Letter | Published:

Climate change selects for heterozygosity in a declining fur seal population

Nature volume 511, pages 462465 (24 July 2014) | Download Citation


Global environmental change is expected to alter selection pressures in many biological systems1,2,3, but the long-term molecular and life history data required to quantify changes in selection are rare4. An unusual opportunity is afforded by three decades of individual-based data collected from a declining population of Antarctic fur seals in the South Atlantic. Here, climate change has reduced prey availability and caused a significant decline in seal birth weight. However, the mean age and size of females recruiting into the breeding population are increasing. We show that such females have significantly higher heterozygosity (a measure of within-individual genetic variation) than their non-recruiting siblings and their own mothers. Thus, breeding female heterozygosity has increased by 8.5% per generation over the last two decades. Nonetheless, as heterozygosity is not inherited from mothers to daughters, substantial heterozygote advantage is not transmitted from one generation to the next and the decreasing viability of homozygous individuals causes the population to decline. Our results provide compelling evidence that selection due to climate change is intensifying, with far-reaching consequences for demography as well as phenotypic and genetic variation.

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The authors thank the many fieldworkers who have contributed to data collection over the years. We are also grateful to W. Amos, J. Bascompte, M. Boerner, K. Dasmahapatra, O. Krüger and I. Staniland for advice and feedback on the manuscript, together with T. Coulson for helpful referee comments. This work contributes to the Long Term Monitoring and Survey project and Ecosystems project of the British Antarctic Survey, Natural Environment Research Council, part of the Polar Science for Planet Earth programme. The genetic work was supported by a Marie Curie FP7-Reintegration-Grant within the 7th European Community Framework Programme (PCIG-GA-2011-303618) and a Deutsche Forschungsgemeinschaft standard grant (HO 5122/3-1) awarded to J.I.H.

Author information


  1. British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK

    • Jaume Forcada
  2. Department of Animal Behaviour, University of Bielefeld, Postfach 100131, 33501 Bielefeld, Germany

    • Joseph Ivan Hoffman


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J.F. conceived, designed and conducted the biometric, mark–recapture, demographic and population modelling and subsequent phenotypic and evolutionary demographic analysis; J.I.H. generated and analysed the genetic data. The authors jointly interpreted the results and wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Jaume Forcada.

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