Master's Theses

Document Type

Thesis - campus only access

Date of Award

Spring 2008

Degree Name

Master of Science (MS)

Department

Biology

Advisor

Elmer Finck

Abstract

Short-tailed shrews (Blarina spp.) are characterized by divergent karyotypes and can be distinguished genetically, but they are identical morphologically and similar morphometrically. Possibly as a result of this similarity, distributions of Blarina species tend to be parapatric along well-defined contact zones. The best studies contact zone separates the northern short-tailed shrew (B. brevicauda) and the Elliot’s short tailed shrew (B. hylophaga) in Nebraska. However, an earlier study suggested that these species occur sympatrically where their ranges extend eastward into Iowa and Missouri. To evaluate this situation, 179 Blarina specimens were collected in southwestern Iowa and northwestern Missouri in the summers of 2004 and 2006. Total length and Karyotypes were used for field identification and to help locate the contact zone. Amplified fragment length polymorphism (AFLP) analysis was used to verify species identification at and to investigate the extent of hybridization based on comparison with reference samples from outside the contact zone. Field identification and AFLP analysis grouped 178 of the 179 specimens into either B. brevicauda or B. hylophaga. The unidentified specimen, despite having a B. brevicauda karyotype (2n=50, FN+48), did not group with either species in the AFLP analysis. In addition, the individual had all 4 fixed loci for both species, which indicated it as a potential hybrid. This specimen was trapped with specimens of B. brevicauda and just north of B. hylophaga locality. No locality yielded both species; however, both species were found approximately 3.71 km from each other at the narrowest point. Therefore, the one possible hybrid specimen indicates a low rate of hybridization and a parapatric contact zone between the 2 species.

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© 2008 Cody W. Thompson

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