Research Training Program

David Ellenberger
Albertson College of Idaho
Caldwell, Idaho

Richard Thorington, Ph.D.
Supervising Scientist
Department of Vertebrate Zoology
Division of Mammals

"The RTP was the high point of my undergraduate education. It allowed me to successfully complete the transition from student to scientist."

Elevational Cranial Variation in a Wasatch Chipmunk (Tamias minimus) Population of Gunnison County, Colorado.

This research involved morphometric analysis of Least chipmunk skulls ( Tamias minimus ), in order to document phenotypic changes over an elevational gradient. Approximately 300 specimens were aged by tooth-wear analysis to remove juveniles and old aged skulls from this study. Skulls were then measured in the morphometrics lab utilizing a computer program called JAVA. This is a video analysis program that allows measured skulls to be viewed on a video screen with a computer mouse. This is the first time that this method has been used with chipmunk skulls, but it was intriguing in that no cumbersome calipers were used, and the fragile skulls did not need to be excessively handled.

Twelve standard, taxonomic, cranial measurements were used to quantify variation. Specimens were divided into three elevational classes, from a gradient that ran from 8500 ft to 11,500 ft in west-central Colorado (Gunnison, Colorado). Both univariate and multivariate statistics were used to test for significance. Significant morphological differences were found between 7 of 10 cranial characters, and between all populations. Since a recognized pattern of cranial size variation was not found (e.g. low elev., middle, high or high, middle, low), this variation was hypothesized to be random throughout populations and influenced by a plethora of ecological factors. The next logical step in this project would be to collect specimens from an equal environment and elevation to find out whether random variation in skull morphology is due to elevation or simply distance between populations.

This research was supported by a grant from the National Science Foundation Research Experiences for Undergraduates Program ( Award: DIR-9200203).