Vol. 42 No. 1, 2003

Dental Variation among Asian Colobines (Nonhuman Primates): Phylogenetic Similarities or Functional Correspondence?

Ruliang Pan^1,2,* and Charles Oxnard¹

¹School of Anatomy and Human Biology, University of Western Australia, Crawley, Perth, WA 6009, Australia
²Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, China

Ruliang Pan and Charles Oxnard (2003) In order to reveal variations among Asian colobines and to test whether the resemblance in dental structure among them is mainly associated with similarities in phylogeny or functional adaptation, teeth of 184 specimens from 15 Asian colobine species were measured and studied by performing bivariate (allometry) and multivariate (principal components) analyses. Results indicate that each tooth shows a significant close relationship with body size. Low negative and positive allometric scales for incisors and molars (M2s and M3s), respectively, are each considered to be related to special dental modifications for folivorous preference of colobines. Sexual dimorphism in canine eruption reported by Harvati (2000) is further considered to be associated with differences in growth trajectories (allometric pattern) between the 2 sexes. The relationships among the 6 genera of Asian colobines found greatly differ from those proposed in other studies. Four groups were detected: 1) Rhinopithecus, 2) Semnopithecus, 3) Trachypithecus, and 4) Nasalis, Pygathrix, and Presbytis. These separations were mainly determined by differences in molar structure. Molar sizes of the former 2 groups are larger than those of the latter 2 groups. This scenario is considered to be relevant to differences in their dietary selection and ecological niche adaptation, and to variations in latitude geographically. Snub-nosed monkeys (Rhinopithecus), especially those in China, are specialized colobines in many respects. The findings also imply that the geographical landscape and vegetation, being greatly shaped by tectonic modification and glaciation in Asia over the last 2 million years, have already forced Asian colobine monkeys to adapt to remarkably different diets and niches. The study of the colobines can thus provide an ideal model for interpreting the relationship between natural selection and adaptation.

Key words: Asian colobines, Dental variation, Functional adaptation, Geographic distribution, Dietary preference.

*Correspondence: Tel: 61-8-93803283. Fax: 61-8-93801051. E-mail: pruliang@anhb.uwa.edu.au