Nymphalidae Rafinesque, 1815

Zhang, Jing, Cong, Qian, Shen, Jinhui, Opler, Paul A. & Grishin, Nick V., 2020, Genomic evidence suggests further changes of butterfly names, The Taxonomic Report of the International Lepidoptera Survey 8 (7), pp. 1-41 : 17-19

Family Nymphalidae Rafinesque, 1815

Speyeria Scudder, 1872 is a subgenus of Argynnis Fabricius, 1807 Argynnis irene Boisduval, 1869 and Argynnis nausicaa W. H. Edwards, 1874 are species distinct from Argynnis hesperis W. H. Edwards, 1864

Argynnis atlantis W. H. Edwards, 1862 (type locality USA: New York, Green Co., mostly eastern in distribution) and Argynnis hesperis W. H. Edwards, 1864 (type locality USA: Colorado, Jefferson Co., mostly western in distribution) form a species complex that requires further investigation ( Dunford 2009). We obtained whole genome shotgun sequences for nearly all its taxa considered valid by Pelham (2020). A number of these taxa were represented by their primary type specimens to ensure correct application of their names ( Fig. 11, indicated as HT for holotype and LT for lectotype). Because protein-coding regions of species in the subgenus Speyeria are quite conserved in their sequences, in order to provide better discrimination between taxa, we used all genomic sequences mapped to Argynnis (Speyeria) diana reference genome ( Zhang et al. 2019d). Furthermore, we considered the autosomes and Z chromosome separately due to their distinct roles in evolution and differences in resistance to introgression ( Cong et al. 2019b). The trees constructed from concatenated coding and non-coding regions of autosomes ( Fig. 11a) and Z chromosome ( Fig. 11b) revealed evolutionary complexities of the taxa included. First, as expected, the entire group consisting of A. hesperis ( Fig. 11 green, red and magenta) and A. atlantis ( Fig. 11 blue) is monophyletic in both trees. Second, in both trees, A. hesperis is paraphyletic with respect to A. atlantis , and a clade composed of south-central subspecies of A. hesperis ( Fig. 11, green), including A. hesperis nausicaa W. H. Edwards, 1874 (type locality USA: Arizona, Graham Co.) is sister to all other taxa combined. Third, the position of the clade consisting of northern and eastern subspecies of A. hesperis that include the nominotypical subspecies ( Fig. 11 magenta) is different in autosome and Z chromosome trees. In the autosome tree ( Fig. 11a), this clade is sister to A. atlantis , and in the Z chromosome tree ( Fig. 11b), it is sister to the clade of western subspecies of A. hesperis that include A. hesperis irene (Boisduval, 1869) (type locality USA: California, Sierra Co. ).

Thus, the trees reveal four groups of taxa in this complex, and applying the oldest name in each group, we call them atlantis , hesperis (sensu stricto), irene and nausicaa . To probe whether these groups are species, we used the Fst/Gmin Z chromosome tests ( Cong et al. 2019b) obtaining the following statistics. First, traditionally treated as distinct species, atlantis and hesperis groups show differences consistent with their species-level distinction: 0.23/0.07, albeit marginally (Fst for distinct species is typically above 0.2, with 0.5 and above indicating strong differentiation, and Gmin is less than 0.1, with 0.02 and below indicating strong isolation). Second, the differences between the atlantis and nausicaa groups are even more pronounced than those for atlantis and hesperis : 0.36/0.026, which is in agreement with the nausicaa group being sister to the clade consisting of the three other groups in both autosome and Z chromosome trees ( Fig. 11). Third, the differences between hesperis and nausicaa are of about the same magnitude as for others: 0.26/0.05, indicating that A. nausicaa is a distinct species rather than a group of subspecies within paraphyletic A. hesperis . Fourth, the hesperis and irene groups did not reveal species-level differences in the Z chromosome: 0.13/0.13, suggesting that they may be conspecific, which is in agreement with their close clustering together in the Z chromosome tree ( Fig. 11b).

Although the irene group is not strongly different from the hesperis group in Z chromosome, it is placed differently in the autosome tree: as sister to both hesperis and atlantis groups, rendering the species A. hesperis that includes irene paraphyletic. While a species paraphyletic in a tree built from concatenated genomic alignments is not inconceivable due to the possibility of extensive introgression from some other species in a part of the species range, such a situation calls for further investigation. Analysis of the trees built from various segments of the nuclear genome revealed that some segments in the hesperis group are similar to the atlantis group, while other segments are similar to the irene group. Hence, we hypothesize that A. hesperis is a hybrid species of A. irene and A. atlantis , because it shares 20% and 67% of its autosome-linked genome, and 71% and 20% of its Z-linked genome with the latter two species respectively, while it possesses only 0.17% of unique polymorphisms, compared to 0.5% and 0.28% unique polymorphisms in A. irene and A. atlantis , respectively. We see that a significant fraction of the A. hesperis genome is shared with either A. irene or A. atlantis , and the number of unique mutations in the A. hesperis lineage is smaller than that compared to either of its putative parental species, suggesting a hybrid origin of A. hesperis . Consequently, we consider A. irene (consisting of four westernmost subspecies presently associated with A. hesperis , Fig. 11) to be a species-level taxon, and the Z chromosome similarity with A. hesperis is therefore explained by the hybrid origin of A. hesperis , which inherited larger segments of this chromosome from A. irene . This scenario of species originating by hybridization is not covered by the Fst/Gmin Z chromosome test for species distinction ( Cong et al. 2019b). The COI barcodes of A. irene are closer to A. atlantis (2.5%, 17 bp difference) than to A. hesperis (5%, 33 bp difference), probably because A. hesperis possesses mitogenomes introgressed from A. nausicaa and does not reveal differences in the barcodes with the latter species. As a side note, the earliernamed species A. hesperis is likely to a be a hybrid species with one of the parental species being a named later ( A. irene ), illustrating that biological reality has little to do with the order species were named in.

Finally, we find ( Fig. 11) that the holotype of Speyeria hydaspe conquista dos Passos & Grey, 1945 (type locality USA: New Mexico, Santa Fe Co., presumed to be in error), presently placed as a synonym of Argynnis hydaspe rhodope W. H. Edwards, 1874 , clusters closely with the holotype of Argynnis hesperis tetonia (dos Passos & Grey, 1945) (type locality USA: Wyoming, Teton Co.) and is therefore placed as a synonym of tetonia, new placement.

In summary, genomic data suggest that the atlantis - hesperis complex consists of four species: A. atlantis , A. hesperis , and two others with reinstated status: A. irene and A. nausicaa . The following subspecies are assigned to A. irene to form new combinations: Argynnis irene dodgei Gunder, 1931 , Argynnis irene cottlei J. A. Comstock, 1925 , and Argynnis irene hanseni (J. Emmel, T. Emmel & Mattoon, 1998) . The following subspecies are assigned to A. nausicaa to form new combinations: Argynnis nausicaa elko (Austin, 1984) , Argynnis nausicaa greyi (Moeck, 1950) , Argynnis nausicaa viola (dos Passos & Grey, 1945) , Argynnis nausicaa tetonia (dos Passos & Grey, 1945) , Argynnis nausicaa chitone W. H. Edwards, 1879 , Argynnis nausicaa schellbachi (Garth, 1949) , Argynnis nausicaa electa W. H. Edwards, 1878 , Argynnis nausicaa dorothea (Moeck, 1947) , and Argynnis nausicaa capitanensis (R. Holland, 1988). The names for other taxa in this complex remain unchanged.