Publication Date


Document Type


First Advisor

Meserve, Peter L.||Parrish, J. Michael, 1953-

Degree Name

Ph.D. (Doctor of Philosophy)

Legacy Department

Department of Biological Sciences




I evaluated several sources of phenotypic variation in the crania of New World flying squirrels (Glaucomys sabrinus and G. volans). I measured 20 craniometric characters on large (N = 1,901), range-wide samples and used statistical techniques common to other studies of craniometric variation in mammals. Results from MANOVA and subsequent post hoc analyses suggested there were differences in patterns of sexual size dimorphism in both Glaucomys sabrinus and G. volans. Females were larger than males in most characters, and the degree of dimorphism was greater in G. volans than in G. sabrinus. These results were evaluated in the context of reproductive and locomotor constraints, ecological factors, and social interactions. Principal components analyses (PCAs) and comparisons of variance-covariance matrices indicated allometric trajectories were not different between sexes but were different between species. Evidence of intraspecific allometric variation and interspecific differences in allometric trajectory may have implications for future studies that assume common patterns of isometric variation among groups. Multiple group PCAs were used to construct size/allometry-free "shapes" for individuals across sexes and species. Geographic distributions of populations in shape space were consistent with previous studies of variation in DNA sequences but contrasted with other studies of phenotypic variation. Unique shape values extracted for several populations suggest that the Pleistocene-Holocene history of the genus is more complicated than proposed previously. Cranial proportions were evaluated separately for jaws and skulls across sexes and species. Latitude was not correlated with jaw proportions in either sex but was correlated positively with skull proportions in both sexes of Glaucomys volans specimens. In contrast, skull and jaw proportions were correlated positively with latitude in both sexes of G. sabrinus specimens. Other research suggests that bite force requirements are consistent across the range of G. volans and may provide a constraint on variation in characters involved in mastication. Generally, G. sabrinus consumes softer food than G. volans and may not experience the same bite force constraints as G. volans. Thus, G. sabrinus individuals may be less constrained than those of G. volans in their developmental response to factors underlying the pattern recognized as Bergmann's rule.


Includes bibliographical references (pages [155]-172).


xii, 172, pages, maps




Northern Illinois University

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