Ecological Archives E092-152-A2

F. Tomas, J. M. Abbott, C. Steinberg, M. Balk, S. L. Williams, and J. J. Stachowicz. 2011. Plant genotype and nitrogen loading influence seagrass productivity, biochemistry, and plant–herbivore interactions. Ecology 92:1807–1817.

Appendix B (TABLE B1). Table showing the results of the meta-analyses conducted to assess the effects of nitrogen addition on isopod feeding preference in experiments with fresh material and agar-based foods (conducted using MetaWin 2.0, Rosenberg et al. 2000).

Experiment Mean Effect Size 95 % CI
Fresh Plant Material -0.9997 -1.6766 to -0.5271
Agar -0.0812 -0.5994 to +0.3761

We used Hedges’ d (the differences in consumption between fertilized and unfertilized means weighted by the sample size and the pooled standard deviation) as the measure of effect size for each experiment (Hedges and Olkin 1985), and estimated non-parametric variances because most of our experimental data did not follow a normal distribution (Adams et al. 1997). The mean effect size was calculated using a fixed-effects model (Gurevitch and Hedges 1999), and we calculated a bias-corrected bootstrap CI generated from 9999 iterations (Adams et al. 1997). When CI does not include 0 the effect size is significant (highlighted in bold), and CI < 0 indicates a significant preference for the unfertilized genotype.

LITERATURE CITED

Adams, D. C., J. Gurevitch, and M. S. Rosenberg. 1997. Resampling tests for meta-analysis of ecological data. Ecology 78:1277–1283.

Gurevitch, J., and L. V. Hedges. 1999. Statistical issues in ecological meta-analyses. Ecology 80:1142–1149.

Hedges, L. V., and I. Olkin. 1985. Statistical methods for meta-analysis. Academic Press, New York, New York, USA.

Rosenberg, M. S., D. C. Adams, and J. Gurevitch. 2000. MetaWin: statistical software for meta-analysis. Sinauer Associates, Sunderland, Massachusetts, USA.


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