Evidence for autosomal meiotic drive in the butterfly Danaus chrysippus L.

Danaus chrysippus (Danaidae) in East Africa is highly polymorphic for colour, the genetic control of which resides at three loci. The B locus has two alleles, B giving a nutbrown ground colour and bb orange on both fore and hindwings. The C locus determines forewing pattern: there are two alleles, C giving a wing uniformly coloured except for a black margin (form dorippus) and cc a large black apical area traversed by a row of white subapical spots (form ae&yptius = form chrysippus of my earlier papers). Heterozygotes (Cc) are basically dorippus but are often phenotypically distinct in showing the “aegyptius” subapical spots on the underside of the forewing. The B and C loci are closely linked (Smith, 1975a). The A locus has a recessive allele a the homozygous possessor of which has a large white patch on the hindwing (form alcippus when combined with the aegyptius forewing and form albinus with the dorippus forewing). The A locus probably assorts independently from the B and C loci (Clarke, Sheppard and Smith, 1973; Smith, 1975a). All-female broods commonly occur in D. chrysippus. These probably result when a Y-linked gene D causes meiotic drive for the Y chromosome so that it always enters the secondary oocyte at the first meiotic division in the female. Females from all-female broods usually themselves produce allfemale broods but a switch to bisexual broods can occur and seems to depend on the acquisition of a dominant autosomal suppressor gene S from the maternal male grandparent. The S locus is probably closely linked with the C locus (Smith, 1975b).