Invasive plants are a major threat to natural ecosystems, with global climate change predicted to further intensify the negative impacts of weeds on native species. Classical biological control of invasive plants using host specific insects from invaders’ native range is a powerful and highly selective tool for mitigating weed spread and impacts. However, climate change may affect multiple factors that determine the efficacy of this important management tool.
Future environmental conditions likely include elevated atmospheric levels of carbon dioxide (CO2) and temperatures, coupled with reduced or altered patterns in precipitation. Such environmental factors can profoundly affect the growth, physiology and phenology of invasive plant species and their co-evolved specialist herbivore insects. A mechanistic approach to understanding how climate change may impact interactions between invasive plants and their biocontrol agents is essential for realistically addressing management needs under likely future field conditions.
Dalmatian toadflax is an aggressive invader of western rangelands. Photo by: Steve Dewey, Utah State University, Bugwood.org
The first step in this research is gaining a greater understanding of how invasive weeds respond to climate change, namely to elevated atmospheric CO2. The impact of elevated atmospheric CO2 on the growth of Dalmatian toadflax (Linaria dalmatica), yellow or common toadflax (L. vulgaris), and their hybrids (L. dalmatica x L. vulgaris) is not currently known but is being experimentally determined by monitoring plants grown under differential levels of CO2.
Initial experiments are being conducted in three reach-in growth chambers (Percival® model PGC-6L fitted with optional CO2 enrichment package). The purpose is to determine if different CO2 levels (ambient – 480 ppm; low – 580 ppm; and high – 780 ppm) induce differential growth responses in toadflax. Plants used in this experiment were clones generated from molecularly confirmed toadflax genotypes. Manipulated, reciprocal crosses were initially supplied by Colorado State University plant geneticist Dr. Sarah Ward, and have been used in a number of related experiments.
Subsequent experiments will measure the interactive effects of elevated CO2 on host plant-herbivore interactions. These will initially focus on determining if and how host plants grown under elevated CO2 might influence the biology and efficacy of approved and candidate weed biocontrol agents. Phenological milestones, fitness correlates, and reproductive success of agents belonging to different feeding and injury guilds – defoliators vs. stem miners vs. root gallers - will be compared. Interactions of agent feeding and injury guilds and elevated CO2 on host plant primary metabolic responses (gas exchange, photosynthetic rate, transpiration), growth, above- and below-ground biomass will also be evaluated to rank agent biocontrol efficacy under one of the most significant predicted influences of climate change.
See the webinar series Invasive Plants — Issues, Challenges, and Discoveries from the RMRS Grassland, Shrubland, and Desert Ecosystems for more information about invasive plants.
To learn more about this topic, see the project page Forecasting the influence of climate change on invasive weeds and biological control.