Persistence of a Geographically-Stable Hybrid Zone in Puerto Rican Dwarf Geckos.
Determining the mechanisms that create and maintain biodiversity is a central question in ecology and evolution. Speciation is the process that creates biodiversity. Speciation is mediated by incompatibilities that lead to reproductive isolation between divergent populations and these incompatibilities can be observed in hybrid zones. Gecko lizards are a speciose clade possessing an impressive diversity of behavioral and morphological traits. In geckos, however, our understanding of the speciation process is negligible. To address this gap, we used genetic sequence data (both mitochondrial and nuclear markers) to revisit a putative hybrid zone between Sphaerodactylus nicholsi and Sphaerodactylus townsendi in Puerto Rico, initially described in 1984. First, we addressed discrepancies in the literature on the validity of both species. Second, we sampled a 10-km-wide transect across the putative hybrid zone and tested explicit predictions about its dynamics using cline models. Third, we investigated potential causes for the hybrid zone using species distribution modeling and simulations; namely, whether unique climatic variables within the hybrid zone might elicit selection for intermediate phenotypes. We find strong support for the species-level status of each species and no evidence of movement, or unique climatic variables near the hybrid zone. We suggest that this narrow hybrid zone is geographically stable and is maintained by a combination of dispersal and selection. Thus, this work has identified an extant model system within geckos that that can be used for future investigations detailing genetic mechanisms of reproductive isolation in an understudied vertebrate group.
['Pinto|Brendan J|BJ|', 'Titus-McQuillan|James|J|', 'Daza|Juan D|JD|', 'Gamble|Tony|T|']
D000818:Animals D044822:Biodiversity D004272:DNA, Mitochondrial D049810:Genetic Speciation D005828:Genetics, Population D005843:Geography D006824:Hybridization, Genetic D008116:Lizards D008957:Models, Genetic D010641:Phenotype D010802:Phylogeny D011647:Puerto Rico D060047:Reproductive Isolation
hybridization geckos speciation Sphaerodactylus hybrid zone dynamics