Molecular phylogenetic analysis of the Pneumoroidea (Orthoptera, Caelifera): Molecular data resolve morphological character conflicts in the basal Acridomorpha

A key transition in the evolution of the insect suborder Caelifera (Orthopt era; Insecta) was from predominantly non-angiosperm-feeding basal lineages to the modern acridomorph fauna (grasshoppers and related insects). However , because of conflicts in the distribution of several complex morphological characters, the relationships of the presumed intermediates, and in partic ular of the superfamily Pneumoroidea, are presently unclear. We undertook a phylogenetic study of representatives of all of the transitional acridomor ph families using mitochondrial and nuclear DNA sequences. No support for p neumoroid monophyly was obtained from nonparametric bootstrap analysis. Fur thermore, adopting a maximum likelihood approach, specific hypotheses of re lationships within the Pneumoroidea were firmly rejected using parametric b ootstrapping and Kishino-Hasegawa tests. The results indicate that the Pneu moroidea are at best a grade. This distinction implies that the evolution o f the proposed pneumoroid synapomorphies, femoro-abdominal stridulation and simple male genital structure, might previously have been misinterpreted a s cases of single character gains or losses within lineages. Reconstruction s of character states for the femoro-abdominal stridulation indicate that, in fact, multiple losses or gains are equally likely. An important implicat ion of our findings is that, in grasshoppers, auditory tympana may have evo lved before stridulation, supporting the argument that the original functio n of tympana may have been related not to conspecific communication but to predator detection. Overall, the results of this study emphasize the high i nformation content of these minor groups tin this case, the four intermedia te families under consideration contain only 0.2% of extant orthopteran spe cies diversity). Our analyses also demonstrate the advantages of model-base d methods in analyzing systematic problems and, in particular, of the impor tance of testing specific phylogenetic hypotheses when a priori support for groupings (e.g., from nonparametric bootstrapping) is marginal, (C) 2000 A cademic Press.