Microorganisms and parthenogenesis

Abstract

Endosymbionts are being discovered in unprecedented numbers of invertebrate species. The bacterium Wolbachia pipientis alone is carried by some 20% of all insect species, in which it is responsible for such reproductive manipulations as cytoplasmic incompatibility, feminization of genetic males, male-killing and parthenogenesis. The discovery of Wolbachia-induced thelytoky in hymenopteran parasitoids has initiated the successful search in other groups of haplodiploid species. Haplodiploidy has arisen at least 17 times during animal evolution and intracellular bacteria that effect sexual development have been found in many of these haplodiploid groups, rekindling the question regarding the origin of haplodiploidy. The detection of Wolbachia in parthenogenetic thrips (Thysanoptera). booklice (Psocoptera), springtails (Collembola), mites (Acari) and Xiphinematobacter in dragger nematodes (Dorylaimida) raises the possibility of bacterial-induced parthenogenesis in diplodiploid species as well. Recent studies indicate that Wolbachia might be just one of a rapidly increasing list of intracellular bacteria capable of inducing parthenogenesis in their host. The search for novel endosymbionts will rely heavily on previous taxonomic work, but the possibilities for discovery remain boundless.