Herbivory and climate effects on plant defenses: an ecological and molecular approach

• Main Author: Benevenuto, Rafael Fonseca
• Other Authors: Hegland, Stein Joar, Moe, Stein Ragnar, Seldal, Tarald, Rodriguez-Saona, Cesar
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Norwegian University of Life Sciences, Ås 2019
• Subjects: Norway; Fennoscandia
• Online Access: https://hdl.handle.net/11250/3039443

Knowledge of plant defense responses and how they interact with biotic (e.g., herbivores) and abiotic (e.g., temperature) factors is of fundamental importance for understanding ecosystem functioning. Increases in temperature can dramatically weaken plant immune systems, and thereby cause elevated herbivory rates. On the other hand, rising temperatures can make plants more alert, and consequently result in investment in more effective defense strategies. Such adaptation can potentially influence plant-animal and plant-plant interactions. The effects of climate change on plant defenses can have particularly strong impacts on biodiversity and ecosystem functioning of vulnerable high-latitude systems. The boreal forest is the dominant biome in Fennoscandia (the Scandinavian peninsula and Finland), where bilberry (Vaccinium myrtillus L.), a widely distributed dwarf shrub, is considered to be a key food source for many species, and an excellent model organism for ecological studies in the boreal system. The main objective of this thesis is to explore bilberry defense responses through plant-herbivore and plant-plant interactions, as well as investigate how these relationships are affected by environmental variation. To investigate this, we experimentally treated bilberry ramets with methyl jasmonate (MeJA) to simulate herbivory and induce plant defenses. Subsequently we observed ecological and molecular responses in relation to growth, reproduction and defense along an elevational gradient in a boreal system in Western Norway. The elevational gradient design mainly reflected variation in temperature and snow cover, and included optimal growing conditions for bilberry (ca. 500 m a.s.l.; mid-montane zone), as well as the plants’ range limits at low (ca. 100 m a.s.l.; submontane zone) and high (ca. 900 m a.s.l.; subalpine zone) altitudes. We observed that MeJA-induced defenses in bilberry plants effectively reduced insect and mammalian herbivory, as well as growth and reproduction across the three years of study. Such ...