Impacts of Invasive Alien Species on Native Ecosystems on the Bonin Islands

Abstract

This part introduces quantitative studies on the impacts of invasive alien animals and plants on native ecosystems on the Bonin Islands. Predation by alien predatory flatworms such as Platydemus manokwari has caused the rapid decline or extinction of many endemic land snails. In addition, predation by black rats can cause micro-evolutionary changes in shell morphology and habitat use of endemic land snails. Feral cats prey upon land birds as well as seabirds characteristic to the Bonin Islands. An introduced lizard, the green anole (Anolis carolinensis), has caused serious damage to many insect populations, resulting in changes in the pollination systems of many native plants. Grazing and trampling by feral goat s has caused destruction of vegetation, leading to accelerated soil erosion on some islands. An alien tree, Bischofia javanica, has replaced native trees due to its greater survival and seedling growth than those of native tree species. Invasion and dominance of an exotic shrub, Leucaena leucocephala, have prevented the establishment of some native woody species. Scientific understanding of the impacts of invasive species and their interactions with native species is essential for conservation and restoration of the native Bonin Island ecosystems.