2.1 Study area and sampling
M. alternatus is the main vector of PWN in Asia and is especially widely distributed in southern China. This study was mainly conducted in Shunchang (26°39′ to 27°121′N, 117°29′ to 118°14′E) and Xiapu (26°25′ to 27°16′N, 119°46′ to 120°28′E) in Fujian Province of southern China, with a geographical distance of approximately 250 km separating the two areas. Both sites have a subtropical monsoon climate. In Shunchang, the average annual temperature is 18.5 °C, and the average annual rainfall is 1,756 mm. In Xiapu, the average annual temperature is 18.8 °C, and the average annual rainfall is 1,800 mm.
P. massoniana and P. elliottii are natural hosts ofM. alternatus , and they are widely distributed in the two areas. Moreover, urban areas, farmlands, roads, and water sources are embedded in the forested landscape. The landscape types were divided into ten categories: P. massoniana , C. lanceolata , P. elliottii , mixed forest (including some hosts), broad-leaved forest, urban, farmland, road, water, and nudation (Figure 1). Samples were collected when adults are active from May to October in 2018 from 22 sites (12 sites in Shunchang (SC) and 10 sites in Xiapu (XP); Figure 1; Table 1) using a trapping method. The sample size ranged from seven to fourteen individuals per site (mean = 9.77 ± 1.93(SE); Table 1). The maximum geographic distance between fine-scale sampling points was 10 km and a the minimum of was 400 m. All adult beetles were perserved in absolute ethanol and stored at −80 °C. A total of 215 adults M.alternatus were collected (115 in SC and 100 in XP).