Dryas iulia (Lepidoptera, Nymphalidae) larval preference and performance on four sympatric Passiflora hosts

Abstract

Host plant quality is determinant for herbivorous insects performance and survival. While on larval stages, insects select their host plants based on factors such as leaf nitrogen and water content, digestibility, and defences. Of great interest is the coevolutionary relationship between the Heliconiini insects and the Passiflora plants. In this study we experimentally evaluated Dryas iulia (Nymphalidae) larval preference to four sympatric Passiflora (Passifloraceae) and subsequently, the larval performance on the two most consumed species. We tested the hypothesis that D. iulia larvae prefer the Passiflora species with higher nutritional quality and lower defence, which supports the greatest larval performance. Dryas iulia larvae preferred P. misera (60.5% leaf consumption) over P. pohlii (28.9%), P. suberosa (15.5%), and P. edulis (not consumed). Passiflora misera presented the highest N concentration, third in water content, second in tector trichomes, and no glandular trichomes (only P. suberosa did). Nitrogen best explained D. iulia larvae leaf consumption; which further explains the greatest larval performance in P. misera than in P. suberosa: i.e. higher survival (23.1%), conversion efficiency of ingested food (32.8%), relative growth rate (14.8%), heavier pupae (15.2%), and lower relative consumption rate (13.8%). This study creates the opportunity to further investigate the Heliconiini-Passiflora system and showed that D. iulia larvae can assess and choose the host plant (even among sympatric species) that supports the greatest performance.