2.2 Current Distribution and Spread of RIFA in 3. Ecological Impacts 161 Fig. 1 Distribution of S. invicta appearances at the county level across China, based on data available from the Ministry of Agriculture and Rural Affairs of the People’s Republic of China (农业农村部) in 2022. Records in Taiwan are not included. The northern limit of prediction from different studies is overlaid. From Wang et al. (2018a), “1” represents the possible limit, and “2,” the certain limit (black numbers, upper right of map). From Wang et al. (2022), “1” represents the low-risk boundary, “2,” the medium-risk limit, and “3,” the high-risk limit (outlined numbers). The northern suitability limit was defined by identifying suitable areas with poor suitability (Song et al., 2021). the Red Imported Fire Ants in Mainland China, Hong Kong and Macau Macau and Hong Kong At a local scale, both Hong Kong and Macau present good examples for tracking the spread of the RIFA, which rapidly dispersed in the years following its first detection. Despite the initial quarantine and inspection efforts by Macau and Hong Kong authorities (Ecotourism, n.d.; China Daily, 2005), RIFA has continued to spread through both territories. In Macau, after its detection in 2003 (Hua, 2006), the species spread to disturbed and non-forested locations within Coloane Island (where the most recent sampling was conducted). The species can be found along trails in forested areas but does not enter deeper into the forest (Brassard et al., 2021) (Fig. 2). In Hong Kong, the species has spread rapidly in lowland areas (Fig. 3). In about ten years, it has occupied almost half of the city’s urban agroecosystems (Chan & Guénard, 2020), and occupies at least 16% of the total area of Hong Kong (Fig. 3). RIFA constructs its mounds in open soil with sunny areas: on fallow land, by roadsides, in gardens, close to ponds and along rivers (Zhang et al., 2007) (Fig. 3). Environmental degradation and disturbance play a significant role in the proliferation of S. invicta (Tschinkel, 2013). RIFA efficiently exploits modified and fragmented ecosystems, which provide the least competition for resources (Zhao & Xu, 2015). Indeed, in Hong Kong, continuous disturbance practices for managing natural habitats in favor of other species (e.g., birds in Mai Po and Lok Ma Chao) indirectly help maintain RIFA populations. 3.1 Effects on Native Biodiversity The introduction and establishment of S. invicta in China has significantly disrupted the country’s native ecosystems and biodiversity. Its interactions with native species negatively affect the native flora and fauna of the invaded ecosystems. Due to their aggressive behavior and rapid exploitation of food resources, these ants have a competitive edge over native ants and other insect species (Wang et al., 2020). RIFA, however, rarely kills and eats other ants; occasionally it attacks nests or founding queens, situations that are usually considered aggressive interference (Porter & Savignano, 1990). The presence of RIFA alters the structure of native communities by disrupting the abundance and diversity of native species (Holway et al., 2002). 3.1.1 Interactions with Native Ant Species Invasive ants like S. invicta significantly affect native ant communities by altering their composition, structure
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