Trans-oceanic population genetic structure of humpback whales in the north and south pacific

We examined genetic diversity of humpback whales in the North and adjacent South Pacific Oceans to investigate the history and dynamics that resulted in their current population structure and for which trans-oceanic gene flow is a phenomenon of great importance. Analysis of mitochondrial DNA variation suggests that humpback whale populations are subjected to contraction and expansion cycles associated with glaciations. Contrast between nuclear and mitochondrial genetic diversities show that expansion phases may be related to regional differentiation dependent upon sex-biased dispersal. To explain trans-oceanic gene flow from sex-biased dispersal, we analysed the species' wintering habits in the Mexican Pacific as described from the sex composition and temporal profile of social groupings. In consideration of the energetic burden for reproduction of female humpback whales and the resultant pre-copulatory competition among males, trans-oceanic gene flow may be explained by changes in winter distribution driven by male dispersal dynamics and gametic exchange across high productivity areas close to the equatorial coast of the American Pacific, as well as by the influence of long-term climatic change in forming trans-equatorial corridors for female interchange. Because of the sensitivity of humpback whale reproduction and dispersal to environment perturbations, our results raise concerns about the effects of climate change on the phylogeographic structure and thereby the evolution and long-term conservation of this species