THE FIXATION OF METACENTRIC CHROMOSOMES DURING THE CHROMOSOMAL EVOLUTION IN THE COMMON SHREW (SOREX-ARANEUS, INSECTIVORA)

Rb fusions between acrocentric chromosomes leading to metacentrics ten d to become fixed during the chromosomal evolution in the common shrew . Using microsatellite markers preliminary results show that populatio ns are only slightly subdivided and genetic drift seems not to play an important role for the fixation of metacentrics. A significant segreg ation distortion in favour of metacentric chromosomes was found during male meiosis. This suggests that cytological factors such as facilita ted fusion between acrocentric chromosomes or choice-effects at the le vel of gametes are more likely to play a role for the chromosomal evol ution in the common shrew.