The butterfly Danaus chrysippus is infected by a male-killing Spiroplasma bacterium
Many insects carry maternally inherited bacteria which kill male offspring. Such bacteria will spread if male death benefits the female siblings who transmit the bacterium, and they are therefore expected in insects with antagonistic sibling interactions. We report that the butterfly Danaus chrysippus is host to a maternally inherited male-killing bacterium. Using diagnostic PCR and rDNA sequence, the bacterium was identified as a Spiroplasma closely related to 2 ladybird beetle male-killers and the tick symbiont Spiroplasma ixodetis. The male-killer was found to have a geographically restricted distribution, with up to 40% of females being infected in East Africa, but no detectable infection in small samples from other populations. Danaus chrysippus is a surprising host for a male-killer as its eggs are laid singly. This suggests that the ecological conditions permitting male-killers to invade may be more widespread than previously realized.(Received October 15 1999)
(Revised December 6 1999)
(Accepted December 6 1999)
Key Words: selfish genetic elements; Spiroplasma; male-killers; Mycoplasma; Danaus chrysippus.
c1 Corresponding author: Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK. Tel: +44 (0)1223 276190. Fax: +44 (0)1223 333992. E-mail: [email protected]