A Multivariate Analysis of Systematic Relationships among Populations of the Short-Tailed Shrew (Genus Blarina) in Nebraska

Abstract

Genoways, H. H., and J. R. Choate (Museum of Natural History, The Univ. Kansas, Lawrence, Kansas 66044. Present addresses: The Museum, Texas Tech University, Lubbock, Texas 79409 and Division of Biological Sciences and Agriculture, Fort Hays Kansas State College, Hays, Kansas 67601). 1972. A multivariate analysis of systematic relationships among populations of the short-tailed shrew (genus Blarina) in Nebraska. Syst. Zool., 21:106-116.The genus Blarina (Mammalia: Soricidae) is represented in Nebraska by two well-differentiated, geographically exclusive phena that generally have been regarded as subspecies. Field studies conducted along their zone of contact resulted in the collection of representatives of both phena at each of five localities. Cluster analysis of distance matrix readily separated reference samples of the phena as well as test samples from near the zone of contact. A three-dimensional projection of the specimens onto their first three principal components, together with a discriminant function analysis, served further to elucidate the degree of differentiation among the phena and to confirm that their characteristic differences are maintained even where they occur sympatrically. The latter technique also indicated that one specimen not singled out by other analyses might be a natural hybrid, but none of the analyses provided even the slightest evidence for panmictic intergradation.. The possibility that the phena represent the ends of a circularly intergrading species is considered, as is the possibility that the phena are distinct, biological species. Two means of speciation, one classical and the other involving formation of stasipatric species, are discussed. [Multivariate analysis; Systematics; Blarina; Populations; Hybridization.] Shrews of the Nearctic genus Blarina (Mammalia: Soricidae) historically have been classified as representatives of two species-one, B. brevicauda (Say), wideranging and geographically variable, and the other, B. telmalestes Merriam, restricted to the Dismal Swamp region of coastal Virginia and North Carolina and of uncertain taxonomic status (see Hall and Kelson, 1959:53, 55). This arrangement stems primarily from Merriam's (1895) revision of Blarina and Bole and Moulthrop's (1942) later synopsis of the genus. As presently understood, the ranges of four nominal subspecies-B. b. brevicauda, B. b. kirtlandi Bole and Moulthrop, B. b. churchi Bole and Moulthrop, and B. b. talpoides (Gapper)-all characterized by large external and cranial dimensions, geographically abut the range of B. b. carolinensis (Bachman), which is characterized by much smaller size. This zone of contact extends from Nebraska to Maryland and effectively divides the range of the species into two parts-a northern segment occupied by comparatively large shrews and a southern segment occupied by smaller shrews (Hall and Kelson, 1959: 53). Jones and Findley (1954), and subsequently Jones and Glass (1960), studied the geographic relationships of taxa of Blarina west of the Mississippi River. They demonstrated the presence of a clinal increase in size from the Gulf coastal region to northern Nebraska. The cline exhibited a significant step in southern Nebraska, which was considered to constitute the line of demarcation between B. b. brevicauda and B. b. carolinensis. The magnitude of the step is such that Nebraskan specimens of B. brevicauda invariably can be assigned to subspecies without regard for location of capture; external and cranial dimensions in B. b. brevicauda are substantially greater than (and seldom over-