カマエカズラ（マメ科）の送粉パートナーとしてのニホンザルの獲得：拡大造林政策の間接的影響

Abstract

Mucuna macrocarpa (Fabaceae) is a vine plant that is distributed mainly in tropical and subtropical areas, as well as in a limited region around a village in Kamae within Kyushu, Japan, although no seeds were observed in this region until the late 1970s. This species requires a pollination partner for seed setting, which was recently found to be the Japanese macaque (Macaca fuscata) in Kamae. We hypothesized that the recent seed setting observed is related to the change in the distribution of the Japanese macaque in recent years as a result of the afforestation policy introduced in the 1950s-1960s. The changes in afforestation activity, distribution of the Japanese macaque, and human population dynamics were investigated. Interviews with villagers revealed that Japanese macaques had seldom appeared in or near the village until the 1960s, but have frequently been observed within the village since the 1970s-1980s, which corresponds to the same period of time when the appearance of M. macrocarpa seeds was first noted. Depopulation and the decrease in farmers and foresters that occurred at the same time as afforestation might have enabled macaques to enter and settle in the village. One reason for the 10-year time lag between the first appearance of Japanese macaques and afforestation could be that the macaques only began to move out of the forest once the conifer forest had grown to a certain level. These results suggest that the afforestation caused a change in the distribution of Japanese macaques, allowing them to exploit M. macrocarpa flowers as a new food item. Consequently, afforestation might have indirectly caused seed setting of M. macrocarpa in Kamae.