Abstract Detail

Ecological Section

Bao, Tan [1], Cahill Jr., James F. [2], Dale, Mark R.T. [3].

Inability to scale up from individuals to communities in competitive networks.

Where competition is important in structuring natural communities, relative competitive abilities or competitive hierarchies may determine key community characteristics such as relative abundance. Competitive hierarchies are common because of consistent patterns of asymmetric competition, but certain properties of hierarchies such as transitivity are only satisfied by specific patterns of asymmetry. Transitivity of competitive hierarchies is often an assumption in competition theories, but there is little empirical evidence quantifying these hierarchies, particularly without the use of a phytometer. Our objective was to quantify a complete competitive network in order: (1) to test for transitivity; (2) to determine how competitive hierarchical structure changes with nutrient level; and (3) to quantify the extent of the network structure that can be recovered by simulating, a posteriori, the use of phytometers. In our experiment, we ran replicated pairwise contests amongst 12 ecotypes of Arabidopsis thaliana at low and high nutrient. We determined competitive effect and response in 132 treatment combinations to construct competitive hierarchies based on the graph theoretic property of in-degrees and out-degrees. We find that our hierarchies are not transitive and that the hierarchical structure changes with nutrient level. We also find that it is difficult to recover the hierarchical structure determined from the competitive tournament by using any one ecotype as a phytometer, particularly those ecotypes that are more competitive. This suggests that the use of phytometers to determine relative competitive ability requires great caution and that there is need to understand more fully the implications of intransitive competitive hierarchies.

1 - University of Alberta, Department of Biological Sciences, CW 405, Biological Sciences Bldg., Edmonton, AB, T6G 2E9 , Canada
2 - University Of Alberta, Department Of Biological Sciences, CW405 Bio Sci Bldg, Edmonton, AB, T6G 2E9, Canada
3 - University of Northern British Columbia, Dean of Regional Programs, 3333 University Way, Prince George, BC, V2N 4Z9, Canada

Keywords:
competition
Network analyses
Competitive hierarchy
Phytometer
Transitivity
community.

Presentation Type: Oral Paper:Papers for Sections
Session: 35
Location: Salon 6/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 10:30 AM
Number: 35010
Abstract ID:1103
Candidate for Awards:Ecological Section Best Graduate Student Paper