Combined molecular phylogenetic analysis of the Orthoptera (Arthropoda, insecta) and implications for their higher systematics

A phylogenetic analysis of mitochondrial and nuclear rDNA sequences from sp ecies of all the superfamilies of the insect order Orthoptera (grasshoppers , crickets, and relatives) confirmed that although mitochondrial sequences provided good resolution of the youngest superfamilies, nuclear rDNA sequen ces were necessary to separate the basal groups. To try to reconcile these data sets into a single, fully resolved orthopteran phylogeny, we adopted c onsensus and combined data strategies. The consensus analysis produced a pa rtially resolved tree that lacked several well supported features of the in dividual analyses. However, this lack of resolution was explained by an exa mination of resampled data sets, which identified the likely source of erro r as the relatively short length of the individual mitochondrial data parti tions. In a subsequent comparison in which the mitochondrial sequences were initially combined, we observed less conflict. We then used two approaches to examine the validity of combining all of the data in a single analysis: comparative analysis of trees recovered from resampled data sets, and the application of a randomization test. Because the results did not point to s ignificant levels of heterogeneity in phylogenetic signal between the mitoc hondrial and nuclear data sets, we therefore proceeded with a combined anal ysis. Reconstructing phylogenies under the minimum evolution and maximum li kelihood optimality criteria, we examined monophyly of the major orthoptera n groups, using nonparametric and parametric bootstrap analysis and Kishino -Hasegawa tests. Our analysis suggests that phylogeny reconstruction under the maximum likelihood criteria is the most discriminating approach for the combined sequences. The results indicate, moreover; that the caeliferan Pn eumoroidea and Pamphagoidea, as previously suggested, are polyphyletic. The Acridoidea is redefined to include all pamphagoid families other than the Pyrgomorphidae, which we propose should be accorded superfamily status.