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1959
Journal of the Lepidopterists' Society
171
CONCERNING SUBSPECIATION IN WESTERN NORTH AMERICAN EUPHYDRYAS (NYMPHALID/E)
by Stanley G. Jewett, Jr.
The description of Euphydryas editha remingtoni by William N. Burdick in a recent issue of this journal (1959) has prompted the following comments.
I am keenly interested in Euphydryas and am gradually accumulating a sizeable collection of this genus from various places in western North America. Of equal importance is the knowledge being acquired of the ecological conditions under which the different forms exist. Material from this region is not presently easy to identify, and it will probably be some time before an entirely satisfactory systematic treatment can be made. As in the case of many other insect groups reliance should probably not be placed solely on morphological characters for specific and subspecific differences.
The pioneer work of Gunder (1929), Hovanitz (1942), and Hovanitz and Gare (1951) serves as a good basis for understanding the taxonomy of the many forms. But recent, and as yet uncompleted, work by David L. Bauer and myself on the genitalia and biology of material from western North America opens questions on the validity of the specific classification proposed by both Gunder and Hovanitz. Present literature is wholly inadequate to distinguish clearly most subspecies.
Euphydryas gillettii Barnes and E. editha Boisduval are distinctive species readily separable on a number of characters, including details of the male genitalia. The former is quite stable in color pattern throughout its range, but many subspecies of the latter occur throughout the Cordillera. The really difficult taxonomic problems arise when attempting to classify the chalcedona - anicia complexity. The pattern of the male genitalia is variable as shown by Gunder's (1929) figures. Two distinct forms of this group fly together at some sites in the Pacific Northwest, and apparently each seeks its own species of Pentstemon upon which to deposit eggs (Bauer observation). A great deal more material and knowledge of their ecological requirements are needed before the specific and subspecific identification of these forms can be determined accurately. Perhaps several species should be recognized. Or perhaps two subspecies now occur at the same location, one or both having originally developed elsewhere. The problem is intriguing and will require much careful work for ultimate solution.
The great variation in color pattern among many species of butterflies has led some lepidopterists, for example, Gillham (1956), to question seriously that a great many subspecific names for butterflies serve a useful purpose. I confess my own present inability to establish parameters within which to apply subspecific names for Euphydryas, but I believe that this can be accomplished after more material and ecological data are available for study. Few
172
Jewett: Euphydryas
Vol.13: no.3
would question the desirability of separating such different-appearing insects as E. editha taylori Edwards, a Transition Life Zone subspecies found from Vancouver Island to the upper Willamette Valley in Oregon and topotypical material of E. editha colonia Wright, a Canadian Life Zone subspecies found on Mt. Hood, Oregon, and nearby mountain areas. These subspecies are so very different in appearance that there is very little likelihood of ever confusing a single insect belonging to either. The problem is much more difficult when attempting to define the differences among such subspecies as remingtoni Burdick, lawrencei Gunder, edithana Strand, and aurilacus Gunder, all of which also belong to the species editha. There is also a question of the usefulness of subspecific names for forms, even though morphologically quite distinct, such as E. editha lawrencei Gunder which so far as known occupies a geographic range consisting of a few acres on a single mountain.
Burdickjs new subspecies of editha from the slopes of Mt. Thielson, Oregon, at an elevation of about six to seven thousand feet represents a population intermediate in size between that of the colony near the eastern shore of Diamond Lake, perhaps distant by a mile or two and perhaps 1,500 feet lower in elevation, and the colony at the upper limit of Canadian Life Zone on Mt. Thielson, perhaps a mile distant and 1,500 feet higher in elevation. I am confident that examination of the male genitalia would prove that it belongs to the species editha. It certainly represents an insect quite different from any described subspecies of editha, and it is to be hoped that it will be found at other localities in the Oregon Cascades. The population at the lake has not yet been named — and I believe that it is inadvisable to do so at present — but Gunder (1931) described the dwarf form near timberline on this mountain and called it lawrencei. I have a good topotypic series of this (about 50 specimens) and a series from the colony at the lake (about 200 specimens). This latter population is very similar in size and color to several others which exist in Canadian and Transition Life Zones northward to the vicinity of Camp Sherman on Metolius River, Oregon. Material from several colonies in this general region are in my collection or in that of other Oregon collectors.
Burdick has made a significant contribution in proposing an outline for use in describing subspecies of Euphydryas. Most of the items listed are good differentiating characters. Additional ones, both objective and subjective, might be added to enhance the descriptions. For example, data on wing shape, anatysis of genitalic differences, and data on ecology and food plants. It is of paramount importance to describe the male genitalia to insure specific identification. Care should be taken to describe morphological differences from and similarities to subspecies described from adjacent geographic areas. Areas of gradation from one subspecies to another should be indicated in so far as possible.
In view of the great variability shown in the editha and chalcedona-an'icia groups, I suggest that further naming of subspecies be held in abeyance
1959 Journal of the 1.epidopterists' Society 173
until some competent worker prepares a monograph of the genus for the western North American forms based on all available material in both institutional and private collections.
Literature Cited Burdick, W. N., 1959. A new race of Euphydryas from the Cascade Range of Oregon
(Nymphalidae). Lepid. News 12: 165-170. Gillham, N. W., 1956. Geographic variation and the subspecies. Syst. Zoology 5:
110-120. Gunder, J. D., 1929. The genus Euphydryas Scud, of boreal America (Lepidoptera,
Nymphalidse). Pan-Pacific Ent. 6: 1-8. Gunder, J. D., 1931. Some new butterflies (Lepid., Rhopalocera). Bull. So. California
Acad. Sci. 30: 47. Hovanitz, Wm., 1942. Genetic and ecologic analyses of wild populations in Lepidoptera.
I. Pupal size and weight variation in some California populations of Melitcea
chalcedona. Ecology 23: 175-188. Hovanitz, Wm., & Sister Mary Jude Le Gare, 1951. Genetic and ecologic analyses of
wild populations in Lepidoptera. II. Color pattern variation in Melitcea chalcedona.
Wasmann Jour. Biol. 9: 257-310.
7742 S. E. 27th Avenue, Portland 2, Ore., U. S. A.
THE EQUATION OF SUBSPECIATION by L. Paul Grey
Algebra is the accepted bedfellow of logic, nowadays; the following ideas have no claim to originality but in the present application perhaps will provide amusement for an idle moment.
Variability in wild populations, from the minor differences peculiar to local strains up to the unique character combinations of independent subspecies, are assumed to be divergencies which are products of isolation in time and isolation by barriers, which is to say,
d = tb.