Morphology and evolution of the mesopleuron in Bethylidae (Hymenoptera: Chrysidoidea) mapped on a molecular phylogeny

The mesopleuron of Bethylidae has morphostructural characters that remain poorly understood, explored, and defined. The wide range of variability of this sclerite has generated confusion both in taxonomic and cladistic studies. Aiming to solve this issue, we describe the general mesopleural anatomy of Bethylidae. Our goal is to propose primary homologies by matching external and internal structures (muscles and apodemes). We reconstruct the ancestral state of the main mesopleural structures by applying the maximum-likelihood method on ten selected character states. The phylogeny of Bethylidae is built by analyzing a dataset of COI and 28S sequences, using maximum-likelihood and Bayesian inference methods. The Bethylidae and all subfamilies are recovered as monophyletic in both resulting phylogenies, with high clade support values. Although the two analyses yielded similar results, we used the tree resulting from the Bayesian inference to map the evolution of the morphological characters, as it is better supported. The study of mesopleural anatomy allows exploration and discussion of the evolution of characters and their present states in Bethylidae and Hymenoptera in general. Reconstruction of the ancestral states shows that many characters arose independently in Bethylidae subfamilies.