Genomic integrity of Phyciodes butterfly species in a region of contact (Lepidoptera: Nymphalidae)

Abstract

Crescent butterflies of the Phyciodes tharos group have a long-standing reputation for taxonomic difficulty. We assessed species boundaries in the P. tharos group using genome-wide single-nucleotide polymorphism (SNP) data, focusing on sampling in western Canada, where 4 species (P. tharos, P. cocyta, P. batesii, and P. pulchella) have classically been recognized. Phylogenetic and cluster-based analyses confirm that there are indeed 4 species based on the maintenance of genomic integrity in the presence of occasional hybridization and low levels of gene flow. Mitochondrial cytochrome c oxidase I (COI) does not consistently distinguish species, with haplotypes extensively shared between species. Limited sampling of P. batesii indicates complex boundaries and interactions with other Phyciodes, especially with P. pulchella and P. cocyta. This study demonstrates the power of a genome-wide perspective to elucidate the integrity of boundaries between recently diverged species that remain capable of occasional hybridization.