Werner Back, Michael A. Miller, Paul A. Opler
The Journal of the Lepidopterists' Society 65 (1), 1-14, (1 March 2011) https://doi.org/10.18473/lepi.v65i1.a1
KEYWORDS: North America, Mexico, mitochondrial DNA, barcode, COI gene
This work presents the results of a molecular investigation (mtDNA: COI) of Nearctic Euchloe species. The five hitherto accepted species, E. creusa (Doubleday & Hewitson, 1847), E. hyantis (W.H. Edwards, 1871), E. guaymasensis Opler, 1986, E. olympia (W.H. Edwards, 1871), and E. ausonides (Lucas, 1852), are supported. They are part of the species groups II and V of the existing phylogeny of Palaearctic Euchloe species (Back et al. 2008). The subspecies so far described, as well as additional populations with respect to ecology and phenotype, show no or little sequence divergences and we conclude that these represent intraspecific variation. This lack of divergence appears for members of the Euchloe hyantis complex where we assert that biological and phenotypic characters indicate that species-level isolation has been attained for E. hyantis, E. lotta Beutenmüller, 1898 and E. andrewsi Martin, 1936, respectively. Interestingly, there are also no differences between Nearctic and Siberian populations of E. creusa. Despite these findings, E. ausonides is supported as a discrete species, while its affiliation to species group V points towards a certain relationship to E. ausonia (Hübner, 1804). However, it is evident, that all samples of E. ausonides ogilvia Back, including one specimen with a dark color pattern that resembles E. ausonia naina Kozhantshikov, are genetically very similar to E. ausonides, which leads to consideration of E. ogilvia as a subspecies of E. ausonia. The occurrence of the Palearctic species E. ausonia naina in Yukon Territory is not treated, because we lacked material suitable for DNA analysis. The species status of the most recently described E. guaymasensis was also reaffirmed. Although this species shows some similarities in phenotype and haplotype to E. hyantis, our genetic analysis, especially the COI DNA sequences detected a closer relation to E. olympia. In fact, there are also specific similarities in phenotype between these two species. E. olympia is distinct according to both phenotype and genetic features. Phylogenetic assignment is not explicit. While the more conservative method of nuclear DNA comparison points towards a closer relationship to E. ausonides, analysis of the faster-evolving, maternally-inherited mitochondrial COI gene shows a closer relatedness with E. hyantis and especially with E. guaymasensis. Male Euchloe use either ridge and peak patrolling or drainage course patrolling as mate location strategies. Use of these disparate strategies by sympatric species may be most important as a barrier to hybridization and may serve as a mechanism for speciation.