Small, isolated populations can be at risk from genetic threats. In particular, inbreeding depression can threaten population viability, however the contribution of large-effect alleles to inbreeding depression in natural populations is largely unknown. Quantification of genetic threats requires estimation of the effective population size (Ne), which can be challenging given age-structure. Further, identification of large-effect alleles and estimation of Ne requires knowledge of a population's genetic mating system, which can itself be difficult to determine in populations with low genetic diversity. In this study, I quantified genetic threats to the small, isolated Scottish population of red-billed choughs (Pyrrhocorax pyrrhocorax), which is of high conservation concern, heightened by the recent occurrence of lethal blindness in nestlings. I first estimated extra-pair parentage rates to be low in Scottish choughs (~5% extra-pair offspring). I quantified inheritance patterns of blindness and found that the pattern of occurrence matched that expected for a single-locus recessive allele. Heterozygous carriers of the blindness allele are likely to be widely distributed in the population, limiting management options. Further, affected families had relatively larger broods than unaffected families, suggesting the blindness allele could persist in the population. Using a candidate gene approach, no consistent polymorphisms were found between blind and non-blind individuals in candidate gene amplicons and therefore a diagnostic marker for blindness could not be developed. I used demographic and genetic data to estimate Ne for Scottish choughs. Both demographic and genetic estimators suggested Ne is critically small (Ne≈30), such that future rates of loss of genetic variation will be high. The small Ne was largely due to high demographic variance, with high contributions to demographic variance from younger females and older males. Overall, this study adds to our understanding of genetic threats to small, wild populations and can thus inform management of threatened populations.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:698856 |
| Date | January 2016 |
| Creators | Trask, Amanda E. |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=230970 |
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