Phylogenomic Analysis of Chelonus (Hymenoptera: Braconidae): Taxonomic Revision and Coevolution with Endogenous Bracoviruses
The genus Chelonus Panzer is a one of the largest genera within the subfamily Cheloninae with 11 subgenera and 973 valid species. However, the phylogenetic relationships within this genus and their coevolutionary relationships with endogenous bracoviruses (BVs) remain unclear. Here we provide the first phylogenomic analysis of 42 taxa representing all 11 subgenera of Chelonus and other species within the Cheloninae using 2,380 loci of ultraconserved elements (UCEs) of species genomes. The results showed that the subgenus Arichelonus forms a monophyletic group and could be elevated to genus rank, and other 10 subgenera formed another monophyletic group, the traditional genus Chelonus. Four subgenera within Chelonus, i.e. Chelonus s. str. Megachelonus, Microchelonus and Parachelonus are polyphyletic, resulting in that the traditional genus Chelonus could be further divided into 14 clades. Divergence time estimates indicated that the subgenus Arichelonus diverged approximately 35.5 million years ago, while most species within the genus Chelonus diversified less than 21.9 million years ago. Ancestral state reconstructions revealed morphological innovations of this subfamily, including metasomal curvature, may link to host-use strategies. Cophylogenetic analyses demonstrated that a strong congruence of parasitoid-bracovirus exist, and confirmed that BV nudivirus genes and virulence genes displayed different evolutionary trajectories. Altogether, our findings provide new insights into the evolutionary history of the genes Chelonus and substantiated the coevolutionary relationships between the parasitoids and their associated bracoviruses.