Abstract

The complex geological history of East Africa has been a driving factor in the rapid evolution of teleost biodiversity. While there is some understanding of how macroevolutionary drivers have shaped teleost speciation in East Africa, there is a paucity of research into how the same biogeographical factors have affected microevolutionary processes within lakes and rivers. To address this deficiency, population genetic diversity, demography, and structure were investigated in a widely distributed and migratory (potamodromous) African teleost species, Ssemutundu (Bagrus docmak). Samples were acquired from five geographical locations in East Africa within two major drainage basins; the Albertine Rift and Lake Victoria Basin. Individuals (N = 175) were genotyped at 12 microsatellite loci and 93 individuals sequenced at the mitochondrial DNA control region. Results suggested populations from Lakes Edward and Victoria had undergone a severe historic bottleneck resulting in very low nucleotide diversity (π = 0.004 and 0.006, respectively) and negatively significant Fu values (−3.769 and −5.049; p < .05). Heterozygosity deficiencies and restricted effective population size (N eLD) suggested contemporary exposure of these populations to stress, consistent with reports of the species decline in the East African Region. High genetic structuring between drainages was detected at both historical (ɸST = 0.62 for mtDNA; p < .001) and contemporary (microsatellite F ST = 0.460; p < .001) levels. Patterns of low genetic diversity and strong population structure revealed are consistent with speciation patterns that have been linked to the complex biogeography of East Africa, suggesting that these biogeographical features have operated as both macro‐ and micro‐evolutionary forces in the formation of the East African teleost fauna.

Highlights

  • East African freshwater systems possess a diverse teleost fauna shaped by a complex geological history, including large-­scale tectonic movements, volcanic activity, and significant uplifting (Danley et al, 2012; Sturmbauer, Baric, Salzburger, Rüber, & Verheyen, 2001; Verheyen, Salzburger, Snoeks, & Meyer, 2003)

  • The low genetic diversity and strong population structure patterns revealed in B. docmak are consistent with patterns observed in other freshwater fish species that have been linked to the complex biogeography of East Africa (Danley et al, 2012)

  • The results in the current study support the hypothesis of Danley et al (2012) and Pinton et al (2013), who postulate that a linkage of paleohydrological changes in a geological context has been a major cause of diversification of the freshwater teleost fauna in East Africa

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Summary

| INTRODUCTION

East African freshwater systems possess a diverse teleost fauna shaped by a complex geological history, including large-­scale tectonic movements, volcanic activity, and significant uplifting (Danley et al, 2012; Sturmbauer, Baric, Salzburger, Rüber, & Verheyen, 2001; Verheyen, Salzburger, Snoeks, & Meyer, 2003). As elsewhere in Africa, the unique East African teleost faunas in both riverine and lacustrine freshwater habitats are currently under threat due to natural and anthropogenic pressures, with many species experiencing rapid population declines. Bagrus docmak (Ssemutundu) is a freshwater catfish with a widespread distribution in African freshwater rivers including the Nile, Chad, Niger, Volta, and Senegal It is found in Lake Victoria as well as the Rift Valley Lakes Edward, George, Albert, Tanganyika, Malawi, and Turkana (Aruho, Basiita, Kahwa, Bwanika, & Rutaisire, 2013; Golubtsov, Darkove, Dgebyadze, & Mina, 1995; Goossens, 2015; Greenwood, 1966; Mwanja et al, 2014). East Africa shapes evolution of the fish fauna biodiversity at below the species level

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