Molecular and ecological plant defense responses along an elevational gradient in a boreal ecosystem

Authors: BENEVENUTO, RAFAEL - Western Norway University Of Applied Sciences; SELDAL, TARALD - Western Norway University Of Applied Sciences; Polashock, James; MOE, STEIN - Norwegian University Of Life Sciences; RODRIGUEZ-SAONA, CESAR - Rutgers University; GILLESPIE, MARK - Western Norway University Of Applied Sciences; HEGLAND, STEIN - Western Norway University Of Applied Sciences

Submitted to: Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2020
Publication Date: 2/1/2020
Citation: Benevenuto, R., Seldal, T., Polashock, J.J., Moe, S.R., Rodriguez-Saona, C., Gillespie, M.A., Hegland, S.J. 2020. Molecular and ecological plant defense responses along an elevational gradient in a boreal ecosystem. Ecology and Evolution. https://doi.org/10.1002/ece3.6074.
DOI: https://doi.org/10.1002/ece3.6074

Interpretive Summary: Plants have the capacity to adapt to their environment and stresses such as insect feeding. However, little is known about how this capacity is influenced by environmental conditions. To investigate this, we used European blueberry plants growing at different elevations in Western Norway and monitored their response to simulated insect feeding (herbivory). Across all altitudes, plants treated to simulate insect feeding allocated resources to be resistant to further insect feeding while reducing growth and reproduction. This response was more pronounced at the lowest altitude. Plants growing at high-altitude exhibited consistently high defense response, suggesting a constant state of ‘alert.’ These results suggest that plants under distinct environmental conditions differentially direct the available resources to respond to stresses. Our findings are important in understanding the complex impact of future climate changes on plant-herbivore interactions, as this is a major driver of ecosystem functioning and biodiversity. This information will be useful to scientists in many fields including ecologists, entomologists, plant pathologists, climatologists and others.

Technical Abstract: Some plants have the capacity to adapt to environmental changes such as herbivory through molecular reprogramming, a phenomenon called phenotypic plasticity. However, little is known about how this capacity is modulated by environmental conditions. To investigate this, we used bilberry (Vaccinium myrtillus L.) ramets and an experimental treatment to simulate herbivory by inducing plant defenses (application of methyl jasmonate; MeJA), to observe ecological responses and gene-expression along an elevational gradient in a boreal system in Western Norway. The gradient included optimal growing conditions for bilberry in this region (ca. 400 m a.s.l.), and the plant’s range limits at high (ca. 900 m a.s.l.) and low (100 m a.s.l.) altitudes. Across all altitudinal sites, MeJA-treated plants allocated more resources to herbivory resistance while reducing growth and reproduction, but this response to simulated herbivory was more pronounced at the lowest altitude. High-altitude plants growing under less herbivory pressure but more resource-limiting conditions, exhibited consistently high expression levels of defense genes in both MeJA-treated and untreated plants at all times, suggesting a constant state of ‘alert.’ These results suggest that plant defense responses at both molecular and ecological levels are modulated by the combination of climate and herbivory pressure, such that plants under different environmental conditions differentially direct the resources available to specific anti-herbivore strategies. Our findings may be important in understanding the complex impact of future climate changes on plant-herbivore interactions, as this is a major driver of ecosystem functioning and biodiversity.