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Admixture and reproductive skew shape the conservation value of ex situ populations of the Critically Endangered eastern black rhino
  • +7
  • Franziska Elsner-Gearing,
  • Petra Kretzschmar,
  • Susanne Shultz,
  • Mark Pilgrim,
  • Deborah Dawson,
  • Gavin Horsburgh,
  • Jìrì Hruby,
  • Jane Hopper,
  • Tony King,
  • Catherine Walton
Franziska Elsner-Gearing
The University of Manchester Faculty of Science and Engineering

Corresponding Author:[email protected]

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Petra Kretzschmar
Leibniz Institute for Zoo and Wildlife Research
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Susanne Shultz
The University of Manchester Faculty of Science and Engineering
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Mark Pilgrim
North of England Zoological Society
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Deborah Dawson
NERC Environmental Omics Facility (NEOF), University of Sheffield
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Gavin Horsburgh
NERC Environmental Omics Facility (NEOF), University of Sheffield
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Jìrì Hruby
Zoo Dvůr Králové
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Jane Hopper
Aspinall Foundation
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Tony King
Aspinall Foundation
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Catherine Walton
The University of Manchester Faculty of Science and Engineering
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Abstract

Small populations of endangered species risk losing already eroded genetic diversity, important for adaptive potential, through the effects of genetic drift. The magnitude of drift can be mitigated by maximising the effective population size, as is the goal of genetic management strategies. Different mating systems, specifically those leading to reproductive skew, exacerbate genetic drift by distorting contributions. In the absence of an active management strategy, reproductive skew will have long-term effects on the genetic composition of a population, particularly where admixture is present. Here we examine the contrasting effects of conservation management strategies in two ex situ populations of the Critically Endangered eastern black rhino (Diceros bicornis michaeli), one managed as a semi-wild population in South Africa (SAx), and one managed under a mean-kinship breeding strategy in European zoos. We use molecular data to reconstruct pedigrees for both populations and validate the method using the zoo studbook. Using the reconstructed pedigree and studbook we show there is male sex-specific skew in both populations. However, the zoo’s mean-kinship breeding strategy effectively reduces reproductive skew in comparison to a semi-wild population with little genetic management. We also show that strong male reproductive skew in SAx has resulted in extensive admixture, which may require a re-evaluation of the population’s original intended role in the black rhino meta-population. With a high potential for admixture in many ex situ populations of endangered species, molecular and pedigree data remain vital tools for populations needing to balance drift and selection.