S. INOUE and S. UEDA been eradicated 38–42 months after the start of treatments, in other words, 16–17 months after their last sighting. Continuing monitoring for two years, however, is often difficult due to economic constraints, and monitoring frequently ceases once no invasive ant species are detected. Nonetheless, if invasive ant species remain, even at low frequencies, there is a possibility that their populations may recover (Holway et al., 2002; Regan et al., 2006; Silverman & Brightwell, 2008). Hayasaka et al. (2022) conducted an acute toxicity test on the browsing ant and revealed that fipronil, which is commonly used in Japan to control Argentine ants and fire ants, can also be effective for controlling this species. Chemical control measures using fipronil-based insecticides have already been implemented at three sites invaded by the browsing ant, with successful eradication at one site (Hoffmann et al., 2016). It will be crucial to implement early control measures using fipronil-based baits during early spring in the southeastern part of Nanko Port where its distribution has been confirmed, before the population of this species increases. However, fipronil is known to exhibit high toxicity to non-target organisms, including fish, aquatic invertebrates, bees and birds (Weston & Lydy, 2014; Hoffmann et al., 2016). To conserve the biodiversity, it will be essential to apply the insecticides exclusively in areas where invasive ant colonies have been detected through monitoring surveys. References Abril, S., Oliveras, J. and Gómez, C. (2014) Foraging activity and dietary spectrum of the Argentine ant (Hymenoptera: Formicidae) in invaded natural areas of the northeast Iberian Peninsula. Environmental Entomology, 36(5): 1166–1173. Bertelsmeier, C., Ollier, S., Liebhold, A. and Keller, L. (2017) Recent human history governs global ant invasion dynamics. Nature Ecology and Evolution, 1(7), Article No. 0184. Blard, F., Dorow, W.H.O. and Delabie, J.H.C. (2003) Les fourmis de l’ile de la Reunion. Bulletin de la Société entomologique de France, 108(2): 127–137. Fowler, H.G., Bernardi, J.V.E., Delabie, J.C., Forti, L.C. and Pereira da Silva V (1990) Major ant problems of South America. In: Vander Meer, R.K., Jaffe, K. and Cedeno, A. (eds.) Applied Myrmecology: A World Perspective, 3–14. Westview Press, Boulder. Global Invasive Species Database (2020) Global Invasive Species Database. Retrieved from http://www.iucngisd.org/gisd/100_ to Along Route A, the invasive Argentine ant was observed in March and April 2022, but not detected in subsequent surveys. It is possible that the number of Argentine ants decreased due to the influence of the previously established the browsing ant. Further investigation is needed to understand the interspecific interactions between these two invasive species. Based on our monitoring survey, we classified Route A and Route B as the sites invaded and non-invaded, respectively, by Le. frauenfeldi. We then compared ant diversity, abundance and evenness between April 2022 and January 2023 at both sites. The diversity and evenness of ants at the invaded site were much lower than at the non-invaded site. These results suggest that the presence of Le. frauenfeldi had a positive effect on ant abundance but a negative effect on diversity and evenness. In Australia, populations of other ant species have declined in areas colonized by this species (Hoffmann et al., 2023). In the invaded sites (Route A), the browsing ant may establish colonies in suitable habitats and rapidly increase its population due to its adaptability to diverse climatic conditions and its high reproductive capacity. This enables the species to dominate key resources for ants, such as food and nesting sites. The browsing ant is known to be highly aggressive and actively preys on other ant species (Blard et al., 2003; Ueda et al., 2022). Consequently, the competition with Le. frauenfeldi has likely led to population declines or forced migrations of other ant species. Our distribution survey of the browsing ant revealed that the species was found only in the southeastern part of Nanko Port. It is thought that the species currently has a limited range in this area, suggesting that early control measures are important before it expands its distribution. Although chemical control of invasive ant species has been implemented worldwide, eradication failures are common, and successful cases have rarely been reported (Hofmann, 2010; Hoffmann et al. 2016, 2023). This is largely due to their high reproductive capacity, which makes it difficult to reduce their populations to near extinction, and it is challenging to demonstrate that eradication has been successful (Sakamoto et al., 2017). Hofmann (2010) demonstrated that if the target invasive ant species is absent for two years after chemical control treatment, it can be considered eradicated. In fact, Sakamoto et al. (2017) showed that Argentine ants had We are grateful to Dr. W. Suehiro, Dr. H. Sakamoto and Dr. N. Hirai for their advice on the Kinki Regional experimental methods, and Environmental Office (Ministry of the Environment), the Greenery Planning Division (Osaka Prefectural Government) and the Ports and Harbors Bureau (Osaka City Prefectural Government) for permission to work in this study. 130 males, however, have been observed engaging in budding behavior in October (Terayama, 2017; Ueda & Murakami, 2022). These results indicate that the peak of egg-laying in the browsing ant occurs before June, suggesting that pest control measures in April and May could be effective. Additionally, implement control measures while minimizing the impact on native ecosystems, it is important to carry out these measures during winter when the browsing ant remains active, while other ant species are dormant. 5. Acknowledgements
元のページ ../index.html#36