Does Escape Parasitoid Attack by Feeding on a Toxic Resource?

Host shifts can drastically change the selective pressures that animals experience from their environment. is a species restricted to the Seychelles islands, where it specializes on the fruit (noni). This fruit is known to be toxic to closely related species, including and , releasing from interspecific competition when breeding on this substrate. Previously, we showed that larvae of are unable to mount an effective immunological response against wasp attack, while larvae of closely-related species can defend themselves from parasitoid attack by melanotic encapsulation. We hypothesized that this inability constitutes a trait loss due to a reduced risk of parasitoid attack in noni. Here we present a lab experiment and field survey aimed to test the hypothesis that specialization on noni has released from the antagonistic interaction with its larval parasitoids. Our results from the lab experiment suggest that noni may be harmful to parasitoid wasps. Our results from the field survey indicate that was found in ripe noni, whereas another species, , was present in unripe and overripe stages. Parasitic wasps of the species emerged from overripe noni, where was the most abundant host, but not from ripe noni. These results indicate that the specialization of on noni has indeed drastically altered its ecological interactions, leading to a relaxation in the selection pressure to maintain parasitoid resistance.