Molecular phylogeny of the live-bearing fish genus Poecilia (Cyprinodontiformes: Poeciliidae).

Members of the genus Poecilia exhibit extensive morphological, behavioral, and life history variation within and between species. This natural variation, coupled with short generation times and the ease with which members of this genus can be cultured in the lab, have made several species model systems for studying the effects of sexual and natural selection on the evolution of natural populations. Given that there is no clear understanding of the phylogenetic relationships within the genus, these studies have not been put into a historical context, and between-species comparisons have been limited. We sequenced the complete NADH Dehydrogenase Subunit 2 (ND2) mitochondrial gene (1047 bp) in representatives of the major divisions of the genus in order to examine these relationships. The subgeneric groups of Rosen and Bailey (1963) are, for the most part, supported, with some adjustment within the subgenera Poecilia and Pamphorichthys. The morphological distinctness of the groups within Poecilia suggest that the original generic designations be reinstated, but this awaits a more thorough analysis. Two implications from the phylogeny are particularly relevant to sexual selection studies: within the North and Central American mollies, the three species of sailfin mollies form a monophyletic group, and within the subgenus Lebistes, the sister taxon to the guppy, P. reticulata, is most likely the group of species previously designated as Micropoecilia.