1 Graduate School of Life and Environmental Sciences, Osaka Prefecture University 1-1 Gakuen-cho, Naka-ku, Sakai-shi, Osaka 599-8531, Japan *2 Graduate School of Agriculture, Osaka Metropolitan University 1-1 Gakuen-cho, Naka-ku, Sakai-shi, Osaka 599-8531, Japan *E-mail: sueda@omu.ac.jp 2024 AIRIES The browsing ant Lepisiota frauenfeldi native to southern Europe has been introduced through human activities to broad areas globally since 2017. In areas it has invaded, the ant is known to rapidly increase its population and particularly to prey on native ant species. We conducted ant monitoring surveys once a month using a time-unit sampling method on two routes, Route A and Route B, at Nanko Port, Osaka, Japan between 2021 and 2023. On Route A, the browsing ant was observed with the highest frequency, accounting for 77 to 100 percent of the population throughout the survey period, and eight other ant species were observed. The number of Le. frauenfeldi individuals decreased from September 2021 to January 2022, peaked in June 2022, and hit a low in January 2023. On Route B, this ant was not observed at any time during the survey period, but ten other ant species were observed. The diversity and evenness of ants at the site that had been invaded were much lower than at the site not invaded, suggesting that the presence of Le. frauenfeldi had a negative effect on diversity and even distribution of local ants. In addition, we investigated the distribution of Le. frauenfeldi using the time-unit sampling method over the wider area of Nanko Port (375 ha), dividing it into 15 grids. Our results showed the browsing ant to be found only in grids in the southeastern part of Nanko Port. These results suggest that the species currently has a limited range in this area, highlighting the importance of early control measures before its distribution expands. Key words: ant nest, browsing ant, colonization, distribution expansion, invasive alien ant, pest control As international trade has expanded, the distribution of invasive species has grown along with the increase in transported commodities, leading to more and more ecological 2009; Bertelsmeier et al., 2017). Approximately 241 species belonging to Formicidae are known as alien species around the world. Among them, the browsing ant Lepisiota (Formicidae: (Mayr, Formicinae) (Fig. 1) has been selected as one of the world’s top 100 worst invasive species (Lowe et al., 2000; IUCN, 2009; Global Invasive Species Database, 2020), and is spreading its impact globally (Holway et al., 2002). The browsing ant is native to southern Europe, and was artificially introduced widely abroad, including in Asia, Australia and Guam. It has been also reported on the Mediterranean coast, the Middle East, Madagascar, India, damage worldwide frauenfeldi (Hulme, 1955) Abstract Malaysia, East Timor, Taiwan and other regions (Guénard et al., 2017; Terayama, 2017; Hoffmann et al., 2023). In Japan, the species was introduced into several locations: in 2017, at Tobishima and Nabeta Piers in Nagoya City, Aichi and Aomi Pier in Koto Ward, Tokyo; in 2018, at the container terminal at Nanko Port in Osaka City, and Hakozaki Pier in Fukuoka City; in 2019, at Shibushi Port in Shibushi City, Kagoshima; Rokko Island in Kobe City, Hyogo; and Honmoku Pier in Yokohama City, Kanagawa; and in 2020, along a national highway in Naha City, in Shizuoka City, Okinawa; and at Shimizu Port (Terayama, 2017; Terayama, 2018; Terayama, 2021, Ueda & Murakami, 2022). In the areas it has invaded, the ant population has increased rapidly due to its adaptability to various climatic conditions and high reproductive capacity, causing and damage biodiversity by preying on native ant species and other arthropods (Hoffmann et al., 2023). In response to these significant 125 ecosystems to Shugoro INOUE1 and Shouhei UEDA2* 1. Introduction Global Environmental Research 28/2024 125-131 printed in Japan Distribution and Seasonal Population Change of the Browsing Ant, Lepisiota frauenfeldi at Nanko Port of Osaka, Japan
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