Cores, edges and beyond: insights into the phylogeography of frigatebirds with a focus on ultraperipheral and endemic populations

In the present context of the ramping up of the global biodiversity crisis, improving our understanding on the genetic and biogeographic patterns of ill-known taxa is central to conservation planning. This is especially relevant for geographically isolated populations that suffer from little or no gene flow and an increased extinction risk. The few studies available on the molecular phylogeny and phylogeographic diversity of Frigatebirds have only focused on populations of three species, Fregata magnificens , F. andrewsi from Christmas Islands and F. minor in the Galapagos. To improve our knowledge on these tropical seabirds, our study aimed at assessing worldwide phylogeographic patterns and relationships among all five extant species of the genus Fregata . To accomplish it, we sampled museum specimens corresponding to 18 frigatebird populations spatially distributed by Brazil, Mexico, Ascension Islands, Cabo Verde and the Indo-Pacific region, and fresh samples from Cabo Verde, and amplified them for a mtDNA cytochrome b fragment. We complemented our dataset with previously available data representing a total of 36 populations in this study. Similar to the well-known endemic populations of the Galapagos and Christmas Island, the isolated ultraperipheral populations in the Atlantic were shown to be genetically divergent from their main populations for the three widespread species, F. magnificens , F. ariel and F. minor . We provide the first genetic data for F. ariel , whilst building upon the existing knowledge of the genetic patterns of F. magnificens , F. aquila and F. minor . Furthermore, our molecular data comes in support of most but not all the morphologically recognized frigatebird subspecies. This study provides important genetic insights into the evolutionary history of the genus Fregata and acts as a baseline for future molecular work and conservation efforts.