The Eucoilinae are a diverse and important group of parasitoids of Diptera, particularly in the tropics, but they are poorly known systematically and their generic classification is partly chaotic. Here, we present the first comprehensive cladistic analysis of higher eucoiline relationships. The analysis is based on 148 skeletal characters of adults documented in more than 1100 digital images available in an Internet-accessible database. The characters were coded for 45 taxa representing 35 eucoiline genera, spanning the entire diversity of the group, and 7 outgroup genera. Relationships were partly difficult to resolve and parsimony analysis under implied weights performed considerably better than analysis under uniform weights. The results support the monophyly of the Eucoilinae and show that eucoilines are most closely related to the figitid subfamilies Emargininae and Pycnostigminae, but are ambiguous concerning the exact relationships among these three lineages. Of the 6 eucoiline genus groups recognized by Nordlander in 1982 (Entomol. Scand. 13, 269–292), only 2 are supported as monophyletic: the Trybliographa and Kleidotoma groups. The Gronotoma group is a paraphyletic assemblage of two different basal clades of eucoilines. The Rhoptromeris group is unnatural and only the 2 core genera, Rhoptromeris and Trichoplasta, form a monophyletic lineage. The data are ambiguous concerning the Ganaspis group, which appears to be paraphyletic, and the Chrestosema group, which may be a good clade. Based on the results we propose a modified system of informal genus groups in the Eucoilinae and discuss putative synapomorphies supporting each genus group. The proposed relationships imply that the first eucoilines were parasitoids of leaf-mining agromyzids. The earliest split in the group was apparently between an Afrotropical and a Neotropical lineage, and much of the early radiation of the group occurred in these regions, particularly in the Neotropics.

Fieldwork in Spain and Panama by F.F.C. and J.L.N.A. was funded by the Spanish projects DGES (PGC) PB97-1241 and AECI (Agencia Española de Cooperación Internacional). F.F.C. was additionally supported by a grant from the Biogeological Station in El Ventorrillo. F.R. and J.L. were supported by the Swedish Natural Science Research Council. Part of the work was performed at the Department of Systematic Zoology,Uppsala University during a 3-month visit by F.F.C. (sponsored by the Swedish Institute) and M.B. (supported by NSF PEET Grant DEB9712543). Robert Wharton, Annie Machordom, Milagros Coca, Mario García-Paris, and two anonymous reviewers provided many helpful comments on the manuscript.

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