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The fish subfamily Poeciliinae (sensu Parenti, 1981) is widely distributed across the Western Hemisphere and a dominant component of the fish communities of Central America. Poeciliids have figured prominently in previous studies on the roles of dispersal and vicariance in shaping current geographic distributions. Most recently, Hrbek et al. combined a DNA-based phylogeny of the family with geological models to provide a biogeographic perspective that emphasized the role of both vicariance and dispersal. Here we expand on that effort with a database enlarged in the quantity of sequence represented per species, in the number of species included, and in an enlarged and more balanced representation of the order Cyprinodontiformes. We combine a robust timetree based upon multiple fossil calibrations with enhanced biogeographic analyses that include ancestral area reconstructions to provide a detailed biogeographic history of this clade. Key features of our results are that the family originated in South America, but its major diversification dates to a later colonization of Central America. We also resolve additional colonizations among South, Central and North America and the Caribbean and consider how this reconstruction contributes to our understanding of the mechanisms of dispersal.

Gyrodactylus pictae n. sp. is recorded from Poecilia picta in heterospecific shoals with the guppy P. reticulata in Northern Trinidad. G. pictae is morphologically similar to G. turnbulli Harris, 1986, but the hamuli and marginal hooks are slightly smaller and more gracile. The toe and the point of the marginal hook have a distinctly different shape, providing the best morphological characters for distinguishing the two species. The rDNA ITS1 and ITS2 sequences differ from those of G. turnbulli (the closest relative) by >5, suggesting that these two taxa are not sibling species. The origin of the two species on poeciliids of the subgenus Micropoecilia is discussed, and it is suggested that this may represent a case of host-parasite co-evolution.