Cultural traditions across a migratory network shape the genetic structure of southern right whales around Australia and New Zealand.

E L Carroll,J Bannister,M Watson,D R Gröcke,R Harcourt,N Patenaude,R Alderman,O E Gaggiotti,C S Baker

doi:10.1038/srep16182

Abstract

Fidelity to migratory destinations is an important driver of connectivity in marine and avian species. Here we assess the role of maternally directed learning of migratory habitats, or migratory culture, on the population structure of the endangered Australian and New Zealand southern right whale. Using DNA profiles, comprising mitochondrial DNA (mtDNA) haplotypes (500 bp), microsatellite genotypes (17 loci) and sex from 128 individually-identified whales, we find significant differentiation among winter calving grounds based on both mtDNA haplotype (FST = 0.048, ΦST = 0.109, p < 0.01) and microsatellite allele frequencies (FST = 0.008, p < 0.01), consistent with long-term fidelity to calving areas. However, most genetic comparisons of calving grounds and migratory corridors were not significant, supporting the idea that whales from different calving grounds mix in migratory corridors. Furthermore, we find a significant relationship between δ13C stable isotope profiles of 66 Australian southern right whales, a proxy for feeding ground location, and both mtDNA haplotypes and kinship inferred from microsatellite-based estimators of relatedness. This indicates migratory culture may influence genetic structure on feeding grounds. This fidelity to migratory destinations is likely to influence population recovery, as long-term estimates of historical abundance derived from estimates of genetic diversity indicate the South Pacific calving grounds remain at <10% of pre-whaling abundance.

Highlights

Structure and connectivity in marine species as diverse as leatherback turtles Dermochelys coriacea[8], bull sharks Carcharhinus leucas[9], and humpback whales Megaptera novaeangliae[10]
We provide an understanding of the role of migratory culture as a driver of genetic structure in the contemporary population and provide targets to inform our understanding of the recovery of the species in the New Zealand and Australia
No loci significantly deviated from the Hardy-Weinberg equilibrium and there was no evidence of significant linkage across the loci

Summary

Introduction

Structure and connectivity in marine species as diverse as leatherback turtles Dermochelys coriacea[8], bull sharks Carcharhinus leucas[9], and humpback whales Megaptera novaeangliae[10]. The delineation of southeast and southwest Australia into distinct management units was proposed based on the difference in recovery rate and photo-identification data suggesting movement within each region is greater than between the two regions[20,22]. This hypothesis was previously tested using genetic data that showed southeast Australia, represented by Victoria and New South Wales, and southwest Australia management units were genetically differentiated from each other and from the New Zealand wintering ground, based on mitochondrial control region (mtDNA) haplotype frequencies[23]

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Discussion

Conclusion