Understanding the evolution of two species of highly migratory cetacean at multiple scales and the potential value of a mechanistic approach

Abstract

An improved understanding of how behavior influences the genetic structure of populations would offer insight into the inextricable link between ecological processes and evolutionary patterns. This dissertation aims to demonstrate the need to consider behavior alongside genetics by examining the population genetic structure of two species of highly migratory cetacean across multiple scales and presenting an exploration of some potential lines of enquiry into the behavioral mechanisms underlying the patterns of genetic population structure observed. The first empirical chapter presents a population genetic analysis conducted on a data set of new and existing samples of Bryde’s whale (Balaenoptera edeni spp.) collected from the Western and Central Indo-Pacific and the Northwest Pacific Ocean. Levels of evolutionary divergence between two subspecies (B. e. brydei and B. e. edeni) and the degree of population structure present within each subspecies were explored. The subsequent three empirical chapters represent a series of population- and individual-level genetic analyses on a data set of more than 4,000 individual humpback whales (Megaptera novaengliae) sampled from across the South Atlantic and Western and Northern Indian Oceans over two decades. Patterns of genetic population structure and connectivity between breeding populations are examined across the region, and are complemented by an assessment of genetic structure on shared feeding areas for these populations in the Southern Ocean. Collectively, these studies demonstrate that a hierarchy of behavioral processes operating at different spatial scales is likely influencing patterns of genetic population structure in highly migratory baleen whales. Notably, for humpback whales, the widely assumed model of maternal fidelity to feeding areas and natal philopatry to breeding areas was found not to be applicable at all spatial scales. From an applied perspective, the complex population patterns observed are not currently accounted for in current management designation and recommendations for applying these findings to the management and protection of these species are presented. As these empirical studies highlight the importance of behavior as a potential mechanism for shaping the genetic structure of species, the final chapter offers a research prospectus describing how behavioral and genetic data may be integrated using new individual-based modeling techniques to integrate data and information from the fields of behavioral ecology and population genetics