PHYLOGENY AND EVOLUTION OF HOST-PARASITOID INTERACTIONS IN HYMENOPTERA

Recent studies of hymenopteran phylogeny using both comparative morpho logy and DNA sequence data have greatly enhanced our understanding of the evolution of that order. Resulting phylogenetic hypotheses make po ssible more rigorous investigations of the evolution of various biolog ical life-styles, among them the parasitoid habit. This paper reviews the current findings from higher-taxon phylogenetic analyses of the or der. A ''consensus'' phylogeny derived from these findings is used to trace the most likely evolutionary pathways leading to the current div ersity of parasitoid habits. Taxa and biological phenomena for which o ur current understanding is fragmentary are highlighted. Based on curr ent evidence, it appears that parasitism arose, from mycophagous ances tors, 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.