On the evolution of Gomphocythere (Crustacea, Ostracoda) in Lake Nyassa/Malawi (East Africa), with the description of 5 new species

Five new species of the ostracod genus Gomphocythere are described from Lake Nyassa/Malawi (East Africa). The morphology of the hemipenis in this genus is redescribed and the different parts are homologised with those of the Limnocytherinae and of other Timiraseviinae. The female abdominal structures are re-examined and a new terminology is proposed. Based on both valve and soft part morphology, the five new species are assumed to belong to a monophyletic cluster, which to all probability evolved within the lake itself. Indications for speciation by both natural and sexual selection are found. Natural selection could have been parapatric along a bathymetric cline; sexual selection involves at least characters related to the copulatory complex of the hemipenis. Closest congeners to the present species flock are the non-Tanganyikan, East African species, rather than those belonging to the southern African G. capensis complex.