Ecological correlates of species differences in the Lake Tanganyika crab radiation Saskia A. E. Marijnissen · Ellinor Michel (*) · Marjolein Kamermans · Kim Olaya-Bosch · Moniek Kars · Daniel F. R. Cleary · E. Emiel vanLoon · Paola G. Rachello Dolmen · Steph B. J. Menken <?InsertOnReleaseOF OFYear?><?InsertOnReleaseOF OFMonth?><?InsertOnReleaseOF OFDay?> ©Springer Science+Business Media B.V. 2008 Abstract The endemic crabs of Lake Tanganyika include a phenotypically diverse clade that exhibits recent divergence and low phylogenetic species resolution. There are indications that ecological niche segregation has played a prominent role in the divergence of this clade. We used habitat surveys, gut content analyses and stable isotope analyses to test the extent to which morphological species are ecologically different. Our data show some interspecific segregation in depth, substrate type and mean stable isotope signatures. At the same time, a considerable level of ecological niche overlap is evident among species of Platythelphusa that coexist in rocky littoral habitats. We consider these results in the framework of adaptive radiation theory, and we discuss general ramifications for the maintenance of species diversity in Lake Tanganyika. Introduction Lake Tanganyika is unique among the African Great Lakes in harbouring an endemic radiation of freshwater crabs (genus Platythelphusa) (Cumberlidge et al., 1999; Marijnissen et al., 2004; Reed &amp; Cumberlidge, 2006). In spite of marked levels Saskia Marijnissen Daniel Cleary Paola Rachello Dolmen Steph Menken Institute for Biodiversity and Ecosystem Dynamics/Dynamics, Section of Evolutionary Biology University of Amsterdam Kruislaan 318, 1098 SM, Amsterdam, Netherlands Ellinor Michel Department of Zoology The Natural History Museum Cromwell Road, London, SW7 5BD, UK Marjolein Kamermans School of Natural Sciences, Trinity College, Zoology Building University of Dublin Dublin 2, Ireland Kim Olaya-Bosch Department of Geography, Trinity College University of Dublin Dublin 2, Ireland Moniek Kars c/o Department of Zoology and Marine Biology University of Dar es Salaam Observation Hill, P.O. BOXBox 35064, Dar es Salaam, Tanzania Daniel Cleary E. Loon Institute for Biodiversity and Ecosystem Dynamics/Dynamics, Section of Computational Geo-Ecology University of Amsterdam Nieuwe Achtergracht 166, 1018 WV, Amsterdam, Netherlands DOI:10.1007/s10750-008-9566-y SPECIATION IN ANCIENT LAKES