The suprageneric groups of the Pimplinae (Hymenoptera: Ichneumonidae):: a cladistic re-evaluation and evolutionary biological study

The phylogenetic relationships of the suprageneric groups of the ichneumonid subfamily Pimplinae (Hymenoptera) are re-assessed using 166 morphological and biological characters for 162 species, representing all of the available described genera and subgenera. The cladistic analysis was repeated using abstracted genera, re-coded from the initial set of species, as terminal taxa. The topology of the resulting cladograms was similar. In the first (primary) analysis several genera (including Neotheronia, Itoplectis, Dolichomitus, Dreisbachia, Polysphincta, Oxyrrhexis and Zonopimpla) were not retrieved as monophyletic groups; however, all except the last were found to be monophyletic in the second analysis. These results suggest that using abstracted taxa may force a 'false monophyly' on the preselected groups. Thus we reject the use of such abstractions, preferring instead to use exemplar species that together show much of the variation that occurs within a hypothesized genus. Within the Pimplinae three major groupings were recognized, the Delomeristini (including the Perithoini syn. nov.), the Pimplini and the Ephialtini. Within the Pimplini, two generic groups were recovered, the Xanthopimpla and Pimpla genus-groups, but a third postulated group, the Theronia genus-group, was found to be paraphyletic. Within the Ephialtini five groups were recognized, the Pseudopimpla, Alophosternum, Camptotypus, Ephialtes and Sericopimpla genus-groups. The spider parasitizing complex of genera (the Polysphincta genus-complex) was found to nest within the Sericopimpla genus-group confirming the placement of Polysphinctini as a synonym of Ephialtini. Problems with the status of some existing genera are highlighted, but formal nomenclatural changes are not proposed. The ancestral Pimplinae are hypothesized to have been solitary ectoparasitic idiobionts on weakly concealed immature Hymenoptera. The major radiations within the Pimplinae are shown as: (1) a progressive exploitation of cocooned, then weakly cocooned, lepidopterous pupae in the Pimplini leading to idiobiont endoparasitism; (2) increasing specialization to attack hosts deeply concealed in wood in the Ephialtes genus-group, and (3) specialization on a variety of cocooned hosts, including spider egg sacs, leading to koinobiont ectoparasitism of spiders. A brief synopsis of the distribution of the group is given, and some biogeographical inferences drawn. The group is presumed to have originated and radiated on Laurasia; no evidence for trans-Antarctic relationships can be found. (C) 2002 The Linnean Society of London.