Chromosomal polymorphism and racial evolution of Sorex uruneus L. in Finland

Abstract

Halkka, L., Söderlund, V., Skarén, U. and Heikkilä, J. 1987. Chromosomal polymorphism and racial evolution of Sorex araneus L. in Finland. —Hereditas 106: 257–275. Lund, Sweden. ISSN 0018–0661. Received October 2, 1986 Karyotypes of 197 Sorex araneus specimens from 26 populations throughout Finland were studied. Six chromosomal races with different combinations of arms, g, h, k, m, n, o, q and r were found to form chromosomes nos 3,5,7 and 8. The races may have evolved from a common ancestral karyotype through a series of reciprocal translocations. Postglacial geological development and distribution routes of Sorex support this hypothesis. Ancestor 3=qg, 5=nh, 7=rk, 8=om (Northern Russia)—race II 3=mg, 5=nh, 7=rk, 8=qo easternmost Finland) — race I 3=mg, 5=nh, 7=qk, 8=ro (Northern Finland and Lapland). Ancestor —race IV 3=qg, 5=nh, 7=ok, 8=rm (Central and Southern Finland, via Salpausselka ridge) — race V13, 5, 7, 8 =g, h, k, m, n, o, q, r (Åland Islands), race IV — race V3=k, g, 5=nh, 7=rm, 8=qo(Rauma, new centric fusion or hybrid). Ancestor — race III 3=qg, 5=kh, 7=om, 8=rn (Southeastern Finland, via Karlelian Isthmus). Chromosomes 3, 5, 7, 8, 4=li and 6=pi form an internal chromosomal polymorphism with two arms being combined to one metacentric chromosome (m) or being separated into two telocentric arms (t). The lowest frequencies of telocentrics were found in Central Finland and the highest, in Southwestern Finland and Åland. The chromosomal phenotypes mm, mt and tt seem to stay in Hardy-Weinberg equilibrium inside populations. The possible role of transposable elements in chromosomal evolution of Sorex araneus is discussed.