Speciation in the Central American Seaway: the importance of taxon sampling in the identification of trans‐isthmian geminate pairs

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Abstract
Aim To create a molecular phylogenetic hypothesis for the closely related serranid generaAlphestesBloch and Schneider andDermatolepisGill and assess the role of the Panamanian Isthmus in speciation within these reef fishes.Location Tropical eastern Pacific, Caribbean, and Indian Oceans.Methods Sequence data from one nuclear (TMO‐4C4) and three mitochondrial genes (16S, 12S, and cytochromeb) were used in maximum parsimony and maximum likelihood analyses.Results Here we show that previously hypothesized trans‐isthmian geminate species are not each other's closest living relatives. Species ofAlphestesBloch and Schneider in the eastern Pacific are sister taxa indicating post‐closure speciation. WithinDermatolepisGill, we identify a sister group relationship between the Caribbean and western Indian Ocean species, a rarely reported biogeographic pattern. Based on sequence divergence, speciation among the three species ofDermatolepiswas, however, nearly simultaneous around the time of the isthmian closure event.Main conclusions Our molecular phylogenetic analysis of two closely related genera of reef fishes, each with presumed trans‐isthmian geminates, cautions against the uncritical use of morphological similarity in identification of geminates, as well as the assumption that trans‐isthmian sister groups date to the isthmian closure event. These findings suggest that in some instances incomplete sampling of species within a clade including putative geminates may lead to improper conclusions regarding the pattern and timing of speciation, as well as incorrect estimation of the rate at which evolution has proceeded.