Global diversity and oceanic divergence of humpback whales (Megaptera novaeangliae)

Abstract

Humpback whales (Megaptera novaeangliae) annually undertake the longest migrations between seasonal feeding and breeding grounds of any mammal. Despite this dispersal potential, discontinuous seasonal distributions and migratory patterns suggest that humpbacks form discrete regional populations within each ocean. To better understand the worldwide population history of humpbacks, and the interplay of this species with the oceanic environment through geological time, we assembled mitochondrial DNA control region sequences representing approximately 2700 individuals (465 bp, 219 haplotypes) and eight nuclear intronic sequences representing approximately 70 individuals (3700 bp, 140 alleles) from the North Pacific, North Atlantic and Southern Hemisphere. Bayesian divergence time reconstructions date the origin of humpback mtDNA lineages to the Pleistocene (880 ka, 95% posterior intervals 550-1320 ka) and estimate radiation of current Northern Hemisphere lineages between 50 and 200 ka, indicating colonization of the northern oceans prior to the Last Glacial Maximum. Coalescent analyses reveal restricted gene flow between ocean basins, with long-term migration rates (individual migrants per generation) of less than 3.3 for mtDNA and less than 2 for nuclear genomic DNA. Genetic evidence suggests that humpbacks in the North Pacific, North Atlantic and Southern Hemisphere are on independent evolutionary trajectories, supporting taxonomic revision of M. novaeangliae to three subspecies.

Spatially Explicit Analysis of Genome-Wide SNPs Detects Subtle Population Structure in a Mobile Marine Mammal, the Harbor Porpoise

“…The determinants of genetic structure in cetacean species are often complex–local environmental differences, ecological specializations along with complex social and behavioral structure can promote divergence [1,6–8]. For instance, many species are known to migrate seasonally around feeding grounds, but may return to distinct areas for mating and breeding [9–13]. Pelagic and offshore ecotypes have been reported in the Atlantic common bottlenose dolphin ( Tursiops truncatus ) populations [14,15], a hierarchical genetic structure has been observed in the Atlantic spotted dolphin ( Stenella frontalis ) [16], and prey specialization has contributed to genetic differentiation in killer whales ( Orcinus orca ) [17].…”

Introduction to the special issue on the Life in Antarctica: Boundaries and Gradients in a Changing Environment (XIth SCAR Biology Symposium)

“…This pressure has been very relevant for some species (whaling and sealing activities) (e.g., Jackson et al 2014), but in most parts of the continent the effects have been small. The intense industrialization of the world brought new compounds and new hazards to Earth ecosystems, and Antarctica was not an exception.…”

Comparative phylogeography of the ocean planet

“…For Mysticetes (baleen whales), patterns of gene flow are shaped by migratory pathways, with individuals typically exhibiting maternally based site fidelity to tropical breeding and temperate/Arctic feeding areas. This fidelity leads to population genetic separations between ocean basins and among breeding areas, with F ST values of 0.05 to 0.1 for right whales (111), blue whales (112), and humpback whales (113).…”