Parallel ecogenotypical color variations in butterflies

Abstract

The pigment colors of N. American butterflies are divided into 3 basic groups for comparing their variation with the variation of the environmental conditions I. the black, brown and gray pattern elements found in all families; II. (a) the tawny, rufous or "red-brown" pigment of the Nymphalidae, Riodinidae, Satyridae, Lycaenidae, Danaiidae and Libytheidae; (b) the yellow pigments of these same families; and (c) the orange and yellow border spots of the Pieridae and Papilionidae (central spots of Parnassius); III. the white, yellow and orange pterine ground color pigments of the Pieridae and the Papilionidae. The variation of each of these 3 pigment groups is correlated with the ecol. conditions present in the regions in which the butterflies live. Lower temp., increased available moisture, decreased solar radiation and decreased development rate were in most cases observed to be correlated with the following pigment change: Group I pigments increase in area and intensity on the wing; Group II pigments increase in intensity or darkness and may increase or decrease in area; and Group III pigments show increased development of the lighter of the 3 pterine pigments. The evidence for these correlations was derived primarily from a field and distributional study of N. American butterflies and illustrated with illustrations and maps primarily with Pacific Coast material because of the more favorable conditions for this study in this region. After the terminology of Turesson, the variation is termed ecogenotypical, being adaptive to the ecological conditions and genetic in most cases when the variation is not seasonal. The adaptiveness is not considered in the sense of "protective coloration" but rather that the colors are only a secondary product of some physiol. change in development, metabolism or "hardiness" of the different races which is of adaptive value. A limited review of recent work on this phenomenon is given and the results developed are found to compare favorably with work in other organisms. There is a similarity between natural melanism in color variation and industrial melanism in regard to the climatic conditions and the suggestion is made that the mechanism of both may be the same. || ABSTRACT AUTHORS: W. Hovanitz