The distribution of short-tailed shrews, Blarina carolinensis and B. brevicauda, demonstrates contiguous allopatry in peninsular situations in the Coastal Plain of Virginia, and in other areas. The distribution of these two species is unusual in that they do not exhibit syntopy except within a narrow corridor along the borders of their ranges. Interestingly, along the Coastal Plain of Virginia, B. carolinensis is generally found only at the distal ends of the peninsular areas, existing as local populations that appear to be isolated from each other and from the primary population that exists in south-central Virginia. It is thought that the disjunct distribution of B. carolinensis populations results from the unique physiography of Chesapeake Bay, namely peninsular water barriers, and that the intervening distribution of its congener, B. brevicuada, should promote morphometric and population differentiation due to isolation. Whether populations of B. carolinensis along the Coastal Plain of Virginia are truly isolated (and possibly morphologically and/or genetically dissimilar to the continuous southeastern Unites States distribution) is unknown. I examined cranial morphometrics and molecular genetic characters (mitochondrial DNA control region and exon-primed intron-crossing nuclear DNA, EPIC) from peninsular populations of B. carolinensis and compared them to shrews of the mainland population to address this question. The sources of specimens were shrews ensnared in discarded bottles along roadsides, museum skins, and specimens frozen in alcohol. Principle coordinate analyses did not indicate a correlation between cranial morphology and genetic structuring of the populations. MANOVA analyses correlate distinct geographic regions with variation of four cranial measurements related to length. A 492 base pair region of the mitochondrial control region was obtained for many specimens and found to be polymorphic resulting in 27 unique haplotypes evenly partitioned across populations reflecting low levels of differentiation. Nuclear DNA markers were not found to exhibit repeatable amplification and therefore were not useful. Genetic variance detected among populations ranged from ΦPT = 0.001 to 0.045. The effective number of migrants (Nem), as estimated from the standard relationship with ФPT values, indicated panmixia. Both sets of observations indicated that physiography and B. brevicauda are not as severe factors limiting migration among the Coastal Plain populations of B. carolinensis as was thought.
| Identifer | oai:union.ndltd.org:vcu.edu/oai:scholarscompass.vcu.edu:etd-1290 |
| Date | 01 January 2011 |
| Creators | Kersten, Devon |
| Publisher | VCU Scholars Compass |
| Source Sets | Virginia Commonwealth University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | © The Author |
Page generated in 0.0018 seconds