Current and potential distribution of Senecio madagascariensis Poir. (fireweed), an invasive alien plant in Japan

摘要

The short-lived perennial (sometimes annual) plant, Senecio madagascariensis Poir. (fireweed) is native to South Africa and Madagascar. This plant is an invasive weed becoming naturalized over a wide range of the world, and has caused agricultural damage mainly due to its toxicity to livestock. In Japan, fireweed was first found in 1976, and has been spreading throughout the country. In this study, the current distribution of fireweed in Japan was investigated. Using a maximum entropy ecological niche modeling algorithm, the relationship between the distribution records of fireweed and climatic variables was modeled, and the potential distribution of fireweed was predicted. Many growing sites of fireweed have been observed on the Pacific coast and Seto Inland Sea coast. The northern and southern ends of the current distribution were the Pacific coast of southern Tohoku (36.9172 degrees N, 140.8613 degrees E) and southern Kyushu (31.5654 degrees N, 130.3438 degrees E), respectively. The results of modeling showed that mean temperature in the warmest quarter was the most influential predictor, and suggested that geographical distribution of fireweed in Japan is restricted mainly by temperature, not by precipitation. The predicted areas of potential distribution were mainly on the Pacific coast and eastern Seto Inland Sea coast. Of the regions where fireweed had not been found, the following regions were predicted as potential distribution areas of fireweed: southern Kanto region along Tokyo Bay, coastal area of western Tokai region, western part of Seto Inland Sea coast and northern Kyushu. The Pacific coast of central Tohoku (39.058 degrees N, 141.843 degrees E) was predicted as the northern end of the potential distribution, and Amami-oshima Island (28.304 degrees N, 129.519 degrees E) as the southern end.