Neo Sex Chromosomes, Colour Polymorphism and Male-Killing in the African Queen Butterfly, Danaus chrysippus (L.)

Abstract

Danaus chrysippus (L.), one of the world’s commonest butterflies, has an extensive range throughout the Old-World tropics. In Africa it is divided into four geographical subspecies which overlap and hybridise freely in the East African Rift: Here alone a male-killing (MK) endosymbiont, Spiroplasma ixodetis, has invaded, causing female-biased populations to predominate. In ssp. chrysippus, inside the Rift only, an autosome carrying a colour locus has fused with the W chromosome to create a neo-W chromosome. A total of 40–100% of Rift females are neo-W and carry Spiroplasma, thus transmitting a linked, matrilineal neo-W, MK complex. As neo-W females have no sons, half the mother’s genes are lost in each generation. Paradoxically, although neo-W females have no close male relatives and are thereby forced to outbreed, MK restricts gene flow between subspecies and may thus promote speciation. The neo-W chromosome originated in the Nairobi region around 2.2 k years ago and subsequently spread throughout the Rift contact zone in some 26 k generations, possibly assisted by not having any competing brothers. Our work on the neo-W chromosome, the spread of Spiroplasma and possible speciation is ongoing.

Euploea dorippus Klug, 1845: species, semispecies, subspecies, junior subjective synonym of Danaus chrysippus chrysippus (Linnaeus), and/or form – what does Klug’s dorippus represent? (Lepidoptera: Nymphalidae, Danainae)

“…Gordon 1984;Herren et al 2007;Lushai et al 2003a;Smith et al 1997Smith et al , 2002. As noted above, Smith et al (2016Smith et al ( , 2019 have recently reverted to this usage.…”

“…Smith 2014, fig. 1.13.1; Smith et al 2019, fig. 2a), Khartoum lies within the range of D. c. chrysippus, beyond that of D. c. dorippus.…”

“…Instances of all nine uses that I have found are listed sequentially below (ciphers in square brackets refer to the usages listed above Gordon et al 2014Gordon et al , 2015 [Note -square brackets around chrysippus used here indicate that dorippus is a member of a superspecies of which Danaus chrysippus is the first-named taxon, in accordance with the proposals of Amadon (1966; see also Helbig et al 2002).] [5] Danaus chrysippus dorippus -Bryk, 1937: 66;?Talbot 1943: 121;Gordon 1984;Smith et al 1997Smith et al , 1998Smith et al , 2002Smith et al , 2016Smith et al , 2019Lushai et al 2003aLushai et al , 2003bLushai et al , 2005 (Aurivillius 1911, as Danaida dorippus). In that work he states that the forewing apex is brown-yellow without any subapical white band, and "the hindwing is not white [sic]".…”

“…In recent publications (e.g. Smith et al 2016Smith et al , 2019Traut et al 2017; they have reverted to calling dorippus a subspecies of D. chrysippus.…”

“…"None of these specimens have [sic] Aurivillius, 1909), the epithet dorippus is used today in two fundamentally different ways -first, as the trinomen for a semispecies or subspecies considered to have its 'heartland', in the sense of Smith et al (2019), in the Horn of Africa;…”