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Genetic consequences of isolation: island tammar wallaby (Macropus eugenii) populations and the conservation of threatened species

Abstract

Isolation and restricted gene flow can lead to genetic deterioration in populations. Populations of many species are increasingly becoming fragmented due to human impacts and active management is required to prevent further extinctions. Islands provide an ideal location to protect species from many mainland threatening processes such as habitat loss and fragmentation, disease and competition/predation from introduced species. However their isolation and small population size renders them prone to loss of genetic diversity and to inbreeding. This study examined two endemic and one introduced population of tammar wallaby (Macropus eugenii) on three islands in the Houtman Abrolhos Archipelago, Western Australia: East Wallabi (EWI), West Wallabi (WWI) and North Islands (NI). Nine autosomal and four Y-linked microsatellite loci, and sequence data from the mitochondrial DNA (mtDNA) control region were used to examine the impact of long-term isolation (EWI and WWI) and small founder size (NI) on genetic diversity and inbreeding. This study found all three populations had low genetic diversity, high levels of effective inbreeding and increased frequency of morphological abnormalities. Isolation has also led to significant inter-population genetic differentiation. These results highlight the importance of incorporating genetic management strategies when utilising islands as refuges for declining mainland populations.

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Acknowledgments

This research was funded by an ARC Linkage Grant (LP0560344) and forms part of the Koala and Kangaroo Contraception Program. Special thanks to Neil Thomas, Brent Johnson, Peter Orell from DEC (WA) for field assistance; John Fitzharding; The Rat Patrol; Lee Ann Rollins (UNSW) and Greg Eldridge. All experimental work carried out was approved by the Department of Environment and Conservation, Western Australia under the approval numbers 10/2005 and 40/2007.

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Correspondence to Emily J. Miller.

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Miller, E.J., Eldridge, M.D.B., Morris, K.D. et al. Genetic consequences of isolation: island tammar wallaby (Macropus eugenii) populations and the conservation of threatened species. Conserv Genet 12, 1619–1631 (2011). https://doi.org/10.1007/s10592-011-0265-2

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Keywords

  • Conservation genetics
  • Population structure
  • Genetic differentiation
  • Genetic diversity
  • Inbreeding
  • Microsatellite