Mitogenome evolution in Cephini (Hymenoptera: Cephidae): Evidence for parallel adaptive evolution

Abstract

Two mitogenomes of remarkable size of the stem-boring sawflies, Trachelus tabidus (18539 bp) and T. iudaicus (20730 bp), were characterized and compared with previously known mitogenomes of Cephini. A rearrangement in the IQM gene cluster, an unusual elongation in rrnS gene and supposedly functional tandem repeat sequences in the A+T- rich region are synapomorphies of Cephini. Mitogenome evolution of the Cephini was investigated in a dataset of seven species representing all genera. The noticeably divergent mitogenomes of the Cephini both at nucleotide and amino acid level, and the variable rates of omega values, indicate the effects of different selective forces, rather than neutral evolution. The effect of positive selection is revealed by radical amino acid changes with ten physicochemical properties (P-alpha, B-r, pK', h, E-l, H-nc, alpha(c), alpha(n), R-alpha and H-p) throughout each branch of the tree. The radical changes in the ND and ATP complexes are mostly related to chemical and energetic properties due to different energy requirements among species. The phenology of Cephini species and their host plants, together with habitat structure, rather than host plant preferences or phylogenetic constraint, are suggested to explain the role of adaptive evolution in shaping Cephini mitogenomes. (C) 2017 Elsevier Ltd. All rights reserved.