• Geographic distribution of genetic variation in ten species of North American forest birds: island endemism and transcontinental ranges

      Topp, Carrie M. (2008-05)
      Comparative genetic studies of geographically co-occurring species can lend insight into current and historic relationships among populations and species. This enables examination of similarities and differences among species and provides information about historic processes leading to current genetic and geographic distributions. I used this approach to study two different types of avian co-distribution: island endemism and transcontinental ranges. The Queen Charlotte Islands (QCI), Canada, have many endemic subspecies; historically it may have been a glacial refugium. I used genetic analyses to determine subspecies uniqueness and to identify units of conservation for five species, four with endemic QCI subspecies. I found that QCI populations were genetically differentiated from mainland populations, although each species had a different isolation history, and that QCI is an important area for avian conservation and management. East-to-west genetic splits across North America are seen in vertebrates and may be the result of Pleistocene glacial cycles. Five migratory thrushes successfully colonized northern North America. They have overlapping transcontinental ranges and similar ecological niches in woodland communities. I used genetics to determine how these thrushes established continent-wide ranges. Despite their ecological and distributional similarities these five thrush species had different patterns of colonization across North America.
    • Speciation genetics in two pairs of high-latitude, migratory bird taxa

      Withrow, Jack J.; Winker, Kevin; Hundertmark, Kris; Takebayashi, Naoki (2013-05)
      I investigated and characterized the divergence of two pairs of putatively young, high-latitude, migratory bird taxa with data from mitochondria) and nuclear DNA. I chose pairs exhibiting natural history attributes suggesting divergence scenarios that probably did not involve strict allopatry. First, I examined Pluvialis dominica and P. fulva, migratory plover species with a largely parapatric breeding range in Beringia. Secondly, I examined Aegolius acadicus acadicus and A. a. brooksi, a subspecies pair of owls where one subspecies (brooksi) is endemic to Haida Gwaii, Canada, a location where subspecies acadicus occurs during migration, resulting in cyclic sympatry (heteropatry) with brooksi. Using mtDNA sequence data and AFLPs I made inferences about population parameters, inferred the likely number of populations, and sought evidence of selection. Gene flow was very low in both pairs. The plovers are much older than was anticipated (1.8 Mybp), although hybridization does occur. Evidence for parapatric or speciation with gene flow scenarios was not found in the plovers, perhaps because the speciation event occurred far in the past. The owl's divergence date was relatively young (~16,000 ybp). Some evidence was found suggesting that heteropatric divergence contributed to the owl's differentiation, although the process could also have reinforced differences acquired largely in allopatry.