(A) Represents the monthly values for the seasonal effect (red), the mean rainfall for the period under study and the 3-month cumulative rainfall (blue). (B) Shows a clear linear relationship …
The seasonal effect was tested through sin (A) and cosine (B) functions with frequencies of 12 and 4 months (solid and dashed lines, respectively).
(A) Links between water conditions in the first two principal components obtained through principal component analysis (PCA). Comp.1, explaining more than 50% of the variation in physico-chemical …
For the construction of histograms (A–D), the relative frequency of the variable within each region is normalized by dividing each frequency by its maximum frequency. It can be noted that the …
Description of environments defined by principal components analysis (PCA) of physico-chemical parameters
Akonolinga | Bankim | |||||||
---|---|---|---|---|---|---|---|---|
PC1 | PC2 | PC3 | PC4 | PC1 | PC2 | PC3 | PC4 | |
Variance explained | 0.47 | 0.31 | 0.14 | 0.09 | 0.59 | 0.22 | 0.13 | 0.07 |
Loadings | ||||||||
pH | −0.33 | 0.7 | −0.47 | 0.41 | −0.51 | 0.51 | −0.43 | 0.55 |
Dissolved oxygen | −0.6 | 0.31 | 0.31 | −0.67 | −0.57 | 0.33 | 0.11 | −0.75 |
Water flow | −0.59 | −0.32 | 0.46 | 0.59 | −0.51 | −0.29 | 0.72 | 0.36 |
Temperature | 0.43 | 0.55 | 0.69 | 0.19 | 0.4 | 0.74 | 0.53 | 0.1 |
Separate PCA was performed for Akonolinga and Bankim, and only the most potentially relevant parameters were included.
Results from multi-model selection for Akonolinga (12 months of sampling)
Variable | Avg. effect (b) | Uncond. SE | Lower CL | Upper CL | Relative importance (wi) | Nb. models |
---|---|---|---|---|---|---|
(Intercept) | 2.71 | 4.04 | −5.21 | 10.63 | 1.00 | 39 |
Seasonality | ||||||
Sine (2pi*Month/12) | 0.36 | 0.16 | 0.04 | 0.67 | 1.00 | 39 |
Sine (2pi*Month/4) | – | – | – | – | – | – |
Cosine (2pi*Month/12) | – | – | – | – | – | – |
Cosine (2pi*Month/4) | – | – | – | – | – | – |
Physico-chemical parameters | ||||||
pH | 7.15 | 2.34 | 2.56 | 11.73 | 0.44 | 17 |
Flow | – | – | – | – | – | – |
Temperature | – | – | – | – | – | – |
Dissolved oxygen | – | – | – | – | – | – |
Conductivity | – | – | – | – | – | – |
Iron | – | – | – | – | – | – |
Physico-chemical parameters (PCA) | ||||||
PC2 | 0.49 | 0.14 | 0.21 | 0.76 | 0.56 | 22 |
PC1 | – | – | – | – | – | – |
PC3 | – | – | – | – | – | – |
Community | ||||||
Abundance | −0.71 | 0.18 | −1.07 | −0.35 | 1.00 | 39 |
Shannon | – | – | – | – | – | – |
Aquatic taxa (%) | ||||||
Gastropoda | −0.58 | 0.17 | −0.92 | −0.24 | 1.00 | 39 |
Oligochaeta (Presence) | 0.40 | 0.28 | −0.14 | 0.95 | 0.92 | 36 |
Odonata | 0.08 | 0.15 | −0.21 | 0.37 | 0.87 | 34 |
Hydracarina | 0.19 | 0.29 | −0.39 | 0.76 | 0.85 | 33 |
Trichoptera | −0.01 | 0.16 | −0.31 | 0.30 | 0.67 | 26 |
Decapoda (Presence) | −1.10 | 0.38 | −1.84 | −0.35 | 0.59 | 23 |
Hirudinea (Presence) | 0.48 | 0.26 | −0.02 | 0.99 | 0.59 | 23 |
Coleoptera | 0.24 | 0.20 | −0.15 | 0.63 | 0.54 | 21 |
Hemiptera | −0.54 | 0.21 | −0.94 | −0.13 | 0.54 | 21 |
Anura | −0.41 | 0.16 | −0.73 | −0.09 | 0.41 | 16 |
Ephemeroptera | 0.07 | 0.15 | −0.21 | 0.36 | 0.21 | 8 |
Diptera | −0.07 | 0.15 | −0.38 | 0.23 | 0.10 | 4 |
Variables within each category are ordered by their relative importance. Variables with their 95% confidence interval (CI) with the same sign are represented in bold. Rare aquatic taxa are introduced in the model as Presence/Absence variables, while relative abundance is used for more abundant taxa.
Results from multi-model selection for Bankim (4 months of sampling)
Variable | Avg. effect (b) | Uncond. SE | Lower CL | Upper CL | Relative importance (wi) | Nb. Models |
---|---|---|---|---|---|---|
(Intercept) | −13.98 | 4.13 | −22.07 | −5.89 | 1.00 | 100 |
Seasonality | ||||||
Sine (2pi*Month/12) | – | – | – | – | – | – |
Sine (2pi*Month/4) | – | – | – | – | – | – |
Cosine (2pi*Month/12) | – | – | – | – | – | – |
Cosine (2pi*Month/4) | – | – | – | – | – | – |
Physico-chemical parameters | ||||||
Water flow (lentic) | −1.80 | 0.63 | −3.04 | −0.56 | 1.00 | 100 |
Water flow (lotic) | −3.63 | 0.88 | −5.35 | −1.91 | 1.00 | 100 |
pH | – | – | – | – | – | – |
Temperature | – | – | – | – | – | – |
Dissolved oxygen | – | – | – | – | – | – |
Conductivity | – | – | – | – | – | – |
Iron | – | – | – | – | – | – |
Physico-chemical parameters (PCA) | ||||||
PC3 | 0.44 | 0.39 | −0.33 | 1.21 | 0.07 | 7 |
PC2 | 0.34 | 0.41 | −0.47 | 1.15 | 0.03 | 3 |
PC1 | 0.67 | 0.33 | 0.03 | 1.32 | 0.01 | 1 |
Community | ||||||
Abundance | 0.86 | 0.47 | −0.06 | 1.79 | 1.00 | 100 |
Shannon | 4.29 | 1.21 | 1.93 | 6.66 | 1.00 | 100 |
Aquatic taxa (%) | ||||||
Gastropoda | −0.39 | 0.30 | −0.97 | 0.18 | 0.90 | 90 |
Anura | −0.54 | 0.37 | −1.26 | 0.19 | 0.89 | 89 |
Trichoptera | −0.05 | 0.64 | −1.30 | 1.20 | 0.89 | 89 |
Odonata | −0.05 | 0.30 | −0.63 | 0.53 | 0.87 | 87 |
Fish | −0.89 | 0.56 | −1.98 | 0.20 | 0.86 | 86 |
Coleoptera | −0.04 | 0.35 | −0.73 | 0.65 | 0.84 | 84 |
Diptera | 0.70 | 0.49 | −0.26 | 1.66 | 0.84 | 84 |
Hirudinea (Presence) | −0.41 | 0.43 | −1.25 | 0.44 | 0.69 | 69 |
Hydracarina | −1.42 | 0.55 | −2.50 | −0.33 | 0.58 | 58 |
Decapoda (Presence) | 1.76 | 1.23 | −0.66 | 4.17 | 0.53 | 53 |
Hemiptera | −0.07 | 0.33 | −0.72 | 0.57 | 0.22 | 22 |
Oligochaeta (Presence) | −0.02 | 0.48 | −0.96 | 0.92 | 0.14 | 14 |
Ephemeroptera | −0.84 | 0.25 | −1.33 | −0.35 | 0.13 | 13 |
Variables within each category are ordered by their relative importance. Variables with their 95% CI with the same sign are represented in bold. Rare aquatic taxa are introduced in the model as Presence/Absence variables, while relative abundance is used for more abundant taxa. Results for lentic and lotic ecosystems represent the decrease in MU respective to stagnant ecosystems.
Description of explanatory variables from our environmental data set and their usage in the statistical model
Variable | Min | Max | Median | Prop. zeros | Prop. NAs | Usage | |
---|---|---|---|---|---|---|---|
Physico-chemical parameters | |||||||
Temperature | 20.9 | 30.2 | 23 | 0 | 0 | – | Raw |
pH | 4.5 | 7.1 | 5.5 | 0 | 0 | – | Log |
Dissolved oxygen | 0.01 | 7.6 | 2 | 0 | 0 | – | Log |
Conductivity | 10.2 | 110.6 | 22.7 | 0 | 0 | – | Log |
Water flow | 0 | 0.5 | 0.03 | 0.34 | 0.01 | – | Categorical |
Turbidity | 2 | 250 | 50 | 0.19 | 0.19 | – | Removed |
Iron | 0 | 10 | – | 0 | 0 | – | Categorical |
Phosphates | 0 | 250 | – | 0.07 | 0.07 | – | Removed |
Sulphates | 0 | 600 | – | 0.22 | 0.22 | – | Removed |
Aquatic community | |||||||
Abondance | 46 | 10,591 | 686.5 | 0 | 0 | – | Log |
Shannon | 0.35 | 2.34 | 1.7 | 0 | 0 | – | Raw |
Aquatic taxa (%) | |||||||
Fish | 0 | 0.32 | 0 | 0.32 | 0 | Aquatic | Log |
Anura | 0 | 0.54 | 0 | 0.33 | 0 | Aquatic | Log |
Gastropoda | 0 | 0.8 | 0 | 0.37 | 0 | Aquatic | Log |
Bivalvia | 0 | 0.13 | 0 | 0.91 | 0 | Aquatic | Removed |
Araneae | 0 | 0.3 | 0.01 | 0.01 | 0 | Terrestrial | Removed |
Decapoda | 0 | 0.59 | 0 | 0.68 | 0 | Aquatic | Dichotomous |
Odonata | 0 | 0.54 | 0.11 | 0.02 | 0 | Aquatic | Log |
Ephemeroptera | 0 | 0.78 | 0.16 | 0.03 | 0 | Aquatic | Log |
Hemiptera | 0 | 0.41 | 0.08 | 0 | 0 | Aquatic | Log |
Trichoptera | 0 | 0.19 | 0 | 0.35 | 0 | Aquatic | Log |
Lepidoptera | 0 | 0.12 | 0 | 0.44 | 0 | Terrestrial | Removed |
Plecoptera | 0 | 0.01 | 0 | 0.92 | 0 | Aquatic | Removed |
Oligochaeta | 0 | 0.18 | 0 | 0.69 | 0 | Aquatic | Dichotomous |
Hirudinea | 0 | 0.45 | 0 | 0.58 | 0 | Aquatic | Dichotomous |
Coleoptera | 0.01 | 0.94 | 0.1 | 0 | 0 | Aquatic | Log |
Diptera | 0 | 0.79 | 0.15 | 0 | 0 | Aquatic | Log |
Hydracarina | 0 | 0.11 | 0 | 0.31 | 0 | Aquatic | Log |
Collembola | 0 | 0.06 | 0 | 0.4 | 0 | Terrestrial | Removed |
Cladocera | 0 | 0.24 | 0 | 0.47 | 0.63 | Aquatic | Removed |
Results of multivariate analyses for Akonolinga (12 months of sampling) and Bankim (4 months of sampling)
Variable | Akonolinga (n = 183) | Bankim (n = 61) | ||||
---|---|---|---|---|---|---|
Effect | Std. error | p-value | Effect | Std. error | p-value | |
Model AIC | 400.7 | – | – | 182.7 | – | – |
Variance of random effect | 0.20 | – | – | 1.77 | – | – |
(Intercept) | −12.56 | 4.40 | <0.001 | −7.40 | 1.97 | <0.001 |
Seasonality | ||||||
Sine(2pi*Month/12) | 0.34 | 0.14 | 0.02 | – | – | – |
Sine(2pi*Month/4) | – | – | – | – | – | – |
Cos(2pi*Month/12) | – | – | – | – | – | – |
Cos(2pi*Month/4) | – | – | – | – | – | – |
Physico-chemical parameters | ||||||
Temperature | – | – | – | – | – | – |
pH | 8.63 | 2.44 | <0.001 | – | – | – |
Dissolved oxygen | – | – | – | – | – | – |
Conductivity | – | – | – | – | – | – |
Iron | – | – | – | – | – | – |
Water flow (Lentic) | – | – | – | −2.10 | 0.47 | <0.001 |
Water flow (Lotic) | – | – | – | −3.18 | 0.69 | <0.001 |
Physico-chemical parameters (PCA) | ||||||
PC1 | – | – | – | – | – | – |
PC2 | – | – | – | – | – | – |
PC3 | – | – | – | – | – | – |
Community | ||||||
Abundance | −0.64 | 0.17 | <0.001 | – | – | – |
Shannon | – | – | – | 4.16 | 0.97 | <0.001 |
Orders (%) | ||||||
Fish | – | – | – | −1.62 | 0.35 | <0.001 |
Anura | −0.34 | 0.14 | 0.02 | −0.84 | 0.32 | 0.01 |
Gastropoda | −0.64 | 0.16 | <0.001 | – | – | – |
Decapoda (presence) | −1.37 | 0.37 | <0.001 | – | – | – |
Odonata | – | – | – | – | – | – |
Ephemeroptera | – | – | – | −0.94 | 0.21 | <0.001 |
Hemiptera | −0.47 | 0.20 | 0.02 | – | – | – |
Tricoptera | – | – | – | – | – | – |
Oligochaeta (presence) | – | – | – | – | – | – |
Hirudinea (presence) | 0.59 | 0.23 | 0.01 | – | – | – |
Coleoptera | – | – | – | – | – | – |
Diptera | – | – | – | 1.08 | 0.36 | <0.001 |
Hydracarine | – | – | – | −1.58 | 0.49 | <0.001 |
The models used are Binomial regressions with random effect site, selected with forward–backwards procedure (see section 1 for details).
Differences in community composition between Akonolinga and Bankim
Taxonomic group | Relative abundance (%) | Mann–Whitney test | |||
---|---|---|---|---|---|
Akonolinga | Bankim | ||||
Mean | SD | Mean | SD | p-value | |
Fish | 1.04 | 2.20 | 2.39 | 4.93 | <0.001 |
Anura | 2.56 | 6.62 | 2.08 | 6.73 | 0.009 |
Gastropoda | 2.70 | 7.76 | 3.41 | 9.33 | 0.449 |
Bivalvia | 0.19 | 1.08 | 0.00 | 0.03 | 0.016 |
Decapoda | 5.36 | 12.37 | 0.90 | 2.78 | 0.010 |
Odonata | 12.72 | 9.96 | 15.79 | 15.03 | 0.616 |
Ephemeroptera | 21.77 | 17.22 | 15.56 | 14.74 | 0.010 |
Hemiptera | 8.15 | 5.85 | 11.84 | 8.55 | <0.001 |
Tricoptera | 2.62 | 4.20 | 1.23 | 2.23 | 0.011 |
Hirudinea | 1.29 | 4.76 | 2.63 | 7.31 | 0.005 |
Oligochaeta | 0.64 | 1.94 | 0.67 | 2.11 | 0.291 |
Coleoptera | 18.98 | 20.54 | 11.99 | 11.37 | 0.023 |
Diptera | 17.58 | 14.23 | 23.69 | 16.25 | 0.004 |
Hydracarine | 0.83 | 1.38 | 0.90 | 1.77 | 0.171 |
For each taxon included in the statistical model, the mean and standard deviation (SD) of the relative abundance (%) for each region are given, along with the p-value of a Mann–Whitney test comparing the mean relative abundance in the two regions.