Meiotic evidence for pericentric inversion polymorphism in Junco (Aves).

Species of the genus Junco are polymorphic for chromosomes 2 and 5. Diplotene karyotypes of 61 adult male Dark-eyed Juncos, Junco hyemalis, were analyzed in order to determine the basis of the polymorphisms. Individuals carrying heterozygous bivalents of the polymorphic chromosomes have fewer chiasma than homozygous individuals. These data suggest that two separate pericentric inversions are at the basis of the polymorphisms.