The Use of Genetic Markers to Study the Human-Assisted Dispersal of California Black Bears and Old-World Indigenous Dogs

• Main Author: Brown, Sarah Kathleen
• Format: Thesis
• Language: English
• Published: University of California, Davis 2011
• Subjects: Genetics; Ursus arctos
• Online Access: http://pqdtopen.proquest.com/#viewpdf?dispub=3456810

Species distributions are affected by a myriad of factors both natural and human caused, including; geography, climate, habitat, elevation, competition, habitat fragmentation, and habitat destruction, to name a few. Additionally, though less frequently, species distributions are affected by human mediated movements. These actions can be intentional (e.g. salamanders used as bait), or inadvertent (e.g. Zebra mussels in the ballast of a boat), and affect both wild and domesticated species. The effects of such human-mediated movements can be cryptic, unless molecular genetic markers are used to detect breaks or differences in population genetic structure. Here, we use molecular markers to detect potential human-mediated movements of black bears (Chapter 1), domestic dogs in Southeast, Southwest Asia (Chapter 2) and in Africa (Chapter 3). Microsatellite genotypes of 540 black bears (Ursus americanus ) were used to assess the population genetic structure in California (Chapter 1). In addition to revealing population genetic structure throughout the state, two colonization events were detected. One was a human-mediated movement of black bears from Yosemite National Park to the mountains of Southern California, several hundreds of miles away. Historical records corroborate this genetic finding, that 28 black bears were purposefully moved further south. The second event was a natural colonization event from the Southern Sierra Nevada, following an apparent competitive release in the Central Coast, since the time the California Grizzly (Ursus arctos californicus) went extinct. Previous research with mitochondrial DNA and breed dogs has left the origins of the domestic dog, one of man’s closest companions, largely unknown. We used five Y chromosome STR and eleven SNP markers in village dogs from Southwest and Southeast Asia to assess the origins of dogs (Chapter 2). Mitochondrial and Y chromosome markers revealed a longer history of dogs in Southeast Asia. Furthermore, near monophyly between Southwest and Southeast Asia was revealed, with a corresponding Neolithic divergence date (10,000 – 16,000 BP). Southwest and Southeast Asia were found to be centers of diversification, with most modern (European breeds, Australian Dingo) stemming from the Southeast, and African and Southwest Asian breeds showing affinity to Southwest Asia. We then hypothesized that these regions served as regions from which humans, on their migratory routes, spread the domestic dog globally. Like many domesticated species, the dog was introduced to Africa through human migrations. However, from where and when the dog arrived in Africa has remained unclear (Chapter 3). We applied Y chromosomal STR and SNP markers to African village dogs, in direct comparison to Southwest and Southeast Asia. We found African village dogs to derive from the Neolithic Period from both Southwest and Southeast Asia. Migrations of pastoralists from the Middle East likely brought dogs to North Africa in the Neolithic era. Similarly, Austronesian sailors from Southeast Asia are implicated in bringing dog (e.g. Dingoes) to Madagascar and East Africa. This dissertation focused on detecting human mediated movements in a wild mammal, the black bear, and indigenous Old-world dogs. With genetic tools, we were able to reveal otherwise cryptic population genetic structure caused, most likely, by both a modern and ancient movement of black bears and dogs, respectively. The results provided by the black bear study could inform future translocations of black bears, with the purpose of conservation in mind. Finally, additional studies of village dogs need to be performed. Such studies will not only inform how and when dogs spread throughout the world, but how their human companions migrated as well. Studies using commensal animals have shown their importance in elucidating human movements.