Admixture and environmental fluctuations shape the evolutionary history of a predator radiation in East Africa’s Lake Tanganyika
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Top predators have oversized impacts on food webs and ecosystem dynamics, and introducing a novel predator to a naive environment can have dramatic consequences for endemic biodiversity. Lake Tanganyika is unique among African lakes in the diversity of the pelagic top predators in the genus Lates , where four species are endemic to the lake. Using a combination of reduced-representation and whole genome resequencing data, and pairing these with phylogenetic and demographic modeling approaches, we find that Lates colonization of Lake Tanganyika was much more recent (∼1–2 Mya) than other major and diverse clades within the lake. Demographic modeling suggests that diversification among Lates species within the lake occurred during a time period of dramatic changes in lake levels driven by glacial-interglacial cycles, supporting a role of these fluctuations as a “species pump” for lacustrine taxa. We further find that these lake level fluctuations likely contributed to multiple bouts of admixture among Lates species during the mid- to late-Pleistocene (∼90–500 Kya). Together, our findings suggest a dynamic and environmentally linked evolutionary history of the Lates radiation with the potential for dramatic ecosystem consequences for the taxa already present in Lake Tanganyika prior to Lates colonization and diversification.
Significance Statement
When introduced to novel ecosystems, top predators can cause major alterations to biodiversity and food webs. Species introductions to novel habitats can also provide invading taxa with ecological opportunities that facilitate evolutionary diversification. Here, we find evidence that the radiation of endemic top predators in East Africa’s Lake Tanganyika originated surprisingly recently, and that these species have experienced periods of hybridization with a widespread riverine relative throughout their history. These findings have major implications for the history of the lake and suggest that the introduction of Nile perch into Lake Victoria, which caused dramatic ecosystem and food web changes, may be a contemporary analog to the historical events in Lake Tanganyika.
