Latitudinal variation in plant defense against herbivory in a marine foundation species does not follow a linear pattern: The importance of resource availability

Link To Share This Poster: https://cdmcd.co/LdDggd
Live Discussion Link: https://cdmcd.co/3wqGEz

Gema Hernan, Department of Biological Science, Florida State University, Tallahassee, FL, Gema Hernan, Josep Alos and Fiona Tomas, Department of Marine Ecology, Mediterranean Institute for Advanced Studies (IMEDEA/CSIC), Esporles, Spain, María J. Ortega, Department of Organic Chemistry, University of Cadiz, Puerto Real, Spain, Jeremy Henderson, Stephanie L. Kiriakopolos and Fiona Tomas, Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR, Katharyn Boyer and Stephanie L. Kiriakopolos, Department of Biology, San Francisco State University, San Francisco, CA, Stephanie Cimon and Mathieu Cusson, Aquatic science laboratory, Université du Québec à Chicoutimi, Quebec, QC, Canada, Vincent Combes, College of Earth, Ocean and Atmospheric science, Oregon State University, Corvallis, OR, Clara Hereu, College of Marine Science, Autonomous University of Baja California, Baja California, Mexico, Margot Hessing-Lewis, Hakai Institute, Calvert Island, BC, Canada, Kevin Hovel and Erin Voigt, Coastal and Marine Institute, San Diego State University, San Diego, CA, Pablo Jorgensen, Geomare, A.C., Ensenada, Mexico, Nicole Kollars and Pamela L. Reynolds, Department of Ecology and Evolution, University of California Davis, Davis, CA, Mary O'Connor, Zoology, University of British Columbia, Vancouver, BC, Canada, Jeanine Olsen, Marine Benthic Ecology & Evolution (MarBEE), University of Groningen, Groningen, Netherlands, Pamela L. Reynolds, Data Science and Informatics, University of California Davis, Davis, CA, Jennifer Ruesink, Biology, University of Washington, Seattle, WA

Background/Question/Methods
Studies on latitudinal patterns in plant defense have traditionally overlooked the potential effect that resource availability may have in shaping plant defense. Likewise, latitudinal patterns of tolerance traits have rarely been studied, yet they can be a critical component of plant defense. Therefore, the aim of our study was to examine latitudinal variation in the production of tolerance and resistance traits against herbivory along a latitudinal range and a natural gradient of resource availability from upwelling conditions.
We conducted experiments simulating macroherbivore (e.g., bird, fish) damage on the seagrass Zostera marina at 10 sites across the Eastern Pacific coast (Canada-Mexico) and Quebec and analyzed several traits related to resistance and tolerance strategies against herbivory. In addition, we examined the effects of potential seagrass changes in defense strategies by performing a series of feeding experiments with mesoherbivores in a subset of sites.
Results/Conclusions
We found that eelgrass resistance defenses did not follow a linear latitudinal pattern but rather followed a bell-shaped curve which correlated with bottom-up control. In sites with higher nutrient availability, plants allocated resources to tolerance strategies and had lower resistance traits. Furthermore, seagrasses did not respond linearly to increased herbivory pressure; while they tolerated moderate levels of herbivory, they underwent a significant reduction in tolerance and resistance under high herbivory levels, which also made them more susceptible to consumers in feeding experiments.
Our results highlight the importance that nutrient availability has in shaping latitudinal patterns of plant defense against herbivory and show how these defenses may not respond linearly to increased herbivory pressure in seagrasses.