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ABSTRACT. Findings of gene flow across hybrid zones between karyotypic races of the common shrew, Sorex araneus Linnaeus, 1758, have contributed to the debate over the role of chromosomal changes in speciation. The correlation between chromosomal and morphological evolution was examined here across the full geographic range of the species. Previous studies on selected karyotypic races yielded ambiguous results: some found significant differences between races, but others concluded that local variation was more important than karyotype for morphological structuring. Forty three samples, representing 24 karyotypic races and three species were studied here. Geometric morphometrics were used to determine whether karyotypic, geographic or population-level structuring was present in the size and shape of molars, skulls and mandibles. Significant structuring was found in all traits among populations, among karyotypic races, among phylogenetic groups of karyotypic races and among species, greatest among populations (FST ranged from 0.08 to 0.11) and groups (FST 0.04 to 0.15). Within S. araneus structuring was greater in skull centroid size and molar shape than in skull or mandible shape. Large-scale east-to-west clines were found in molar and skull shape. The skull cline is probably associated with changes in the frequency of the upper fifth antemolar. Mandible shape was not highly differentiated between karyotypic races compared to molar shape, but it was better at discriminating among karyotypic groups and species. It is likely that fossil specimens can be determined to the level of karyotypic group, but not to a specific karyotypic race.
KEY WORDS: FST, geometric morphometrics, karyotypic race, phenotypic evolution, Sorex araneus.
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