## 2 Materials and Sample Acquisition  
Sampling location: An artificial pool, Nanshe Village, Dapeng New District, Shenzhen City, Guangdong Province, China, \(22^{\circ}28^{\prime}45^{\prime\prime}\) N \(114^{\circ}31^{\prime}6^{\prime\prime}\) E, 1 m above sea level (Figure 1). This pool has not been interfered with by humans for over 30 years. Figure 1: Map of sampling location. **Sampling time**: November 2020-October 2021. The sample was carried out within 1 or 2 days in the middle of or late each month. **Sampling method**: A D-type net was swept 10 times in the same direction in each 1 m \(\times\) 1 m sampling square. The aquatic beetles that were collected were placed in a bottle containing adsorbent paper soaked with ethyl acetate. Each bottle containing aquatic beetles was labeled and transferred to the laboratory where the beetles were identified. **Selection of ecological factors**: Pearson correlation coefficient analysis, multiple regression analysis, and marginal effect analysis were used to determine the following factors affecting Dapeng Peninsula aquatic beetle. **Determination of ecological factors**:  
**Water temperature**. A thermometer was used to determine the real-time water temperature at each collection time. **pH**. A precise pH test paper was used to determine the pH of the water at each collection time. **Salinity**. A pen salinometer was used to determine the salinity three times at each collection time, and the mean of the three consecutive measurements was used. **Water depth**. Each sample was collected from an area of water <1.5 m deep. The water depth was determined five times using a tape measure, and the mean depth was used. **Proportional area of aquatic plants. ** The area of exposed plants as a percentage of the total area in a sampling square was estimated. **Proportional area of submerged plants. ** The area of submerged plants as a percentage of the total area of the sampling square was estimated. **Water area**. The water area was calculated from measurements made using a tape measure. **Water level**. The weighted water level method was used to divide the zones of the pool according to depth. The contribution of each zone to the total water area of the pool was calculated. The water depth in each zone was then measured five times. The maximum and minimum values were removed, then the mean of the remaining values was used to represent the water level in the zone. The water level proportion in each zone was multiplied by the area proportion in each zone, and then the sum was defined as the weighted water level of the water area, calculated using Equation (1)  
\[W=\sum_{i=1}^{n}L_{i}S_{i}, \tag{1}\]  
where \(W\) is the weighted water level of the water area, \(L_{i}\) is the water level proportion for zone \(i\), and \(S_{i}\) represents the proportion of the area in each zone. **Data processing**: In order to eliminate the dimensional influence among the indicators, the eight ecological factors were normalized respectively, and the normalization formula is as follows:  
\[X^{\prime}=\frac{X-X_{min}}{X_{max}-X_{min}} \tag{2}\]  
where \(X\) is the measured value for each environmental factor, \(X_{min}\) is the minimum value for the environmental factor (in the whole dataset), \(X_{max}\) is the maximum value for the environmental factor (in the whole dataset), and \(X^{\prime}\) is the normalized value. Raw data \begin{table}
\begin{tabular}{c c} \hline \hline
**Materials and Equipment** & **Brand Models** \\ \hline pH test paper & Shanghai Sanaisi Reagent Company Limited (Shanghai, China); Precision paper pH 5.5–9.0, \\  & B-extensive paper pH 1-14 \\ Pen salinometer & Hong Kong Sigam Instrument Group Company Limited (Hong Kong, China); AR8012 \\ Thermometer & MITIR Electric Company Limited (Bangalore, India); Electronic folding thermometer TP502 \\ Binocular anatomy mirror & Nikon (Tokyo, Japan) SMZ1270 \\ D-type water net & 26 cm \(\times\) 28 cm, net depth of about 40 cm, 120 mesh \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Experimental materials and equipment.