Plant functional traits and the multidimensional nature of species coexistence

6 páginas, 3 figuras.-- 3 tablas.-- 41 referencias.-- This article contains supporting information online at http://www.pnas.org/lookup/suppl/doi:10.1073/pnas.1413650112/-/DCSupplementalUnderstanding the processes maintaining species diversity is a central problem in ecology, with implications for the conservation and management of ecosystems. Although biologists often assume that trait differences between competitors promote diversity, empirical evidence connecting functional traits to the niche differences that stabilize species coexistence is rare. Obtaining such evidence is critical because traits also underlie the average fitness differences driving competitive exclusion, and this complicates efforts to infer community dynamics from phenotypic patterns. We coupled fieldparameterized mathematical models of competition between 102 pairs of annual plants with detailed sampling of leaf, seed, root, and whole-plant functional traits to relate phenotypic differences to stabilizing niche and average fitness differences. Single functional traits were often well correlated with average fitness differences between species, indicating that competitive dominance was associated with late phenology, deep rooting, and several other traits. In contrast, single functional traits were poorly correlated with the stabilizing niche differences that promote coexistence. Niche differences could only be described by combinations of traits, corresponding to differentiation between species in multiple ecological dimensions. In addition, several traits were associated with both fitness differences and stabilizing niche differences. These complex relationships between phenotypic differences and the dynamics of competing species argue against the simple use of single functional traits to infer community assembly processes but lay the groundwork for a theoretically justified trait-based community ecology.Lindsey Rice provided field assistance in all stages of the project. We thank Janneke HilleRisLambers and Marti Anderson for discussion and statistical advice and Peter Adler, Mark Vellend, and members of the J.M.L. and N.J.B.K. laboratories for comments. Peter Chesson helped us derive the stabilizing niche difference and average fitness difference in our annual plant model. The D’Antonio laboratory at University of California, Santa Barbara and the Dawson laboratory at University of California, Berkeley made the nutrient and isotope analyses possible.Peer Reviewe