africa, health systems are fragile and staffing is grossly inadequate to meet rising health needs. Despite growing international attention, donors have been reluctant to undertake the significant investments required to address the human resources problem comprehensively, given social and political sensitivities, and concerns regarding sustainability of interventions and risks of rising donor dependency. In Malawi, one of the poorest nations in Africa, declining human resource levels have fueled an accelerating collapse of public health services since the late 1990s. In an effort to improve health outcomes, in 2004 the government launched a new health initiative to deliver an Essential Health Package, including a major scale-up of HIV and AIDS related services. Improving staffing levels is the single biggest challenge to implementing this approach. Donors agreed to help the government develop an Emergency Human Resources Programme with five main facets: improving incentives for recruitment and retention of staff through salary top-ups, expanding domestic training capacity, using international volunteer doctors and nurse tutors as a stop-gap measure, providing international technical assistance to bolster planning and management capacity and skills, and establishing more robust monitoring and evaluation capacity. Industrial relations were a prominent consideration in determining the shape of the Programme. The combination of short- and long-term measures appears to be helpful in maintaining commitment to the programme.

  5. The introduced Asian parasitic copepod Neoergasilus japonicus (Harada) (Cyclopoida: Ergasilidae) from endangered cichlid teleosts in Mexico.

    PubMed

    Suárez-Morales, Eduardo; Paredes-Trujillo, Amelia; González-Solís, David

    2010-11-01

    The cyclopoid copepod Neoergasilus japonicus ( Harada, 1930 ) is recorded from three endangered or threatened fish species from southeast Mexico: the tailbar cichlid Vieja hartwegi (Taylor and Miller, 1980); the Angostura cichlid V. breidohri (Werner and Stawikowski, 1987); and the sieve cichlid C. grammodes (Taylor and Miller, 1980). This ectoparasitic copepod is considered, together with most other members of Neoergasilus, an Eastern Asian form. N. japonicus is one of the most widespread parasitic Asian copepods, as it has rapidly invaded Europe and North America, including Mexico. We estimated the prevalence, mean abundance, and intensity of infection of N. japonicus in these cichlid teleosts; our data agree with previous works stating the high prevalence of this ectoparasite. This copepod has a wide range of hosts among freshwater fish taxa, but this is only the second published report from cichlids in the Neotropical region. The three cichlids surveyed, V. hartwegi, V. breidohri, and C. grammodes, are new hosts of this copepod. Its occurrence in Mexico is attributed to different events of introduction by human agency. This is the southernmost record of N. japonicus in continental America. It is a matter of concern that this copepod is parasitizing endangered or threatened endemic cichlids in the Neotropical region. Because its high infective efficiency and ability to shift hosts, this Asian parasite is expected to spread farther southwards into Central and South America.

  6. Continental monophyly of cichlid fishes and the phylogenetic position of Heterochromis multidens.

    PubMed

    Keck, Benjamin P; Hulsey, C Darrin

    2014-04-01

    The incredibly species-rich cichlid fish faunas of both the Neotropics and Africa are generally thought to be reciprocally monophyletic. However, the phylogenetic affinity of the African cichlid Heterochromis multidens is ambiguous, and this distinct lineage could make African cichlids paraphyletic. In past studies, Heterochromis has been variously suggested to be one of the earliest diverging lineages within either the Neotropical or the African cichlid radiations, and it has even been hypothesized to be the sister lineage to a clade containing all Neotropical and African cichlids. We examined the phylogenetic relationships among a representative sample of cichlids with a dataset of 29 nuclear loci to assess the support for the different hypotheses of the phylogenetic position of Heterochromis. Although individual gene trees in some instances supported alternative relationships, a majority of gene trees, integration of genes into species trees, and hypothesis testing of putative topologies all supported Heterochromis as belonging to the clade of African cichlids. Copyright © 2014 Elsevier Inc. All rights reserved.

  7. Constraints on the 3D Sediment and Crustal Architecture of the Weakly Extended Malawi Rift from the Onshore/Offshore Wide-Angle Refraction Experiment

    NASA Astrophysics Data System (ADS)

    Accardo, N. J.; Shillington, D. J.; Scholz, C. A.; McCartney, T.; Ebinger, C. J.; Gaherty, J. B.; Nyblade, A.; Eatmon, A.; Chindandali, P. R. N.; Kamihanda, G.; Ferdinand, R.; Salima, J.; Mruma, A. H.

    2016-12-01

    Current models of continental rifting increasingly point to the important role of weakening mechanisms like the addition of magmatic products in overcoming the disparity between the magnitude of tectonic forces available for rifting and the forces required to break strong, cold lithosphere. However, many rifts have limited volcanism. To understand the controls on rifting in magma-poor systems, we conduct 3D first arrival time tomography from active-source wide-angle refraction data collected in the Malawi Rift to constrain crustal structure along and across the rift. The Malawi Rift represents a weakly extended rift system located within the southernmost portion of the EARS. The only surface magmatism present occurs within the Rungwe Volcanic Province (RVP) located at the northern termination of the Malawi Rift. We utilize active-source data collected in Lake Malawi as a part of SEGMeNT (Study of Extension and maGmatism in Malawi aNd Tanzania). Over 86,000 unique air gun shots were recorded on an array of 33 offshore "lake" bottom seismometers and 55 onshore seismometers. The resulting ray-coverage encompasses the entire northern section of the Malawi Rift spanning the North and Central basins of Lake Malawi, portions of the surround plateaus, as well as the RVP. First arrivals are picked for all shot-receiver pairs with sufficient signal-to-noise ratio and included in a 3D first-arrival tomography model. Direct arrivals (Ps and Pg) and reflections (PmP) are observed on the majority of instruments, with clear arrivals observed to offsets >220 km. Data and preliminary models indicate variations in fault structure and overall sediment thickness between and within rift basins. The North Basin is characterized by a series of synthetic intrabasin faults and sediments thickening to the east along the Livingstone border fault. The Central Basin is characterized by sediments thickening to the west along the Nkhata border fault in the south near Usisya, Malawi and then

  8. Monogeneans of West African Cichlid Fish: Evolution and Cophylogenetic Interactions

    PubMed Central

    Mendlová, Monika; Desdevises, Yves; Civáňová, Kristína; Pariselle, Antoine; Šimková, Andrea

    2012-01-01

    The goals of this paper were to investigate phylogenetic and evolutionary patterns of cichlid fish from West Africa and their Cichlidogyrus and Scutogyrus monogenean parasites, to uncover the presence of host-parasite cospeciation and to assess the level of morphological adaptation in parasites. This required the following steps, each one representing specific objectives of this paper: (1) to build phylogenetic trees for Cichlidogyrus and Scutogyrus species based on ribosomal DNA sequences, (2) to investigate phylogenetic relationships within West African cichlid fish based on the analysis of mitochondrial cytochrome b DNA sequences, (3) to investigate host-parasite cophylogenetic history to gain clues on parasite speciation process, and (4) to investigate the link between the morphology of the attachment apparatus and parasite phylogeny. Phylogenetic analyses supported the monophyletic origin of the Cichlidogyrus/Scutogyrus group, and suggested that Cichlidogyrus is polyphyletic and that Scutogyrus is monophyletic. The phylogeny of Cichlidae supported the separation of mouthbrooders and substrate-brooders and is consistent with the hypothesis that the mouthbrooding behavior of Oreochromis and Sarotherodon evolved from substrate-brooding behavior. The mapping of morphological characters of the haptor onto the parasite phylogenetic tree suggests that the attachment organ has evolved from a very simple form to a more complex one. The cophylogenetic analyses indicated a significant fit between trees using distance-based tests, but no significant cospeciation signal using tree-based tests, suggesting the presence of parasite duplications and host switches on related host species. This shed some light on the diversification process of Cichlidogyrus species parasitizing West African cichlids. PMID:22662139

  9. Breeding experience and parental behaviour in convict cichlids (Cichlasoma nigrofasciatum ).

    PubMed

    Colgan, P W; Salmon, A B

    1986-06-01

    Changes in the levels of activities by parental female and male convict cichlids were studied over three successive reproductive episodes and within each episode. No evidence was found for behavioural maturation independent of experience. With successive episodes, young survived for longer times, nests were cleaner, males ate less and females more, and males became more aggressive while females focused more on the nest. Within an episode there were also marked variations in activities by each sex. Reproductive behaviour is therefore open in a number of respects both within and across episodes to environmental inputs.

  10. Hybridization generates a hopeful monster: a hermaphroditic selfing cichlid

    PubMed Central

    Smith, Alan; García-Alonso, Javier; van Oosterhout, Cock

    2016-01-01

    Compared with other phylogenetic groups, self-fertilization (selfing) is exceedingly rare in vertebrates and is known to occur only in one small clade of fishes. Here we report observing one F1-hybrid individual that developed into a functional hermaphrodite after crossing two closely-related sexually reproducing species of cichlids. Microsatellite alleles segregated consistent with selfing and Mendelian inheritance and we could rule out different modes of parthenogenesis including automixis. We discuss why selfing is not more commonly observed in vertebrates in nature, and the role of hybridization in the evolution of novel traits. PMID:27069660

  11. Hybridization generates a hopeful monster: a hermaphroditic selfing cichlid.

    PubMed

    Svensson, Ola; Smith, Alan; García-Alonso, Javier; van Oosterhout, Cock

    2016-03-01

    Compared with other phylogenetic groups, self-fertilization (selfing) is exceedingly rare in vertebrates and is known to occur only in one small clade of fishes. Here we report observing one F1-hybrid individual that developed into a functional hermaphrodite after crossing two closely-related sexually reproducing species of cichlids. Microsatellite alleles segregated consistent with selfing and Mendelian inheritance and we could rule out different modes of parthenogenesis including automixis. We discuss why selfing is not more commonly observed in vertebrates in nature, and the role of hybridization in the evolution of novel traits.

  12. Headteacher Preparation in Mzuzu, Malawi, Africa

    ERIC Educational Resources Information Center

    Wamba, Nathalis

    2015-01-01

    The purpose of this researcher was to examine the in-service experiences of seven headteachers in Luwinga ward in Mzuzu, Malawi, and the challenges they encountered in their first year on the job. A modified version of the questionnaire and interview guide developed by the members of the International Study of the Preparation of Principals at the…

  13. Chichewa Language Manual. Peace Corps Malawi.

    ERIC Educational Resources Information Center

    Samu, Samu M.

    This Peace Corps guide to individual, independent, or group study of Chichewa provides basic conversational vocabulary and phrases necessary for Peace Corps volunteer survival skills in Malawi. The 20 lessons consist of dialogues, vocabulary, and exercises on these topics: greetings; self-introduction; discussing others; relatives; professions;…

  14. Malawi Basic Education Policy Recommendations. Position Papers

    ERIC Educational Resources Information Center

    Sedere, Upali M.

    2005-01-01

    This paper summarizes several policy issues that were discussed during the years 2003-2005 periods while Dr. Upali Sedere was serving as Senior Policy Adviser and COP of USAID financed Equip-2 program with Education Development Center, Newton, Massachusetts. All data were from the Malawi School Census carried out by the Ministry of Education with…

  15. Farmer Experience of Pluralistic Agricultural Extension, Malawi

    ERIC Educational Resources Information Center

    Chowa, Clodina; Garforth, Chris; Cardey, Sarah

    2013-01-01

    Purpose: Malawi's current extension policy supports pluralism and advocates responsiveness to farmer demand. We investigate whether smallholder farmers' experience supports the assumption that access to multiple service providers leads to extension and advisory services that respond to the needs of farmers. Design/methodology/approach: Within a…

  16. Farmer Experience of Pluralistic Agricultural Extension, Malawi

    ERIC Educational Resources Information Center

    Chowa, Clodina; Garforth, Chris; Cardey, Sarah

    2013-01-01

    Purpose: Malawi's current extension policy supports pluralism and advocates responsiveness to farmer demand. We investigate whether smallholder farmers' experience supports the assumption that access to multiple service providers leads to extension and advisory services that respond to the needs of farmers. Design/methodology/approach: Within a…

  17. Strides in Preservation of Malawi's Natural Stone

    NASA Astrophysics Data System (ADS)

    Kamanga, Tamara; Chisenga, Chikondi; Katonda, Vincent

    2017-04-01

    The geology of Malawi is broadly grouped into four main lithological units that is the Basement Complex, the Karoo Super group, Tertiary to Quaternary sedimentary deposits and the Chilwa Alkaline province. The basement complex rocks cover much of the country and range in age from late Precambrian to early Paleozoic. They have been affected by three major phases of deformation and metamorphism that is the Irumide, Ubendian and The Pan-African. These rocks comprise gneisses, granulites and schists with associated mafic, ultramafic, syenites and granite rocks. The Karoo System sedimentary rocks range in age from Permian to lower Jurassic and are mainly restricted to two areas in the extreme North and extreme Alkaline Province - late Jurassic to Cretaceous in age, preceded by upper Karoo Dolerite dyke swarms and basaltic lavas, have been intruded into the Basement Complex gneisses of southern Malawi. Malawi is endowed with different types of natural stone deposits most of which remain unexploited and explored. Over twenty quarry operators supply quarry stone for road and building construction in Malawi. Hundreds of artisanal workers continue to supply aggregate stones within and on the outskirts of urban areas. Ornamental stones and granitic dimension stones are also quarried, but in insignificant volumes. In Northern Malawi, there are several granite deposits including the Nyika, which is the largest single outcrop occupying approximately 260.5 km2 , Mtwalo Amazonite an opaque to translucent bluish -green variety of microcline feldspar that occurs in alkali granites and pegmatite, the Ilomba granite (sodalite) occurring in small areas within biotite; apatite, plagioclase and calcite. In the Center, there are the Dzalanyama granites, and the Sani granites. In the South, there are the Mangochi granites. Dolerite and gabbroic rocks spread across the country, treading as black granites. Malawi is also endowed with many deposits of marble. A variety of other igneous

  18. Origin and evolution of B chromosomes in the cichlid fish Astatotilapia latifasciata based on integrated genomic analyses.

    PubMed

    Valente, Guilherme T; Conte, Matthew A; Fantinatti, Bruno E A; Cabral-de-Mello, Diogo C; Carvalho, Robson F; Vicari, Marcelo R; Kocher, Thomas D; Martins, Cesar

    2014-08-01

    Approximately 15% of eukaryotes contain supernumerary B chromosomes. When present, B chromosomes frequently represent as much as 5% of the genome. Despite thousands of reports describing the distribution of supernumeraries in various taxa, a comprehensive theory for the origin, maintenance, and evolution of B chromosomes has not emerged. Here, we sequence the complete genomes of individual cichlid fish (Astatotilapia latifasciata) with and without B chromosomes, as well as microdissected B chromosomes, to identify DNA sequences on the B. B sequences were further analyzed through quantitative polymerase chain reaction and in situ hybridization. We find that the B chromosome contains thousands of sequences duplicated from essentially every chromosome in the ancestral karyotype. Although most genes on the B chromosome are fragmented, a few are largely intact, and we detect evidence that at least three of them are transcriptionally active. We propose a model in which the B chromosome originated early in the evolutionary history of Lake Victoria cichlids from a small fragment of one autosome. DNA sequences originating from several autosomes, including protein-coding genes and transposable elements, subsequently inserted into this proto-B. We propose that intact B chromosome genes involved with microtubule organization, kinetochore structure, recombination and progression through the cell cycle may play a role in driving the transmission of the B chromosome. Furthermore, our work suggests that karyotyping is an essential step prior to genome sequencing to avoid problems in genome assembly and analytical biases created by the presence of high copy number sequences on the B chromosome. © The Author 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  19. The Edinburgh Malawi Cancer Partnership: helping to establish multidisciplinary cancer care in Blantyre, Malawi.

    PubMed

    Brown, E; Gorman, D; Knowles, G; Taylor, F; Jere, Y; Bates, J; Masamba, L

    2016-03-01

    In response to the growing incidence of cancer in Malawi, a new oncology unit was established at the Queen Elizabeth Central Hospital, Blantyre. The unit opened in 2010, the first in the country, and is led by a single consultant oncologist. In 2012, a healthcare partnership was formed between the oncology and palliative care unit at Queen Elizabeth Central Hospital and the Edinburgh Cancer Centre, UK. The principal objective of the partnership is to help develop high quality multidisciplinary cancer care in Malawi. Methods A needs assessment identified three priority areas for further improvement of cancer services: nurse-led treatment delivery; management of clinical data; and multidisciplinary working. The partnership received grant funding from the Scottish Government Malawi Development Programme in 2013 and a three year project plan was implemented. This has been conducted through a series of reciprocal training visits. Results Key achievements have been completion of a programme of oncology nursing education attended by 32 oncology nurses and other healthcare professionals, which has resulted in increased experience in cancer practice and standardisation of chemotherapy delivery procedures; development of a clinical database that enables prospective collection of data of all new patients with cancer and which links to the Malawi Cancer Registry; development of weekly multidisciplinary meetings involving oncology, gynaecology and surgery that has enabled a cross-specialty approach to patient care. Conclusion The Edinburgh Malawi Cancer Partnership is supporting nursing education, data use and cross-specialty collaboration that we are confident will improve cancer care in Malawi. Future work will focus on the further development of multidisciplinary breast cancer care and the development of a radiotherapy service for patients in Malawi.

  20. Patients' perceptions of chamba (marijuana) use in Malawi.

    PubMed

    MacLachlan, M; Page, R C; Robinson, G L; Nyirenda, T; Ali, S

    1998-05-01

    This study examines the perceptions of the social aspects, triggers, and effects of chamba (marijuana) use among psychiatric patients at Zomba Mental Hospital in Malawi. Focus groups were used to elicit responses from 44 male and 10 female psychiatric patients about their perceptions of chamba use in Malawi. This study provides insight into these patients' perceptions of the triggers and effects of their chamba use, and it has implications for the development of treatment and prevention programs for chamba users in Malawi.

  1. Total evidence: molecules, morphology, and the phylogenetics of cichlid fishes.

    PubMed

    Farias, I P; Ortí, G; Meyer, A

    2000-04-15

    We present a most comprehensive phylogenetic analysis of the family Cichlidae. New data analyzed include mitochondrial 16S rRNA sequences and two nuclear loci (Tmo-M27 and Tmo-4C4) for a large taxonomic sampling with emphasis on South American species. We also incorporate a published morphological data set for a total evidence analysis. Character congruence among mitochondrial (74 taxa) and nuclear data (50 taxa) was high. However, partition-homogeneity tests suggest significant heterogeneity among molecular and morphological data. In agreement with results obtained from molecular data alone, total evidence analysis (1,460 characters for 34 taxa) supports a robust phylogenetic hypothesis for the family Cichlidae that is congruent with drift-vicariance events associated with the fragmentation of Gondwana. Our analyses confirm the placement of Malagasy/Indian cichlids as the most basal lineages, with a sister-group relationship to the monophyletic African and Neotropical clades. Total evidence suggests that the controversial African genus Heterochromis is at the base of the African radiation. Among more than 50 Neotropical genera analyzed, Retroculus is identified as the basal taxon, with successive branching of Cichla, Astronotus, geophagines (including crenicichlines) + chaetobranchines, and cichlasomines + heroines. Relative rate tests applied to mitochondrial DNA suggest significantly higher rates of genetic variation in Neotropical than in African taxa, and both mitochondrial and nuclear sequences show that rate heterogeneity among Neotropical lineages is confined to the geophagine cichlids.

  2. Isotocin neuronal phenotypes differ among social systems in cichlid fishes

    PubMed Central

    O'Connor, Constance M.; Nesjan, Erin; Cameron, Jason; Hellmann, Jennifer K.; Ligocki, Isaac Y.; Marsh-Rollo, Susan E.; Hamilton, Ian M.; Wylie, Douglas R.; Hurd, Peter L.; Balshine, Sigal

    2017-01-01

    Social living has evolved numerous times across a diverse array of animal taxa. An open question is how the transition to a social lifestyle has shaped, and been shaped by, the underlying neurohormonal machinery of social behaviour. The nonapeptide neurohormones, implicated in the regulation of social behaviours, are prime candidates for the neuroendocrine substrates of social evolution. Here, we examined the brains of eight cichlid fish species with divergent social systems, comparing the number and size of preoptic neurons that express the nonapeptides isotocin and vasotocin. While controlling for the influence of phylogeny and body size, we found that the highly social cooperatively breeding species (n = 4) had fewer parvocellular isotocin neurons than the less social independently breeding species (n = 4), suggesting that the evolutionary transition to group living and cooperative breeding was associated with a reduction in the number of these neurons. In a complementary analysis, we found that the size and number of isotocin neurons significantly differentiated the cooperatively breeding from the independently breeding species. Our results suggest that isotocin is related to sociality in cichlids and may provide a mechanistic substrate for the evolution of sociality. PMID:28573041

  3. Colour variation in cichlid fish: Developmental mechanisms, selective pressures and evolutionary consequences☆

    PubMed Central

    Maan, Martine E.; Sefc, Kristina M.

    2013-01-01

    Cichlid fishes constitute one of the most species-rich families of vertebrates. In addition to complex social behaviour and morphological versatility, they are characterised by extensive diversity in colouration, both within and between species. Here, we review the cellular and molecular mechanisms underlying colour variation in this group and the selective pressures responsible for the observed variation. We specifically address the evidence for the hypothesis that divergence in colouration is associated with the evolution of reproductive isolation between lineages. While we conclude that cichlid colours are excellent models for understanding the role of animal communication in species divergence, we also identify taxonomic and methodological biases in the current research effort. We suggest that the integration of genomic approaches with ecological and behavioural studies, across the entire cichlid family and beyond it, will contribute to the utility of the cichlid model system for understanding the evolution of biological diversity. PMID:23665150

  4. Prey vulnerability to peacock cichlids and largemouth bass based on predator gape and prey body depth

    USGS Publications Warehouse

    Hill, Jeffrey E.; Nico, Leo G.; Cichra, Charles E.; Gilbert, Carter R.

    2005-01-01

    The interaction of prey fish body depth and predator gape size may produce prey assemblages dominated by invulnerable prey and excessive prey-to-predator biomass ratios. Peacock cichlids (Cichla ocellaris) were stocked into southeast Florida canals to consume excess prey fish biomass, particularly spotted tilapia (Tilapia mariae). The ecomorphologically similar largemouth bass (Micropterus salmoides) was already present in the canals. We present relations of length-specific gape size for peacock cichlids and largemouth bass. Both predators have broadly overlapping gape size, but largemouth bass ?126 mm total length have slightly larger gape sizes than peacock cichlids of the same length. Also, we experimentally tested the predictions of maximum prey size for peacock cichlids and determined that a simple method of measuring gape size used for largemouth bass also is appropriate for peacock cichlids. Lastly, we determined relations of body depth and length of prey species to investigate relative vulnerability. Using a simple predator-prey model and length frequencies of predators and bluegill (Lepomis macrochirus), redear sunfish (Lepomis microlophus), and spotted tilapia prey, we documented that much of the prey biomass in southeast Florida canals is unavailable for largemouth bass and peacock cichlid predation.

  5. Female economic activity in Rural Malawi

    PubMed Central

    Hyder, Asma; Behrman, Jere R.

    2015-01-01

    This study investigates economic activities and their determinants for women in households of rural Malawi, one of the poorest countries in Sub-Saharan Africa (SSA). Three waves of household panel data for years 2006, 2008 and 2010 from the Malawi Longitudinal Study of Families and Health (MLSFH) are used to examine female labor market participation. This study includes certain important characteristics of Malawian households i.e., polygamy, ethnicity, religion and self reported health status. The study reports five different labor market outcomes for women's participation i.e., agriculture related work, market & sales activities, cottage industry, other economic activities and out of the labor market. The study finds significant relationships between these five different labor market outcomes and age cohorts, ethnicity and marriage (monogamous or polygamous). PMID:26120564

  6. AIDS epidemic in Malawi: shaking cultural foundations.

    PubMed

    Chirwa, I

    1993-05-01

    Many young men and women in Malawi are infected with HIV and dying from AIDS. The head of the Malawi AIDS Control Program estimates that as many as 10% of all adults in the country may be infected with HIV, with the rate being higher in urban areas. While more than 90% of the population is now aware of the existence of AIDS and its dangers, changes in behavior have not taken place and HIV continues to spread. Early campaigns attempted to generate condom use through peer educators among bar girls, truck drivers, and STD patients. Many men state, however, that they prefer to have sex without condoms because it is more exciting. Others cite alcohol consumption, ignorance of the dangers of HIV infection, and/or a fear of suggesting mistrust in a partner as reasons for not using condoms. Many women also find it difficult to negotiate condom use among reluctant men. Making condoms readily accessible and giving them a positive image may help increase their rate of use; the opposition of some religious groups must be thwarted and the distribution system needs to be improved to realize these ends. Condoms are provided to Malawi free of charge by the US Agency of International Development. Supplies are then either distributed free through health centers and bars or sold in shops. The failure of free condoms to be readily available in rural areas where 90% of the population resides, however, poses concern. Finally, training programs, counseling, anonymous HIV testing centers, and peer educators are among some of the interventions being made against AIDS in Malawi.

  7. Male courtship preferences demonstrate discrimination against allopatric colour morphs in a cichlid fish.

    PubMed

    Zoppoth, P; Koblmüller, S; Sefc, K M

    2013-03-01

    Whether premating isolation is achieved by male-specific, female-specific or sex-independent assortative preferences often depends on the underlying evolutionary processes. Here we test mate preferences of males presented with females of different allopatric colour variants of the cichlid fish Tropheus sp., a Lake Tanganyika endemic with rich geographical colour pattern variation, in which the strength of sexual isolation varies between populations. We conducted two-way mate choice experiments to compare behaviour of males of a red-bodied morph (population Moliro) towards females from their own population with behaviour towards females from four allopatric populations at different stages of phylogenetic and phenotypic divergence. Males courted same-population females significantly more intensely than females of other populations, and reduced their heteromorphic courtship efforts both with increasing genetic and increasing phenotypic distinctness of the females. In particular, females of a closely related red-bodied population received significantly more courtship than either genetically distinct, similarly coloured females ('Kirschfleck' morph) or genetically related, differently coloured females ('yellow-blotch' morph), both of which were courted similarly. Genetically and phenotypically distinct females (Tropheus polli) were not courted at all. Consistent with previous female-choice experiments, female courtship activity also decreased with increasing genetic distance from the males' population. Given successful experimental and natural introgression between colour morphs and the pervasive allopatry of related variants, we consider it unlikely that assortative preferences of both sexes were driven by direct selection during periods of secondary contact or, in turn, drove colour pattern differentiation in allopatry. Rather, we suggest that sexual isolation evolved as by-product of allopatric divergence.

  8. ROLE OF GRASSROOTS ENVIRONMENTAL LITERACY: The case of water security at Bwaila Secondary School in Malawi

    NASA Astrophysics Data System (ADS)

    Chasukwa Mwalwenje, Yvonne; Chasukwa, Steria

    2015-04-01

    Malawi is popularly known as the Warm Heart of Africa. Malawi has a total land area of 45,747 sq. miles. Of the total area, 80 % is covered by fresh water from Lake Malawi and other rivers. The country boasts that it holds large amounts of fresh water and has the third largest lake in Africa. Ironically, the number of households with reliable water access is low (Water Aid, 2014, UNDP, Human Development Report 2008). Regardless of signs of economic development, water security still remains a challenge in the Warm Heart of Africa. The problem with access to water prompted the Government of Malawi to introduce a National Water Policy in 1994 with the vision of 'Water and Sanitation for All'. Since then, other water access interventions have impacted on the ability to manage water sustainably. Over the past few years, more inclusive and diversified interventions have been put in place to reverse the situation. For instance, the government of Malawi has taken action to increase the number of water tanks in schools (UNICEF 2005). Several stakeholders' support the government in their role provides policy direction and coordinate management of the water sector. The outlined National Water and Sanitation Policy strategies includes promoting water conservation and catchment protection; incorporating local governments and communities in planning, development and management of water supplies and sanitation services; rehabilitating the existing infrastructure; creating an enabling environment for public-private partnerships in water supply and sanitation activities; undertaking rehabilitation and reduction of unaccounted-for-water of existing urban, peri-urban, as a priority; promoting economic incentives and opportunities to encourage the participation of small-scale water and sanitation service providers; and promoting water recycling and re-use. Despite of all these interventions, Malawi still continues to face significant challenges with issues of access and quality of

  9. Language Proficiency Testing and the Expatriate Medical Practitioner in Malawi

    ERIC Educational Resources Information Center

    Kamwendo, Gregory H.

    2008-01-01

    According to the Medical Council of Malawi, one of the conditions for a licence to be granted to an individual who wants to practise medicine in Malawi is the practitioner's ability to speak and write English fluently. This means that the expatriate medical practitioner is not required by law to demonstrate fluency in Chichewa (the national…

  10. Influences on Children's Human Capital in Rural Malawi: Three Essays

    ERIC Educational Resources Information Center

    Appiah-Yeboah, Shirley Afua

    2013-01-01

    The circumstances that characterize poor, rural communities in Malawi suggest that children's health-wealth gradient can vary from other settings. This dissertation begins with a description of the methods used to create a household wealth variable using assets data in the Malawi Longitudinal Study of Families and Health project. By using a fixed…

  11. Culturally Responsive Professional Development for Inclusive Education in Rural Malawi

    ERIC Educational Resources Information Center

    Blanks, Brooke

    2014-01-01

    Malawi is one of the poorest countries in the world (World Bank, 2014). Yet, our experiences working with rural schools suggest that the Malawi education system may be far ahead of many developed nations, including the United States, in terms of their practical and philosophical commitment to inclusive education for all children, including…

  12. Culturally Responsive Professional Development for Inclusive Education in Rural Malawi

    ERIC Educational Resources Information Center

    Blanks, Brooke

    2014-01-01

    Malawi is one of the poorest countries in the world (World Bank, 2014). Yet, our experiences working with rural schools suggest that the Malawi education system may be far ahead of many developed nations, including the United States, in terms of their practical and philosophical commitment to inclusive education for all children, including…

  13. Influences on Children's Human Capital in Rural Malawi: Three Essays

    ERIC Educational Resources Information Center

    Appiah-Yeboah, Shirley Afua

    2013-01-01

    The circumstances that characterize poor, rural communities in Malawi suggest that children's health-wealth gradient can vary from other settings. This dissertation begins with a description of the methods used to create a household wealth variable using assets data in the Malawi Longitudinal Study of Families and Health project. By using a fixed…

  14. Kinship reinforces cooperative predator inspection in a cichlid fish.

    PubMed

    Hesse, Saskia; Anaya-Rojas, Jaime M; Frommen, Joachim G; Thünken, Timo

    2015-11-01

    Kin selection theory predicts that cooperation is facilitated between genetic relatives, as by cooperating with kin an individual might increase its inclusive fitness. Although numerous theoretical papers support Hamilton's inclusive fitness theory, experimental evidence is still underrepresented, in particular in noncooperative breeders. Cooperative predator inspection is one of the most intriguing antipredator strategies, as it implies high costs on inspectors. During an inspection event, one or more individuals leave the safety of a group and approach a potential predator to gather information about the current predation risk. We investigated the effect of genetic relatedness on cooperative predator inspection in juveniles of the cichlid fish Pelvicachromis taeniatus, a species in which juveniles live in shoals under natural conditions. We show that relatedness significantly influenced predator inspection behaviour with kin dyads being significantly more cooperative. Thus, our results indicate a higher disposition for cooperative antipredator behaviour among kin as predicted by kin selection theory.

  15. Molecular phylogenetic investigations of the Viviparidae (Gastropoda: Caenogastropoda) in the lakes of the Rift Valley area of Africa.

    PubMed

    Sengupta, Mita E; Kristensen, Thomas K; Madsen, Henry; Jørgensen, Aslak

    2009-09-01

    The freshwater gastropod family Viviparidae is nearly cosmopolitan, but absent from South America. On the African continent, two genera are recognized; the widespread Bellamya and the monotypic Neothauma, which is confined to Lake Tanganyika. Most of the African Bellamya species are confined to the major lakes of the Rift Valley area in Africa, i.e. Lake Albert, Lake Malawi, Lake Mweru, and Lake Victoria. The phylogenetic analyses of mitochondrial (COI and 16S) and nuclear (H3, 18S and 28S) DNA inferred three major lake-clades; i.e. Lake Victoria/Kyoga/Albert, Lake Malawi and Lake Mweru/Bangweulu. The endemic B. rubicunda from Lake Albert and B. unicolor from Lake Kyoga were inferred to be part of the Lake Victoria clade. Bellamya capillata as identified by shell characters was polyphyletic in gene trees. The monophyletic Bellamya species radiation in Lake Malawi was most nearly related to the Lake Victoria/Kyoga/Albert-clade. Taxa from the Zambian lakes, Mweru and Bangweulu, were inferred together and placed ancestral to the other lakes. Neothauma tanganyicense was inferred as the sister-group to the Zambian Bellamya. Within the lake-clades the endemic radiations show very low genetic diversities (0-4.1% in COI), suggesting much faster morphological divergence than molecular divergence. Alternatively, Bellamya in Africa constitutes only a few species with several sub-species or eco-phenotypic morphs. The African viviparids were inferred to be the sister-group to a clade comprising Asian species, and the relatively low genetic diversity between the clades (12.6-15.5% in COI) makes a recent Miocene dispersal event from Asia to Africa much more likely than an ancient Gondwana vicarience distribution.

  16. Schistosomiasis in Malawi: a systematic review.

    PubMed

    Makaula, Peter; Sadalaki, John R; Muula, Adamson S; Kayuni, Sekeleghe; Jemu, Samuel; Bloch, Paul

    2014-12-10

    Schistosomiasis remains an important public health problem that undermines social and economic development in tropical regions of the world, mainly Sub-Saharan Africa. We are not aware of any systematic review of the literature of the epidemiology and transmission of schistosomiasis in Malawi since 1985. Therefore, we reviewed the current state of knowledge of schistosomiasis epidemiology and transmission in this country and identified knowledge gaps and relevant areas for future research and research governance. We conducted computer-aided literature searches of Medline, SCOPUS and Google Scholar using the keywords: "schistosomiasis", "Bilharzia", "Bulinus" and "Biomphalaria" in combination with "Malawi". These searches were supplemented by iterative reviews of reference lists for relevant publications in peer reviewed international scientific journals or other media. The recovered documents were reviewed for their year of publication, location of field or laboratory work, authorship characteristics, ethics review, funding sources as well as their findings regarding parasite and intermediate host species, environmental aspects, geographical distribution, seasonality of transmission, and infection prevalence and intensities. A total of 89 documents satisfied the inclusion criteria and were reviewed. Of these, 76 were published in international scientific journals, 68 were peer reviewed and 54 were original research studies. Most of the documents addressed urinary schistosomiasis and about two thirds of them dealt with the definitive host. Few documents addressed the parasites and the intermediate hosts. While urinary schistosomiasis occurs in most parts of Malawi, intestinal schistosomiasis mainly occurs in the central and southern highlands, Likoma Island and Lower Shire. Studies in selected communities estimated prevalence rates of up to 94.9% for Schistosoma haematobium and up to 67.0% for Schistosoma mansoni with considerable geographical variation. The main

  17. Global leaf companies control the tobacco market in Malawi

    PubMed Central

    Otañez, Marty G; Mamudu, Hadii; Glantz, Stanton A

    2007-01-01

    Objective To examine the influence of US‐based tobacco leaf‐buying companies, Universal Corporation and Alliance One International, on Malawi's economy and trade policy in 2000–6. Design Analyses of ethnographic data and tobacco industry documents. Results Universal Corporation and Alliance One International, through their subsidiary companies Limbe Leaf and Alliance One, respectively, in Malawi, control policy‐making advisory groups and operate a tobacco cartel to influence Malawi's economic and trade sectors. Limbe Leaf's corporate secretary and lawyer is a member of several policy‐making committees that advise the Malawi government on tobacco‐related trade policy. The corporate representative's presence prevents other committee members from taking positions against the tobacco industry and ensures government policy that advances industry interests to obtain low‐cost tobacco. The World Bank and Malawi's Anti‐corruption Bureau report allegations of collusion between Limbe Leaf and Alliance One over prices at tobacco markets. Allegations of collusion between Limbe Leaf and Alliance One prompted Malawi President Bingu Mutharika in 2006 to warn the companies to end non‐competitive practices or leave the country, but there was no meaningful follow‐up action. Findings from interviews with small‐scale tobacco traders in Malawi suggest that Universal and Alliance One International purchase smuggled raw tobacco from the neighbouring countries, Zambia and Mozambique, undermining growers' efforts to benefit from tobacco farming in Malawi. Conclusion These actions restrict competition, depress tobacco prices for Malawi's farmers and contribute to poverty in Malawi, while keeping the country dependent on tobacco growing. PMID:17652242

  18. Nile perch: the great lake experiment.

    PubMed

    Ogutu-ohwayo, R

    1998-01-01

    In order to improve the fishery of Lake Victoria, a large predatory fish, the Nile perch (Lates niloticus), was introduced into the lake to feed on the smaller but abundant haplochromines, thereby producing a larger fish for food consumption. Originally the lake had a very high fish species diversity, dominated by more than 300 species of haplochromine cichlids; however, they were too small to be exploited for food. It took about 20 years for the population of the Nile perch in the lake to increase significantly. Although increased fish production has benefited riparian communities by providing revenue, employment, and food, the introduction of the Nile perch has also resulted in extinction and has transformed the lake ecosystem. In response to the concern caused by the introduction of the Nile perch, the deteriorating water quality, and the need to sustain the lucrative fishery, the governments of Uganda, Kenya, and Tanzania have initiated the multisectoral Lake Victoria Environment Management Programme. Its goals are to control the loading of nutrients and contaminants into the lake, manage land use in the catchment area, manage the introduced fish species, conserve biodiversity, and control the spread of water hyacinths.

  19. Quantifying filariasis and malaria control activities in relation to lymphatic filariasis elimination: a multiple intervention score map (MISM) for Malawi.

    PubMed

    Stanton, Michelle C; Mkwanda, Square; Mzilahowa, Themba; Bockarie, Moses J; Kelly-Hope, Louise A

    2014-02-01

    To quantify the geographical extent of filariasis and malaria control interventions impacting lymphatic filariasis (LF) in Malawi and to produce a multiple intervention score map (MISM) for prioritising surveillance and intervention strategies. Interventions included mass drug administration (MDA) for LF and onchocerciasis, and bed nets and indoor residual spraying (IRS) for malaria. District and subdistrict-level data were obtained from the Ministry of Health in Malawi, the Demographic and Health Survey (DHS) and President's Malaria Initiative reports. Single intervention scores were calculated for each variable based on population coverage thresholds, and these were combined in a weighted sum to form a multiple intervention score, which was then used to produce maps, that is MISMs. Districts were further classified into four groups based on the combination of their baseline LF prevalence and multiple intervention score. The district- and subdistrict-level MISMs highlighted specific areas that have received high and low coverage of LF-impacting interventions. High coverage areas included the LF-onchocerciasis endemic areas in the southern region of the country and areas along the shores of Lake Malawi, where malaria vector control had been prioritised. Three districts with high baseline LF prevalence measures but low coverage of multiple interventions were identified and considered to be most at risk of ongoing transmission or re-emergence. These maps and district classifications will be used by LF programme managers to identify and target high-risk areas that may not have received adequate LF-impacting interventions to interrupt the transmission of the disease.

  20. Outgroup effects on root position and tree topology in the AFLP phylogeny of a rapidly radiating lineage of cichlid fish☆

    PubMed Central

    Kirchberger, Paul C.; Sefc, Kristina M.; Sturmbauer, Christian; Koblmüller, Stephan

    2014-01-01

    Phylogenetic analyses of rapid radiations are particularly challenging as short basal branches and incomplete lineage sorting complicate phylogenetic inference. Multilocus data of presence-absence polymorphisms such as obtained by AFLP genotyping overcome some of the difficulties, but also present their own intricacies. Here we analyze >1000 AFLP markers to address the evolutionary history of the Limnochromini, a cichlid fish lineage endemic to Lake Tanganyika, and to test for potential effects of outgroup composition on tree topology. The data support previous mitochondrial evidence on the tribe’s taxonomy by confirming the polyphyly of the genus Limnochromis and – in contradiction to a recent taxonomic revision – nesting the genus Greenwoodochromis within the Limnochromini. Species relationships suggest that ecological segregation occurred during the rapid basal radiation of the Limnochromini. The large phylogenetic distance between candidate outgroup taxa and the Limnochromini radiation caused random outgroup effects. Bootstrap support for ingroup nodes was lower in outgroup-rooted than in midpoint-rooted trees, and root positions and ingroup tree topologies varied in response to the composition of the outgroup. These observations suggest that the predisposition for homoplastic evolution makes AFLP-based phylogenetic analyses particularly susceptible to random biases introduced by too-distant outgroup taxa. PMID:24055738

  1. Changes in reproductive life-history strategies in response to nest density in a shell-brooding cichlid, Telmatochromis vittatus

    NASA Astrophysics Data System (ADS)

    Ota, Kazutaka; Hori, Michio; Kohda, Masanori

    2012-01-01

    To determine whether the appearance of a reproductively parasitic tactic varies, and how this variation affects territorial males of the Lake Tanganyika cichlid fish Telmatochromis vittatus, we examined the reproductive ecology of territorial males in Mtondwe and compared it with that of a neighboring Wonzye population, where nest density differs from that at Mtondwe. In Wonzye, with high nest density, male tactics change with their body size from a territorial to a non-territorial parasitic tactic called piracy in which they conquer several nests defended by territorial males and take over the nests while females are spawning. These "pirate" males could decrease the costs incurred by travelling among nests by exclusively targeting aggregations of nests in close proximity while avoiding separate nests. Territorial males in Wonzye sacrifice the potential higher attractiveness offered by large nests and instead compete for nests farther from neighbors on which pirates less frequently intrude. In contrast, the Mtondwe population had lower nest density and piracy was absent. Given that the success of piracy depends on the close proximity of nests, nest density is likely responsible for the observed variation in the occurrence of piracy between the two populations. Furthermore, in Mtondwe, territorial males competed for larger nests and were smaller than the territorial males in Wonzye. Thus, this lower nest density may free territorial males from the selection pressures for increased size caused by both defense against nest piracy and the need to develop into pirates as they grow.

  2. Changes in reproductive life-history strategies in response to nest density in a shell-brooding cichlid, Telmatochromis vittatus.

    PubMed

    Ota, Kazutaka; Hori, Michio; Kohda, Masanori

    2012-01-01

    To determine whether the appearance of a reproductively parasitic tactic varies, and how this variation affects territorial males of the Lake Tanganyika cichlid fish Telmatochromis vittatus, we examined the reproductive ecology of territorial males in Mtondwe and compared it with that of a neighboring Wonzye population, where nest density differs from that at Mtondwe. In Wonzye, with high nest density, male tactics change with their body size from a territorial to a non-territorial parasitic tactic called piracy in which they conquer several nests defended by territorial males and take over the nests while females are spawning. These "pirate" males could decrease the costs incurred by travelling among nests by exclusively targeting aggregations of nests in close proximity while avoiding separate nests. Territorial males in Wonzye sacrifice the potential higher attractiveness offered by large nests and instead compete for nests farther from neighbors on which pirates less frequently intrude. In contrast, the Mtondwe population had lower nest density and piracy was absent. Given that the success of piracy depends on the close proximity of nests, nest density is likely responsible for the observed variation in the occurrence of piracy between the two populations. Furthermore, in Mtondwe, territorial males competed for larger nests and were smaller than the territorial males in Wonzye. Thus, this lower nest density may free territorial males from the selection pressures for increased size caused by both defense against nest piracy and the need to develop into pirates as they grow.

  3. Functional groups in the social behavior of a cichlid fish, the Oscar, Astronotus ocellatus.

    PubMed

    Beeching, S C

    1997-01-01

    Dummy conspecifics were presented to isolated adults of the cichlid fish Astronotus ocellatus to investigate the functional organization of cichlid social behavior. Body size and 15 dummy-elicited activities were recorded during 15 min sessions and analyzed by principal components analysis (PCA) to reveal their temporal organization. Five principal components explained almost 80% of the variation in dummy-elicited behavior, and these five factors define functional groups for Nest-oriented and attack modal action patterns are not mutually inhibitory during this time frame, and biting does not appear to function exclusively during an attack on a conspecific. Comparison with previous studies of New and Old World cichlids suggests evolutionary conservation of the functional organization of social behavior.

  4. Extraordinarily long sperm in the socially monogamous cichlid fish Pelvicachromis taeniatus

    NASA Astrophysics Data System (ADS)

    Thünken, Timo; Bakker, Theo C. M.; Kullmann, Harald

    2007-06-01

    The main function of the spermatozoon is the transfer of the male haploid genome during fertilisation. In animals in general and in fishes in particular, there is huge variation in sperm size. In fishes, sperm size ranges from 13 μm in Mugil cephlus to nearly 100 μm in the channel catfish Ictalurus punctatus. We examined intra-specific variation in sperm morphometry in the socially monogamous cichlid Pelvicachromis taeniatus using scanning electron microscopy. The mean total sperm length of nearly 70 μm was extraordinarily large for cichlids. Furthermore, within-male variation was remarkably high. To our knowledge, P. taeniatus produces the longest cichlid sperm ever documented. Several hypotheses concerning the adaptive significance of these results are presented.

  5. The Thermal History of the East African Rift Lakes Region Since the Last Glacial Maximum Using TEX86 Paleothermometry

    NASA Astrophysics Data System (ADS)

    Berke, M. A.; Johnson, T. C.; Werne, J. P.; Schouten, S.; Sinninghe Damsté, J. S.

    2008-12-01

    We present preliminary results from a study using the TEX86 temperature proxy from sediments of East African Rift Lakes (including Lakes Turkana, Albert, and Malawi) to reconstruct the thermal history of tropical Africa for the last ~ 20,000 years at a subcentennial to multicentennial resolution. The TEX86 proxy, based on tetraether membrane lipids produced by lacustrine Crenarchaeota, has been shown to be successful at recording lake surface temperatures of some large lakes, including Lakes Malawi and Tanganyika, while providing unreasonable surface temperatures for lakes that receive a large input of soil material. The East African Rift Lakes are climatically sensitive, with the majority of water loss due to evaporation rather than outflow. Thus, they are useful for paleoclimate studies, being sensitive to even small changes in aridity. Temperature records from the northern and central basins of Lake Malawi agree well and fall within modern surface lake temperatures. A 2.5°C cooling is evident during the Younger Dryas in the northern basin record, with no response seen in the central basin. We are currently investigating mechanisms to explain why both records show a gradual cooling of 3°C during the late Holocene. Lake Albert shows an intriguing two-step cooling during the Younger Dryas, reaching temperatures 2.5°C lower than temperatures preceding or following this interval. The temperature record of Lake Turkana shows an interesting ~ 500 year cyclicity of low temperatures punctuated by abrupt warming events. Lakes Turkana and Albert show TEX86 paleotemperatures considerably lower (8°C cooler in Lake Albert and ~ 4°C cooler in Lake Turkana) than modern surface water temperatures. Although these records appear to fall in the range of temporal variability, these temperature discrepancies may indicate varying Crenarcheotal populations between lakes or other influencing factors.

  6. Hormonal anticipation of territorial challenges in cichlid fish

    PubMed Central

    Antunes, Raquel A.; Oliveira, Rui F.

    2009-01-01

    In many territorial species androgens respond to social interactions. This response has been interpreted as a mechanism for adjusting aggressive motivation to a changing social environment. Therefore, it would be adaptive to anticipate social challenges and reacting to their clues with an anticipatory androgen response to adjust agonistic motivation to an imminent social challenge. Here we test the hypothesis of an anticipatory androgen response to territorial intrusions using classical conditioning to establish an association between a conditioned stimulus (CS = light) and an unconditioned stimulus (US = intruder male) in male cichlid fish (Oreochromis mossambicus). During the training phase conditioned males (CS−US paired presentations) showed a higher decrease in latency for agonistic response toward the intruder than unconditioned males (CS–US unpaired presentations). In the test trial, conditioned males showed an increase in androgen levels (i.e., testosterone and 11-ketotestosterone) relative to baseline, in response to the CS alone. This increase was similar to that of control males exposed to real intruders after CS, whereas unconditioned males showed a decrease in androgen levels in response to the CS. Furthermore, conditioned males were significantly more aggressive than unconditioned males during the post-CS period on test trial, even though the intruder male was not present during this period. These results reveal the occurrence of a conditioned androgen response that may give territorial males an advantage in mounting a defense to upcoming territorial intrusions, if the ability to readily elevate androgens does not co-vary with other traits that bear costs. PMID:19805238

  7. Social familiarity modulates personality trait in a cichlid fish

    PubMed Central

    Galhardo, L.; Vitorino, A.; Oliveira, R. F.

    2012-01-01

    Personality traits, such as exploration–avoidance, are expected to be adaptive in a given context (e.g. low-risk environment) but to be maladaptive in others (e.g. high-risk environment). Therefore, it is expected that personality traits are flexible and respond to environmental fluctuations, given that consistency across different contexts is maintained, so that the relative individual responses in relation to others remains the same (i.e. although the magnitude of the response varies the differences between high and low responders are kept). Here, we tested the response of male cichlid fish (Oreochromis mossambicus) to a novel object (NO) in three different social contexts: (i) social isolation, (ii) in the presence of an unfamiliar conspecific, and (iii) in the presence of a familiar conspecific. Males in the familiar treatment exhibited more exploratory behaviour and less neophobia than males in either the unfamiliar or the social isolation treatments. However, there were no overall correlations in individual behaviour across the three treatments, suggesting a lack of consistency in exploration–avoidance as measured by the NO test in this species. Moreover, there were no differences in cortisol responsiveness to an acute stressor between the three treatments. Together, these results illustrate how behavioural traits usually taken as measures of personality may exhibit significant flexibility and lack the expected consistency across different social contexts. PMID:22859562

  8. Social familiarity modulates personality trait in a cichlid fish.

    PubMed

    Galhardo, L; Vitorino, A; Oliveira, R F

    2012-12-23

    Personality traits, such as exploration-avoidance, are expected to be adaptive in a given context (e.g. low-risk environment) but to be maladaptive in others (e.g. high-risk environment). Therefore, it is expected that personality traits are flexible and respond to environmental fluctuations, given that consistency across different contexts is maintained, so that the relative individual responses in relation to others remains the same (i.e. although the magnitude of the response varies the differences between high and low responders are kept). Here, we tested the response of male cichlid fish (Oreochromis mossambicus) to a novel object (NO) in three different social contexts: (i) social isolation, (ii) in the presence of an unfamiliar conspecific, and (iii) in the presence of a familiar conspecific. Males in the familiar treatment exhibited more exploratory behaviour and less neophobia than males in either the unfamiliar or the social isolation treatments. However, there were no overall correlations in individual behaviour across the three treatments, suggesting a lack of consistency in exploration-avoidance as measured by the NO test in this species. Moreover, there were no differences in cortisol responsiveness to an acute stressor between the three treatments. Together, these results illustrate how behavioural traits usually taken as measures of personality may exhibit significant flexibility and lack the expected consistency across different social contexts.

  9. Hydrodynamic drag constrains head enlargement for mouthbrooding in cichlids.

    PubMed

    Van Wassenbergh, Sam; Potes, Nuno Zavattieri; Adriaens, Dominique

    2015-08-06

    Presumably as an adaptation for mouthbrooding, many cichlid fish species have evolved a prominent sexual dimorphism in the adult head. Since the head of fishes serves as a bow during locomotion, an evolutionary increase in head volume to brood more eggs can trade-off with the hydrodynamic efficiency of swimming. Here, the differences between males and females in three-dimensional shape and size of the external head surfaces and the effect thereof on drag force during locomotion was analysed for the Nile tilapia (Oreochromis niloticus), a maternal mouthbrooder. To do so, three-dimensional body surface reconstructions from laser scans and computational fluid dynamics simulations were performed. After scaling the scanned specimens to post-cranial body volume, in order to theoretically equalize propulsive power, the external volume of the head of females was 27% larger than that of males (head length + 14%; head width + 9%). These differences resulted in an approximate 15% increase in drag force. Yet, hydrodynamics imposed important constraints on the adaptation for mouthbrooding as a much more drastic drop in swimming efficiency seems avoided by mainly enlarging the head along the swimming direction.

  10. Aromatase regulates aggression in the African cichlid fish Astatotilapia burtoni.

    PubMed

    Huffman, Lin S; O'Connell, Lauren A; Hofmann, Hans A

    2013-03-15

    The roles of estrogen and androgens in male social behavior are well studied, but little is known about how these hormones contribute to behavior in a social hierarchy. Here we test the role of aromatase, the enzyme that converts testosterone into estradiol, in mediating aggression and reproductive behavior in male Astatotilapia burtoni, an African cichlid fish that displays remarkable plasticity in social behavior. We first measured aromatase expression in subordinate and dominant males in brain regions that regulate social behavior and found that subordinate males have higher aromatase expression than dominant males in the magnocellular and gigantocellular regions of the preoptic area. Next, we functionally tested the role of aromatase in regulating behavior by intraperitoneally injecting dominant males with either saline or fadrozole (FAD), an aromatase inhibitor, and found that FAD treatment decreases aggressive, but not reproductive, behaviors compared to saline controls. To determine the underlying physiological and molecular consequences of FAD treatment, we measured estradiol and testosterone levels from plasma and brain aromatase expression in FAD and saline treated dominant males. We found that estradiol levels decreased and testosterone levels increased in response to FAD treatment. Moreover, FAD treated males had increased aromatase expression in the gigantocellular portion of the POA, possibly a compensatory response. Overall, our results suggest aromatase is a key enzyme that promotes aggression in A. burtoni males through actions in the preoptic area.

  11. Microsatellite support for active inbreeding in a cichlid fish.

    PubMed

    Langen, Kathrin; Schwarzer, Julia; Kullmann, Harald; Bakker, Theo C M; Thünken, Timo

    2011-01-01

    In wild animal populations, the degree of inbreeding differs between species and within species between populations. Because mating with kin often results in inbreeding depression, observed inbreeding is usually regarded to be caused by limited outbreeding opportunities due to demographic factors like small population size or population substructuring. However, theory predicts inclusive benefits from mating with kin, and thus part of the observed variation in inbreeding might be due to active inbreeding preferences. Although some recent studies indeed report kin mating preferences, the evidence is still highly ambiguous. Here, we investigate inbreeding in a natural population of the West African cichlid fish Pelvicachromis taeniatus which showed clear kin mating preferences in standardized laboratory experiments but no inbreeding depression. The presented microsatellite analysis reveals that the natural population has, in comparison to two reference populations, a reduced allelic diversity (A = 3) resulting in a low heterozygosity (H(o) = 0.167) pointing to a highly inbred population. Furthermore, we found a significant heterozygote deficit not only at population (F(is) = 0.116) but also at subpopulation level (F(is) = 0.081) suggesting that inbreeding is not only a by-product of population substructuring but possibly a consequence of behavioral kin preferences.

  12. Secondary contact seeds phenotypic novelty in cichlid fishes

    PubMed Central

    Nichols, Paul; Genner, Martin J.; van Oosterhout, Cock; Smith, Alan; Parsons, Paul; Sungani, Harold; Swanstrom, Jennifer; Joyce, Domino A.

    2015-01-01

    Theory proposes that genomic admixture between formerly reproductively isolated populations can generate phenotypic novelty for selection to act upon. Secondary contact may therefore be a significant promoter of phenotypic novelty that allows species to overcome environmental challenges and adapt to novel environments, including during adaptive radiation. To date, this has largely been considered from the perspective of interspecific hybridization at contact zones. However, it is also possible that this process occurs more commonly between natural populations of a single species, and thus its importance in adaptive evolution may have been underestimated. In this study, we tested the consequences of genomic introgression during apparent secondary contact between phenotypically similar lineages of the riverine cichlid fish Astatotilapia calliptera. We provide population genetic evidence of a secondary contact zone in the wild, and then demonstrate using mate-choice experiments that both lineages can reproduce together successfully in laboratory conditions. Finally, we show that genomically admixed individuals display extreme phenotypes not observed in the parental lineages. Collectively, the evidence shows that secondary contact can drive the evolution of phenotypic novelty, suggesting that pulses of secondary contact may repeatedly seed genetic novelty, which when coupled with ecological opportunity could promote rapid adaptive evolution in natural circumstances. PMID:25392475

  13. Social deprivation affects cooperative predator inspection in a cichlid fish.

    PubMed

    Hesse, Saskia; Anaya-Rojas, Jaime M; Frommen, Joachim G; Thünken, Timo

    2015-03-01

    The social environment individuals are exposed to during ontogeny shapes social skills and social competence in group-living animals. Consequently, social deprivation has serious effects on behaviour and development in animals but little is known about its impact on cooperation. In this study, we examined the effect of social environment on cooperative predator inspection. Predator inspection behaviour is a complex behaviour, which is present in a variety of shoaling fish species. Often, two fish leave the safety of the group and inspect a potentially dangerous predator in order to gather information about the current predation risk. As predator inspection is highly risky, it is prone to conflicts and cheating. However, cooperation among individuals may reduce the individual predation risk. We investigated this complex social behaviour in juveniles of the cichlid fish Pelvicachromis taeniatus that were reared in two different social environments throughout development. Fish reared in a group inspected more often than isolation-reared fish and were more likely to cooperate, i.e. they conducted conjoint inspection of a predator. By contrast, isolation-reared fish were more likely to perform a single inspection without a companion. These results suggest an impairment of cooperative behaviour in isolation-reared fish most probably due to lack of social experience and resulting in lowered social skills needed in coordinated behaviour.

  14. Secondary contact seeds phenotypic novelty in cichlid fishes.

    PubMed

    Nichols, Paul; Genner, Martin J; van Oosterhout, Cock; Smith, Alan; Parsons, Paul; Sungani, Harold; Swanstrom, Jennifer; Joyce, Domino A

    2015-01-07

    Theory proposes that genomic admixture between formerly reproductively isolated populations can generate phenotypic novelty for selection to act upon. Secondary contact may therefore be a significant promoter of phenotypic novelty that allows species to overcome environmental challenges and adapt to novel environments, including during adaptive radiation. To date, this has largely been considered from the perspective of interspecific hybridization at contact zones. However, it is also possible that this process occurs more commonly between natural populations of a single species, and thus its importance in adaptive evolution may have been underestimated. In this study, we tested the consequences of genomic introgression during apparent secondary contact between phenotypically similar lineages of the riverine cichlid fish Astatotilapia calliptera. We provide population genetic evidence of a secondary contact zone in the wild, and then demonstrate using mate-choice experiments that both lineages can reproduce together successfully in laboratory conditions. Finally, we show that genomically admixed individuals display extreme phenotypes not observed in the parental lineages. Collectively, the evidence shows that secondary contact can drive the evolution of phenotypic novelty, suggesting that pulses of secondary contact may repeatedly seed genetic novelty, which when coupled with ecological opportunity could promote rapid adaptive evolution in natural circumstances.

  15. Social deprivation affects cooperative predator inspection in a cichlid fish

    PubMed Central

    Hesse, Saskia; Anaya-Rojas, Jaime M.; Frommen, Joachim G.; Thünken, Timo

    2015-01-01

    The social environment individuals are exposed to during ontogeny shapes social skills and social competence in group-living animals. Consequently, social deprivation has serious effects on behaviour and development in animals but little is known about its impact on cooperation. In this study, we examined the effect of social environment on cooperative predator inspection. Predator inspection behaviour is a complex behaviour, which is present in a variety of shoaling fish species. Often, two fish leave the safety of the group and inspect a potentially dangerous predator in order to gather information about the current predation risk. As predator inspection is highly risky, it is prone to conflicts and cheating. However, cooperation among individuals may reduce the individual predation risk. We investigated this complex social behaviour in juveniles of the cichlid fish Pelvicachromis taeniatus that were reared in two different social environments throughout development. Fish reared in a group inspected more often than isolation-reared fish and were more likely to cooperate, i.e. they conducted conjoint inspection of a predator. By contrast, isolation-reared fish were more likely to perform a single inspection without a companion. These results suggest an impairment of cooperative behaviour in isolation-reared fish most probably due to lack of social experience and resulting in lowered social skills needed in coordinated behaviour. PMID:26064616

  16. Behavioural isolation may facilitate homoploid hybrid speciation in cichlid fish.

    PubMed

    Selz, O M; Thommen, R; Maan, M E; Seehausen, O

    2014-02-01

    Hybrid speciation is constrained by the homogenizing effects of gene flow from the parental species. In the absence of post-mating isolation due to structural changes in the genome, or temporal or spatial premating isolation, another form of reproductive isolation would be needed for homoploid hybrid speciation to occur. Here, we investigate the potential of behavioural mate choice to generate assortative mating among hybrids and parental species. We made three-first-generation hybrid crosses between different species of African cichlid fish. In three-way mate-choice experiments, we allowed hybrid and nonhybrid females to mate with either hybrid or nonhybrid males. We found that hybrids generally mated nonrandomly and that hybridization can lead to the expression of new combinations of traits and preferences that behaviourally isolate hybrids from both parental species. Specifically, we find that the phenotypic distinctiveness of hybrids predicts the symmetry and extent of their reproductive isolation. Our data suggest that behavioural mate choice among hybrids may facilitate the establishment of isolated hybrid populations, even in proximity to one or both parental species. © 2013 The Authors. Journal of Evolutionary Biology © 2013 European Society For Evolutionary Biology.

  17. Malawi study signals need for more research on female genital schistosomiasis.

    PubMed

    1996-06-01

    51 women with urinary schistosomiasis underwent gynecological examinations, including colposcopy and photographic documentation of lesions, in a study conducted in 1994 at Mangochi Hospital near Lake Malawi. Microscopy of genital biopsies determined that 33 women had S. haematobium eggs in their cervix, vagina, and/or vulva. A significant correlation was identified between the size of genital lesion and the number of ova counted. Women with genital pathology had significantly more tumors in the vulva than women with schistosomiasis of the urinary tract only. Most of the observed pathology could be seen with the unaided eye. Even though the sample was very small, significantly more cases of genital schistosomiasis were found in women who had fewer children than desired and whose husbands had children with other women. Reasons for that observation were not investigated. The findings of this pilot study indicate that more research is needed to provide a better understanding of the implications of the disease upon marital and sexual lives.

  18. Population growth and environmental degradation in Malawi.

    PubMed

    Kalipeni, E

    1992-01-01

    Malawi has been ranked by the World Bank as one of the poorest countries in Africa. Malawi's only resources are its people and fertile soil, which comprises about 55% of land area. Environmental degradation and population growth conditions in Malawi were used to illustrate the model of environmental degradation linked to population pressure on land resources and government development strategies that favored large-scale agricultural farms. The result has been deforestation, overgrazing, overuse of land for subsistence, and increased population density. The argument was that population growth in some developing countries has been so rapid that environmental collapse is the result. The theoretical framework linking population growth, environment, and resources emphasized processes: 1) the precursor stage of underlying causes; 2) the problem phase with potential ecological and economic decline; and 3) consequences (environmental decline, reduction in food production systems, and reduction in standard of living). The precursors were identified as an agrarian society, lack of a population policy, and emphasis on large families. The problems were rapid population growth and immigration from Mozambique, which led to increased demand for trees for fuel and consequent deforestation, increased demand for arable land and consequent landlessness, increased investment in livestock and consequent overgrazing, and continued population momentum which was a financial burden to government and resulted in increased labor competition. The ecological consequences were soil erosion, degradation of vegetation, and water supply contamination and decline. Eventually, famines will occur and lead to disease, migration, deserted villages, urbanization, unemployment, ethnic conflicts, and political unrest. Population was estimated at 8.75 million in 1990, with exponential growth expected. Completed family size was 6.6 children per woman. Even replacement fertility would mean growth for 50 more

  19. Comparative Transcriptomics in East African Cichlids Reveals Sex- and Species-Specific Expression and New Candidates for Sex Differentiation in Fishes

    PubMed Central

    Böhne, Astrid; Sengstag, Thierry; Salzburger, Walter

    2014-01-01

    Males and females of the same species differ largely in gene expression, which accounts for most of the morphological and physiological differences and sex-specific phenotypes. Here, we analyzed sex-specific gene expression in the brain and the gonads of cichlid fishes from Lake Tanganyika belonging to four different lineages, so-called tribes (Eretmodini, Ectodini, Haplochromini, and Lamprologini), using the outgroup Nile tilapia (Oreochromis niloticus) as reference. The comparison between male and female brains revealed few differences between the sexes, consistent in all investigated species. The gonads, on the other hand, showed a large fraction of differentially expressed transcripts with the majority of them showing the same direction of expression in all four species. All here-studied cichlids, especially the three investigated mouth-breeding species, showed a trend toward more male- than female-biased transcripts. Transcripts, which were female-biased in expression in all four species, were overrepresented on linkage group (LG)1 in the reference genome and common male-biased transcripts showed accumulation on LG23, the presumable sex chromosomes of the Nile tilapia. Sex-specific transcripts contained candidate genes for sex determination and differentiation in fishes, especially members of the transforming growth factor-β-superfamily and the Wnt-pathway and also prominent members of the sox-, dm-domain-, and high mobility group-box families. We further confirmed our previous finding on species/lineage-specific gene expression shifts in the sex steroid pathway, including synthesizing enzymes as the aromatase cyp19a1 and estrogen and androgen receptors. PMID:25364805

  20. A gene expression study of dorso-ventrally restricted pigment pattern in adult fins of Neolamprologus meeli, an African cichlid species

    PubMed Central

    Sefc, Kristina M.

    2017-01-01

    Fish color patterns are among the most diverse phenotypic traits found in the animal kingdom. Understanding the molecular and cellular mechanisms that control in chromatophore distribution and pigmentation underlying this diversity is a major goal in developmental and evolutionary biology, which has predominantly been pursued in the zebrafish model system. Here, we apply results from zebrafish work to study a naturally occurring color pattern phenotype in the fins of an African cichlid species from Lake Tanganyika. The cichlid fish Neolamprologus meeli displays a distinct dorsal color pattern, with black and white stripes along the edges of the dorsal fin and of the dorsal half of the caudal fin, corresponding with differences in melanophore density. To elucidate the molecular mechanisms controlling the differences in dorsal and ventral color patterning in the fins, we quantitatively assessed the expression of 15 candidate target genes involved in adult zebrafish pigmentation and stripe formation. For reference gene validation, we screened the expression stability of seven widely expressed genes across the investigated tissue samples and identified tbp as appropriate reference. Relative expression levels of the candidate target genes were compared between the dorsal, striped fin regions and the corresponding uniform, grey-colored regions in the anal and ventral caudal fin. Dorso-ventral expression differences, with elevated levels in both white and black stripes, were observed in two genes, the melanosome protein coding gene pmel and in igsf11, which affects melanophore adhesion, migration and survival. Next, we predicted potential shared upstream regulators of pmel and igsf11. Testing the expression patterns of six predicted transcriptions factors revealed dorso-ventral expression difference of irf1 and significant, negative expression correlation of irf1 with both pmel and igsf11. Based on these results, we propose pmel, igsf11 and irf1 as likely components of

  1. Proximate and ultimate causes of variable visual sensitivities: insights from cichlid fish radiations

    PubMed Central

    Carleton, Karen L.; Dalton, Brian E.; Escobar-Camacho, Daniel; Nandamuri, Sri Pratima

    2016-01-01

    Animals vary in their sensitivities to different wavelengths of light. Sensitivity differences can have fitness implications in terms of animals’ ability to forage, find mates and avoid predators. As a result, visual systems are likely selected to operate in particular lighting environments and for specific visual tasks. This review focuses on cichlid vision, as cichlids have diverse visual sensitivities, and considerable progress has been made in determining the genetic basis for this variation. We describe both the proximate and ultimate mechanisms shaping cichlid visual diversity using the structure of Tinbergen’s four questions. We describe 1) the molecular mechanisms that tune visual sensitivities including changes in opsin sequence and expression; 2) the evolutionary history of visual sensitivity across the African cichlid flocks; 3) the ontological changes in visual sensitivity and how modifying this developmental program alters sensitivities among species; and 4) the fitness benefits of spectral tuning mechanisms with respect to survival and mating success. We further discuss progress to unravel the gene regulatory networks controlling opsin expression and suggest that a simple genetic architecture contributes to the lability of opsin gene expression. Finally, we identify unanswered questions including whether visual sensitivities are experiencing selection, and whether similar spectral tuning mechanisms shape visual sensitivities of other fishes. PMID:27061347

  2. Body Size Diversity and Frequency Distributions of Neotropical Cichlid Fishes (Cichliformes: Cichlidae: Cichlinae)

    PubMed Central

    Steele, Sarah E.; López-Fernández, Hernán

    2014-01-01

    Body size is an important correlate of life history, ecology and distribution of species. Despite this, very little is known about body size evolution in fishes, particularly freshwater fishes of the Neotropics where species and body size diversity are relatively high. Phylogenetic history and body size data were used to explore body size frequency distributions in Neotropical cichlids, a broadly distributed and ecologically diverse group of fishes that is highly representative of body size diversity in Neotropical freshwater fishes. We test for divergence, phylogenetic autocorrelation and among-clade partitioning of body size space. Neotropical cichlids show low phylogenetic autocorrelation and divergence within and among taxonomic levels. Three distinct regions of body size space were identified from body size frequency distributions at various taxonomic levels corresponding to subclades of the most diverse tribe, Geophagini. These regions suggest that lineages may be evolving towards particular size optima that may be tied to specific ecological roles. The diversification of Geophagini appears to constrain the evolution of body size among other Neotropical cichlid lineages; non-Geophagini clades show lower species-richness in body size regions shared with Geophagini. Neotropical cichlid genera show less divergence and extreme body size than expected within and among tribes. Body size divergence among species may instead be present or linked to ecology at the community assembly scale. PMID:25180970

  3. Molecular phylogeny and revised classification of the haplotilapiine cichlid fishes formerly referred to as "Tilapia".

    PubMed

    Dunz, Andreas R; Schliewen, Ulrich K

    2013-07-01

    African cichlids formerly referred to as "Tilapia" represent a paraphyletic species assemblage belonging to the so called haplotilapiine lineage which gave rise to the spectacular East African cichlid radiations (EARs) as well as to globally important aquaculture species. We present a comprehensive molecular phylogeny of representative haplotilapiine cichlids, combining in one data set four mitochondrial and five nuclear loci for 76 species, and compare it with phylogenetic information of a second data set of 378 mitochondrial ND2 haplotypes representing almost all important "Tilapia" or Tilapia-related lineages as well as most EAR lineages. The monophyly of haplotilapiines is supported, as is the nested sister group relationship of Etia and mouthbrooding tilapiines with the remaining haplotilapiines. The latter are consistently placed in eight monophyletic clades over all datasets and analyses, but several dichotomous phylogenetic relationships appear compromised by cytonuclear discordant phylogenetic signal. Based on these results as well as on extensive morphological evidence we propose a novel generic and suprageneric classification including a (re-)diagnosis of 20 haplotilapiine cichlid genera and nine tribes. New tribes are provided for the former subgenera Coptodon Gervais, 1853, HeterotilapiaRegan, 1920 and PelmatolapiaThys van den Audenaerde, 1969, in addition for "Tilapia" joka, Tilapia sensu stricto and Chilochromis, Etia, Steatocranus sensu stricto, the mouthbrooding tilapiines and for a clade of West African tilapiines. Copyright © 2013 Elsevier Inc. All rights reserved.

  4. Global Lakes Sentinel Services: Evaluation of Chl-a Trends in Deep Clear Lakes

    NASA Astrophysics Data System (ADS)

    Cazzaniga, Ilaria; Giardino, Claudia; Bresciani, Mariano; Poser, Kathrin; Peters, Steef; Hommersom, Annelies; Schenk, Karin; Heege, Thomas; Philipson, Petra; Ruescas, Ana; Bottcher, Martin; Stelzer, Kerstin

    2016-08-01

    The aim of this study is the analysis of trend in the trophic level evolution in clear deep lakes which, being characterised by good quality state, are important socio- economic resources for their regions. The selected lakes are situated in Europe (Garda, Maggiore, Constance and Vättern), North America (Michigan) and Africa (Malawi and Tanganyika) and cover a range of eco- regions (continental, perialpine, boreal, rift valley) distributed globally.To evaluate trophic level tendency we mainly focused on chlorophyll-a concentrations (chl-a) which is a direct proxy of trophic status. The chl-a concentrations were obtained from 5216 cloud-free MERIS imagery from 2002 to 2012.The 'GLaSS RoIStats tool' available within the GLaSS project was used to extract chl-a in a number of region of interests (ROI) located in pelagic waters as well as some few other stations depending on lakes morphology. For producing the time-series trend, these extracted data were analysed with the Seasonal Kendall test.The results overall show almost stable conditions with a slight increase in concentration for lakes Maggiore, Constance, and the Green Bay of Lake Michigan; a slight decrease for lakes Garda and Tanganyika and absolutely stable conditions for lakes Vättern and Malawi.The results presented in this work show the great capability of MERIS to perform trend tests analysis on trophic status with focus on chl-a concentration. Being chl-a also a key parameter in water quality monitoring plans, this study also supports the managing practices implemented worldwide for using the water of the lakes.

  5. Sexual abuse in Malawi: patterns of disclosure.

    PubMed

    Mason, Carole; Kennedy, Neil

    2014-01-01

    Potential human immunodeficiency virus transmission makes prompt disclosure of child sexual abuse in Africa critical. The pattern of disclosure of 133 children presenting to the largest hospital in Malawi were analyzed. Eighty percent presented early enough for effective use of HIV postexposure prophylaxis. Seventy-five percent of children made a disclosure of child sexual abuse; 29% spontaneously and 47% after prompting. Disclosures were most commonly made to a parent, and age did not affect the pattern of disclosure. The number of children reporting child sexual abuse is increasing, possibly because of increasing awareness, availability of services, and fear of HIV. Although prompt disclosure rates were relatively high, facilitating easier disclosure of child sexual abuse by a free telephone help-line and better training of teachers may be helpful.

  6. Husband-wife survey responses in Malawi.

    PubMed

    Miller, K; Zulu, E M; Watkins, S C

    2001-06-01

    Previous efforts by demographers to describe and explain spousal differences in reporting about family planning behavior have focused on individual attributes that are assumed to be related to the practice of contraception. This study extends that research by documenting spousal disagreement on a range of issues--household items, livestock, children, and spousal communication about fertility, family planning, and AIDS. Using data from a 1998 study of 585 monogamous couples in rural Malawi, the analysis identifies a systematic gender component to reporting: For many of the survey questions considered, when spouses disagree, husbands are more likely to say "yes" and wives "no." The findings are interpreted in terms of gendered strategies in the interview process.

  7. Ancyrocephalidae (Monogenea) of Lake Tanganyika: II: description of the first Cichlidogyrus spp. parasites from Tropheini fish hosts (Teleostei, Cichlidae).

    PubMed

    Gillardin, Céline; Vanhove, Maarten P M; Pariselle, Antoine; Huyse, Tine; Volckaert, Filip A M

    2012-01-01

    Although Lake Tanganyika hosts the most diverse endemic cichlid fish assemblage, its monogenean parasite fauna has hardly been documented. The cichlid tribe Tropheini has generated great interest because of its systematic position within the Haplochromini s.l. and its diversity in trophic morphology, reproductive behaviour and population structure. It has the potential to host a diverse Monogenea fauna. Here, we describe the first Cichlidogyrus spp.: Cichlidogyrus steenbergei sp. n., Cichlidogyrus irenae sp. n. and Cichlidogyrus gistelincki sp. n. The three host species, Limnotilapia dardennii, Ctenochromis horei and Gnathochromis pfefferi, are all infected by a single unique Cichlidogyrus sp. The genital and haptoral structure of the new species suggests a close relationship, which might mirror the close affinities between the hosts within the Tropheini. Based on haptoral configuration, the new species belong to a morphological group within the genus containing parasites both of West African cichlids and of Haplochromini, and hence, do not represent a new organisation of the attachment organ (as has recently been described of congeners infecting the ectodine cichlid Ophthalmotilapia).

  8. Malawi's Special Needs Education (SNE): Perspectives and Comparisons of Practice and Progress

    ERIC Educational Resources Information Center

    Itimu, Ambumulire Nellie; Kopetz, Patricia B.

    2008-01-01

    The sub-Saharan country of Malawi is s