Genomics-informed species delimitation to support morphological identification of anglewing butterflies (Lepidoptera: Nymphalidae: Polygonia)

Species delimitation and identification are integral to virtually all biological disciplines, but are far from straightforward tasks. Taxonomy has recently focused on integrative approaches that consider multiple types of data to resolve species boundaries, yet methodologies to that end are still being developed. Here, we assess species limits in an area of wide distributional overlap between several species of anglewing butterflies in western Canada. Focusing on an area of sympatry provides a rich system to test species boundaries in the face of potential gene flow between morphologically variable yet similar species. Mitochondrial DNA and genome-wide single nucleotide polymorphisms provided clear species delimitation, although previously identified cytonuclear discordance was also apparent. Analysis of two morphological data sets, based on characters commonly used as diagnostic characters in the literature and field guides, was variably successful at separating species. Using analyses that were guided by the results of the genetic data increased successful species identification for traditionally used characters, but not for the morphological data set based on digital colour analysis. Our application of genetics to guide morphological analysis demonstrates a useful approach for implementing iterative methodologies as part of integrative taxonomy.