THE WING LENGTH OF LENTIC CAPNIIDAE (PLECOPTERA) AND ITS RELATIONSHIP TO ELEVATION AND WISCONSIN GLACIATION

Abstract

AbstractAlong the Continental Divide in Alberta, British Columbia, and Montana three species of Capniidae were common at some lakes (Capnia confusa Claassen, Isocapnia integra Hanson, and Utacapnia trava (Nebeker and Gaufin)). Females of all three species had substantial reduction in wing length at least at one lake, while most lentic populations had slightly shorter wings than a macropterous river population of the same species. For females of all three species there was a weak positive relationship between functional wing length and lake elevation. Furthermore, there was also a significant negative relationship between functional wing length and the approximate year of Wisconsin deglaciation for C. confusa and U. trava. Suitable data were not available to test the significance of this relationship for I. integra. However, the relationships between wing length and elevation, and between wing length and Wisconsin deglaciation, suggest that wing length of these three capniid species is related to lake age. Present day wing length might be explained by selection for brachypterism over recent millennia.