PARENT SESSION
Oral Session #57: Plant Competition I.
Presiding: T. Seastedt
Wednesday, August 7. 8:00 AM to 11:30 AM. Grand Ballroom Central, Radisson.
Mechanisms of resource competition in Arabidopsis thaliana.
Brautigam, Phillip*,1, Tonsor, Stephen1, 1 University of Pittsburgh, Pittsburgh, PA
ABSTRACT- Theoretical and empirical attempts to predict the outcome of resource competition largely focus on differential rates of resource consumption. Few studies, however, address the physiological characteristics underlying this process. To gain a mechanistic understanding of resource-based competition and its evolutionary inferences, this experiment used three ecotypes of Arabidopsis thaliana to examine the physiological characteristics of resource uptake (RU) and resource-use efficiency (RUE). In a completely factorial design, I competed three ecotypes of A. thaliana in an environmental growth chamber using two light and two nutrient levels. I used path analysis with standardized partial regression coefficients to test the following hypotheses: 1) RU and RUE are both necessary to explain competitive outcomes in diverse resource-ratio environments, and 2) selection favors differing combinations of RUE and RU in varying resource regimes. I found that in high light, RU alone determines the outcome of competition. However, competitive outcomes in low light were determined by both RU and RUE. These results suggest that relying on RU alone is not a predictive measure of competitive outcomes in resource-limited environments. In addition, variation in direct selection, together with the negative indirect selection of RUE in the high light treatments and positive indirect selection in the low light treatments, suggests that variable resource availabilities may maintain the genetic variation of these physiological characteristics in this species.
KEY WORDS: Arabidopsis thaliana, competition, resource uptake, resource-use efficiency