They Heard It Through the Grapevine: How Asclepias syriaca Communicates

Asclepias syriaca, or common milkweed, is a tall, herbaceous plant that reproduces both sexually, through pollination, and asexually, through producing multiple shoots from a single root system. It has strong chemical and physical defenses against herbivory, and when the plant senses that tissue is being disrupted by insects, it accordingly increases its production of latex (a gummy liquid) and cardenolides (toxic compounds). Previous studies have shown that other clonal plants with shoot or root connections are able to share resources such as water and nutrients between stalks. My research will investigate whether stalks of A. syriaca experiencing herbivory can share the signals that induce increased defenses with their clonal relatives; in effect, can milkweed stems “talk” to their fellow clones to warn them about present dangers?

Asclepias syriaca is ecologically important because Danaus plexippus, the monarch butterfly, feeds and reproduces exclusively on milkweed species during its annual migration from Mexico to Canada. It is estimated that over 85% of monarchs feed on A. syriaca during their lifetimes. Currently, both common milkweed and the monarch butterfly are in decline. The decline is frequently attributed to loss of suitable milkweed habitat due to development and mowing, as well as the proliferation of Roundup-Ready crops. These GMO plants allow farmers to use the herbicide glyphosate to kill milkweed (commonly found in and along the margins of agricultural fields) without harming their crops. As A. syriaca populations become fragmented, they are more likely to begin reproducing clonally, as the probability of pollination decreases. This can lead to entire patches of milkweed being made up of a single genetic individual. Because A. syriaca cannot successfully self-pollinate, such populations become sexually extinct and more prone to local extinction. However, if A. syriaca clones are able to communicate and cooperate in the face of herbivory threats, they may have an increased chance of survival until new genetic variation is introduced in the population.

I hope that my research will open up new avenues of thought regarding restoration efforts for declining milkweed populations, as well as what it fundamentally means for plants to think, communicate, and interact with their surroundings. I sincerely thank the generous individuals whose donations to the Charles Center allow me to pursue these goals through my summer research.

Monarch butterfly feeding on nectar from common milkweed. From

Monarch butterfly feeding on nectar from common milkweed. From


  1. Wow Erin sounds great! Love your description of the milkweed background