Frequency and Microenvironmental Pattern of Selection on Plastic Shade-Avoidance Traits in a Natural Population of Impatiens capensis

Heidrun Huber, Nolan C. Kane, M. Shane Heschel, Eric J. Von Wettberg, Joshua Banta, Anne Marie Leuck, Johanna Schmitt

Research output: Contribution to journalArticlepeer-review

Abstract

The frequency and predictability of different selective environments are important parameters in models for the evolution of plasticity but have rarely been measured empirically in natural populations. We used an experimental phytometer approach to examine the frequency, predictability, and environmental determinants of heterogeneous selection on phytochrome-mediated shade-avoidance responses in a natural population of the annual plant Impatiens capensis. The strength and direction of selection on shade-avoidance traits varied substantially on a fine spatial scale. The shade-avoidance phenotype had high relative fecundity in some microsites but was disadvantageous in other microsites. Local seedling density proved to be a surprisingly poor predictor of microenvironmental variation in the strength and direction of selection on stem elongation in this study population. At least some of this unpredictability resulted from microenvironmental variation in water availability; the shade-avoidance phenotype was more costly in dry microsites. Thus, environmental heterogeneity in resource availability can affect the relative costs and benefits of expressing shade-avoidance traits independent of local seedling density, the inductive environmental cue. Theory predicts that these conditions may promote local genetic differentiation in reaction norms in structured populations, as observed in I. capensis.

Original languageEnglish (US)
Pages (from-to)548-563
Number of pages16
JournalAmerican Naturalist
Volume163
Issue number4
DOIs
StatePublished - Apr 2004
Externally publishedYes

Keywords

  • Environmental heterogeneity
  • Impatiens capensis
  • Natural selection
  • Path analysis
  • Phenotypic manipulation
  • Shade-induced plasticity

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