Increasing Aridity May Threaten the Maintenance of a Plant Defence Polymorphism

Area of Science:

• Ecology
• Evolutionary Biology
• Plant Science

Background:

• Environmental changes pose a threat to genetic diversity in wild populations.
• Understanding how environmental factors influence standing genetic variation is crucial for conservation efforts.
• Polymorphic chemical defenses in plants play a key role in adaptation and survival.

Purpose of the Study:

• To investigate the environmental conditions that either protect or erode polymorphic chemical defenses in Boechera stricta.
• To assess the impact of drought and herbivory on the vital rates and overall fitness of different defense genotypes.
• To predict how climate change may affect genetic variation in wild plant populations.

Main Methods:

• A 4-year field experiment manipulating drought and herbivory levels.
• Measuring vital rates (e.g., survival, reproduction) of Boechera stricta genotypes with varying defense chemistry.
• Utilizing demographic models to estimate genotype-specific lineage growth rates (λ) and assess total fitness.

Main Results:

• Drought and herbivory interactively influenced plant vital rates.
• Different defense genotypes exhibited similar total fitness across various environmental conditions.
• Ambient field conditions are near the threshold for maintaining defense polymorphism.
• Increasing aridity pushes populations towards monomorphism.

Conclusions:

• Defense polymorphism in Boechera stricta may persist under current conditions but is vulnerable to increasing aridity.
• Climate change, particularly increased drought intensity and frequency, could lead to the erosion of genetic variation for chemical defenses.
• Conservation strategies may need to consider the impact of climate change on genetic diversity in wild populations.