Diversity and abundance of phyllosphere bacteria are linked to insect herbivory

Parris T. Humphrey, Trang T. Nguyen, Martha M. Villalobos, Noah K. Whiteman

Research output: Contribution to journalArticlepeer-review

67 Scopus citations


Simultaneous or sequential attack by herbivores and microbes is common in plants. Many seed plants exhibit a defence trade-off against chewing herbivorous insects and leaf-colonizing ('phyllosphere') bacteria, which arises from cross-talk between the phytohormones jasmonic acid (JA, induced by many herbivores) and salicylic acid (SA, induced by many bacteria). This cross-talk may promote reciprocal susceptibility in plants between phyllosphere bacteria and insect herbivores. In a population of native bittercress (Cardamine cordifolia, Brassicaceae), we tested whether simulating prior damage with JA or SA treatment induced resistance or susceptibility (respectively) to chewing herbivores. In parallel, we conducted culture-dependent surveys of phyllosphere bacteria to test the hypothesis that damage by chewing herbivores correlates positively with bacterial abundance in leaves. Finally, we tested whether bacterial infection induced susceptibility to herbivory by a major chewing herbivore of bittercress, Scaptomyza nigrita (Drosophilidae). Overall, our results suggest that reciprocal susceptibility to herbivory and microbial attack occurs in bittercress. We found that JA treatment reduced and SA treatment increased S. nigrita herbivory in bittercress in the field. Bacterial abundance was higher in herbivore-damaged vs. undamaged leaves (especially Pseudomonas syringae). However, Pedobacter spp. and Pseudomonas fluorescens infections were negatively associated with herbivory. Experimental Pseudomonas spp. infections increased S. nigrita herbivory in bittercress. Thus, plant defence signalling trade-offs can have important ecological consequences in nature that may be reflected in a positive correlation between herbivory and phyllosphere bacterial abundance and diversity. Importantly, the strength and direction of this association varies within and among prevalent bacterial groups.

Original languageEnglish (US)
Pages (from-to)1497-1515
Number of pages19
JournalMolecular ecology
Issue number6
StatePublished - Mar 2014
Externally publishedYes


  • Pseudomonas
  • coinfection
  • endophyte
  • herbivore
  • inducible defences
  • microbiome
  • specialist
  • trade-off

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Genetics


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