Tundra Colias F. (Papilionoidea, Pieridae): Lessons in Arctic Insect Biogeography through the Discovery of Old Errors and a New Subspecies

Across the Arctic region, sulphur butterflies of the genus Colias F. comprise a significant proportion of butterfly diversity and an important exemplar taxon for Arctic insect biogeography. Yet, many Colias species-groups have eluded taxonomic consensus over the decades: highly conserved interspecific structural variation is juxtaposed upon large intraspecific variability in many Arctic Colias. Perhaps no other Colias group typifies this symptom better than the Colias tyche (Böber) – boothii Curtis complex. Here, we document a striking new population of Colias boothii Curtis from the Ungava Peninsula, representing the first records of this species-group east of Hudson Bay. This population is described as a new subspecies, Colias boothii siajae ssp. nov. Although geographically distant from the Rocky Mountain taxon C. boothii canadensis Ferris, C. b. siajae is externally similar, but intriguingly these two taxa are widely separated by two subspecies, C. b. boothii and C. b. thula Hovanitz. The biogeographical and evolutionary reasons behind this remain speculative, but the discovery of unique populations in Ungava add a significant new piece to the puzzle. A review of the eastern Arctic C. hecla Lefèbvre, the only orange sulphur species visually similar to C. boothii there, reveals that erroneous records propagated in the literature have resulted in historically persistent and considerable geographical range errors. In the eastern continental Arctic, Colias hecla is restricted to the northern Ungava Peninsula, and contrary to literature depictions, no verifiable records exist for Labrador.