Thu, Aug 05, 2021:On Demand
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.
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.