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Intraspecific competition reduces mycorrhizae conferred susceptibility to herbivores
  • Zoe Getman-Pickering,
  • Danielle Rutkowski,
  • Jennifer Thaler
Zoe Getman-Pickering
Cornell University
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Danielle Rutkowski
UC Davis
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Jennifer Thaler
Cornell University
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Abstract

Mycorrhizal fungi alter their host plant’s resistance to herbivores and their competitive ability. However, most studies on how mycorrhizae alter resistance have been conducted in single plant studies, and so the interacting effects of mycorrhizae and competition on constitutive and induced plant resistance is largely unexplored. We tested whether mycorrhizal colonization with Rhizophagus intraradice would alter herbivore performance and the expression of chemical resistance traits in tomato plants with and without intraspecific competition. We treated the plants with jasmonic acid to measure their induced chemical resistance traits which we evaluated by measuring leaf consumption by Trichoplusia ni caterpillars and two traits that affect herbivore performance: protease inhibitors, an antinutritive protein, and carbon/nitrogen ratio, a metric of plant nutritional quality. Mycorrhizae decreased resistance (increased leaf consumption) to herbivores when the plants were not in competition but had no effect in competition. While mycorrhizae reduced protease inhibitors, independent of competition or treatment with jasmonic acid, this did not increase caterpillar feeding. However, mycorrhizae, competition and induction with jasmonic acid interacted to decrease plant nutrition, measured as C/N ratio, which was correlated with caterpillar feeding. Here, we show that mycorrhizae induced decreases in plant nutritional quality; a novel mechanism by which mycorrhizae affect resistance to herbivores. Mycorrhizae and competition interact to decrease plant nutritional quality and alter resistance to herbivores.

Peer review status:IN REVISION

27 Jan 2020Submitted to Ecology and Evolution
28 Jan 2020Assigned to Editor
28 Jan 2020Submission Checks Completed
29 Jan 2020Reviewer(s) Assigned
12 Feb 2020Review(s) Completed, Editorial Evaluation Pending
17 Feb 2020Editorial Decision: Revise Minor