High cryptic diversity and persistent lineage segregation in endemic **Romecytheridea** (Crustacea, Ostracoda) from the ancient Lake Tanganyika (East Africa)
Faculty of Sciences. Biology
Hydrobiologia. - The Hague
, p. 1-13
Ostracods form a substantial part of the endemic fauna of ancient lakes. Here, we have investigated the phylogenetic and phylogeographic patterns and genetic diversities of species of the endemic genus Romecytheridea from the Southern and Central part of Lake Tanganyika. We found that ostracod populations from four different localities are genetically highly differentiated from each other when analyzing the mitochondrial 16S region, while they are almost identical with genetic markers from the nuclear genome (D1-D2 from the large ribosomal subunit (LSU) and ITS). The criteria of the K/θ method for the evolutionary species concepts are fulfilled when analyzing 16S DNA sequence data, indicating that these populations are in fact different (cryptic) species with allopatric distribution. We discuss various hypotheses on how this high diversity could have originated. The complete lineage segregation can partly be explained by geographic isolation during periods of low lake level stands. But, other factors must have contributed to genetic isolation and speciation, as the two closest populations (Chimba and Katoto) from shallow parts of the Southern basin of Tanganyika are also geographically fully segregated.