Last week our whole program took a trip to the Galapagos Islands. We began our trip on Isla Santa Cruz, and later took a sea taxi to Isla Isabela. We had the opportunity to snorkel, hike and bike. Fresh drinking water does not exist on either of these islands. This made us all more acutely aware of our water consumption, as all that we used had been imported. This excursion raised questions surrounding environmental ethics for me, and because I am personally very interested in the plant sciences, I largely experienced the trip through this lens.

Can anyone name a poisonous plant? Most likely, the first that comes to mind is poison ivy or poison oak. One can also assume that many of you may have some negative first-hand experience with this plant.

You may or may not have heard of the manzanilla tree, a plant native to the Galapagos islands off the coast of Ecuador. It is a fruit tree belonging to the Euphorbiaceae family. It is also the only plant species which is both toxic and native to the islands. If the milky internal fibers are touched, it can cause a painful skin rash; if the fruit is consumed, it can be fatal to humans.

Both the flowers and fruits are a light green-yellow, and the fruits are similar in appearance to an apple. In addition to poisonous fruit, all other parts of the tree contain toxins. If burned, it can even cause damage to the eyes and lungs. Some of the toxins in the tree remain unidentified to this day.

So what makes the presence of this tree on the Galapagos so interesting?

The manzanilla is the only fruit tree native to the islands, which clearly shows the lack of shared evolution between humans and the plants there. In fact, very few medicinal and edible plants exist on the islands.

coevolution galapagos islandsIn areas with high human impact, few plants exist with this level of toxicity to humans. This is in part due to our impact on the land. As humans, we have the tendency to eradicate that which poses a threat to us, but it is also because of our lack of shared evolutionary history with the species on the Galapagos islands. There are many more plants both serving as food and medicine for human use in places with a history of shared evolution with human civilization.

This demonstrates to us the concept of coevolution, which Charles Darwin actually touches on in The Evolution of Species. Species which have evolved in close proximity enact selective pressures on one other.

Darwin was interested in the relationship between insects and flowering plants. Perhaps the most famous example of coevolution that exists is the one between pollinators and flowering plants, whom rely on one other for their survival as species.

The manzanilla plant and the Galapagos tortoise are another example of a relationship existing which demonstrates this principle, as they have enacted selection pressures on each other. The fruit of the manzanilla plant is not toxic to the famous Galapagos tortoise. In fact, this tortoise has evolved to use the fruit for its own benefit; they consume the fruit periodically in order to rid their bodies of parasitic organisms that they acquire from drinking from mud puddles and swampy areas.

The manzanilla plant is perpetuated because the tortoise consumes the fruit and excretes the seeds, allowing for the spread of the species.

Humans do not share evolutionary history with the flora of the Galapagos, which is particularly interesting considering the toxic nature of this particular plant to us. The two species have not evolved in close quarters, rendering it irrelevant to the survival of the manzanilla whether or not its fruit is edible to humans.

The lack of freshwater on the islands, coupled with the deficiency of native edible plants all raise important questions about the ethics of human presence on the islands. I will end this topic today with a question; is our presence ethical in places like the Galapagos, with which we lack a shared evolutionary history?

Studying abroad challenges you to think more critically about your impact on the world. BCA programs encourage students to reflect on their experiences and impacts at all stages of the study abroad process.

Annaleigh Baremore BCA Storyteller

About the Author – Annaleigh Baremore, Spring 2018 Quito, Ecuador & Juniata College student

Annaleigh is a junior at Juniata College, studying Global Sustainable Development and French. Her passions include plants, world foods, ceramic arts, music and traveling. Join her and other BCA Storytellers as they navigate new cultures and countries!

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