Abstract
To study the impact of the local extinction of a large frugivore species on plant populations, we compared the seed dispersal of the large-seeded tree Myrica rubra in two forests. One forest had a population of Japanese macaques, which are large seed dispersers of M. rubra, and the other did not. Observations were made from 25 May to 7 June, 2004 on four trees on Yakushima Island (with macaques) and three trees of Tanegashima Island (without macaques). The total observation period was 137h 30min (Yakushima Island: 73h 46min, and Tanegashima Island: 63h 44min). M. rubra trees were primarily visited by Japanese macaques (Yakushima Island) and brown-eared bulbuls (both islands). The mean number of fruits consumed per visit by the macaques on Yakushima Island was 20 times more than that consumed by the bulbuls on both islands. In short, the mean number of fruits consumed per day per tree on Yakushima Island (Total: 918.1 fruits; macaques: 893.0, and bulbuls: 25.1) was higher than that on Tanegashima Island (bulbuls: 24.0). These results suggested that macaques may be the 'keystone' seed dispersers for M. rubra, and that the reduction in macaque numbers may lead to a decrease in the number of seeds dispersed from these trees.
