Integrative taxonomy of Polygonia Hubner 1819 (Lepidoptera:Nymphalidae) in Alberta

Abstract

Speciation can be an elaborate process. Delimiting species and reconstructing evolutionary relationships may be similarly complex, revealing gene tree discordance, cryptic species, geographic structuring or hybridization. In order to solve such systematic problems, a careful balance should be struck between evidence from morphology and molecules. Relationships among Polygonia species have been explored using mitochondrial genes (ND1, COI), nuclear genes (wgl, EF-1α, GAPDH, RpS5) and morphology (wing patterns, venation, genitalia), but their topology remains inconclusive, due at least in part to phylogenetic discordance. Here, I used mitochondrial COI gene sequence in tandem with genomic single nucleotide polymorphisms (SNPs) genotyped using genotyping-by-sequencing (GBS) methods to assess species and subspecies boundaries. I also reconstructed phylogenetic relationships in the genus to further investigate phylogenetic discordance. Distinct genetic clusters resulted from discriminant analysis on principal components (DAPC) of SNPs, while COI sequencing revealed a new mitochondrial lineage, making P. gracilis paraphyletic. Genetic clusters were carried forward into the morphological analysis to serve as prior categories for the specimens. Ten visually scored diagnostic characters selected based on personal observations and appearance in the taxonomic literature clustered the specimens into the same groups as genetic characters, while digital colour analysis of wing areas gave less congruent groupings. I used discriminant correspondence analysis (DCA) of the visually scored characters to compare their diagnostic utility and construct a new species-level dichotomous key. This integrative approach to constructing diagnostic keys supports species identifications that are designed to correspond more closely to genetic clusters.