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A global cline in a colour polymorphism suggests a limited contribution of gene flow towards the recovery of a heavily exploited marine mammal.

Hoffman, J. I. and Bauer, E. and Paijmans, A. J. and Humble, E. and Beckmann, L. M. and Kubetschek, C. and Christaller, F. and Kröcker, N. and Fuchs, B. and Moreras, A. and Shihlomule, Y. D. and Bester, M. N. and Cleary, A. C. and De Bruyn, P. J. N. and Forcada, J. and Goebel, M. E. and Goldsworthy, S. D. and Guinet, C. and Hoelzel, A. R. and Lydersen, C. and Kovacs, K. M. and Lowther, A. (2018) 'A global cline in a colour polymorphism suggests a limited contribution of gene flow towards the recovery of a heavily exploited marine mammal.', Royal Society open science., 5 (10). p. 181227.


Evaluating how populations are connected by migration is important for understanding species resilience because gene flow can facilitate recovery from demographic declines. We therefore investigated the extent to which migration may have contributed to the global recovery of the Antarctic fur seal (Arctocephalus gazella), a circumpolar distributed marine mammal that was brought to the brink of extinction by the sealing industry in the eighteenth and nineteenth centuries. It is widely believed that animals emigrating from South Georgia, where a relict population escaped sealing, contributed to the re-establishment of formerly occupied breeding colonies across the geographical range of the species. To investigate this, we interrogated a genetic polymorphism (S291F) in the melanocortin 1 receptor gene, which is responsible for a cream-coloured phenotype that is relatively abundant at South Georgia and which appears to have recently spread to localities as far afield as Marion Island in the sub-Antarctic Indian Ocean. By sequencing a short region of this gene in 1492 pups from eight breeding colonies, we showed that S291F frequency rapidly declines with increasing geographical distance from South Georgia, consistent with locally restricted gene flow from South Georgia mainly to the South Shetland Islands and Bouvetøya. The S291F allele was not detected farther afield, suggesting that although emigrants from South Georgia may have been locally important, they are unlikely to have played a major role in the recovery of geographically more distant populations.

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Publisher statement:© 2018 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License, which permits unrestricted use, provided the original author and source are credited.
Date accepted:18 September 2018
Date deposited:06 December 2018
Date of first online publication:01 October 2018
Date first made open access:06 December 2018

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