MOLECULAR SYSTEMATICS AND BIOGEOGRAPHY OF LONG-TAILED SHREWS (INSECTIVORA: SOREX) AND NORTHERN FLYING SQUIRRELS (RODENTIA: GLAUCOMYS)

THESIS

Dr. John Richard Demboski
Dr. Joseph Anthony Cook




ABSTRACT

Insight into phylogenetic and biogeographic relationships among several mammalian taxa in western North America was provided with DNA sequences of two mitochondrial genes (cytochrome b and ND4). Members of two species complexes of long-tailed shrews (genus Sorex) and northern flying squirrels (genus Glaucomys) were examined, and a common theme of responses to past climate change and glacial cycles was evident. Diversification events indicated by the DNA sequences provide new perspectives regarding the deep and shallow history of these taxa. Analysis of seven species of the Sorex cinereus complex (and related species) revealed two major clades within the complex, Northern and Southern. These generally corroborate proposed morphological relationships and correspond to broadly defined habitat affiliations (xeric and mesic), respectively. Within the Northern clade, amphiberingian species represented a monophyletic group suggesting Beringia was a center of endemism. Next, five species of the S. vagrans complex and related species were assessed. Significant molecular variation was revealed that does not correspond to morphological differences within the complex. Two major clades within S. monticolus were observed, a widespread Continental clade (Arizona to Alaska, including S. neomexicanus) and a restricted Coastal clade (Oregon to southeast Alaska, including S. bairdi and S. pacificus). A regional examination of genetic variation in the northern flying squirrel in southeast Alaska was also performed. Results suggested that southern islands in the Alexander Archipelago were the result of recent colonization (founder event). Finally, a comparative phylogeographic analysis of a reduced data set (S. monticolus), a molecular data set for the American Pine Martin, Martes americana, and other published molecular studies were used to reexamine the role of glacial refugia in the biogeography of the north Pacific coast. Previous ideas regarding purported refugia may be overstated and may be the result of limited geographic sampling. This thesis provides new perspectives on processes (e.g., post-glacial colonization) driving mammalian phylogenetic and biogeographic structuring in western North America.


PUBLICATIONS

  • Conroy, C. J., J. R. Demboski, & J. A. Cook 1999. Mammalian biogeography of the Alexander Archipelago of Alaska: a north temperate nested fauna. Journal of Biogeography 26:343-352.

  • Demboski, J. R., B. K. Jacobsen, and J. A. Cook. 1998. Endemism in the Alexander Archipelago: an assessment of genetic variation in flying squirrels (Rodentia: Glaucomys sabrinus). Canadian Journal of Zoology 76:1771-1777.

  • Halanych, K. M, J. R. Demboski, B. J. Van Vuuren, D. R. Klein, & J. A. Cook 1999. Cytochrome b phylogeny of North American hares and jackrabbits (Lepus, Lagomorpha) and the effects of saturation in outgroup taxa. Molecular Phylogenetics and Evolution11 11:213-221.

  • Demboski, J. R. Mammalian Phylogeography of the Alexander Archipelago: A Multitaxa Molecular Study. Global Glimpses 5: 3-4.

  • Demboski, J. R., G. Kirkland, & J. A. Cook (in press). Glaucomys sabrinus. in D. J. Hafner, E. Yensen, and G. Kirkland.(eds) Rodents of conservation concern in North America. IUCN Species Survival Commission, Special Report.

  • Demboski, J.R., K.D. Stone, & J.A. Cook (in press). Further Perspectives on the Haida Gwaii Glacial Refugium Controversy. Evolution.