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UBC Theses and Dissertations

Barn owl genetics in Western North America : diversity, phylogeographic structure, connectivity, and potential for a genetic basis to anticoagulant rodenticide susceptibility Huang, Andrew Cheng-An


The barn owl (Tyto alba) is distributed across much of North America in areas with extensive old-field and grassland habitat. Barn owls are threatened in British Columbia (BC), where the population has declined by 50% in the last 3 decades. I investigated the genetic diversity and phylogeographic patterns of barn owls in western North America, ranging from BC to California, and one eastern population from Pennsylvania. Using 8 polymorphic microsatellite markers (N=126) and ND2 mitochondrial sequences (N=37), I found a high degree of gene flow among the continental sampled regions (global FST = 0.028). The BC mainland population, despite its northwestern geographic peripheral location and ongoing habitat degradation, is not genetically depauperate. However, individuals from Vancouver Island exhibited the lowest genetic diversity of all sampled locations, likely as a result of its insular nature. The low global FST value estimated from this study suggests that their habitat is well connected across North America. Additionally, microsatellite data revealed that the Santa Barbara Island population showed genetic divergence from its continental counterpart. Mitochondrial data, however, demonstrated that this island population is not monophyletic, and thus cannot be designated as an Evolutionarily Significant Unit. Anticoagulant rodenticides (ARs) are pesticides widely employed worldwide to reduce rodent infestations. Avian predators that hunt extensively for small rodents are at risk of secondary poisoning. AR causes internal bleeding by disrupting the Vitamin K cycle, which is essential for blood clotting. Tolerance to AR appears to be highly variable among individuals for any given avian species. I examined whether single point mutations in the CYP2C45 gene are associated with increased or decreased susceptibility to AR in barn owls. I identified a position that showed a heterozygous C/T in one particular individual with low tolerance, whereas all other individuals exhibited a homozygous C. This transversion results in an amino acid substitution from alanine to valine at a conserved region that could potentially have deleterious effects on the function of and structure the protein. However, it is also possible that the CYP2C45 enzyme was not severely affected due to this amino acid change since both alanine and valine are non-polar/hydrophobic.

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