Open Collections

Malamud, Nathan David

University of British Columbia

Trait-based ecology seeks to understand how environmental variation influences organismal performance and fitness via functional traits. The morphology-performance-fitness (MPF) framework hypothesizes directional causal relationships linking functional traits, performance traits, and fitness. However, the mediating role of functional traits in linking environmental variation to performance has not been fully articulated or tested within this framework. To address this gap, I extended the MPF framework by explicitly incorporating causal links between environmental variation and functional traits. I tested these hypotheses using data for three leaf economics traits — leaf mass per area (LMA), leaf dry matter content (LDMC), and chlorophyll content (CHL) — and a performance trait (aboveground growth rate) in three plant species grown across a broad nitrogen addition gradient. Leaf traits responded strongly to nitrogen addition, with variation structured primarily along a leaf economics axis and secondarily along a photosynthetic pigment axis. Increasing nitrogen drove phenotypic convergence, shifting trait expression toward a common region of multivariate trait space at high nitrogen levels. Structural equation modeling strongly supported MPF hypotheses, demonstrating that nitrogen addition influenced growth rates primarily through its effects on chlorophyll content and LDMC, as well as unmeasured functional traits. By clarifying the pathways linking environmental variation to plant functional and performance traits, these findings enhance our understanding of plant responses to nutrient gradients and their broader implications for global change ecology.

Text

2025-04-25

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/90799

Botany

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/