Impact of volcanic activity on a plant-pollinator module in an island ecosystem: The example of the association of Camellia japonica and Zosterops japonica

Abstract

Volcanic activity provides an indispensable opportunity to study the ecological responses of organisms to environmental devastation. We examined the reproductive success of Camellia trees to identify how volcanic activity affects the processes of leaf survival, flowering activity, fruit and seed production, pollinator abundance, pollinator visitation frequency, pollination rate, and fruit and seed maturation at different damage sites on Miyake-jima, which experienced an eruption in the summer of 2000. Volcanic gases negatively affect leaf survival and reduce flowering activity in heavily damaged areas. Pollen transfer was sufficient to ensure that higher pollination rates (83%) occurred in heavily damaged areas than in less damaged areas (26-45%), but pollinator densities were lower in response to reduced flower resources. Fruit abortion rates were greater in heavily damaged sites (78%) than in less-damaged sites (53-63%). Consequently, fruit-set rates (16-29%) did not differ significantly among sites. Seed set rates tended to increase with increasing volcanic damage. The negative correlation between seed-set rates and seed mass suggests that the decreased seed mass in severely damaged sites was attributable to the better pollination rates observed there. These results indicate that compensation mechanisms ensure better reproductive success at sites that are more strongly affected by volcanic activity. © 2007 The Ecological Society of Japan.