Within population variation in the demography of Speyeria mormonia (Lepidoptera: Nymphalidae)

Abstract

The adult demography of a population of Speyeria mormonia (Lepidoptera: Nymphalidae) near Gothic, Colorado USA was studied for four years. Values of demographic parameters, including survival, dispersal and sex ratio, varied yearly, without major changes in density. Shift in sex ratio with constant population numbers entails variation in effective population size among years. Flight period, catchability, relationship between body size and eclosion date, and significance of correlation between weather and daily survival rates differed between the sexes. Sexual dimorphism in correlation of wheather with survival rate may partially explain the lack of yearly variation in total population size. There was no significant sexual dimorphism in large scale habitat use, or in dispersal, except in 1982.The demography of this insect is compared to that of related species of Argynnis and heliconiines, from the old world temperate zone and new world tropics, respectively. While some differences are observed which can be ascribed to differences in length of the growing season, many patterns are similar. This implies conservation of demographic traits, even across broad habitat and geographic areas.