Ecological Archives E091-195-A5

Jennifer G. Howeth and Mathew A. Leibold. 2010. Species dispersal rates alter diversity and ecosystem stability in pond metacommunities. Ecology 20:2727–2741.

Appendix E. Analysis of regional and local plankton biomass as a function of dispersal rate and predation regime.

TABLE E1. Effects of planktonic dispersal rate on regional zooplankton and phytoplankton biomass (mean biomass of the three communities) of pond metacommunities, as analyzed with repeated measures ANOVA.

Biomass response

df

SS

F

P value

Contrasts

Zooplankton§

Dispersal

2

1.31

8.71

0.007 (0.013)

[C, L↑*], [C, H↑**];
(C, L↑‡), (C, H↑*)

Time

11

4.67

17.23

<0.001

 

Time × disp

22

1.02

1.87

0.019 (0.004)

 

Phytoplankton ψ

Dispersal

2

50.12

23.75

<0.001

[C↑, L*], [C↑, H***], [L↑, H*]

Time†

6

1.60

1.37

0.243

 

Time × disp†

12

6.21

2.66

0.007

 

§ log transformed
ψ log(x + 1) transformed
† Greenhouse-Geisser modified probability values

For zooplankton biomass, probability values from final 7 wk of the experiment are noted in parenthesis, if the significance level is different from the 12 wk analysis. Post hoc pairwise contrasts (Tukey’s HSD) reported for significant main effects. Contrasts notation, dispersal: C = closed (no dispersal); L = low dispersal; H = high dispersal. Contrasts significance levels: ‡, marginally significant P < 0.08; *, P < 0.05; **, P < 0.01; ***, P < 0.001; ↑, greater biomass value. For zooplankton biomass, 7 wk contrasts results are noted in parentheses if different from the 12 wk analysis.


 

TABLE E2. Effects of planktonic dispersal rate and bluegill sunfish (Lepomis macrochirus) predation on local (community) biomass of zooplankton and phytoplankton in pond metacommunities, as analyzed with repeated measures ANOVA. Adapted from Howeth and Leibold (2008).

Biomass response

df

SS

F

P value

Contrasts

Zooplankton§

Dispersal

2

3.95

9.50

<0.001 (0.007)

[C, L↑**], [C, H↑**];(C, L↑‡), (C, H↑**)

Predation

2

4.30

10.31

<0.001 (0.014)

[N↑, P***], [N↑, N+P‡];(N↑, P**)

Disp × pred

4

0.82

0.99

0.432

 

Time†

11

14.03

20.65

<0.001

 

Time × disp†

22

3.05

2.25

0.011

 

Time × pred†

22

1.67

1.23

0.266

 

Time × disp × pred†

44

2.19

0.80

0.729

 

Phytoplanktonψ

Dispersal

2

150.36

38.25

<0.001

[C↑, L***], [C↑, H***], [L↑, H***]

Predation

2

9.12

2.32

0.117

 

Disp × pred

4

10.05

1.28

0.303

 

Time†

6

4.80

1.61

0.147

 

Time × disp†

12

18.63

3.13

0.003

 

Time × pred†

12

6.67

1.12

0.353

 

Time × disp × pred†

24

8.60

0.72

0.774

 

 

§ log transformed
ψ log (x + 1) transformed
† Greenhouse-Geisser modified probability values
For zooplankton biomass, probability values from final 7 wk of the experiment are noted in parenthesis, if the significance level is different from the 12 wk analysis. Post-hoc pairwise contrasts (Tukey’s HSD) reported for significant main effects.  Contrasts notation, dispersal: C = closed (no dispersal); L = low dispersal; H = high dispersal; predation: N = press predator-free; P = press predation; N + P = pulse predation.  Contrasts significance levels: ‡, marginally significant P < 0.08; *, P < 0.05; **, P < 0.01; ***, P < 0.001; ↑, greater biomass value.  For zooplankton biomass, 7 wk contrasts results are noted in parentheses if different from the 12 wk analysis. 


 

LITERATURE CITED

Howeth, J. G., and M. A. Leibold. 2008. Planktonic dispersal dampens temporal trophic cascades in pond metacommunities. Ecology Letters 11:245–257.


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