Minor dental traits in East African cape hares and savanna hares (Lepus capensis and Lepus victoriae1): A study of intra- and interspecific variablity

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Abstract

Occlusal variants of a total of 6252 teeth of 246 specimens of cape hares and 42 specimens of savanna hares were studied. Most hares were collected in the Great Rift Valley (Kenya) during 1967-1968. Some savanna hares were obtained from the Queen Elizabeth National Park (now Ruenzori NP, Uganda) in the same period. In total, 61 variants concerning enamel folds, plication, and lakes were described. Only three teeth (I2, M3, I1) proved invariant in both species. In each species, three regional units (sampling locations) were specified. Quantitative analyses of nonmetric (epigenetic) variability and geographic divergence between the regional units and between the two species were based on 31 dichotomized (0/1 scores) characters. They were created from the commonly encountered variants. A high degree of bilateral symmetry was revealed in most characters, but characters varied independently from one another. This indicated a lack of complex morphotypes in the occlusal patterns. The frequencies of all character states were calculated for all regional units and the combined species samples. No categorical differences were found in occlusal characters between the two species. The interindividual epigenetic variability was calculated as the mean of standard deviations of single characters in each sample based on the character scores. It did not differ between the two species and among the regional units within each species. Only in savanna hares from the Queen Elizabeth Park was the tendency of folding and plication of enamel structures somewhat reduced. Divergence of occlusal character states between the two species and among regional units was assessed by using C. A. B. Smith's ‘mean measure of divergence’as a distance measurement. Thirteen of 15 pairwise morphological distances differed significantly from zero. A UPGMA dendrogram based on these distance measurements revealed distinct epigenetic separation of the two species. Within each species, slight geographic divergence corresponded to the spatial distribution of the regional units. In cape hares, spatial divergence also paralleled some changes in climatic conditions. In view of the lack of complex occlusal types and the larger interspecific divergence as compared to the intraspecific, character variation is likely to be caused by phylogenetic rather than by ecogenetic processes.

Ancillary