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<br />Molecular Ecology (2007)
<br />
<br />Q709
<br />
<br />doi: 1O.1111/j.1365-294X.2007.03399.x
<br />
<br />INVITED REVIEW
<br />Genetic adaptation to captivity in species conservation
<br />programs
<br />
<br />RICHARD FRANKHAM
<br />Key Centre for Biodiversity and Bioresources, Department of Biological Sciences, Macquarie University, NSW 2109, Australia, and
<br />Australian Museum, 6 College Street, Sydney, NSW 2010, Australia
<br />
<br />Abstract
<br />
<br />As wild environments are often inhospitable, many species have to be captive-bred to save
<br />them from extinction. In captivity, species adapt genetically to the captive environment and
<br />these genetic adaptations are overwhelmingly deleterious when populations are returned
<br />to wild environments. I review empirical evidence on (i) the genetic basis of adaptive
<br />changes in captivity, (ii) factors affecting the extent of genetic adaptation to captivity, and
<br />(iii) means for minimizing its deleterious impacts. Genetic adaptation to captivity is primarily
<br />due to rare alleles that in the wild were deleterious and partially recessive. The extent of
<br />adaptation to captivity depends upon selection intensity, genetic diversity, effective popu-
<br />lation size and number of generation in captivity, as predicted by quantitative genetic the-
<br />ory. Minimizing generations in captivity provides a highly effective means for minimizing
<br />genetic adaptation to captivity, but is not a practical option for most animal species. Popu-
<br />lation fragmentation and crossing replicate captive populations provide practical means for
<br />minimizing the deleterious effects of genetic adaptation to captivity upon populations
<br />reintroduced into the wild. Surprisingly, equalization of family sizes reduces the rate of
<br />genetic adaptation, but not the deleterious impacts upon reintroduced populations. Genetic
<br />adaptation to captivity is expected to have major effects on reintroduction success for species
<br />that have spent many generations in captivity. This issue deserves a much higher priority
<br />than it is currently receiving.
<br />
<br />Keywords: captivity, Drosophila, fitness, genetic adaptation, genetic diversity, selection
<br />
<br />Received 26 January 2007; revision accepted 20 April 2007
<br />
<br />Introduction
<br />
<br />Many endangered species require captive breeding to save
<br />them from extinction, as they are incapable of surviving in
<br />inhospitable natural environments due to direct or indirect
<br />human impacts in the form of habitat loss, overexploitation,
<br />pollution, or introduced predators, competitors or diseases
<br />(Millennium Ecosystem Assessment 2005; IUCN 2006).
<br />Many more species are destined to require captive breeding
<br />in the future. For terrestrial vertebrates alone, it has been
<br />estimated that approximately 2000-3000 species may have
<br />to be captive-bred (Souleet al. 1986; Seal 1991; Tudge 1995).
<br />The recent amphibian crisis has approximately doubled
<br />this number (Anonymous 2006; Lacy 2006). There are only
<br />
<br />Correspondence: Emeritus Professor Richard Frankham, Fax:
<br />612-9850-8245; E-mail: rfrankha@els.mq.edu.au
<br />
<br />@ 2007 The Author
<br />Journal compilation @ 2007 Blackwell Publishing Ltd
<br />
<br />spaces for captive breeding of approximately 500 animal
<br />species in zoos and associated institutions (IUDZG/CBSG
<br />& (IUCN/SSC) 1993), plus some additional capacity from
<br />government agencies, but information on spaces in the latter
<br />is not available.
<br />A range of species have been preserved in captivity fol-
<br />lowing extinction in the wild, including 25 animal species,
<br />such as addax (Addax nasomaculatus), Arabian oryx (Oryx
<br />leucoryx), black-footed ferret (Mustela nigripes), California
<br />condor (Gymnogyps califomianus), Pere David's deer (Elap-
<br />hurus davidianus), Przewalski's horse (Equus przewalskii),
<br />scimitar-homed oryx (Oryx dammah), and 11 species ofPar-
<br />tula snail, plus several plants, including the Franklin tree
<br />(Franklinia alatamaha), and Cooke's kok'ia (Kokia cookie)
<br />(Frankham et al. 2002). Further, many threatened species
<br />have captive populations that act as insurance against
<br />extinction in the wild. As of 1989/1990, 245 threatened
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