Population genetic structure of North Atlantic minke whales, Balaenoptera acutorostrata

Xênia Moreira Lopes, Martine Berube, Simon Berrow, Finn Larsen, Tore Haug,  Jeroen Hoekendijk, Rus Hoelzel, Brian Kot, Nils Øien, Tom Oosting, Christophe Pampoulie, Christian Ramp, Jooke Robbins, Conor Ryan, Richard Sears, Malene Simon, Hans Julius Skaug, Yvonne Verkuil, Gisli Vikingsson, Lars Witting, Jurjan van der Zee, Per J. Palsbøll

Abstract:

Previous genetic studies attempting to resolve North Atlantic minke whale population structure  have mostly resulted in contradictory conclusions. In addition, the breeding and feeding grounds of North Atlantic minke whales are not well known. Here we present results from genetic analyses that determined the gender, mitochondrial control region, and genotype at 19 microsatellite loci of 936 individuals (excluding duplicates) from seven North Atlantic areas. We also obtained 10,104 SNPs (ddRAD) from 29 individuals from three areas. Using traditional population genetic methods (e.g., Fst and clustering methods), we observed low levels of genetic differentiation among the sampling locations and one “cluster”, independent of genetic marker. The average relatedness within and among areas yielded a similar result, except when comparing areas with small sample sizes (<12 individuals). Although these results may be interpreted as the absence of population genetic structure, the data also showed that North Atlantic minke whales appear to have expanded their range after the last glacial maximum (~20,000 years ago). The “recent” common ancestry could explain the low level of genetic differentiation. In addition, inter-annual genetic recaptures of North Atlantic minke whales in the Gulf of Saint Lawrence (GSL) in eastern Canada suggest some degree of site-fidelity. The GSL is the only area in this study in which biopsies are associated with photo-identification across years. Of 5,000 photographs from minke whales encountered during the summers of 2007-2015 in the GSL, twelve individuals were recaptured in multiple years, and one individual recaptured in 6 years. Moreover, the gender of the biopsied whales in the GSL was skewed toward females (around 80%). Broader impacts of this research include the contribution of new information that supports little genetic differentiation in minke whales distributed throughout the North Atlantic, and demonstrates evidence of gender-based site fidelity in some seasonal feeding areas.