Social structure can increase genomic diversity and population structure within many marine and terrestrial species. In the marine environment, where long-distance vision is of limited value and there are few boundaries to dispersal, vocal repertoire may be an important mechanism to maintaining social structure. Short-finned pilot whales form stable social groups for periods of a decade or more, and have highly variable vocal repertoires. Because of these traits, we expect to see genetic structure driven by the retention of individuals within family units, and genetic structure driven by an effect of social structure on mate selection. Furthermore, we hypothesize that vocal repertoire is an important mechanism used by short-finned pilot whales to maintain group segregation, and therefore plays an important role in driving social and genetic structure. Here, we focus on short-finned pilot whales in the Hawaiian Islands, which have a well-documented hierarchical social structure of resident island communities, which comprise clusters of individuals that often associate, and in turn comprise one or more social units that spend the majority of their time in association. We used 123 mitochondrial sequences (mtDNA), and 49 nuclear SNPs (nuDNA) from 106 short-finned pilot whales, and collected recordings from 26 encounters throughout the Hawaiian Islands. Our genetic data indicate a reciprocal link between social structure and genetic structure in this population. Our ability to differentiate among clusters on the basis of vocal repertoire indicates that it is an important mechanism maintaining social structure, and therefore helps stabilize the reciprocal relationship between social and genetic structure in this population. Socially-driven population structure, as seen in Hawaiian pilot whales, can increase genomic, ecological and cultural diversity, as well as ecological resilience, but could also indicate a greater degree of vulnerability to anthropogenic threats.
Van Cise, A., P. Morin, K. Martien, R. Baird, S. Mahaffy, D. Webster, A. Mooney, E. Oleson, J. Barlow. 2017. Song of my people: Short-finned pilot whales in Hawai’i use vocal repertoire diversity to maintain social and genetic population structure. Abstract (Proceedings) 22nd Biennial on the Biology of Marine Mammals, Halifax, Nova Scotia, October 22-27, 2017.