Ecological Archives E088-131-A4

S. Declerck, M. Vanderstukken, A. Pals, K. Muylaert, and L. De Meester. 2007. Plankton biodiversity along a gradient of productivity and its mediation by macrophytes. Ecology 88:2199–2210.

Appendix D. Results of additional GLM analyses.

TABLE D1. Results of general linear models that explain the evenness of substrate dwelling and seston feeding zooplankton and of phytoplankton in relation to the plant treatment (categorical variable) and to the initial primary productivity gradient (continuous variable).

 

 Explanatory variables‡

df

SS

MS

F

P

Substrate dwellers

Intercept

1

2.32

2.32

99

< 0.0001

 

PLANT

2

0.47

0.24

10

< 0.001

 

CHLAin

1

0.01

0.01

0.4

0.514

 

Error

53

1.24

0.02

   

Seston feeders

Intercept

1

3.24

3.24

165

< 0.0001

 

PLANT

2

0.25

0.13

6

0.003

 

CHLAin

1

0.16

0.16

8.35

0.006

 

PLANT × CHLAin

2

0.30

0.15

7.54

0.001

 

Error

53

1.04

0.02

   

Phytoplankton

Intercept

1

4.51

4.51

223

< 0.0001

 

PLANT

2

0.09

0.05

2.17

0.124

 

CHLAin

1

0.45

0.45

22.4

< 0.0001

 

Error

54

1.09

1.09

   

Substrate dwellers§

Intercept

1

5.21

5.21

222

< 0.001

 

PLANT

2

0.47

0.24

10

< 0.001

 

PERIPH

1

0.01

0.01

0.4

0.556

 

Error

53

1.24

0.02

   

   Note: Nonsignificant interactions between the predictor variables were omitted from the GLM models. For more information on the statistical analyses see Materials and Methods.

‡ PLANT is the plant treatment (no macrophytes, artificial macrophytes, real macrophytes; CHLAin is the initial chlorophyll a concentration at the moment of zooplankton inoculation and represents the initial primary productivity gradient; PERIPH: periphyton dry weight on container walls.

§ Evenness of substrate dwelling zooplankton analyzed with periphyton dry weight as continuous predictor variable.




TABLE D2. Results of general linear models that explain the taxon richness of substrate dwelling and seston feeding zooplankton and of phytoplankton in relation to the plant treatment (categorical variable), the imposed initial primary productivity gradient (CHLAin) and the realized productivity gradient at the end of the experiment (CHLAfin).

Organism group

 

df

SS

MS

F

P

Substrate dwellers

Intercept

1

259

259

182

< 0.001

 

PLANT

2

120

60

42

< 0.001

 

CHLAin

1

9.9

9.9

6.99

0.011

 

CHLAfin

1

4.2

4.2

2.92

0.093

 

Error

54

77

1.4

   

Seston feeders

Intercept

1

340

340

357

< 0.001

 

PLANT

2

5.1

2.6

2.7

0.078

 

CHLAin

1

8.9

8.9

9.3

0.004

 

CHLAfin

1

7.1

7.1

7.4

0.009

 

Error

54

52

0.95

   

Phytoplankton

Intercept

1

722

722

125

< 0.001

 

PLANT

2

198

99

17

< 0.001

 

CHLAin

1

5.9

5.9

1

0.316

 

CHLAfin

1

40

40

6.9

0.011

 

Error

53

307

5.8

   

   Note: Nonsignificant interactions between the predictor variables were omitted from the GLM models. For more information on the statistical analyses see Materials and Methods.




TABLE D3. Results of general linear models that explain the evenness of substrate dwelling and seston feeding zooplankton and of phytoplankton in relation to the plant treatment (categorical variable) the imposed initial primary productivity gradient (CHLAin) and the realized productivity gradient at the end of the experiment (CHLAfin).

Organism group

 

df

SS

MS

F

P

Substrate dwellers

Intercept

1

1.63

1.63

89.8

< 0.001

 

PLANT

2

0.67

0.33

18.4

< 0.001

 

CHLAin

1

0.10

0.10

5.72

0.020

 

CHLAfin

1

0.299

0.299

16.5

< 0.001

 

Error

52

0.943

0.018

   

Seston feeders

Intercept

1

3.219

3.219

178.26

< 0.001

 

PLANT

2

0.232

0.116

6.421

0.003

 

CHLAin

1

0.063

0.063

3.479

0.068

 

PLANT × CHLAin

2

0.240

0.120

6.649

0.003

 

CHLAfin

1

0.104

0.104

5.777

0.019

 

Error

52

0.939

0.018

   

Phytoplankton

Intercept

1

4.26

4.26

232

< 0.001

 

PLANT

2

0.06

0.03

1.63

0.205

 

CHLAin

1

0.21

0.21

11.6

0.001

 

CHLAfin

1

0.116

0.116

6.34

0.015

 

Error

53

0.973

0.018

   

   Note: Nonsignificant interactions between the predictor variables were omitted from the GLM models. For more information on the statistical analyses see Materials and Methods.




TABLE D4. Results of two alternative general linear models that explain the taxon richness of seston feeding zooplankton in relation to the proportional density of Daphnia (D. galeata and D. magna) and the plant treatment, with and without incorporation of the initial primary productivity gradient (CHLAin).

 

 Explanatory variables‡

df

SS

MS

F

P

CHLAin not in model

           
 

Intercept

1

768.95

768.95

799.87

< 0.001

 

PLANT

2

3.42

1.71

1.78

0.178

 

DAPHNIA%

1

6.94

6.94

7.22

0.010

 

Error

55

52.87

0.96

   

CHLAin in model

           
 

Intercept

1

194.41

194.41

252.75

< 0.001

 

PLANT

2

3.50

1.75

2.28

0.112

 

CHLAin

1

11.34

11.34

14.74

< 0.001

 

DAPHNIA%

1

0.50

0.50

0.64

0.426

 

Error

54

41.53

0.77

   

   Notes: For more information on the statistical analyses see Materials and Methods. Species richness in this analysis refers to the total number of seston feeding zooplankton species except Daphnia and was obtained through rarefaction with cut off levels of 90 individuals.

‡ PLANT is the plant treatment (no macrophytes, artificial macrophytes, real macrophytes); DAPHNIA% is the relative density (%) of Daphnia in the community of seston feeding zooplankton; CHLAin is the initial chlorophyll a concentration at the moment of zooplankton inoculation and represents the initial primary productivity gradient.



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