Morphological Variation between Pleistocene and Recent Samples of Cryptotis (Insectivora: Soricidae) from the Yucatan Peninsula, Mexico

Abstract

Fossil mandibles of soricids recovered from cave sediments in Actun Spukil, Yucatan, Mexico, are similar in most physical characteristics to those of modern Cryptotis mayensis from the Yucatan Peninsula and Guerrero. However, principal-components analysis reveals differences in shape between the modern and fossil populations. This morphological change correlates temporally with climatic and environmental instability during the Pleistocene-Holocene transition. Despite this correlation, the morphological change seen in C. mayensis may not represent either phenetic flexibility or selective adaptation to a new environment because the two modern populations inhabit distinct, geographically isolated environments, and, yet, are morphologically inseparable. It is most likely that morphological differences between fossil and modern samples represent a different microevolutionary process (i.e., mutation or genetic drift) and that differentiation preceded geographical separation of the two modern populations.