Phylogenetics of the Nearctic inquiline genus, Periclistus (Hymenoptera: Cynipidae): Insights and challenges

The inquiline wasp genus Periclistus (Hymenoptera: Cynipidae) is a group of nest parasites that exploit galls induced by rose gall wasps (Diplolepis) on wild roses (Rosa spp.). Although Periclistus cannot initiate galls themselves, they modify gall morphology upon invasion, often leading to high mortality of the gall inducer's larvae. Despite their ecological importance and unusual life history, both genera remain taxonomically and phylogenetically underexplored. We sought to resolve evolutionary relationships within Nearctic Periclistus using ultraconserved elements (UCEs), a phylogenomic tool that has proven effective in clarifying species-level relationships across diverse insect groups. This approach contributes to a broader integrative taxonomic revision of both Periclistus and Diplolepis. By combining genomic and morphometric data, we aim to better resolve species boundaries and evolutionary relationships within this system. In addition to the production of the first comprehensive UCE-based phylogeny of Periclistus, this work also highlights the technical challenges of working with small-bodied insects. Due to the exceptionally small size of Periclistus, DNA extraction was limited by low tissue volume and correspondingly low yields. Overcoming these challenges required special consideration. Our findings could offer practical insights for researchers working with similarly minute taxa.