The origin and distribution of the Lund Y chromosome in Microtus agrestis (Rodentia, Mammalia).

The Lund Y (Lu-Y) chromosome of the field vole (Microtus agrestis) is distinguished from the standard Y (St-Y) by its much longer short arm. G-banding revealed that the Lu-Y originated by a pericentric inversion in the St-Y. Chromosome analysis of 297 male field voles from 92 localities in Fennoscandia. Germany, and England, in addition to data from the literature, made it possible to map the distribution area of the Lu-Y. It is restricted to the south-western parts of Sweden. The question of when and where the Lund Y population originated is discussed. Adding data from a hybrid zone (Jaarola et al. 1997) and from females, totally 491 specimens from 120 localities were analyzed without detecting any variation in chromosome number and autosome morphology. Other cases of intraspecific Y chromosome polymorphism in mammals, and the use of Y chromosome variants as population genetic markers, are discussed.