Using left-right asymmetry to estimate non-genetic variation in vole teeth (Arvicolinae, Muridae, Rodentia)

P. David Polly, Laura Killick, and Mark Ruddy

Abstract

Arvicoline rodents, which are important index fossils for late Cenozoic terrestrial deposits, are often said to have the greatest amount of dental variation of any mammal. If true, if that variation is environmental (ecophenotypic) in nature, and if variation within species is greater than between species, then the scientific basis of taxonomic identifications of these common fossils is questionable. We used left-right asymmetry in the shape of the lower first molar of four arvicoline species as a measure of the environmental (non-genetic) component of variance within vole species. Using both Eigenshape and semilandmark (Procrustes) analysis, we found that environmental variance accounted for about 10%-30% of within-species variance, suggesting heritabilities (h²) of 0.71 to 0.89 for molar tooth shape. However, the magnitude of this non-genetic variance was considerably smaller than that found between individuals belonging to the same species and nearly an order of magnitude smaller than differences between species. It is unlikely that environmental variance or within-species variation regularly confound species-level taxonomic identifications of vole teeth.

P. David Polly, Department of Geological Sciences, Indiana University,
1001 E. 10th Street, Bloomington, IN 47401 USA
Laura Killick, Department of Anthropology, University of Durham, 43 Old Elvet, Durham DH1 3HN, United Kingdom
Mark Ruddy, Department of Geography, Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom

KEY WORDS: ecomorphology; fluctuating asymmetry; geometric morphometrics; morphological evolution; teeth

PE Article Number: 14.3.41A
Copyright: Palaeontological Association November 2011
Submission: 15 June 2007. Acceptance: 1 August 2011