Defense mutualisms enhance plant diversification

Other Titles
The ability of plants to form mutualistic relationships with animal defenders has long been suspected to influence their evolutionary success, both by decreasing extinction risk and by increasing opportunity for speciation through an expanded realized niche. Nonetheless, the hypothesis that defense mutualisms consistently enhance plant diversification across lineages has not been well tested due to a lack of phenotypic and phylogenetic information. Using a global analysis, we show that the >100 vascular plant families in which species have evolved extrafloral nectaries (EFNs), sugar-secreting organs that recruit arthropod mutualists, have twofold higher diversification rates than families that lack species with EFNs. Zooming in on six distantly related plant clades, trait-dependent diversification models confirmed the tendency for lineages with EFNs to display increased rates of diversification. These results were consistent across methodological approaches. Inference using reversible-jump Markov chain Monte Carlo (MCMC) to model the placement and number of rate shifts revealed that high net diversification rates in EFN clades were driven by an increased number of positive rate shifts following EFN evolution compared with sister clades, suggesting that EFNs may be indirect facilitators of diversification. Our replicated analysis indicates that defense mutualisms put lineages on a path toward increased diversification rates within and between clades, and is concordant with the hypothesis that mutualistic interactions with animals can have an impact on deep macroevolutionary patterns and enhance plant diversity.
Journal / Series
Proceedings of the National Academy of Sciences
Volume & Issue
A.A.A. was supported by Grant 1118783 of the Division of Environmental Biology of the National Science Foundation (NSF) and by the John Templeton Foundation. M.G.W. was supported by the Society for the Study of Evolution’s Rosemary Grant Award and by the NSF (Graduate Research Fellowship and Doctoral Dissertation Improvement Grant).
Date Issued
National Academy of Sciences
mutualism; extrafloral nectaries; plant-insect interactions; lineage diversification rates; plant defense
Effective Date
Expiration Date
Union Local
Number of Workers
Committee Chair
Committee Co-Chair
Committee Member
Degree Discipline
Degree Name
Degree Level
Related Version
Weber, M. G., & Agrawal, A. A. (2014). Defense mutualisms enhance plant diversification. Proceedings of the National Academy of Sciences, 111(46), 16442–16447.
Related To
Related Part
Based on Related Item
Has Other Format(s)
Part of Related Item
Related To
Related Publication(s)
Link(s) to Related Publication(s)
Link(s) to Reference(s)
Previously Published As
Government Document
Other Identifiers
Rights URI
Accessibility Feature
Accessibility Hazard
Accessibility Summary
Link(s) to Catalog Record