Delayed Chemical Defense: Timely Expulsion of Herbivores Can Reduce Competition with Neighboring Plants
Authored by Pia Backmann, Volker Grimm, Gottfried Jetschke, Yue Lin, Matthijs Vos, Ian T Baldwin, Dam Nicole M van
Date Published: 2019
DOI: 10.1086/700577
Sponsors:
No sponsors listed
Platforms:
NetLogo
Model Documentation:
Other Narrative
Flow charts
Model Code URLs:
https://github.com/PiaBackmann/TIMELY-MODEL
Abstract
Time delays in plant responses to insect herbivory are thought to be the
principal disadvantage of induced over constitutive defenses, suggesting
that there should be strong selection for rapid responses. However,
observed time delays between the onset of herbivory and defense
induction vary considerably among plants. We postulate that strong
competition with conspecifics is an important codeterminant of the
cost-benefit balance for induced responses. There may be a benefit to
the plant to delay mounting a full defense response until the herbivore
larvae are mobile enough to leave and large enough to cause severe
damage to neighboring plants. Thus, delayed responses could reduce the
competitive pressure on the focal plant. To explore this idea, we
developed an individual-based model using data from wild tobacco,
Nicotiana attenuata, and its specialized herbivore, Manduca sexta.
Chemical defense was assumed to be costly in terms of reduced plant
growth. We used a genetic algorithm with the plant's delay time as a
heritable trait. A stationary distribution of delay times emerged, which
under high herbivore densities peaked at higher values, which were
related to the time larvae need to grow large enough to severely damage
neighboring plants. Plants may thus tip the competitive balance by
expelling insect herbivores to move to adjacent plants when the
herbivores are most damaging. Thus, herbivores become part of a plant's
strategy for reducing competition and increasing fitness.
Tags
Individual-based model
Simulation
population
Intraspecific competition
Germination
Specialist
Biomass allocation
Induced defense
Plant-herbivore
interactions
Trait diversity
Induced responses
Nicotiana-attenuata
Tobacco
hornworm
Fitness costs
Jasmonic acid
Wild tobacco