HOST-PLANT UTILIZATION IN THE COMMA BUTTERFLY - SOURCES OF VARIATION AND EVOLUTIONARY IMPLICATIONS

A major challenge in the study of insect-host plant interactions is to understand how the different aspects of offspring performance interac t to produce a preference hierarchy in the ovipositing females. In thi s paper we investigate host plant preference of the polyphagous butter fly Polygonia c-album (Lepidoptera: Nymphalidae) and compare it with s everal aspects of the life history of its offspring (growth rate, deve lopment time, adult size, survival and female fecundity). Females and offspring were tested on four naturally used host plants (Urtica dioic a, Ulmus glabra, Salix caprea, and Betula pubescens). There was substa ntial individual Variation in host plant preference, including reversa ls in rank order, but the differences were largely confined to differe nces in the ranking of Urtica dioica and S. caprea. Different aspects of performance on these two plants gave conflicting and complementary results, implying a trade-off between short development time on U. dio ica, and larger size and higher fecundity on S. caprea. As all perform ance components showed low individual variation the large variation in host plant preference was interpreted as due to alternative ovipositi on strategies on the basis of similar 'performance hierarchies'. This indicates that the larval performance component of host-plant utilizat ion may be more conservative to evolutionary change than the preferenc e of ovipositing females. Possible macro-evolutionary implications of this are discussed.