Meeting Abstract

16.7  Wednesday, Jan. 4  Holocene biogeography of Neotoma: Mandibular geometric morphometrics and implications for climate change STEGNER, M. Allison; FERRER, Elizabeth A.*; UC Berkeley; UC Berkeley

The modern biodiversity crisis has generated great interest in historic species response to climate change. Hundreds of fossil specimens have been recovered from Mescal Cave in San Bernardino County, California, estimated to be from 10,000 to 20,000 y.a. Mescal Cave is located on the edge of the Mojave National Preserve, in an arid desert ecosystem. Neotoma (woodrats) are abundant in this fossil site and are common in the area today; like many other rodents, Neotoma are good indicators of climate. Although some teeth were found, much of the material is comprised of toothless mandibles, and loose teeth of Neotoma are notoriously difficult to identify to species. We used geometric morphometrics on extant Neotoma jaws to (1) determine if we could identify toothless mandibles to species, and (2) determine if food preference, elevation, habitat, or sexual dimorphism correlate with differences in mandible shape. We photographed lateral views of 121 right mandibles from 8 species of Neotoma found in the Western US. A procrustes analysis was conducted on 12 landmarks, and also on a reduced number of landmarks (8) in order to include 20 of the best-preserved fossil mandibles from the site. N. cinerea is distinct from the other species, dominating the right section of the morphospace and over-lapping with one of the fossil morphotypes. The presence of N. cinerea at this site also suggests a cooler ecosystem when the fossils were deposited. This kind of analysis in synergy with analysis of teeth by more traditional comparative methods can provide much information on the identity and ecology of fossil populations. Future studies include more species life history data, landmarks, morphometrics on other skeletal elements, and inclusions of other associated taxa.