We examined the distribution of 44 morphological characters for 16 extant species of an ostracode genus, Gomphocythere, in Africa, to test hypotheses concerning character development and speciation patterns. Using heuristic searches conducted with the phylogenetic reconstruction program PAUP (beta version, 4.0), we found 2 trees of 98 steps (CI = 0.56). The skewness of tree length distribution reveals significant phylogenetic structure in the data. Nodes are supported by 1 to 11 character-state changes, and these character changes are sometimes reversed or paralleled elsewhere, accounting for much of the homoplasy in the reconstructions. By systematically removing both hard- and soft-part characters in separate analyses, hard-part characters were found to be far more homoplasious in their distribution across the phylogenetic tree, while soft parts are minimally homoplasious, suggesting that they are far more conservative while the hard parts are more prone to ecophenotypic variation. This phylogeny provides the basis for evaluating speciation mechanisms and the role of ecological factors in the diversification of ostracodes in this lake system. |
