Genetic Differentiation of Polish Populations of Sorex araneus L. III. Interchromosomal Recombination in a Hybrid Zone

Abstract

Two parapatric chromosomal races of the common shrew (Sorex araneus) in Poland differ in their complement of metacentric arm combinations: hk, io, gr, nm (race IV), and hi, ko, gm, np (race II). In hybrids, these eight race-diagnostic metacentrics form two randomly segregating complexes. The first complex (C ) occurs in the form of a ring configuration ok/kh/hi/io, or a chain o/ok/kh/hi/i (when there is Robertsonian polymorphism of the element io). The second complex (C ) always takes the form of a six-element chain configuration r/rg/gm/mn/np/p. The C complex may be shortened to five or even four elements, when acrocentrics g, m and n are present. In the contact zone we found shrews of pure races (race II or IV), as well as hybrids with C or C complexes, and recombinants hi, ko, gr, nm. Complex heterozygotes are likely to suffer reduced fertility due to malsegregation at meiosis. However, the C hybrids with ring configurations occur with a high frequency throughout the contact zone. This suggest that their fitness is only slightly lowered relative to pure race individuals, in contrast to the hybrids with C or C chain configurations, which presumably have a more heavily reduced fertility. On the other hand, at the center of the zone there is a high proportion of recombinants, which, being chromosomal homozygotes, should display normal meiotic segregation. Furthermore, the high frequencies of recombinants within the contact zone should facilitate gene flow between the races. The occurrence of recombinants plays a similar role as the appearance of the maximum frequencies of acrocentric homozygotes described in several contact zones of S. araneus.

Karyotypic variation of the common shrew Sorex araneus in Belarus, Estonia, Latvia, Lithuania and Ukraine

“…The Lepel race was first found in Belarus by Bulatova et al (2000) and the Kiev race first found in Ukraine by Mishta (1994). af, be, g/r, h/k, i,jl, m/n, o, p, q, tu This race is found locally in north-eastern Poland (Fedyk 1986, 1995, Fedyk and Lenieć 1987 and in the Kaliningrad region (Orlov et al 1996). We found this race in one population on the Baltic coast of western Latvia.…”

“…It is noticeable that most of the races possess metacentric hk. This metacentric is also found in the Łęgucki Młyn race (Wójcik 1986) and Gołdap race (Fedyk 1986(Fedyk , 1995 in Poland and in the Lemi race (Halkka et al 1987) in south-eastern Finland. So, our data allow the range of hk to be determined: it occurs along the coast of the Baltic Sea from north-eastern Poland to south-eastern Finland.…”

Chromosome races of the common shrew Sorex araneus in Poland: a model of karyotype evolution

“…Malczyce 51°14'N,16°30'E 6 20 hi,gm,ko,nr,p,q The description of the chromosome races of the common shrew in Poland was made according to the preliminary suggestions of the International Sorex araneus Cytogenetics Committee (Searle et al 1991). Data used for description of the races came from Wójcik and Fedyk (1985), Wójcik (1986), Fedyk (1987, Fedyk and Lenieć (1987), and the present study. Fig.…”

“…Numerous karyotypic races have been described all over the extensive range of the common shrew (Halkka et al 1974, Fredga and Nawrin 1977, Krai et al 1981, Searle 1984, 1988a, b, Wójcik and Fedyk 1985, Zima and Krai 1985, Fedyk 1986, Hausser etal. 1986, Wójcik 1986, 1989, Fedyk and Lenieć 1987, Frecga 1987, Zima et al 1988, Aniskin and Lukianova 1989, Briinner 1991.…”

“…1986, Wójcik 1986, 1989, Fedyk and Lenieć 1987, Frecga 1987, Zima et al 1988, Aniskin and Lukianova 1989, Briinner 1991. Some of these races have been found in Poland (Fedyk 1980, Wójcik 1986, 1989, Fedyk and Lenieć 1987. The complex situation of Polish races needs to be clarified.…”