Phylogenetic study of Diadegma species (Hymenoptera: Ichneumonidae) inferred from analysis of mitochondrial and nuclear DNA sequences

The genus Diadegma consists of a large group of parasitoid wasps with a confusing taxonomy based on morphological characters. No phylogenetic studies on this genus or any of its species have been published so far. We examined DNA variations in a 498 bp segment of the cytochrome oxidase I gene (COI) of mitochondrial DNA (mtDNA) and in the internal transcribed spacer 2 (ITS2) of ribosomal DNA (rDNA) and compared nine different Diadegma species (i.e., D. semiclausum, D. insulare, D. fenestrale, D. mollipla, D. rapi., D. leontiniae, D. chrysostictos, D. armillata, D. blackburni) from various geographical origins. Interspecific variation ranged from 3.9 to 16.8% in the COI region and from 5.4 to 32.5% in the ITS2. Phylogenetic relationships were constructed on maximum parsimony and maximum likelihood trees for each marker. Likelihood ratio tests were used to find the best evolutionary model fitting each of the data sets. The cladistic analysis of both data sets yielded different tree topologies. The sequences of the COI gene provided very little resolution of relationships among species whereas the nuclear DNA sequence data (ITS2 region) seems to be phylogenetically more valuable.