Phylogeny and evolution of host-parasitoid interactions in Hymenoptera

Recent studies of hymenopteran phylogeny using both comparative morphology andDNAsequence data have greatly enhanced our understanding of the evolution of that order. Resulting phylogenetic hypotheses make possible more rigorous investigations of the evolution of various biological life-styles, among them the parasitoid habit. This paper reviews the current findings from higher-taxon phy- logenetic analyses of the order. A “consensus” phylogeny derived from these findings is used to trace the most likely evolutionary pathways leading to the current diversity of parasitoid habits. Taxa and biological phenomena for which our current understanding is fragmentary are highlighted. Based on current evi- dence, it appears that parasitism arose, from mycophagous ancestors, a single time within the order. Many subsequent elaborations of the parasitic mode of life (e.g. endoparasitism, secondary phytophagy, etc) apparently evolved independently more than once.