Date of Award

8-2002

Level of Access

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Wildlife Ecology and Wildlife Conservation

Advisor

Judith Rhymer

Second Committee Member

Frederick Servello

Third Committee Member

William E. Glanz

Abstract

The Penobscot meadow vole (Microtus pennsylvanicus shattucki) (PMV) is an insular subspecies of meadow vole (M. pennsylvanicus) inhabiting the islands of North Haven, Islesboro, and Tumbledown Dick in Penobscot Bay, Maine. It is one in a suite of island meadow vole subspecies which has been described from southern New England through eastern Canada. The subspecific recognition of M. p. shattucki, along with the others in this group, was solely based on a univariate analysis of a few morphological characters, which has fostered debate about the validity of the subspecies. Despite this uncertainty, the taxonomy is widely applied and conservation issues have been raised: M. p. shattucki was listed as a Species of Special Concern in the state of Maine when that listing was in use. The U.S. Fish and Wildlife Service did not propose M. p. shattucki for listing at the federal level because of lack of information on the subspecies. Concern about losing unique island taxa such as the PMV is warranted because another subspecies in this group, M. p. nesophilus, which was found on Gull Island, NY has already gone extinct. To clarify the taxonomic status of M. p. shatrucki for conservation purposes, I used multivariate discriminant function analysis (DFA) to examine historical and recent morphological differences in 14 cranial and three external characters. Historical differentiation was quantified through DFA of museum specimens. To study recent morphological differentiation, e x h t populations were sampled from the type localities of M. p. shatrucki (Islesboro and North Haven), as well as populations of M. p. pennsylvunicus on another island in Penobscot Bay (Isle au Haut), the closest mainland coastal populations to Islesboro and North Haven (Northport and Rockport, respectively), and an inland mainland site, Orono. To further clarify distinctiveness of M. p. shatfucki, genetic differentiation of extant populations was investigated by genotyping seven microsatellite loci and doing a phylogenetic analysis of the mitochondria1 DNA control region. M. p. shattucki is morphologically and genetically distinct from the mainland nominant populations of M p. pennsylvunicus. Museum specimens were classified correctly at a 90% rate, while extant specimens had an 80% correct classification rate. Overall, M p. shottucki individuals are larger in cranial and extemal morphology than mainland M. p. pennsylvanicus. Mitochondria1 DNA analysis indicated that M. p. shaftucki formed a monophyletic lineage. Microsatellite analysis supported this result with the highest genetic distances being between M. p. shattuck and populations of M p. pennsylvunicus. All populations of meadow voles appeared to have high levels of inbreeding, heterozygote deficiency and departm hm Hardy-Weinberg equilibrium. This is most likely due to the social structure of meadow vole populations and/or non-amplifying (null) alleles that contribute to high estimates of homozygosity. The morphological and genetic data in this study support the subspecific status of M. p. shattucki. In terms of uniqueness, or exchangeability (whether an individual of one population can be placed in the second population), M. p. shattucki is historically and recently distinct both morphologically and genetically and while this evidence is suggestive of M. p. shattucki as an Evolutionary Significant Unit (ESU), additional study of M. p. shattucki is warranted before this conclusion can be made. The naming of a population as an ESU has possible political ramifications that need to be considered in conjunction with the biological data.

Share