Mitogenome organization and evolutionary history of the subfamily Cephinae (Hymenoptera: Cephidae)

Abstract

Cephinae represents one of the exclusively endophytophagous sawfly lineages with diverse host plant utilizations, in which most species have great economic importance. However, the evolutionary history of the subfamily has not been thoroughly investigated to date. Here, we characterized the mitogenomes of six species representing five genera of Cephinae. Rearrangements of the tRNA genes were found to be notably common. The rearrangements involve the IQM and TP gene clusters, and the former is a synapomorphy of the subfamily. In spite of the seldom occurrence of gene duplication in arthropods, three tRNA duplication events not known elsewhere in Symphyta were detected in Cephinae. The phylogeny of Cephinae was reconstructed using different datasets generated from mitochondrial genes and two nuclear fragments, EF-1 alpha and ITS2, under Bayesian inference (BI) and maximum likelihood (ML) approaches by adding the data of previously reported seven species. Five different tree topologies were recovered in which the tree produced from the nP12RNAexc4genes dataset under the BI and ML approaches was highly resolved with high support values. The phylogeny did not support the traditional tribal concept but it suggested two strongly supported clades. Diversification of the subfamily appears to correspond to a great extent to host plant availability and colonization in the Late Cretaceous, Early Eocene and Oligocene, suggesting speciation via host shift. The nonsynonymous substitutions and the most radical changes observed in mitochondrial protein-coding genes were proposed as evidence for speciation driven by divergent adaptive selection.