Low levels of genetic differentiation characterize Australian humpback whale (Megaptera novaeangliae) populations

Abstract

Humpback whales undertake long‐distance seasonal migrations between low latitude winter breeding grounds and high latitude summer feeding grounds. We report the first in‐depth population genetic study of the humpback whales that migrate to separate winter breeding grounds along the northwestern and northeastern coasts of Australia, but overlap on summer feeding grounds around Antarctica. Weak but significant differentiation between eastern and western Australia was detected across ten microsatellite loci (FST = 0.005, P = 0.001; DEST = 0.031, P = 0.001, n = 364) and mitochondrial control region sequences (FST = 0.017 and ΦST = 0.069, P = 0.001, n = 364). Bayesian clustering analyses using microsatellite data could not resolve any population structure unless sampling location was provided as a prior. This study supports the emerging evidence that weak genetic differentiation is characteristic among neighboring Southern Hemisphere humpback whale breeding populations. This may be a consequence of relatively high gene flow facilitated by overlapping summer feeding areas in Antarctic waters.

First circumglobal assessment of Southern Hemisphere humpback whale mitochondrial genetic variation and implications for management

“…3 & 4), at levels a magnitude greater than those observed between the substocks of BSB and BSC (Olavarría et al 2007, Rosenbaum et al 2009), confirms the results of previous genetic analyses ( Anderson 2013, Schmitt et al 2014 and resighting data (Dawbin 1966). Gene flow between BSD and BSE1 has been considered to be moderate and bidirectional at the regional level (Anderson 2013); however, at the circumpolar scale, we estimate female-mediated gene flow to be low relative to most other pairwise stock comparisons (Fig.…”

“…8cs4f), indicating that population structure at this scale is driven by maternally directed site fidelity to breeding areas (Mackintosh 1942, Baker & Medrano-Gonzalez 2002, Baker et al 2013. The dominant influence of maternally directed site fidelity at the regional scale has also been confirmed by comparative assessments of bi parentally inherited nuclear markers (Ruegg et al 2013, Schmitt et al 2014, Kershaw et al 2017. Although significant genetic differentiation was observed at the regional scale, patterns of estimated gene flow between breeding stocks were found to be relatively high and asymmetric in all cases (Fig.…”

“…The number of statistically significant comparisons between breeding areas is also comparable, although the magnitude of fixation indices is higher in many instances in the North Pacific (Table 2; Baker et al 2013, their Table 4). The lack of clear evidence of fidelity to feeding areas in the Southern Hemisphere (Schmitt et al 2014, Amaral & Loo et al 2016) and lower magnitudes of genetic differentiation in some instances (Table 2; Baker et al 2013, their …”

“…3 & 4). Multiple lines of corollary evidence support individual movements to broad-scale connectivity between BSA-BSB-BSC-BSD, including photo-identification (Stevick et al 2013), genotypic matching (Pomilla & Rosenbaum 2005), genetic mixed-stock analyses (Schmitt et al 2014), population-level comparisons (Amaral & Loo et al 2016), and acoustical studies of song similarity (Darling & Sousa-Lima 2005, Murray et al 2012.…”

“…Levels of genetic connectivity are little known, however, and a better understanding of relationships between these breeding stocks is needed; nonetheless, some low but significant levels of genetic differentiation have been shown based on mtDNA control region sequences and 10 microsatellite loci (Schmitt et al 2014).…”