Prior to recent work in the Short Lab, the hydrophilid genus Chasmogenus was thought to be distributed throughout the tropics of both the old and new world. Current phylogenetic evidence indicates a significant dichotomy between old and new world clades however, and suggests Chasmogenus may be an exclusively Neotropical lineage. In order to understand the evolutionary history of this genus, a multigene dataset was used to construct a well-resolved maximum likelihood phylogeny that encapsulates the previously underestimated Neotropical diversity of this ~70 million year old genus. Having originated in the Cretaceous, Chasmogenus can serve as a potentially useful model for studying biogeographic patterns in the Neotropics during the late Mesozoic and Cenozoic eras. This preliminary study determined that biogeographic partitioning does exist within the group between five major subclades that were each recovered with bootstrap support values of 100. There is a clear relationship between geographic distribution and phylogeny in the genus, and morphological characters to support the independent evolution of these subclades were also identified. Various biogeographic hypotheses may explain the diversification of Neotropical Chasmogenus, yet further study is needed to more clearly elucidate this group’s ancient history.
