A Preliminary nuclear DNA phylogeny of Tursiops species and populations

Determining accurate phylogenetic relationships of species within the genus Tursiops and closely related Delphininae species, has remain a challenging task for evolutionary cetologists. Previous studies have not agreed on the monophyletic status of this genus, and although cross-lineage reticulations has been suggested as a main driver of phylogenetic uncertainty, no formal test of this has been carried out. In this study, we use a double digest RADseq protocol, to carry out a high resolution nuclear phylogenetic study of the Delphininae, with particular emphasis on species/ecotypes of the genus Tursiops. We also carried out cross-lineage reticulation analyses, and tested for several sources of bias in determining phylogenies from whole-genome data. Our results suggest likely monophily for the genus Tursiops, with the recently described T. australis grouping within the T. aduncus lineage. We also show the presence of extensive cross-lineage gene flow between pelagic and European coastal ecotypes of T. truncatus, as well as in the early stages of diversification between spotted (Stenella frontalis; Stenella attenuate), common (Delphinus delphis), spinner (Stenella longirostris), Fraser (Lagenodelphis hosei) and striped dolphins (Stenella coeruleoalba). Our study provides a significant step in our understanding of the group’s evolutionary history, and demonstrates that patterns of cross-lineage gene flow might have been more extensive and complex that previously thought. Furthermore, we make recommendation regarding potential taxonomic classification within the genus Tursiops, and propose a sub-species status for previously well described ecotypes.