Table 2.
Results of the principle component analysis (PCA) calculated for environmental variables of invaded (AS) and non-invaded sites (IS), randomization tests (999 runs) and Mann-Whitney U-test (MWU-test) of the principle component (PC) scores for AS versus IS sites. The eigenvalues, extracted variances (%), P-values, and correlation coefficients are given for the significant PCs. O2, PO4, Cl), NO3, NH4, mean of the warmest quarter (Tmax), mean of the coldest quarter (Tmin), distance to the next navigable waterway (Distance); n.s. = not significant
| PC1 | PC2 | PC3* | |
|---|---|---|---|
| % of variance | 30.72 | 19.41 | 13.97 |
| Eigenvalues | 2.46 | 1.55 | 1.12 |
| P | 0.001 | 0.001 | 0.001 |
| Eigenvectors of Variable | |||
| O2 | 0.54 | 0.15 | 0.53 |
| Cl | −0.62 | 0.25 | −0.02 |
| PO4 | −0.45 | 0.67 | 0.04 |
| NO3 | −0.20 | 0.41 | 0.77 |
| NH4 | −0.29 | 0.72 | −0.36 |
| Tmax | −0.76 | −0.24 | −0.05 |
| Tmin | −0.62 | −0.43 | 0.32 |
| Distance | 0.71 | 0.31 | −0.10 |
| AS versus IS (MWU-test) | P < 0.001 | P = 0.02 | n.s. |
*
As the scores of PC3 did not differ between AS and IS sites, these PC scores were not considered in further analysis.