Print PageAll organisms are have limited resources to allocate to morphological, physiological, and life history traits. Indeed, species tradeoffs in performance and functional traits provide the foundation for niche-based coexistence theory. We examined several critical functional traits and classic trade-offs for competition, colonization, growth rate, and herbivore resistance and tolerance. We hypothesized that certain trait combinations, and potentially the absence of specific tradeoffs, would predict relative abundance. In particular, we used this framework to gain insight into a long-standing pattern in ecology – the repeated dominance of the Canada goldenrod (Solidago canadensis/altissima complex) over dozens of other species in thousands of old-fields throughout the northeastern United States and southeastern Canada. We established and maintained monocultures of nine old-field plant species in 4x4 meter plots, factorially manipulating the exclusion of mammalian and insect herbivores. We monitored clonal spread, resource reduction, growth rate, and herbivore damage.
Results/Conclusions
We found little evidence of predicted tradeoffs along critical axes of allocation. Surprisingly, So. canadensis did not exhibit tradeoffs for any of the examined traits and consistently had the greatest values for growth, colonization, competitive ability, and herbivore resistance and tolerance. A PCA axis of collapsed trait data explained 30% of old-field relative abundance (using published abundance data). While classic tradeoffs may not explain coexistence in some systems, the ability to allocate to key traits and trait combinations provide elusive mechanisms of dominance. Furthermore, our findings contradict previously published claims that the dominance of So. canadensis is specifically tied to being a superior resource competitor; light competition cannot yet be disentangled from other mechanisms.
