Ecological Archives E089-007-A3

Marc T. J. Johnson. 2008. Bottom-up effects of plant genotype on aphids, ants, and predators. Ecology 89:145–154.

Appendix C. The effects of aphid density, ants, and plant genotype on the final number of aphids per plant.

TABLE C1. The effects of initial aphid density, the presence/absence of ants, and plant genotype on the final number of aphids per plant. Spatial block and the person who counted aphids on a plant (counter) were included as blocking factors. I calculated the percent variation (% Var) explained by all main effects and significant interactions using general linear models using the equation: (factor-sums of squares)/(total sums of squares) × 100%. The variance components (VC) for all random effects are also provided. Significant effects (P < 0.05) are in bold.


Source

VC

F/chisqr

P

% Var


Initial density (density)

 

76.52

<0.001

6

Ants

 

9.14

0.003

0.8

Genotype

0.84

31.3

<0.001

27.1

Block

0.1

22.1

<0.001

2.3

Counter

 

1.12

0.33

0.6

Density × Ants

 

5.47

0.02

0.5

Density × genotype

<0.01

0

-

-

Ants × genotype

0.03

0.5

0.24

-

Ants × counter

 

3.55

0.03

0.2

Density × ants × counter

 

2.18

0.07

-

Residual

1.99

     

 Denotes fixed effect in which the significance was assessed using an F statistic. All other effects in the model were random and their significance was tested using achisqr-statistic from log-likelihood ratio tests.



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