Karyotypes from 14 males of Sorex araneus from Kuusijoki, NE Finland, were investigated and found to represent chromosome race C, as defined by Fredga in 1973. The population was found to be polymorphic and show frequencies of cytological types close to a Hardy-Weinberg equilibrium. The polymorphism was slightly more restricted than in another race C population investigated by Fredga. Q and ASG stainings were used for the first time to obtain banding patterns in the chromosomes of the genus Sorex. The banding pattern of race C is presented and proposed as a basis for comparisons between chromosomal races of Sorex araneus.

Halkka, L., Soderlund, V., Skaren, U. and Heikkila, 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 (Aland 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 Aland. 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.

The chromosome numbers of the species Formica aquilonia Yarr., Formica uralensis Ruzsk. and Formica pressilabris Nyl. were all found to be n=26. The chromosome number of F. uralensis thus does not accord with the view that this species belongs to be subgenus Serviformica. Chromosomal polymorphism was found in Formica truncorum Fabr., one population having the haploid number n=28, instead of n=26. The chromosome numbers obtained for South Finnish populations of Formica polyctena Foerst., Formica pratensis Retz., Formica lugubris Zett., Formica rufibarbis Fabr. and Formica transkaucasica Nas. were the same as those reported from Central Europe.