Gene-culture coevolution in a social cetacean: integrating acoustic and genetic data to understand population structure in the short-finned pilot whale (Globicephala macrorhynchus)

Abstract

The evolutionary ecology of a species is driven by a combination of random events, ecological and environmental mechanisms, and social behavior. Gene-culture coevolutionary theory attempts to understand the evolutionary trajectory of a species by examining the interactions between these potential drivers. Further, our choice of data type will affect the patterns we observe, therefore by integrating several types of data we achieve a holistic understanding of the various aspects of evolutionary ecology within a species.In order to understand population structure in short-finned pilot whales, I use a combination of genetic and acoustic data to examine structure on evolutionary (genetic) and cultural (acoustic) timescales. I first examine structure among geographic populationsin the Pacific Ocean. Using genetic sequences from the mitochondrial control region, I show that two genetically and morphologically distinct types of short-finned pilot whale, described off the coast of Japan, have non-overlapping distributions throughout their rangein the Pacific Ocean. Analysis of the acoustic features of their social calls indicates that they are acoustically differentiated, possibly due to limited communication between the two types. This evidence supports the hypothesis that the two types may be separate species orsubspecies.Next, I examine structure among island communities and social groups within the Hawaiian Island population of short-finned pilot whales. Using a combination of mitochondrial and nuclear DNA, I showed that the hierarchical social structure in Hawaiianpilot whales is driven by genetic relatedness; individuals remain in groups with their immediate family members, and preferentially associate with relatives. Similarly, social structure affects genetic differentiation, likely by restricting access to mates. Acousticdifferentiation among social groups indicates that social structure may also restrict the flow of cultural information, such as vocal repertoire or dialect. The qualitative correlation between social structure, cultural information transfer, and genetic structure suggest that gene-culture coevolution may be an important mechanism to the evolutionary ecology of short-finned pilot whales. Further research may reveal asimilar structure in the transmission of ecological behaviors, such as diet preference, habitat use, or movements. The results of this research underscore the applicability of gene-culture coevolutionary theory to non-human taxa