PARENT SESSION
Poster Session #44: Plant Ecology II.
Friday, August 10, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

Limiting traits in forest herbs.

ADKISON, GREG¹, ¹

ABSTRACT- Understanding distributions is a fundamental problem in ecology. Although the problem of distributions is probably unsolvable in its entirety, an explanation would involve linking the study of abundance in different environments to variation in traits that reduce individual fitness–i.e., identifying suboptimal traits that cause species to fail. Combining methods for defining environmental gradients and species niches with techniques for estimating selection, this study tested for limiting traits in the herb community of an eastern deciduous forest. The primary gradient in this system is complex with an increase in diversity and biomass corresponding to higher moisture and soil nutrients. Light declines along the gradient as the tree canopy thickens. Four traits–leaf size, SLA, etiolation and leaf:shoot mass (LSR)–were measured on every plant found within 60, 0.25m² quadrats that were randomly placed along a transect spanning the gradient. Averaging over plants within quadrats, each trait increased along the gradient except LSR which declined. These results were consistent with predicted changes in optima across the gradient. Leaf size was more variable within quadrats than the other traits. These results suggest more intense selection on LSR, etiolation, and SLA, and thereby predict failure for individuals/species with suboptimal values in these traits as opposed to apparently nonlimiting traits such as leaf size.

KEY WORDS: distributions, community composition, suboptimality