Andrea Glassmire

Position in canopy changes plant chemistry and herbivory

Contributed by Elizeth Cinto Mejia @Elizethcm & Andrea Glassmire


Chemical ecology, Community ecology, Consumption, Ecology, Experimental, Field, Forest, Fundamental research, Indirect, Interactions, Natural history, Plants, South America, Terrestrial, Woman



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Andrea E. Glassmire, Casey Philbin, Lora A. Richards, Christopher S. Jeffrey, Joshua S. Snook, and Lee A. Dyer. 2019. Proximity to canopy mediates changes in the defensive chemistry and herbivore loads of an understory tropical shrub, Piper kelleyi. Ecology Letters 22:332-341.  link



Slide 1: Researcher’s Background

Andrea is broadly interested in the ecology of plant-insect interactions and how trait diversity shapes community structure. Her research focuses on how plant chemistry mediates interactions with herbivores and natural enemies in a spatial context.


PB: Why did you become a biologist?

AG: To find answers to questions about the environment.


PB: What is your favorite part about your job?

AG: Working outside.


PB: What obstacles have you overcome to get where you are?

AG: Being told I couldn’t do something to only prove that I could.


PB: What advice do you have for aspiring biologists?

AG: Follow your heart.


PB: Do you feel that any dimension of your identity is invisible or under-represented/marginalized in STEM?

AG: Yes. It’s hard being a woman in science and in the world.


Slide 2: Research Overview

Take home message of study

Light availability and position in the canopy of a forest can be an important predictor of phytochemical diversity and indirectly reduce herbivory in a tropical shrub (Piper kelleyi)

The composition of defensive chemicals in plants was dependent on the amount of light available. Subtle differences in light in the shaded forest understory induced changes in the kinds of defense chemicals found in the plant. Herbivory was reduced by up to 37% in plants with different chemical blends compared to plants with similar chemical blends.


Study system

Study plant Piper kelleyi. This plant is a mid‐canopy shrub, from Ecuador and Peru. The picture was taken at Yanayacu Biological Station, Cosanga, Napo Province, Ecuador. 

The experimental design consisted of paired clonal plants hung at different heights along the vertical strata in the forest. Clonal pairs of individual plants were randomly selected and suspended in pots from tree limbs. High and low heights in the canopy were used to simulate differences in natural variation in light intensity that are present beneath the forest understory. Plants in close proximity to the canopy were exposed to more light while understory plants near the soil were exposed to less light.


Slide 3: Key Research Points

Main figure

Relationships between phytochemical diversity, herbivory, vertical stratification in the forest, and light heterogeneity. The experimental design consisted of paired clonal plants hung at different heights along the vertical strata in the forest. The blue colour represents plants hanging closer to the canopy while the red colour represents understory plants hanging near the soil. 

Vertical stratification influenced phytochemical diversity of Piper kelleyi plants by shifting the chemotype towards chromene production (blue bars) as plants increased in proximity to the canopy, while understory plants near the soil shifted the chemotype towards piplartine production (red bars). 

Increases in phytochemical diversity significantly reduced herbivory for understory plants near the soil (red line), but it did not vary with plants in close proximity to the canopy (blue line). 

Societal Relevance

Understanding variation in plant chemistry allows us to understand the fundamentals of plant life. Not only does this allow us to understand how plants live in their natural habitats, but can have important implications for understanding phytochemicals (plant chemicals) that are important pharmaceuticals. Learning how phytochemicals affect herbivory can also help us understand how to protect crops from pests. 

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