High levels of population genetic differentiation in the American crocodile (Crocodylus acutus)

The American crocodile (Crocodylus acutus) is a widely distributed species across coastal and brackish areas of the Neotropical region of the Americas and the Greater Antilles. Available information on patterns of genetic differentiation in C. acutus shows a complex structuring influenced by interspecific interactions (mainly hybridization) and anthropogenic actions (mostly historical hunting, recent poaching, habitat loss and fragmentation, and unintentional translocation of individuals). In this study, we used data on mitochondrial DNA control region and 11 nuclear polymorphic microsatellite loci to assess the degree of population structure of C. acutus in South America, North America, Central America and the Greater Antilles. We used traditional genetic differentiation indices, Bayesian clustering and multivariate methods to create a more comprehensive picture of the genetic relationships within the species across its range. Analyses of mtDNA and microsatellite loci show evidence of a strong population genetic structure in the American crocodile, with unique populations in each sampling locality. Our results support previous findings showing large degrees of genetic differentiation between the continental and the Greater Antillean C. acutus. We report three new haplotypes unique to Venezuela, which are considerably less distant from the Central and North American haplotypes than to the Greater Antillean ones. Our findings reveal genetic population differentiation between Cuban and Jamaican C. acutus and offer the first evidence of strong genetic differentiation among the populations of Greater Antillean C. acutus.
Research was carried out with financial support of the Sackler Institute of Comparative Genomics of the American Museum of Natural History (AMNH). AMNH support included the provisioning of laboratory space, laboratory materials and technical training. The Wildlife Conservation Society provided financial support to carry out C. acutus ‘skin tissue sample collection in the Wildlife Refuge Monte Cabaniguan, Cuba. The Department of Ecology, Evolution and Environmental Biology and the Institute of Latin American Studies at Columbia University in the City of New York provided financial support via travel grants for Dr. Rossi to conduct fieldwork at the Wildlife Refuge Monte Cabaniguan in Cuba and the Everglades National Park in the United States.