Phenotypic selection favors missing trait combinations in coexisting annual plants

Sarah Kimball, Jennifer R. Gremer, Travis E. Huxman, D. Lawrence Venable, Amy L. Angert

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


Trade-offs among traits are important for maintaining biodiversity, but the role of natural selection in their construction is not often known. It is possible that trade-offs reflect fundamental constraints, negative correlational selection, or directional selection operating on costly, redundant traits. In a Sonoran Desert community of winter annual plants, we have identified a trade-off between relative growth rate and water-use efficiency among species, such that species with high relative growth rate have low water-use efficiency and vice versa. We measured selection on water-use efficiency, relative growth rate, and underlying traits within populations of four species at two study sites with different average climates. Phenotypic trait correlations within species did not match the among-species trade-off. In fact, for two species with high water-use efficiency, individuals with high relative growth rate also had high water-use efficiency. All populations experienced positive directional selection for water-use efficiency and relative growth rate. Selection tended to be stronger on water-use efficiency at the warmer and drier site, and selection on relative growth rate tended to be stronger at the cooler and wetter site. Our results indicate that directional natural selection favors a phenotype not observed among species in the community, suggesting that the amongspecies trade-off could be due to pervasive genetic constraints, perhaps acting in concert with processes of community assembly.

Original languageEnglish (US)
Pages (from-to)191-207
Number of pages17
JournalAmerican Naturalist
Issue number2
StatePublished - Aug 2013


  • Phenotypic selection analysis
  • Relative growth rate
  • Sonoran Desert
  • Trade-offs
  • Water-use efficiency
  • Winter annual plants

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics


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