Demographic history of the Magnificient Frigatebird (Fregata magnificens) populations off Brazil: an approach using microsatellite genetic markers and approximate Bayesian computation

Abstract

The magnificent frigatebird Fregata magnificens is a seabird mainly distributed off the Pacific and Atlantic coast of America. A previous study using genetic data showed that Brazilian and Caribbean populations are isolated, representing independent “lineages”, and that the Brazilian population have lower genetic diversity and effective population size compared to populations belonging to the Caribbean lineage. However, several details of the demographic history of the Brazilian lineage remain elusive. In this study, we used a previously published set of microsatellite markers to gain insight on the demographic history of Brazilian populations of Fregata magnificens. More specifically, we ask when population size reduction occurred and if there is evidence of recent population bottlenecks in breeding colonies off Brazil. Approximate Bayesian Computation analysis found that the divergence between Brazilian and Caribbean lineages was recent (less than 18,000 years ago), and that population size reduction in the Brazilian lineage dates back to this moment. Moreover, we found no evidence of further population size reductions in the Brazilian populations. Therefore, differences in genetic diversity may be due to a relatively small effective population size that colonized Brazil (around 450 individuals), leading the population to higher inbreeding. The Brazilian population of Fregata magnificens may require special attention from the conservation point of view in order to maintain its genetic diversity and ensure the preservation of this species.