Context dependence in the coevolution of plant and rhizobial mutualists

Katy D. Heath, Peter Tiffin

Research output: Contribution to journalArticle

Abstract

Several mechanisms are expected to rapidly rid mutualisms of genetic variation in partner quality. Variation for mutualist quality, however, appears to be widespread. We used a model legume-rhizobium mutualism to test for evidence that context-dependent selection may maintain variation in partner quality. In a greenhouse experiment using 10 natural populations of Medicago truncatula and two strains of Sinorhizobium medicae, we detected significant genotype X genotype (G X G) interactions for plant fitness, indicating that the most beneficial rhizobium strain depends on the host genotype. In a second experiment using a subset of the plant populations used in the first experiment, we detected significant G X G interactions for both plant and rhizobium fitness. Moreover, the plant population with which rhizobium strains gained the greatest benefit depended on the nitrogen environment. Finally, we found that in a high nitrogen environment, all plant populations had lower fitness when inoculated with a 1:1 mixture of strains than with the worse single strain alone, suggesting that nitrogen shifts the exchange of benefits in favour of rhizobia. Our data suggest that genotype, nitrogen and biotic dependency might contribute to the maintenance of genetic variation in mutualist quality when coupled with spatial or temporal heterogeneity in the environment.

Original languageEnglish (US)
Pages (from-to)1905-1912
Number of pages8
JournalProceedings of the Royal Society B: Biological Sciences
Volume274
Issue number1620
DOIs
StatePublished - Aug 7 2007
Externally publishedYes

Keywords

  • Cheating
  • Coevolution
  • Cooperation
  • Genotype by environment
  • Partner choice
  • Symbiosis

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)
  • Environmental Science(all)
  • Agricultural and Biological Sciences(all)

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