Potential for host shifting in Papilio palamedes following invasion of laurel wilt disease

In the southeastern US, laurel wilt disease (LWD) is causing widespread mortality of species in the Lauraceae. The principal target, Persea borbonia, is the primary larval host of Papilio palamedes, which is known to feed on other Lauraceae species. Among these potential hosts, the exotic Cinnamomum camphora is the only species that has shown resistance to LWD. We hypothesized that oviposition preference for C. camphora and P. borbonia would correspond to larval performances on these species and that the relative host suitability of C. camphora would indicate an opportunity for host-switching. We used laboratory experiments and field observations to compare performance and preference of P. palamedes between C. camphora and P. borbonia foliage. Our results indicate moderate survivorship on C. camphora compared to P. borbonia and no differences in first and fourth instar growth rates between treatments. Fourth instars consumed relatively less of C. camphora foliage compared to that of P. borbonia, but metabolic efficiency did not differ between treatments. Rearing on the foliage of P. borbonia stump sprouts from LWD-infected trees resulted in significantly higher growth rates and metabolic efficiency as first and fourth instars, respectively. In the field and laboratory, we found no oviposition preference for C. camphora. While females laid eggs on C. camphora during laboratory trials, the same number of eggs was also laid on inanimate objects. We conclude that C. camphora is suitable for larval development but host-switching to this species by P. palamedes will be primarily constrained by the ecological factors that govern oviposition behaviors.