Expanded Home Range of Pollinator Birds Facilitates Greater Pollen Flow of Camellia japonica in a Forest Heavily Damaged by Volcanic Activity

Abstract

Single-pollen genotyping enables us to track pollen flow that is mediated by animal vectors. By applying this innovative technique to a Camellia japonica and pollinator bird system on Miyake-jima, a volcanic island of the Izu Islands, Japan, we evaluated pollen flow mediated by the pollinator Zosterops japonica under different C. japonica flower densities. These flower densities were affected by a volcanic eruption in 2000 and subsequent large emissions of volcanic gases. The genetic diversity of pollen grains adhering to pollinators in areas with low flower density was greater than in an area with high flower density. This result was consistent with bird pollinator movement elucidated by radio tracking. In areas with low flower density, resulting from volcanic activity, pollinator birds ranged over larger areas to satisfy their energy demands rather than moving to areas with higher flower density. These results indicate that the C. japonica and pollinator bird system can ensure reproductive success even though external environmental factors, such as volcanic activity, have decreased flower density.