Phylogenetic analyses of the subgenus Mollienesia (Poecilia, Poeciliidae, Teleostei) reveal taxonomic inconsistencies, cryptic biodiversity, and spatio-temporal aspects of diversification in Middle America.

The subgenus Mollienesia is a diverse group of freshwater fishes, including species that have served as important models across multiple biological disciplines. Nonetheless, the taxonomic history of this group has been conflictive and convoluted, in part because the evolutionary relationships have not been rigorously resolved. We conducted a comprehensive molecular phylogenetic analysis of the subgenus Mollienesia to identify taxonomic discrepancies and potentially identify undescribed species, estimate ancestral areas of origin and estimate dates of divergence, as well as explore biogeographical patterns. Our findings confirm the presence of three main clades composed of the P. latipinna, P. sphenops, and P. mexicana species complexes. Unlike previously hypothesized morphology-based analyses, species found on the Caribbean Islands are not part of Mollienesia, but are more closely related to species of the subgenus Limia. Our study also revealed several taxonomic inconsistencies and distinct lineages in the P. mexicana species complex that may represent undescribed species. The diversity in the subgenus Mollienesia is a result of dynamic geologic activity leading to vicariant events, dispersal across geologic blocks, and ecological speciation.