OVIPOSITION PREFERENCE AND LARVAL PERFORMANCE OF LIRIOMYZA-HELIANTHI (DIPTERA, AGROMYZIDAE) ON NORMAL AND NOVEL HOST PLANTS

The relationship between oviposition preference and larval performance has often been regarded as central to the evolution of insect-plant i nteractions. Studies examining correlations between oviposition prefer ence and larval performance have yielded results ranging From good to poor suggesting that features other than a positive correlation betwee n the preference and performance may influence the evolution of host p lant use. In this study, we examined oviposition behavior and larval p erformance of the specialist leafminer Liriomyza helianthi spencer on normal host plants-sunflower, Helianthus annuus L., and cocklebur, Xan thium strumarium L. (Asteraceae, tribe Heliantheae), and a number of n ovel, but related, plants in the Asteraceae. Using choice and no-choic e oviposition experiments, L, helianthi was observed to oviposit prefe rentially in its normal host plants and in some novel hosts in the sam e tribe (Heliantheae). Plants outside the normal tribe in both subfami lies of the Asteraceae were rarely used for oviposition. Larval perfor mance, as assayed by development time, developmental rate, larval surv ivorship and pupal weight, wits assessed by transfers of larvae betwee n normal and novel hosts as well as by direct oviposition into those h osts. The transfer of leafminer larvae allows the decoupling of ovipos ition and larval performance components of host use, a traditionally d ifficult task when studying herbivores living inside plant tissues. Ou r results found no significant relationship between oviposition prefer ence and larval performance in normal and novel hosts. Leafminer larva e have greater latitude than adults in successful use of novel hosts, including use of plants in the alternate subfamily, Cichorioideae. The re are some novel plants that are riot used, for oviposition but are a s suitable for development as the normal host. Thus, there is an asymm etry between oviposition preference and larval performance in novel ho sts.