Whole genome scan of regional genetic variation in the common bottlenose dolphin (Tursiops spp.)

Abstract

As anthropogenic activity continues to alter the marine landscape, species including Tursiops truncatus are developing complex population structures. This can be in the formation of ecotypes and populations or differentiation into a new species. The mechanisms and evidence of this formation have recently been a topic of discussion, specifically in the western North Atlantic identifying the inshore ecotype as a distinct species (Tursiops erebennus). However, this conversation of possible speciation stretches beyond the western North Atlantic encompassing almost all Tursiops populations. These discussions focus largely on morphological distinctions and targeted genetic diversity differences. However, in depth, whole genome sequencing (WGS) looking at the genetic differences between the ecotypes/populations could provide a more detailed look at the mechanisms that drive this speciation. This study aims to show that the differing environmental pressures and behaviors in the coastal and pelagic zones lead to genetic variation in these distinct population groups. This study consisted of a large-scale whole genome resequencing of 4 Tursiops individuals from 3 populations to ~10x coverage located in the western North Atlantic (data obtained from Duke University sampling effort) and 57 Tursiops individuals located in the western North Atlantic, eastern North Atlantic, and eastern North Pacific (data obtained from Louis et. al, 2021) to observe population variance in each region. This study shows distinct population formation in the three regions and provides a comprehensive overview of the genes under possible ecological selection. These results contribute to the larger evolutionary story of the common bottlenose dolphin and the possibility of speciation driven by the selection of particular genes to better adapt and succeed in an ever changing global environment.