The potential for laurel wilt disease-induced host switching in the palamedes swallowtail, Papilio palamedes

Biological invasions facilitate the mixing of species and increase opportunities for “ecological fitting” whereby species that possess compatible traits form novel associations, despite having no shared coevolutionary history. In the southeastern US, laurel wilt disease (LWD) has spread throughout many Coastal Plain habitats. Most incidences of LWD-induced mortality occur in redbay (Persea borbonia Lauraceae), an abundant sub-canopy species and well known as the primary larval host of the palamedes swallowtail butterfly (Papilio palamedes). Following the decline of redbay, it is unclear whether this abundant herbivore can achieve fitness on other Lauraceous hosts. We hypothesize that the exotic camphor tree (Cinnamomum camphora) will be a suitable host due to high LWD-resistance and its physical and chemical similarities to redbay. In coastal Mississippi, we quantified the performance of larvae and the oviposition preferences of wild-caught adult females using foliage of both redbay and camphor. Larval survival was significantly higher on redbay (87%) compared to camphor (46%). Although duration of each larval stage was greater on camphor, only larvae in their second and third instars showed significantly lower growth rates on this host species. In choice trials, females laid a significantly greater proportion of eggs on redbay (97%) compared to camphor (1%). In no-choice trials, significantly more eggs were laid on redbay compared to camphor and synthetic foliage, which did not differ. Our results indicate that camphor is suitable for the growth and survivorship of P. palamedes larva, but LWD-induced host switching may be restricted by factors governing oviposition preferences in this species.