Molecular phylogeny of the scorpionflies Panorpidae (Insecta: Mecoptera) and chromosomal evolution

Panorpidae is the most species-rich family in Mecoptera with ca. 470 species in the Northern Hemisphere. However, the intergeneric phylogenetic relationships of Panorpidae remain unsatisfactorily resolved to date. Here, we used molecular and cytogenetic approaches to determine the phylogenetic relationships of Panorpidae in the evolutionary scenario of chromosomes, and estimated their divergence times using fossil-calibrated Bayesian analysis. In total, 89 species representing all seven genera of Panorpidae were used to reconstruct the phylogenetic trees using maximum parsimony, maximum likelihood and Bayesian inference based on the nuclear 28S rRNA and mitochondrial cox1 and cox2 genes. The results reveal that Panorpidae is a well-supported monophyletic group that can be categorized into two major clades. Major Clade I comprises Neopanorpa and Leptopanorpa, and Major Clade II consists of all the other genera (Cerapanorpa, Dicerapanorpa, Furcatopanorpa, Panorpa and Sinopanorpa). Neopanorpa and Cerapanorpa are regarded as paraphyletic groups for the first time. BEAST analysis indicates that Panorpidae originated in the Lower Cretaceous approximately 122.5 Ma (96.8-149.3 Ma), and that most diversification occurred from the Selandian (59.8 Ma) to the Middle Pleistocene (0.6 Ma) in the Cenozoic. Cytogenetic data plotted on the cladogram show that the lineage differentiation of Panorpidae is closely related to the chromosomal evolution, especially the reduction of chromosome number. Our study suggests that a taxonomic revision of Panorpidae is urgently needed at the generic level.