Phylogenetics of Crabronini, with a consideration of the evolution of predatory and nesting behaviors (Insecta: Hymenoptera: Crabronidae)

Abstract

The phylogeny of the genera of the wasp tribe Crabronini was estimated based on a cladistic analysis of 177 adult morphological characters and a sampling of 120 taxa. This represents nearly 80% of the genera of Crabronini and also includes relatives from the tribes Oxybelini, Bothynostethini, and Larrini. In the resulting strict consensus tree, the tribe was recovered as monophyletic, but its constituent subtribes, Anacrabronina and Crabronina were not. A major clade comprising about half of the genera of the tribe was recovered with strong support. Based on these results, the current classification is evaluated and the following nomenclatural changes are suggested: 1) Entomognathus should be excluded from the Anacrabronina and recognized within a new subtribe, Entomognathina; 2) Quexua and Holcorhopalum should be transferred to the Anacrabronina; 3) Ectemnius and Williamsita should be synonymized with Lestica. The evolution of predatory and nesting behaviors are discussed in light of the new phylogenetic information. Nesting in the ground is ancestral for Crabronini. The number of transitions to plant-nesting is ambiguous; it has arisen anywhere from one to six times. Reversals to ground-nesting have occurred five to nine times. Predation on Hemiptera is likely ancestral for the tribe, and predatory behaviors largely correspond to subtribal categories. Anacrabronina (in the suggested sense) prey mainly on Hemiptera, Entomognathina prey on Coleoptera, and Crabronina are mainly Diptera predators. Transitions to novel prey items have occurred numerous times in the latter group.