Population Behavior and Adult Feeding Capability in Lepidoptera

Abstract

Population behavior in Lepidoptera is increasingly being shown to correlate with life-system or intrinsic factors. Two examples of such factors are larval gregariousness (and associated egg clustering) and overwintering stage (and associated larval feeding phenology). Adult feeding capability, also an intrinsic factor, has received scant attention in Lepidoptera population studies. It varies from species that are incapable of feeding to species that feed daily or hourly. Because adult feeding capability determines reproductive duration, it could affect vulnerability to mortality agents during a critical period and thereby influence population behavior. Using comparative methodology, I tested whether long-term population density and variability are related to adult feeding capability. Test data were published density records for >200 species in 16 families during 10–60 yr in Canada, the United Kingdom, and Germany, with species assigned to low, medium, and high classes of adult feeding capability. Mean logarithmic population densities, as well as standard deviations, were inversely related to degree of adult feeding capability. I also indirectly explored history of phenotypic variation through evolutionary time in the 3 intrinsic factors. Results suggested that adult feeding capability diverged earlier and was evolutionarily tracked by larval gregariousness and overwintering stage. Among 29 phylogenetically independent lineages of outbreak Lepidoptera, there was a significant association with low adult feeding capability. Study results lead to the conclusion that adult feeding capability is a primary intrinsic factor that influences population behavior more than has hitherto been recognized.