Within the Euphydryas genus there are many locally adapted populations and subspecies that have been the focus of population and evolution studies over the past five decades. For example, it has been argued whether three named species, E. chalcedona, E. anicia, and E. colon, constitute separate species or if they should be grouped under a single species using morphological data, such as wing color patterns, male genitalia, or genetics. Furthermore the subspecies of E. chalcedona, are distinguished from each other primarily by morphology and host plant preference. Little work has been done on the phylogeny of Euphydryas species differentiation in the southwestern United States. This area is particularly interesting with eight subspecies of E. chalcedona defined by a host of characteristics. This study was conducted to assess whether E. anicia and E. chalcedona represent separate evolutionary species, quantified as well supported monophyletic groups. A second aim was to develop a phylogeny to identify monophyletic groups among the southwestern E. chalcedona subspecies. The final goal was determine whether two characteristics used to define subspecies, color pattern and host plant use, represent a pattern reflected by phylogeny.
Results/Conclusions
A total of thirty-nine mtDNA sequences were used to develop a phylogeny rooted with E. editha as an outgroup. Within the ingroup there were twenty-six E. chalcedona sequences and nine E. anicia. Nineteen haplotypes were indentified in the ingroup, eleven E. chalcedona and eight E. anicia. A Bayesian phylogenetic analysis showed that E. chalcedona and E. anicia represented two weakly separated monophyletic groups. No E. chalcedona subspecies could be differentiated from one another based on haplotypes or monophyletic lineages. Isolation by distance analysis showed genetic and geographic distances were positively correlated within E. chalcedona subspecies. Subspecies could be separated from each other based on wing coloration, which appeared to be correlated with geographic location. No single clade could be distinguished from others based on larval monophagy. The low support for differentiation between E. chalcedona and E. anicia justifies considering populations in the southwestern United States as a single species. Mitochondrial DNA was not able to distinguish E. chalcedona subspecies into their respective subspecies. Additional genes may provide a better representation of the variation used to distinguish the various subspecies.
