%0 Journal Article
%T Evolutionary History of Lake Tanganyika¡¯s Predatory Deepwater Cichlids
%A Paul C. Kirchberger
%A Kristina M. Sefc
%A Christian Sturmbauer
%A Stephan Koblm¨¹ller
%J International Journal of Evolutionary Biology
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/716209
%X Hybridization among littoral cichlid species in Lake Tanganyika was inferred in several molecular phylogenetic studies. The phenomenon is generally attributed to the lake level-induced shoreline and habitat changes. These allow for allopatric divergence of geographically fragmented populations alternating with locally restricted secondary contact and introgression between incompletely isolated taxa. In contrast, the deepwater habitat is characterized by weak geographic structure and a high potential for gene flow, which may explain the lower species richness of deepwater than littoral lineages. For the same reason, divergent deepwater lineages should have evolved strong intrinsic reproductive isolation already in the incipient stages of diversification, and, consequently, hybridization among established lineages should have been less frequent than in littoral lineages. We test this hypothesis in the endemic Lake Tanganyika deepwater cichlid tribe Bathybatini by comparing phylogenetic trees of Hemibates and Bathybates species obtained with nuclear multilocus AFLP data with a phylogeny based on mitochondrial sequences. Consistent with our hypothesis, largely congruent tree topologies and negative tests for introgression provided no evidence for introgressive hybridization between the deepwater taxa. Together, the nuclear and mitochondrial data established a well-supported phylogeny and suggested ecological segregation during speciation. 1. Introduction Cichlid fishes have undergone spectacular radiations in different parts of the world. In particular, the species flocks of the East African Great Lakes are well-known examples for rapid evolution and speciation [1¨C5]. Each of the three Great Lakes¡ªTanganyika, Malawi, and Victoria¡ªis inhabited by hundreds of mostly endemic cichlid species [6, 7]. Notably, most of the diversity is found in the littoral habitat, whereas reduced species richness in the deep benthal and pelagial seems to be a common phenomenon in all East African Great Lakes [7¨C10]. At least three factors may have contributed to this pattern: (i) reduced niche diversity in the pelagic and in deepwater benthic zones, (ii) a narrow ambient light spectrum consisting only of short-wavelength blue light and hence less promotive of diversification mechanisms contingent on color perception than the shallow clear-water habitats [11¨C14], and (iii) the absence of strong barriers to gene flow. Indeed, deepwater cichlid species often have lake-wide distributions with very low, if any, population genetic structure over large geographic distances [10, 15, 16]
%U http://www.hindawi.com/journals/ijeb/2012/716209/