Paleoecological Significance of the Short-Tailed Shrew (Blarina), with a Systematic Discussion of Blarina ozarkensis

Abstract

The parapatric distributions of Recent Blarina brevicauda brevicauda, B. b. kirtlandi, and B. b. carolinensis correspond to the subhumid microthermal, humid microthermal, and humid mesothermal climatic regions. Three late Pleistocene populations of Blarina can be equated with the extant “subspecies” B. b. brevicauda, B. b. kirtlandi, and B. b. carolinensis by means of statistical analysis of mandibular parameters. All three ecotypes are found together, distinct and sympatric, in the Pleistocene deposits of Cumberland, New Paris No. 4, and Peccary Caves, whereas Meyer Cave, Crankshaft Pit, Natural Chimneys, and Welsh Cave local faunas contain two distinct phena. Coexistence of these phena in the same deposit without apparent interbreeding suggests a specific rather than subspecific relationship. Sympatry of these phena during the Pleistocene suggests that a more equable climate existed during glacial time than at present and that sympatric phena of Blarina coexisted in partitioned niches that presently are not defined. Post-glacial continental climates subsequently divided the three phena into their existing parapatric distributions. Blarina brevicauda fossilis is synonymized with B. b, brevicauda. Blarina ozarkensis, an extinct species from the Conard Fissure, is distinguished from other species of Blarina by (1) the absence of the lingual accessory cone posterior to the protoconid on the first lower unicuspid of extant species; (2) the proportionally larger and more bulbous cingula of the third and fourth upper unicuspids, the second lower unicuspid, and the lower molars; (3) its reduced fifth upper unicuspid; (4) its reduced talonid of M₃. The Conard Fissure population of B. ozarkensis is more variable than any modern population of Blarina examined.