Chemical defense lowers plant competitiveness
Daniel J Ballhorn1, Adrienne L Godschalx, Savannah M Smart
1Department of Biology, Portland State University, 1719 SW 10th Ave, Portland, OR, 97201, USA, ballhorn@pdx.edu.
Oecologia
|September 1, 2014
Summary
Plant defense and competition shape ecosystems. This study shows high cyanogenesis (plant defense) in lima beans incurs costs, but herbivores can mitigate these, supporting the growth-differentiation balance hypothesis.
Area of Science:
- Ecology
- Plant Science
- Evolutionary Biology
Background:
- Plant competition and defense are crucial for biodiversity and food webs.
- Evolutionary pressures on plant resource allocation between defense and growth are not fully understood.
- The growth-differentiation balance (GDB) hypothesis posits herbivory drives defense evolution, while competition drives growth traits.
Purpose of the Study:
- To test the GDB hypothesis by examining lima bean responses to competition and herbivory.
- To assess how varying levels of cyanogenesis (a plant defense) influence competitive ability.
- To understand the trade-offs between plant defense and growth under different ecological pressures.
Main Methods:
- Used high (HC) and low cyanogenic (LC) lima bean genotypes.
- Exposed plants to various competition (intraspecific, interspecific) and herbivory (Mexican bean beetle) treatments.
- Quantified vegetative (biomass) and generative (seed production) plant parameters.
Main Results:
- Highly cyanogenic (HC) plants showed reduced biomass and seed production without herbivores, indicating defense costs.
- Herbivore presence mitigated the performance disadvantage of HC plants compared to LC plants.
- Different plant genotypes responded distinctively to competition and herbivory stresses.
Conclusions:
- The study supports the GDB hypothesis by demonstrating differential effects of competition and herbivory on plant genotypes.
- Variation in plant defense within a species can be explained by the interplay of growth and defense trade-offs.
- Findings contribute to understanding the ecological and evolutionary drivers of plant defense strategies.
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