Preference and performance of Pūrerehua Kahukura (Vanessa gonerilla gonerilla) on native and introduced nettles of Aotearoa

The preference-performance hypothesis suggests that female insects prefer to oviposit on the host plant that provides the highest fitness for offspring. However, introduced plants can cause ecological traps, wherein animals lay eggs on low quality (often introduced) species instead of higher quality (usually native) species. Pūrerehua kahukura/New Zealand red admiral butterfly (Vanessa gonerilla gonerilla) lay eggs on native and introduced nettles (Urtica spp.). We tested both host preference for female oviposition and host performance for development of larvae. To test preference, we used oviposition cages in which we provided adult kahukura with native Urtica ferox, native/introduced U. australis hybrid, and introduced U. urens. To test performance, we collected the eggs and, after hatching, provided them with one of the three nettles for their development to adulthood. Kahukura only laid on U. ferox (n = 8) and U. australis hybrid (n = 2). No butterflies laid eggs on more than one Urtica species, even though some individuals laid >10 eggs while in the oviposition cages. Pupal weights were significantly higher for larvae reared on U. ferox compared to those reared on U. australis hybrid and U. urens. Although larvae were significantly heavier when fed U. ferox, larvae raised on U. australis hybrid had higher probability of survival to adulthood and faster development rates. Kahukura oviposition preference ranking (U. ferox ≥ U. australis > U. urens) qualitatively matched larval development ranking (U. ferox > U. australis = U. urens), supporting the preference-performance hypothesis for this population. If kahukura have the option to oviposit on native Urtica spp., our results suggest that they are unlikely to be duped into ovipositing on a lower quality host plant. While U. urens may act as a trap in some areas, kahukura may be able to escape that fate if native plant species are made more readily available.