Systematics of Locally Endemic Populations of Short-tailed Shrews, Blarina (Insectivora: Soricidae), in Bastrop and Aransas Counties, Texas

Abstract

Two isolated populations of short-tailed shrews exist in Texas; one in the Lost Pines region including Bastrop County and one at Aransas National Wildlife Refuge on the Gulf Coast. Fossil evidence suggests that two species of short-tailed shrew once were widespread in central Texas; Blarina hylophaga now inhabits Nebraska, Kansas, Oklahoma and Montague County, Texas, and Blarina carolinensis inhabits the Southeastern United States through the eastern third of Texas. Molecular and morphological methods were used to determine the systematic status of the two disjunct Texas populations. In morphological analyses, nine cranial measurements were analyzed using principal components analysis (PCA), and it was determined that Texas specimens were intermediate between the smaller B. carolinensis and larger B. hylophaga. Multivariate analysis of variance (MANOVA) determined that the nine cranial measures could be used to differentiate among three groups: B. carolinensis, B. hylophaga, and Texas Blarina (Pillai’s Trace= 1.23, P< 0.001). Phylogenetic analyses of the mitochondrial cytochrome b gene for three specimens from Aransas County and 20 specimens from Bastrop County revealed that the Texas groups are sister to B. hylophaga from Kansas and Nebraska. Based on the available evidence, subspecies status is warranted for the Texas short-tailed shrews. Because the Aransas population previously had been designated Blarina hylophaga plumbea, it is recommended that this subspecies now include the Bastrop County population as well. Biogeographic hypotheses are examined with respect to Texas as a Pleistocene refugium and these disjunct populations as relictual isolates. Areas in Texas inhabited by short-tailed shrews may harbor other locally endemic taxa; these areas should be examined closely as they may represent high value habitat for conservation efforts.