1.3 Stratified sampling
We systematically established 282 stratified sampling sites acording to Yunnan’s hydrographic network. We were unable to sample from sites located in inaccessible terrain, including deep valleys and high mountains. Sites with strong human disturbance was also avoided. At last 228 randomly distributed sites (Ripley’s K, p = 0.2435) were remained(Figure 2). To ensure the phenological consistency and clear aquatic-terrestrial boundary of the sites, sampling was conducted from the southernmost to the northernmost and between February 27th, 2014 and June 8th, 2014. At each site, 5 sampling points were set paralleled with the river both in the aquatic and terrestrial habitats with a distance of 10 meters (Figure 1b). Totally 2,250 sampling points were set (Figure 1a), 30 sampling points were lost due to no soil there. Using the five-point sampling method in 1m×1m squares (Figure 1b), samples consisted of ~50 g of mixed soil (or sediment) and were collected at a depth of 0~10 cm below the surface at each sampling point. Totally we collected 2,250 specimens from 228 sites. Samples were then stored in a disposable self-sealing bag at room temperature. We recorded habitat information, including location, longitude, latitude, and altitude of each sampling site. Samples were sent to the laboratory within 1 week of collection, immediately followed by NTF identification processing.