Marsden, Clare Diana
Evolutionary & ecological genetics of African wild dogs.
PhD thesis, University of Glasgow.
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Loss of adaptive variation arising from population declines and fragmentation is a
primary concern in conservation. However, many conservation programmes assess only neutral genetic variation. Whilst assessments of neutral variation are informative about demographic history, inbreeding and genetic structure, they do not provide information on adaptive variation. The Major Histocompatibility Complex (MHC) is a group of genes that has been extensively studied and are known to be important in effective immune responses. Given the threat posed by infectious diseases to wildlife, the MHC is increasingly being assessed in endangered species.
African wild dogs (Lycaon pictus, hereafter wild dog) are an endangered canid that
has suffered extensive declines in the wild and now persist as small and fragmented
populations totalling less than 8,000 individuals. The purpose of this study was to assess how neutral and MHC marker data genetic data can be used to assist conservation of this species. As such, I assessed sequence diversity across ~300bp of mitochondrial DNA, patterns of polymorphism and heterozygosity at 10 neutral microsatellite loci, compared to sequence variation and haplotype diversity at the MHC.
Wild dogs were found to be genetically depauperate at the MHC compared to
other canids. Patterns of variation indicate a historical loss of variation, followed by more recent diversification. However, it was also shown that evolutionary history contributes to differences in diversity between species. The spatial and temporal structure of MHC diversity was found to be largely correlated with neutral markers, which may suggest that selection is unable to counter strong genetic drift in such small populations. Overall, genetic diversity of both neutral and MHC markers appeared to be largely determined by demographic stability and size of populations. Habitat fragmentation and loss were associated with genetic isolation of wild dog populations, which showed strong structuring.
However, the barriers to, or corridors for, dispersal of wild dogs were not always clear. The European captive breeding population was found to have comparable diversity metrics to wild populations, and was found to contain a large proportion of the MHC variation from the Southern African populations from which they were originally sourced. Careful genetic management is now required to correct the severe over- and underrepresentation of some founder lineages in this captive population to reduce inbreeding and loss of genetic variation.
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