The effects of invertebrate herbivores on plant population growth: a meta-regression analysis
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Over the last two decades, an increasing number of studies have quantified the effects of herbivory on plant populations using stage-structured population models and integral projection models, allowing for the calculation of plant population growth rates (λ) with and without herbivory. In this paper, I assembled 29 studies and conducted a meta-regression to determine the importance of invertebrate herbivores to population growth rates (λ) while accounting for missing data. I found that invertebrate herbivory often induced important reductions in plant population growth rates (with herbivory, λ was 1.08 ± 0.36; without herbivory, λ was 1.28 ± 0.58). This relationship tended to be weaker for seed predation than for other types of herbivory, except when seed predation rates were very high. Even so, the amount by which studies reduced herbivory was a poor predictor of differences in population growth rates—which strongly cautions against using measured herbivory rates as a proxy for the impact of herbivores. Herbivory reduced plant population growth rates significantly more when potential growth rates were high, which helps to explain why there was less variation in actual population growth rates than in potential population growth rates. The synthesis of these studies also shows the need for future studies to report variance in estimates of λ and to quantify how λ varies as a function of plant density.
KeywordsInsect herbivory Plant–insect interactions Integral projection models Matrix population models Meta-analysis
Thanks are due to Inés Ibáñez for excellent advice and support throughout this project, and to Don Zak, Mark Hunter, Knute Nadelhoffer, Ben Lee, Teegan McClung, Natalie Tonn, and two anonymous reviewers for their helpful comments on an earlier version of this manuscript. The author was supported in part by a graduate research fellowship from the National Science Foundation.
Author contribution statement
DSWK conceived, designed, and executed this study and wrote the manuscript. No other person is entitled to authorship.
Compliance with ethical standards
Conflict of interest
The author declares that he has no conflict of interest.
- Caswell H (1989) Matrix population models construction, analysis, and interpretation. Sinauer Associates, SunderlandGoogle Scholar
- Ehrlén J (1995) Demography of the perennial herb Lathyrus vernus. II. Herbivory and population dynamics. J Ecol 83:297–308Google Scholar
- Fine PVA, Mesones I, Coley PD (2004) Herbivores promote habitat specialization by trees in Amazonian forests. Science 305:663–665Google Scholar
- Gurevitch J, Hedges LV (2001) Meta-analysis: combining the results of independent experiments, 2nd edn. Oxford University Press, OxfordGoogle Scholar
- Hartley SE, Jones CG (1997) Plant chemistry and herbivory, or why the world is green. In: Crawley M (ed) Plant ecology. Blackwell Scientific, Cambridge, pp 284–324Google Scholar
- Huwaldt J, Steinhorst S (2013) Plot Digitizer. Available at: http://plotdigitizer.sourceforge.net/
- Lajeunesse M (2013) Recovering missing or partial data from studies: a survey of conversions and imputations for meta-analysis. In: Koricheva J, Gurevitch J, Mengersen K (eds) Handbook of meta-analysis in ecology and evolution. Princeton University Press, Princeton, pp 196–206Google Scholar
- Plummer M (2003) JAGS: A program for analysis of Bayesian graphical models using Gibbs sampling. Available at: http://mcmc-jags.sourceforge.net/
- Plummer M (2014) rjags: Bayesian graphical models using MCMC. Available at: https://cran.r-project.org/web/packages/rjags/rjags.pdf
- R Core Team (2013) R: a language and environment for statistical computing. R Foundation for Statistical Computing, ViennaGoogle Scholar