COS 43-4
Prediction and evolution of response to plurispecific competition in a polymorphic local population of Arabidopsis thaliana
Competition is a key local process in structuring plant community. However, while studies on competition have often been based on pairwise interacting species, a plant is rarely surrounded by a single species in natura, but rather by several species. Similarly, studies on competition generally neglect intra-population variability, potentially leading to a misinterpretation of the actual dynamics and functioning of local communities. Studying response to competition requires therefore considering an assembly of species while accounting for intra-population variability. The present work aims to study the response to multispecific competition as well as its evolution in a natural population of Arabidopsis thaliana. We tested whether response to multispecific competition can be described as an additive function of responses to monospecific competition. We considered the importance of genetic variability in competition response and its deviation from the additive model, by using 96 genotypes of A. thaliana (target plant) sampled in 2002 and 2010 in a permanent meadow. Those genotypes were grown in competition with three co-occurring species: Veronica arvensis, Poa annua and Stellaria media. Using combinations of those three species, ten monospecific and multispecific competition treatments were realized. Phenological and biomass accumulation related traits have been scored for 4608 target plants.
Results/Conclusions
The response to multispecific competition can be predicted across the population from responses to monospecific competition for phenological and architectural traits. In contrast, the prediction for biomass accumulation traits requires a non-additive parameter like effects of interactions between competitors and effects of the genotypes on interactions between competitors. An intraspecific variability was found for mono- and multispecific competition responses, competitive ability, plasticity of response to competition and also the deviation from the additive model. Those results stress the need to consider intra-population variability of biotic interactions at a population scale to study community dynamics. We also showed that competition response and its prediction for traits linked to growth strategy evolved between the two sampled generations. Plants tend to be more competitive over time by increasing their diameter and biomass face to P. annua and V. arvensis, but less competitive face to S. media. Altogether, this suggests an adaptation to multispecific competition that may depend on the evolution of the community assembly. The on-going genome sequencing of the 96 accessions will soon reveal by Genome-Wide Association mapping whether the genes underlying plant-plant interactions differ between monospecific interaction and multispecific interactions.