PARENT SESSION
Poster Session 35: Evolutionary Ecology
Thursday, August 11, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Assessing local and global constraints on plant community structure: Quantifying small-scale distributions of size, functional traits, and phylogenetic affiliations.

Enquist, Brian^*,1, Kerkhoff, Andrew ¹, Boyle, Brad, McCarthy, Megan¹, Swenson, Nathan¹, ¹ Dept. Ecology and Evolutionary Biology, Tucson, AZ, USA

ABSTRACT- Recent findings have shown global generalities in how plant metabolism, production, and leaf stoichometry are influenced by organismal size and life-history. Within community ecology, the forces responsible for structuring local assemblages have been argued to range from purely neutral to highly deterministic (based on niche differences). It is unclear, however, if global generalities in metabolism and life-history can be used to provide a theoretical framework for communities. Here we assess the general importance of variability in leaf functional traits, plant size, and phylogeny on community structure. We extend metabolic scaling and niche theories to assess how global constraints on leaf allocation and metabolic production influence the distributions of leaf functional traits, plant size and phylogenetic relatedness of plant communities. The model assumes: (i) local distributions of leaf traits reflect local life-history and climate optima; (ii) patterns of leaf and organ allocation, while governed by global generalities, are independent of the allometric scaling of production; but that (iii) more closely related taxa compete more intensely than more distantly related taxa. Our model makes several predictions. First, independent of functional traits and climate, communities should be characterized by an invariant size structure. Second, the community distribution of leaf traits should show directional shifts with climate. Third, the distribution of functional traits should be a non-random subset of regional species pools. Lastly, local community composition is phylogenetically overdispersed. We assess these predictions by quantifying the distributions of sizes, leaf traits, and phylogenetic relatedness for numerous woody plant communities along altitudinal gradients. We sampled tropical to temperate communities within the El Cielo Biosphere Preserve in Tamalipas Mexico as well as well as in the Cordillera Central in Costa Rica. Our results generally confirm the predictions made by the metabolic/niche model. Together, these results can contribute to the linking of how global generalities of metabolism and life-history variation together with local biotic and abiotic filters influence the nature of plant community organization.

Key words: Community Ecology, Allometric Scaling, Forest Ecology, Functional traits