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Summary Stress often induces plant trait plasticity, and microbial communities also alter plant traits. Therefore, it is unclear how much plasticity results from direct plant responses to stress vs indirect responses due to stress‐induced changes in soil microbial communities.To test how microbes and microbial community responses to stress affect the ecology and potentially the evolution of plant plasticity, I grew plants in four stress environments (salt, herbicide, herbivory, and no stress) with microbes that had responded to these same environments or with sterile inoculant.Plants delayed flowering under stress only when inoculated with live microbial communities, and this plasticity was maladaptive. However, microbial communities responded to stress in ways that accelerated flowering across all environments. Microbes also affected the expression of genetic variation for plant flowering time and specific leaf area, as well as genetic variation for plasticity of both traits, and disrupted a positive genetic correlation for plasticity in response to herbicide and herbivory stress, suggesting that microbes may affect the pace of plant evolution.Together, these results highlight an important role for soil microbes in plant plastic responses to stress and suggest that microbes may alter the evolution of plant plasticity.
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Herbivores disrupt clinal variation in plant responses to water limitation
Abstract Plasticity in plant traits, including secondary metabolites, is critical to plant survival and competitiveness under stressful conditions. The ability of a plant to respond effectively to combined stressors can be impacted by crosstalk in biochemical pathways, resource availability and evolutionary history, but such responses remain underexplored. In particular, we know little about intraspecific variation in response to combined stressors or whether such variation is associated with the stress history of a given population.Here, we investigated the consequences of combined water and herbivory stress for plant traits, including relative growth rate, leaf morphology and various measures of phytochemistry, using a common garden ofAsclepias fascicularismilkweeds. To examine how plant trait means and plasticities depend on the history of environmental stress, seeds for the experiment were collected from across a gradient of aridity in the Great Basin, United States. We then conducted a factorial experiment crossing water limitation with herbivory.Plants responded to water limitation alone by increasing the evenness of UV‐absorbent secondary metabolites and to herbivory alone by increasing the richness of metabolites. However, plants that experienced combined water and herbivory stress exhibited similar phytochemical diversity to well‐watered control plants. This lack of plasticity in phytochemical diversity in plants experiencing combined stressors was associated with a reduction in relative growth rates.Leaf chemistry means and plasticities exhibited clinal variation corresponding to seed source water deficits. The total concentration of UV‐absorbent metabolites decreased with increasing water availability among seed sources, driven by higher concentrations of flavonol glycosides, which are hypothesized to act as antioxidants, among plants from drier sites. Plants sourced from drier sites exhibited higher plasticity in flavonol glycoside concentrations in response to water limitation, which increased phytochemical evenness, but simultaneous herbivory dampened plant responses to water limitation irrespective of seed source.Synthesis. These results suggest that climatic history can affect intraspecific phytochemical plasticity, which may confer tolerance to water limitation, but that co‐occurring herbivory disrupts such patterns. Global change is increasing the frequency and intensity of stress combinations, such that understanding intraspecific responses to combined stressors is critical for predicting the persistence of plant populations.
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- Award ID(s):
- 2145757
- PAR ID:
- 10479723
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Ecology
- Volume:
- 112
- Issue:
- 2
- ISSN:
- 0022-0477
- Format(s):
- Medium: X Size: p. 338-347
- Size(s):
- p. 338-347
- Sponsoring Org:
- National Science Foundation
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