Proceedings of the 21st Asian Pacific Weed Science Society Conference (Editors: B. Marambe, U.R. Sangakkara, W.A.J.M. De Costa, and A.S.K. Abeysekara), 2-6 October 2007, Colombo, Sri Lanka. AN AGGRESSIVE INVADER PLANT Andropogon virginicus L. IN JAPAN AND HAWAII ISLANDS T. Enomoto1, Y. Ozawa1, H. Kataoka2, S. Kariyama3 and J. Yamashita1 1 Research Institute for Bioresources, Okayama University, Kurashiki, Japan [email protected] 2 Tsuguro Nature Park for Contact with Living Things, 1077 Hiruzen-shitao Maniwa, Japan 3Kurashiki Museum of Natural History, Kurashiki, Japan Abstract: Andropogon virginicus is a native from the southeastern United States to northern south America, and it was introduced to Hawaii prior to 1924. It is considered as one of the three most invasive grasses in Hawaii pasture systems. According to the Australian risk assessment system, it scored 13, a score for a plant not allowed to be imported, and likely to be a pest. The specimens of A. virginicus from major herbariums in Japan were checked in the laboratory. The oldest specimen was collected in 1940, in Kyoto Prefecture, and they have spread into central part of Japan. The distribution status of A. virginicus was surveyed in 2006, and was found to have widely distributed from Miyagi prefecture to Kagoshima prefecture (about 1300 km). Most of the invasive plant species in Japan grow where the original vegetation is disturbed by human activities. Andropogon virginicus grows at open sites such as reclaimed land and housing sites. This is a unique feature of the species that grows on non-disturbed places like the Rocky Mountains. It grows along the roadsides, railroad tracks, on the lawns at the golf courses, and gardens. The plant was also found to grow on the granite terrains but very few survives on the lime stone areas. The extension of a root under the different aluminum concentration of the soil was examined and found that it can survive under high aluminum concentrations in soil. The seed has dormancy and germinate at the temperature of 20 to 40°C. A. virginicus seeds germinated under natural conditions in April, bloomed and bear fruits in October of the same year. Key words: Andropogon virginicus, distribution, invasive species Introduction The present study was carried out to identify the distribution of Andropogon virginicus L., an alien plant found in Japan, to locate their growing sites, to investigate the environmental factors affecting their germination and growth and relate it to their botanical information, and to disseminate information on the distribution of the species in Japan on the homepage. Materials and Methods The specimens of the Andropogon virginicus L available at the 16 major herbariums in Japan were investigated to identify the locations where the plant has invaded. The homepage of the Research Institute of Bioresouces, Okayama University, Japan, was used to explain the species distribution where updated information on A. virginicus L. has been made available. The information on the distribution of this species was collected with the help of 1200 associates of Kurashiki museum of Natural History. Field surveys were carried out to record the growing locations by using Geographic Information System (GPS), and gather the information of the surrounding environment. The survey was carried out in two ways. Firstly, the investigators visited many places in Japan where A. virginicus L. was found, and recorded the latitude and longitude of their growing locations were recorded by using a GPS. Most of the time, height above the sea level was recorded, too, however, this parameter was estimated from the locations. Concurrently, the authors requested assistance through the internet, gathered information through e-mail regarding the growing locations of the plant species, including the name of the site. New sites where plant has invaded over the past year were 568 Proceedings of the 21st Asian Pacific Weed Science Society Conference (Editors: B. Marambe, U.R. Sangakkara, W.A.J.M. De Costa, and A.S.K. Abeysekara), 2-6 October 2007, Colombo, Sri Lanka. visited. In areas where new growth was recorded, the relationship with the environment and the coexistence plant species were investigated. Results and Discussion Investigation of the herbarium specimens The authors have investigated 434 specimens from the 16 herbariums around Japan, and the oldest specimen has been recorded in Kyoto in 1940, from the Department of Botany of the Faculty of Science, Kyoto University (KYO). In Okayama, the first record of the specimen was dated back to 1955. According to Figures 1.1 to 1.7, the species has been reported from Keihanshin and Nagoya areas in1940s, and later it has spread to Toukai, Sanyo, Shikoku, Kyushu, Kanto, and to the areas along Japan Sea. Literature survey The authors have investigated 121 literatures, and found that northern limit of the spread of the plant from the side of Sea of Japan was Niigata and from the side of Pacific Ocean was Fukushima, and Kagoshima has been the southern limit of spread. Field survey Through the field visits, and internet and e-mail surveys, 11,067 growing locations of the species was recorded (Figure 1.8). The distribution point was identified to be further north when compared to the reports of the literature survey. The present study revealed that the northern limit of the distribution point is Miyagi, where as the southern limit is the Yakushima Island. In Okayama Prefecture, investigations were conducted thoroughly, and 3,349 locations that the plant grows were identified. The species grew well in the sunny places, along the sides of the railroad, roadsides, newly developed residential sites, and on the lawns. The plant species also existed on places where it is impossible for the wind to carry seeds. The seeds of A. virginicus L. have been transported together with mountain soil that was moved by people to establish housing sites, which has facilitated its invasion. The seeds of the species have spread into lawns from nearby areas, again carried by human beings. The seeds are often mixed with the garden trees when they are transplanting. Invasion of A. virginicus L. has been identified from new environments when compared to that recorded in the previous year. Currently, the soil condition in the newly invaded areas and the construction species are investigated. The species seems to be quite tolerant and adapts itself to the wide moisture ranges of the soil, from the dry granite area to the rice field conditions. The authors also surveyed the spread of A. virginicus L. in Hawaii Island where they have first invaded in 1924. The species was recorded along the roadsides, and on the farmland. Invasion was seen also in the crater in Kilauea Volcano and lava fields (Figure 2). A. virginicus L. has invaded into sparse vegetation with many endemic species, and as a result, it is clear that the rare native species are in danger of extinction. 569 Proceedings of the 21st Asian Pacific Weed Science Society Conference (Editors: B. Marambe, U.R. Sangakkara, W.A.J.M. De Costa, and A.S.K. Abeysekara), 2-6 October 2007, Colombo, Sri Lanka. Fig.1-1 Fig.1-2 Fig.1-3 Up to 1940s Up to 1950s Up to 1960s Fig.1-4 Fig.1-5 Fig.1-6 Up to 1970s Up to 1980s Up to 1990s Fig.1-7 Fig.1-8 Up to 2006 Field survey Figure 1. The history of distribution pattern of A. virginicus L. in Japan. Figure 2. The distribution of A. virginicus L. in Hawaii Island 570 .