Morphometrical characteristics of the common shrews (Sorex araneus L.) from interracial hybrid zones

Abstract

Common shrews are subdivided into numerous chromosome races which make contact and form hybrid zones. To date, no strong differences in morphology have been found between hybrid and pure race individuals from the vicinity of such hybrid zones. To investigate this further, we carried out studies in Poland on three hybrid zones between races belonging to the West and East European Karyotypic Groups using material collected from 1989 to 1994. Shrews were measured (head and body, rail and hindfoot length) and weighed. Statistically significant differences in morphology were only observed in the Stobnica/Legucki Mlyn hybrid zone. The results indicated that both adult and immature animals belonging to the Stobnica race were smaller than those belonging to the Legucki Mlyn race. The hybrids were longer than individuals of pure race karyotype but the mean body mass of the hybrids was the lowest. At the population level, the size of the shrews varied with value of a hybrid index. The absence of similar results for the Druzno/Legucki Mlyn and Drnholec/Bialowieza hybrid zones may reflect their narrowness compared with the Stobnica/Legucki Mlyn zone.