Differential genetic influences on competitive effect and response in Arabidopsis thaliana

Authors

  • JAMES F. CAHILL JR,

    Corresponding author
    1. Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada, and
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  • STEVEN W. KEMBEL,

    1. Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada, and
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  • DANNY J. GUSTAFSON

    1. Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada, and
    2. Department of Biology, University of Pennsylvania, Philadelphia, PA, 18504, USA
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    • *

      Present address: Department of Biology, The Citadel, Charleston, SC, 29409, USA.


James F. Cahill (e-mail jc.cahill@ualberta.ca).

Summary

  • 1Competition plays an important role in structuring populations and communities, but our understanding of the genetic basis of competitive ability is poor. This is further complicated by the fact that plants can express both competitive effect (target plant influence upon neighbour growth) and competitive response (target plant growth as a function of a neighbour) abilities, with these ecological characteristics potentially being independent.
  • 2Using the model plant species Arabidopsis thaliana, we investigated patterns of intraspecific variation in competitive effect and response abilities and their relationships to other plant traits and resource supply rates.
  • 3Both competitive effect and response were measured for 11 genotypes, including the Columbia ecotype and 10 derived mutant genotypes. Plants were grown alone, with intragenotypic competition, and with intergenotypic competition in a replicated blocked design with high nutrient and low nutrient soil nutrient treatments. We quantified competitive effect and response on absolute and per-gram bases.
  • 4Competitive effect and response varied among genotypes, with the relative competitive abilities of genotypes consistent across fertilization treatments. Overall, high rates of fertilization increased competitive effect and competitive response abilities of all genotypes. Both competitive effect and response were correlated with neighbour biomass, though genotype-specific traits also influenced competitive response.
  • 5At the genotype level, there was no correlation between competitive effect and response in either fertilization treatment. Overall patterns in competitive response appeared consistent among inter- and intragenotypic competition treatments, indicating that a target genotype's response to competition was not driven by the genetic identity of the competitor.
  • 6These findings indicate that within A. thaliana, there is the potential for differential selection on competitive effect and response abilities, and that such selection may influence different sets of plant traits. The concept of a single competitive ability for a given plant is not supported by these data, and we suggest continued recognition of these dual competitive abilities is essential to understanding the potential role of competition in influencing intra- and interspecific processes.

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