Sex differences in chiasma frequency and distribution in natural populations of eyprepocnemis plorans containing b-chromosomes

Abstract

Chiasma frequencies and distributions were compared in males and females, with and without different types of B-chromosomes, from four Spanish natural populations of Eyprepocnetnis plorans. Mean cell chiasma frequency and mean autosomal chiasma frequency were substantially and significantly lower in females than in males. Females also showed altered chiasma distributions compared with males, with fewer proximal chiasmata and more interstitial and distal chiasmata. A variety of sex differences in meiotic chiasmata have now been described in the Orthoptera and these are compared and discussed, B-chromosomes had no effects on mean chiasma frequency and relatively little general effect on chiasma distribution, although some minor effects of B-chromosomes on chiasma distribution were detected in certain populations and classes of bivalents. In some of these cases B-chromosomes affected chiasma distribution in females but not in males. © 1987, The Genetical Society of Great Britain.