The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

Dental metric variation in two species of howler monkeys and their hybrids


1Department of Anthropology, University of Texas at San Antonio, 2Instituto de Neuroetologia, Universidad Veracruzana, 3Museum of Zoology, Department of Ecology and Evolutionary Biology, University of Michigan

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Understanding dental variation in extant primates serves to inform questions about what constitute adaptive species-specific differences as well what degree of variation is expected within and between species. Dentition is known to have a strong heritable component; therefore, differences across taxa are suggestive of selection, often associated with feeding behavior. Here we investigate postcanine dental metric variation among two species of howler monkeys and their hybrids. Alouatta palliata and A. pigra are considered to be distinct species based on various lines of evidence, including morphological, genetic, and behavioral differences. Dental data from parental and hybrid individuals allowed for the unique opportunity to address within and between species variation. Measurements were obtained from casts of wild captured individuals as well as museum specimens. In particular, we measured the maximum mesiodistal and buccolingual dimensions of the right maxillary P1 thru M3. Measurements on hybrid individuals only came from wild captured individuals, where hybrid status was determined using a combination of diagnostic genetic markers, including mitochondrial, Y-chromosome, and autosomal microsatellite data. Results indicate that the mesiodistal dimensions of some teeth for both males and females on average discriminated among the parent species. Hybrid individual tooth size resembled that of the parental individuals with which they share most of their alleles and intermediate hybrids overlapped with both parent species. Some intermediate hybrids exhibited values well outside the ranges of all other individuals. The implications of these differences for species recognition in the fossil record as well as selection on tooth size are explored.

This study was supported by PROMEP-UVER Mexico, Universidad Veracruzana, OVPR at the University of Michigan, and NSF grants DEB-0640519 and BCS-0962807 for L. Cort├ęs-Ortiz, and by the Museum of Zoology, Department of Anthropology, and Rackham Graduate School at the University of Michigan for M. Kelaita.

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