Genetic evidence of a recent successful colonization of introduced species on islands: Boa constrictorimperator on Cozumel Island

Only one study has described the population genetic structure of Boa constrictor imperator and only in a single naturally colonized island. B.c. imperator, a snake with a naturally wide distribution across the Neotropics, was introduced to Cozumel Island, Mexico, in 1971. At present, it is one of the most abundant, widely distributed, terrestrial vertebrate on the island. We analysed the genetic diversity and structure, based on seven microsatellite loci, of 76 individuals of B.c. imperator from Cozumel. We also included 96 samples from different localities across mainland Mexico, to review the potential origin of the founder individuals. We identified two genetically differentiated populations on Cozumel that showed moderate levels of genetic diversity (H o = 0.590–0.620), with a low but significant level of genetic structure (F ST = 0.032). Individuals were highly unrelated (71 %) and the majority of genetic variation was distributed within individuals (84 %). We detected a signal of reduction in population size and evidence of genetic bottleneck. The genetically closest mainland populations, indicating potential source of island founders, are localities from the Gulf of Mexico and Yucatan peninsula. Results are in agreement with a recently introduced population, founded by a few individuals originating from several sources, which has been successful. B.c. imperator is jeopardizing a highly vulnerable insular ecosystem, hence its eradication from Cozumel is urgently needed. Our information is also valuable for other introduced-boa cases or as a basis for its conservation elsewhere given its classification as a threatened species.