KARYOTYPIC AND BIOCHEMICAL STATUS OF CERTAIN MARGINAL POPULATIONS OF SOREX-ARANEUS

Karyotypes of common shrews from Mt. Pelister in southern Macedonia (2 Na=28, jl, metacentric Y1 chromosome), the Istranca Mts. in the Europe an part of Turkey (2Na=24), and the eastern bank of Lake Baikal in Sib eria (2Na=26-28, hi, j/l) were studied. Populations of the common shre w distributed at the margins of the recent range often exhibit a high number of free acrocentric chromosomes in their karyotypes. The high n umber of acrocentric autosomes indicates a primitive state of the kary otype. Therefore, the situation observed in marginal populations suppo rts the view that there is an evolutionary tendency towards low 2Na nu mbers, and that fusions of large arms (hi, jl) have priority. A sample of individuals collected in Mt. Pelister was compared biochemically t o other populations in Central Europe. Very close genetic similarity w ere found between the Pelister and the Czech populations, whereas shre ws from Slovenia appeared to be more distant from both the Czech and t he Macedonian samples. The marginal areas of the distribution range pr obably do not represent the centres or starting sites of karyotypic ev olution in Sorex araneus. We suggest that the initiation sites of the Robertsonian process should be looked for in areas situated more centr ally within the recent range.