Colonization of Nishino-Shima island by plants and arthropods 31 years after eruption

摘要

Although many researchers have studied colonization, the process has rarely been observed on newly emerged oceanic islands. To describe the colonization process of a remote oceanic island, I investigated the flora, vegetation, and pollinators of Nishino-shima Island 31 yr after a major eruption in 1973. Nishino-shima Island, which is 22 ha in size, is located 1,000 kin south of mainland Japan. Vegetation cover had increased, especially on new lowland area, since a preliminary survey done 10 yr after the eruption, but plant species richness remained poor (only six species). Thus, the plant colonization rate (0.10 species/yr) was far slower than that of other volcanic islands such as Krakatau. Most plants (four species) had ocean-dispersed seeds, but two species were likely dispersed via attachment to seabirds. Despite colonization by only a few plant species, there were abundant flower visitors including ants, bugs, a butterfly, and a fly (but no bee species), and the average visitation rate per flower was 5.5 visits/12 hr in total observations. Most of the insects used multiple food sources, concurrently acting as scavengers or herbivores.