An 18S rDNA-based molecular phylogeny of aphidiinae (Hymenoptera: braconidae).

We have obtained a molecular phylogeny of the subfamily Aphidiinae (Hymenoptera: Braconidae) by sequencing the 18S rDNA in 37 aphidiine taxa. Approximately 1857 nucleotides were sequenced in each species. Evolutionary relationships were established by comparing the results of maximum-parsimony, maximum-likelihood, and distance analyses. The most variable region of this gene, V4 (approx 403 nucleotides), was employed to establish the basality of the tribe Ephedrini within this subfamily. All phylogenetic reconstructions yielded trees with very similar topologies that confirmed the existence of two of the four traditionally accepted tribes, Ephedrini and Praini, but questioned the existence of Trioxini and Aphidiini. To better ascertain the status of some groups, the same analyses were repeated with a reduced taxonomic sample in which some species that produced systematic errors in the former phylogenetic reconstructions had been removed. The results from this second analysis favor either the three-tribes hypothesis (Ephedrini, Praini, and Aphidiini) or a new classification with at least five tribes (Ephedrini, Praini, Monoctonini, Trioxini, and Aphidiini). The 18S rDNA gene is a useful marker to recover relationships not only at the tribe but also at the subtribe and genus levels in this group. The natural status of some traditionally accepted clusters is also corroborated with the present data whereas the placement of other clusters is questioned or remains unresolved.