Dietary Competition in an Extant Mammalian Guild: Application of a Quantitative Method to Evaluate Reconstructed Niche Overlap in Paleocommunities

Abstract

The evaluation of competition, contingent on the identification of niche similarity, is a challenge in the fossil record. Specifically, a method for quantifying the degree of niche overlap is needed, as niches in paleocommunities can be reconstructed only using ecomorphological characters. In this study, I suggest the use of nonparametric multivariate pairwise comparisons for testing the presence or absence of niche overlap, wherein niches are defined as Hutchinsonian multidimensional hypervolumes. I applied this method to an extant mammalian guild, comprising primates and their dietary competitors, to determine the significance of dimensionality in niche construction and to examine the ability of molar morphology to capture dietary niche overlap. I conducted principal component analyses of eight molar measurements across all members of this guild, and dietary niches were defined by principal component scores. Niche overlap was assessed through the comparison of distances among individuals both within and between niches. To demonstrate the application of the proposed method, I compared dietary niches of 1) seven predefined dietary groups and 2) genera within and across dietary groups using multivariate pairwise comparisons. Results indicated that the typically unexplored higher principal components, or “niche axes,” may be integral to niche separation. As predicted, almost all niches of genera from different dietary groups did not overlap; however, niche overlap among genera within the same dietary category was less than expected. This highlights our need to investigate further the structure of niches within extant guilds to better inform our examination of competition in paleocommunities.