Figs, pollinators, and parasites: a longitudinal study on the effects of nematode infection on fig wasp fitness

Publication

Publication Type:

Journal Article

Source:

Acta Oecologica (Submitted)

Abstract:

Mutualisms are interactions between two species in which the fitnesses of both symbionts benefit from the relationship. Although examples of mutualism are ubiquitous in nature, the ecology, evolution, and stability of mutualism has rarely been studied in the broader, multi-species community context in which they occur. The pollination mutualism between figs and fig wasps provides an excellent model system for investigating interactions between obligate mutualists and antagonists. The fig pollination mutualism is exploited by a diverse community of non- pollinating fig wasps that develop within fig fruit at the expense of fig seeds and pollinators. Much less well studied, however, are consequences of the interaction between female pollinating wasps and their host-specialist nematode parasites. Here we focus on a tri-trophic system comprised of a fig (Ficus petiolaris), pollinating wasp (Pegoscapus sp.), and nematode (Parasitodiplogaster sp.), investigating geographical variation in the incidence of attack and mechanisms through which nematodes may limit the fitness of their wasp hosts at successive life history stages. Observational data reveals that nematodes are ubiquitous across their host range in Baja California, Mexico, that the incidence of nematode infection varies across seasons within- and between locations, and that infected pollinators experience fitness declines through reduced offspring production. Experimental results indicate that high levels of infection by infective, dauer-stage nematodes significantly reduce wasp lifespan. Further, the finding of fewer nematodes in successfully pollinating than in initially dispersing wasps indicates that high infection decreases the probability of successful host dispersal as well. These findings – and the unexpected finding of nematodes infecting non-pollinating wasps - highlight gaps in our knowledge of pollinator-Parasitodiplogaster interactions and suggest previously unappreciated ways in which this nematode may influence fig and pollinator fitness, mutualism persistence, and non-pollinator community dynamics.