New family-level characters for Platygastroidea

Abstract

Platygastridae (Hymenoptera) is a diverse family of parasitoid wasps for which few studies of internal morphology have been conducted. The monophyly of the group is undisputed based on recently published molecular data, but based on morphology, the family is diagnosable from other platygastroids only by a combination of character reductions. In the present study we explored the mesosoma of Platygastroidea and found two new synapomorphies for Platygastridae: an externally visible anterior mesofurcal pit, which corresponds to an invagination that connects to the anterior portion of the mesofurca, and internally, a posteriorly shifted origin of the first wing flexors. The absence of a mesofurcal bridge and the exclusively mesopectal origin of the fore wing flexors are treated as synapomorphies for Platygastridae+Janzenellidae. Phylogenetic implications and evolutionary hypotheses regarding these traits are discussed.