¹Department of Genetics and Evolution, Institute of Biology, Biaystok University, wierkowa, Biaystok, Poland

Correspondence: Professor S Fedyk, Department of Genetics and Evolution, Institute of Biology, Biaystok University, wierkowa 20 B, 15-950 Biaystok, Poland. E-mail: fedyk@uwb.edu.pl

Received 24 May 2007; Accepted 19 June 2007; Published online 15 August 2007.

Abstract

One of the hypotheses explaining preferential transmission of metacentrics among simple Robertsonian (Rb) heterozygotes of the common shrew (Sorex araneus L.) invokes the existence of meiotic drive. Thus far, evidence that metacentrics are favoured at meiosis has been obtained indirectly, on the basis of crosses made under controlled conditions. The aim of the present work was to test the hypothesis in a direct study. We analysed products of chromosome segregation among 12 simple heterozygote male subjects from a wild population, with regard to jl, io, nr and mn Rb fusions. We were able to demonstrate significant segregation distortion in favour of all four metacentrics. The level of preferential segregation was independent either of the composition of chromosome arms or the dimensions of metacentrics. We also found that X chromosomes were favoured over Y1Y2 chromosomes during segregation. We discuss the role of meiotic drive in the evolutionary success of metacentric chromosomes in S. araneus, as well as in the emergence of post-hybridization modifications in the zones of contact between races.