Meeting Abstract

P2.52  Monday, Jan. 5  Osteology as a predictor of ecology in the Marmotini KEMP, AD*; THORINGTON, RW; Mount Holyoke College; National Museum of Natural History kemp20a@mtholyoke.edu

The 273 species of the Sciuridae are exceptionally diverse in terms of the habitats they utilize and range from entirely terrestrial to strictly arboreal. These differences are reflected in their hand morphology- in arboreal squirrels the fourth digit is longest, while terrestrial squirrels possess a longer third digit. To test the hypothesis that hand morphology shows similar trends in a smaller, less ecologically diverse clade, we examined various proportions of hand bones within the largely terrestrial tribe Marmotini. We took digital x-rays of over 1,500 specimens representing roughly 50 species and digitized the lengths of all metacarpals and phalangeal bones. The ratio of the length of digit four to digit three varies in a way that is loosely tied to ecology at the intergeneric level. For example, the most terrestrial genus, Cynomys, possesses the smallest fourth to third ratio (0.86 +/- 0.02; N=84) while the semi-arboreal Tamias genus possesses the highest (0.97+/- 0.03; N=183). However, hand proportions are not a consistently accurate predictor of ecology at the species level. The morphological data also fit well with the current taxonomic breakdown- the genera and super-generic groups are generally morphologically homogenous and distinct from the rest of the sampling. The recent breakdown of Spermophilus, sensu lato, into eight genera is supported by our findings in that the new genera are more morphologically homogenous than the previous grouping. Fluctuating asymmetry between the bones of the right and left hands was also investigated and found to be within the normal biological range. In summary, while hand proportions can be used to predict ecology as low as the generic level, the lower the taxonomic level the less consistent the trends and the less reliable the predictions.