Effects of volcanic disturbance on the reproductive success of Eurya japonica and its reproductive mutualisms

Ecological observation of surviving organisms and their interactions during and after volcanic activity provides an indispensable opportunity to study how organisms respond to environmental devastation. Eurya japonica satisfies the criteria as a facilitator plant species in recovering forest on the volcanic Miyake Island, which erupted in 2000, because this species is more resistant to volcanic gases than other tree species on the island. We examined the effects of volcanic disturbance on reproductive success of E. japonica and compared the visitation frequencies of pollinator insects and frugivorous birds at nine sites showing different degrees of disturbance. The leaf health was strongly decreased by frequent volcanic gas exposure, whereas flower bud formation was not suppressed. The fruit abortion rate did not differ among sites, whereas the fruit set rate significantly decreased with increasing volcanic damage. The frequencies of pollinator and frugivorous bird visits were higher in heavily damaged areas. These results indicate that the pollination and seed-dispersal system of E. japonica was potentially maintained under volcanic disturbance, though the final reproductive success decreased.