UNCORRECTED PROOF Genetic evaluation of the captive breeding program of the Persian wild ass R. K. Nielsen 1 , C. Pertoldi 1,2 & V. Loeschcke 1 1 Department of Ecology and Genetics, Institute of Biological Science, University of Aarhus, Ny Munkegade, Aarhus C, Denmark. 2 Department of Landscape Ecology, National Environmental Research Institute, Kalø, Rønde, Denmark. Keywords conservation; microsatellites; genetic structure; relatedness; effective population size; bottleneck. Correspondence Rikke Kruse Nielsen, Department of Ecology and Genetics, Institute of Biological Science, University of Aarhus, Ny Munkegade, Building 1540, DK-8000 Aarhus C, Denmark. Fax: +45 894 22722 Email: [email protected]Received 11 September 2006; accepted 28 November 2006 doi:10.1111/j.1469-7998.2007.00294.x Abstract During the last century, many species have become endangered and conservation in terms of captive breeding has been crucial for their survival. Classical manage- ment of captive species is based on recorded genealogies. However, if pedigrees are incomplete or inaccurate, it can bias the interpretation of the results obtained from analyses based on such data. In this investigation, 12 microsatellite loci were investigated to evaluate the studbook information of the critically endangered Persian wild ass Equus hemionus onager. Relatedness and inbreeding coefficients were calculated in order to compare the same coefficients estimated from the recorded studbook. A significant correlation between coefficients obtained by microsatellites and the studbook validates the recorded studbook as a reasonable tool for future genetic management. Furthermore, a Bayesian-based method divided the captive onager population into four subgroups that indicate departure from random mating, and thus minor rotation of animals between zoos. Lastly, analyses for inferring past demographic changes revealed a gradual population decline and inbreeding over several generations. This may indicate a low genetic load in captive onagers as a consequence of some degree of purging. Consequently, the risk of inbreeding depression should currently be minimal in the captive breeding program. Therefore, it is recommended to increase the connectivity between the four subgroups of onagers in order to reduce the risk of demographic and genetic stochasticity. This study underlines the importance of using molecular markers to evaluate genetic management of captive breeding programs. Introduction Many species have become endangered in the last century and require active management to ensure their survival (Olech & Perzanowski, 2002; Wisely, McDonald & Buskirk, 2003; Wilson et al., 2005). Genetic variation is a primary component of adaptive evolution, and its loss or reduction will decrease the long-term survival probability of popula- tions. Therefore, maintaining genetic variation has been a major goal in captive breeding programs (Reed & Frank- ham, 2003). Minimizing kinship, which involves choosing individuals with the lowest mean kinship to be parents of subsequent generations, has been a strategy used in various breeding programs to maximize the retention of genetic variation. Minimizing kinship reduces the overall level of relatedness and maximizes founder representation in captive populations, and additionally minimizes the expression of deleterious alleles in inbred animals (Montgomery et al., 1997). Deleterious alleles are expressed through consanguineous mating and through random genetic drift in small popula- tions in which deleterious alleles can be fixed (Hedrick & Kalinowski, 2000). This increases the risk of inbreeding depression in populations, which can reduce individual fitness (Seymour et al., 2001). Removal of deleterious alleles by natural selection (purging) has become increasingly interesting in breeding programs, especially in cases when the number of founders is low and inbreeding unavoidable. However, as deliberate inbreeding to purge deleterious alleles causes a further reduction in fitness, ‘maximum avoidance of inbreeding’ is the currently accepted breeding strategy for eliminating inbreeding depression in captive species (Hedrick & Kalinowski, 2000). In many breeding programs, the complete pedigrees are often unknown. When the ancestry of founders is unspeci- fied, they are assumed to be non-inbred and unrelated, referred to as ‘founder assumption’ (Russello & Amato, 2004). This may lead to an underestimation of relatedness within the population and result in incorrect calculations of mean kinship and inbreeding coefficients that conservation decisions normally rely on (Russello & Amato, 2004). However, Willis (2001) showed that it is more appropriate to underestimate than overestimate relatedness in unpedi- greed populations in order to maintain genetic variation. Application of polymorphic molecular markers has allowed ‘black holes’ in pedigrees to be eliminated and to infer JZO 294 B Dispatch: 19.1.07 Journal: JZO CE: Chandrika Journal Name Manuscript No. Author Received: No. of pages: 9 TE: Rathna/Suresh Journal of Zoology (2007) c 2007 The Authors. Journal compilation c 2007 The Zoological Society of London 1 Journal of Zoology. Print ISSN 0952-8369 JZO 294 (BWUK JZO 294.PDF 19-Jan-07 19:55 196527 Bytes 9 PAGES n operator=Suresh Babu)
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UNCORRECTED PROOF
Genetic evaluation of the captive breeding program of thePersian wild ass
R. K. Nielsen1, C. Pertoldi1,2 & V. Loeschcke1
1 Department of Ecology and Genetics, Institute of Biological Science, University of Aarhus, Ny Munkegade, Aarhus C, Denmark.
2 Department of Landscape Ecology, National Environmental Research Institute, Kalø, Rønde, Denmark.
relatedness of individuals with previously unknown ancestry
(Jones et al., 2002; Wilson et al., 2005).
One species that threatened to go extinct is the Persian
wild ass Equus hemionus onager. Equus hemionus comprises
six subspecies including onagers that are categorized on the
IUCNRed List: The critically endangered Asiatic wild asses
(E. h. onager and Equus hemionus kulan); the Syrian wild ass
Equus hemionus hemippus categorized as extinct; the Indian
wild ass Equus hemionus khur classified as endangered; the
Mongolian wild ass Equus hemionus hemionus; and the Gobi
khulan Equus hemionus luteus as vulnerable (Feh et al., 2002;
IUCN Red List, 2004). In historical time, the distribution
of E. hemionus ranged from Turkey to northern China, and
from Kazakhstan to Saudi Arabia and India. Today,
E. hemionus are found restricted to a few places in China,
Mongolia, Turkmenistan, Kazakhstan, India and Iran (Feh
et al., 2002).
Wild onagers are now restricted to only two geographi-
cally isolated populations in Iran consisting of c. 100 and
500 individuals, respectively (Feh et al., 2002; Tatin et al.,
2003). The major threats to onagers are poaching, but also
habitat destruction, competition from domestic animals and
disturbance during mating and breeding periods are affect-
ing their survival. In 1954, a captive population of onagers
was founded and today it comprises c. 62 individuals in
Europe and worldwide 106 individuals, when the American
captive population is included. Genetic research is essential
to improve the captive breeding program and to plan future
management strategies to secure survival of the species.
This investigation only included individuals from the
European captive population. The main aims were (1) to
determine relatedness and inbreeding coefficients by means
of microsatellites in order to compare the same estimates
calculated from the recorded studbook, (2) to assess the
genetic structure in the captive population of onagers in
order to validate or invalidate random mating in the breed-
ing program, (3) to reconstruct the demographic history of
the onager population in order to examine whether the
observed genetic structure was due to recent demographic
changes and/or a more ancient event. Finally, the informa-
tion revealed was used to discuss the best genetic manage-
ment strategy for the captive onager population.
Methods
Study population and sample collection
Tissue or blood samples were collected from 60 onagers (21
males and 39 females) kept in captivity in 12 different
institutions taking part in the European Endangered Species
breeding Program (EEP) of onagers. The 12 institutions and
number of samples were: Germany: Tierpark Hagenbeck
(n=5), Zoologischer Garten Augsburg (n=5), Wilhelma
Zoologisch-botanischer Garten Stuttgart (n=4) and Zool-
ogischer Garten Koln (n=3); Switzerland: Werner Stamm –
Stiftung zur Erhaltung seltener Einhufer, Oberwil (n=7);
France: Reserve Africaine de Sigean (n=11), Parc Zoologi-
que de Lunaret, Montpellier (n=10) and Parc Zoologique
de Paris (n=1); the Netherlands: Rotterdam Zoo (n=5)
and Zoo Parc Overloon (n=4); and England: Chester Zoo
(n=1) and Whipsnade Wild Animal Park (n=4). The
samples consisted primarily of tissue collected with a biopsy
needle and a Daninject injection rifle (model JM Special).
Only four of the 60 samples were blood samples. Tissue
samples were preserved in 60% alcohol and together with
blood samples stored at �20 1C until use.
Microsatellite genotyping procedure
DNA extraction was performed with the standard CTAB
procedure (Doyle & Doyle, 1987). A total of 12 horse
microsatellite markers were applied to examine the geno-
types of the onagers by cross-species PCR amplification.
The chosen microsatellite markers were from a genotyping
kit normally used for genotyping and parentage testing
of horses (StockMarkss, Applied Systems, http://www.
appliedbiosystems.com). The loci examined were: AHT4,
AHT5, ASB17, ASB23, HMS2, HMS3, HMS6, HMS7,
HTG4, HTG7, HTG10 and VHL20. The PCR reactions
for all 12 markers were carried out in a 6mL reaction
containing 0.6 mL reaction buffer (1.5mM MgCl2), 0.96mLdNTP (1.25mM of A, C, G and T, respectively), 0.5 mLprimer mix (forward/reverse), 0.06mL Taq polymerase (Am-
plitaq Gold Q1, 5UmL�1), topped up with distilled water to 5
and 1mL DNA template added. PCR conditions using a
9700 GeneAmp Q2machine were: an initial denaturation at
95 1C for 10min, followed by 30 cycles of denaturation at
95 1C for 30 s, annealing at 60 1C for 30 s and extension at
72 1C for 60 s. Cycling culminated with a 60-min extension
at 72 1C. The amplified loci were analyzed on an ABI 310
Genetic Analyzer Q3. All alleles were scored manually using the
program GENOTYPER version 2.5.2 (Applied Biosystem Q4).
Population genetic analysis
All microsatellite loci were tested for deviation from Hard-
y–Weinberg expectations (HWE) using the Markov chain
method in FSTAT version 2.9.3.2 (Goudet, 1995); http://
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