Non-metrical polymorphism of the first lower premolar (P3) in Austrian brown hares (Lepus europaeus): a study on regional differentiation

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Abstract

The pattern of the occlusal surface of 1018 first lower premolars (P3) was studied in 527 brown hares (Lepus europaeus) collected in 1988 and 1989 at 21 localities in Austria. In total, 29 variants were described. For analysis of geographic variation in the P3-pattern, the locality samples were grouped into five regional units with respect to spatial distances and putative barriers for gene flow. From the primarily encountered variants. 15 dicholomized characters were created and their frequencies within the five regional units were calculated. Strong right/left dependencies of character states suggested a high degree of bilateral symmetry in each character. In contrast, character varied largely independently from one another. This indicated the absence of complex types of the P3. One character showed sex-dependence but no age dependence was found. Intraregional differences in trait frequency were found in one character. Non-metrical morphological divergence among the five regional units was revealed by using C. A. B. Smith's ‘mean measure of divergence’ and ‘percentage dissimilarity’ as distance measurements. Six pairwise morphological distances differed significantly from zero. Phenetic affinities among the five populations showed good correspondence to the geographic distribution of the samples. However, whereas the alpine chains of mountains appeared to separate the hare populations, the River Danube did not, Generally, good concordance was found between the current pattern of phenetic differentiation and earlier results of cluster analyses using non-metrical skull traits and allozymes of the same populations. This suggested that geographic differentiation of the P3-traits was largely due to random historical rather than to ecogenetic causes. Nevertheless, in one population the striking discordance between the three character-systems compared could indicate some influence of a selection pressure on certain P3-variants.

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