Abstract
The relationship between animal-dispersed plants and frugivorous animals was observed in a warm temperate evergreen forest on Yakushima Island from following four viewpoints.
1. Fruiting phenology. Some of the observed consumers were year-round residents, but the most of consumers migrated to Yakushima Island from the main islands of Japan to over winter (from November to March), and their abundance in winter was four times as high as during the rest of the year. In 23 of 27 plant species investigated sapfruit production coincided with their immigration season.
2. Feeding patterns of frugivores. Sapfruits were consumed by birds and Japanese macaques. Birds with small gapes consumed only small fruits (less than 6mm in diameter); while birds with large gapes and Japanese macaques consumed a wide range of fruits (from 4 to 16mm in diameter). The larger animals did not ignore the smaller fruits.
3. The spatial distribution patterns of dispersed seeds, saplings and fruiting trees. As for species whose seeds were dispersed only by gravity, the distributions of seeds and saplings were restricted within the narrow area around fruiting trees. Seeds of sapfruits were dispersed widely by birds and monkeys. The distribution of saplings of these species were concentrated but differ from the area around fruiting trees.
4. Eight-year fluctuations of fruit production. Total numbers of sapfruits or capsules fluctuated in eight years for each species. Fruiting fluctuations of these species were assorted in tree types. The degree of fluctuations of annual fruiting species and biennial fruiting species was smaller than that of nuts previously reported, but there were no significant difference between the degree of mass fruiting species and that of nuts. For every species except two species great fruiting years tended to coincide among individuals within a species. Great fruiting year among inter species showed mild synchronization.
