Habitat and Phenetic Variation in Phymata Americana Melin (Heteroptera: Phymatidae). II. Climate and Temporal Variation in Color Pattern

Abstract

Mason, L. G. (Department of Biological Sciences, State University at Albany, 1400 Washington Ave., Albany, New York 12222) 1976. Habitat and phenetic variation in Phymata americana Melin (Heteroptera: Phymatidae). 11. Climate and temporal variation in color pattern. Syst. Zool. 25:123-128.-The striking year-to-year color variation in natural populations of Phymata americana Melin is strongly correlated with an environmental variable, average April temperature, i.e., temperature during the egg stage. Amount of dark pigment in the color pattern (as measured by the character Ca) was strongly negatively correlated (-0.42 to -0.89) with April temperature in nine out of ten populations monitored over a period of six to eight years. Comparisons of color variation in P. americana are made with that of some other insects whose adaptive strategies require a more stringent control of yearto-year color variation. [Heteroptera; Phymatidae; Polymorphism.] Studies of animal variation, past and present, have too often ignored variation in time, with the result that the spatial patterns of variation observed are often misinterpreted, and conclusions distorted. If temporal variation resulting from environmental fluctuations is great, the distortion may be considerable. In an earlier paper (Mason, 1973), patterns of year-to-year variation in metrical characters were investigated for New York and New England populations of the ambush bug, Phymata americana Melin (Heteroptera: Phymatidae). Not unexpectedly, different patterns emerged in different kinds of characters. Characters associated with structure have tended to be stable (i.e., to show little change in means from year-to-year) in habitats; they are, however, less predictable in areas in which substantial human influence (urban or agricultural) is evident. On the other hand, the character which best indicates variation in color pattern (the character Ca, chosen to represent the amount of dark pigmentation on the yellow background of the insect, see Mason, 1973) showed a very different result. There was very great yearto-year variation in the color character at virtually every locality; this applied equally well to disturbed and relatively undisturbed sites. Year-to-year variation, in fact, accounted for a much greater proportion of the total variation in Ca than did locality-to-locality variation (Table 1). Any study of geographic variation in the color pattern of this insect which did not take account of yearto-year variation would unquestionably produce a muddled and inaccurate picture. The purpose of the present paper is to examine ecological factors which might be responsible for the remarkable year-to-year fluctuation in the color pattern of P. americana; and to compare temporal color variation in this species with that observed in certain other insects, in an effort to understand the circumstances under which color pattern might tend to vary greater or lesser amounts from year to year.