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Table 6 Principal component analysis and Spearman’s rank correlation coefficients between stream variables and principal components for all collections (n = 432)

From: Distribution pattern of black fly (Diptera: Simuliidae) assemblages along an altitudinal gradient in Peninsular Malaysia

Variable Stream sites Principal components
Min Max Mean ± SE PC-1 PC-2 PC-3 PC-4 PC-5
Altitude (m) 159.00 1813.00 891.40 ± 30.1 −0.751** 0.268** 0.522** 0.224** 0.049
Temperature (°C) 14.40 28.40 25.30 ± 0.17 0.636** −0.230** −0.622** −0.285** −0.059
Width (m) 0.12 7.90 2.95 ± 0.11 0.692** 0.322** −0.132** 0.044 0.037
Depth (m) 0.02 0.85 0.54 ± 0.005 0.616** 0.171 0.34 0.034 0.124
Velocity (m/s) 0.16 1.03 0.42 ± 0.009 0.416** 0.544** −0.217** 0.115 0.360**
Conductivity (mS/cm) 0.01 0.15 3.48 ± 0.001 −0.297** 0.162 −0.327** 0.001 0.328**
Dissolved oxygen (mg/l) 1.27 17.20 15.77 ± 0.14 0.148 0.336** −0.051 0.363** −0.576**
pH 4.32 8.53 5.20 ± 0.04 0.036 −0.080 −0.337** 0.739** −0.155
Discharge (m3/s) 0.002 1.56 2.23 ± 0.01 0.786** 0.376** −0.208** 0.049 0.137
Canopy cover open complete 2a 0.213** −0.718** 0.175 0.315** 0.306**
Riparian open forest 2a 0.400** −0.763** 0.174 0.122 −0.015
Streambed sand bedrock 3a 0.449** 0.176 −0.503** 0.274** 0.366**
% Variance explained in PCA       
Proportion     24.8 15.1 13.8 9.3 8.4
Cumulative     24.8 39.7 53.6 62.8 71.2
  1. ** P < 0.001
  2. aMedian values given for riparian vegetation (1 = open, 2 = brush and 3 = forest), streambed-particle size (min; 1 = mud/silt and max; 6 = bedrock), and canopy cover. (1 = open, 2 = partial and 3 = complete). Rankings followed McCreadie et al. [34]