TY - JOUR
T1 - Emergent shapes of trait-based competition functions from resource-based models
T2 - a Gaussian is not normal in plant communities
AU - Falster, Daniel S.
AU - Kunstler, Georges
AU - Fitzjohn, Richard G.
AU - Westoby, Mark
PY - 2021/8
Y1 - 2021/8
N2 - In community ecology, it is widely assumed that organisms with similar traits compete more intensely with one another for resources. This assumption is often encoded into theory and empirical tests via a unimodal competition function, which predicts that per capita competitive effect declines with separation in traits. Yet it remains unknown how well this function represents the true effect of traits on competitive outcomes, especially for long-lived plant communities, where lifetime fitness is difficult to estimate. Here, we evaluate the shape of competition functions embedded in two resource-based (RB) models, wherein plants compete for shared, essential resources. In the first RB model individuals compete for two essential nutrients, and in the second they compete for light in a size-based successional setting. We compared the shapes of the competition functions that emerged from interactions within these RB models to the unimodal function and others shapes commonly applied. In few instances did the trait-based competition function emerging from the RB model even vaguely resemble any of the shapes previously used. The mismatch between these two approaches suggests that theory derived using fixed competition functions based on trait separation may not apply well to plant systems, where individuals compete for shared resources. The more promising path will be to model depletion of resources by populations in relation to their traits, with its consequences for fitness landscapes and competitive exclusion.
AB - In community ecology, it is widely assumed that organisms with similar traits compete more intensely with one another for resources. This assumption is often encoded into theory and empirical tests via a unimodal competition function, which predicts that per capita competitive effect declines with separation in traits. Yet it remains unknown how well this function represents the true effect of traits on competitive outcomes, especially for long-lived plant communities, where lifetime fitness is difficult to estimate. Here, we evaluate the shape of competition functions embedded in two resource-based (RB) models, wherein plants compete for shared, essential resources. In the first RB model individuals compete for two essential nutrients, and in the second they compete for light in a size-based successional setting. We compared the shapes of the competition functions that emerged from interactions within these RB models to the unimodal function and others shapes commonly applied. In few instances did the trait-based competition function emerging from the RB model even vaguely resemble any of the shapes previously used. The mismatch between these two approaches suggests that theory derived using fixed competition functions based on trait separation may not apply well to plant systems, where individuals compete for shared resources. The more promising path will be to model depletion of resources by populations in relation to their traits, with its consequences for fitness landscapes and competitive exclusion.
KW - Coexistence
KW - Competition
KW - Resource
UR - http://www.scopus.com/inward/record.url?scp=85107337531&partnerID=8YFLogxK
UR - http://purl.org/au-research/grants/arc/FL100100080
UR - http://purl.org/au-research/grants/arc/FT160100113
U2 - 10.1086/714868
DO - 10.1086/714868
M3 - Article
C2 - 34260875
AN - SCOPUS:85107337531
SN - 0003-0147
VL - 198
SP - 253
EP - 267
JO - American Naturalist
JF - American Naturalist
IS - 2
ER -