Hilda Castaneda translates for Mitzila Gaitan: “Yeah... the monkeys are very crazy... she felt one day that somebody was staring at her... and she looked back and it was a monkey.. A white faced monkey...in the back of the tree... on the ground…and he was looking at her like that”.
Mitzila Gaitan shared a memorable experience of a curious Capuchin monkey watching her collect field samples in the tropical forest of Barro Colorado Island. She has been a technical assistant at the Smithsonian tropical research institute for sixteen years, working on numerous projects involving plant ecology. Gaitan plays a vital role for this multi-institutional project, supported by the National Science Foundation. Hilda Castaneda the Barro Colorado Island site administrator is translating for her. Gaitan works in the field every single day, collecting plant samples for the project.
“She gets a list of plants that she has to search for in the forest... and she searches for the fruits and also for the mature leaves.. the dry and also the fresh. When they bring them in the forest they weigh them... and when they pass them through the drying equipment they also weigh them again and then they go in the freezer”, Castaneda translated.
The samples are processed by being weighed, dried, and weighed again before being sent to Carlos Rios, professor of organic chemistry at the University of Panama.
Rios described the chemical extraction process of the samples: “When it’s dry, it’s easier to extract the metabolites...We use ethanol to extract the metabolites that are with the sample”.
Secondary metabolites are chemical compounds produced in specific tissues of plants. They play a variety of roles such as repelling an insect or to attract a pollinator or seed disperser or warn nearby plants of enemies. Plants produce thousands of these chemicals, and we don’t know why.
Noelle Beckman, principal investigator of this project and associate professor in Biology and the Ecology Center at USU sees the importance of studying them:
“A lot of our medicine is from these compounds that we found in plants. And there's been a lot of work trying to use the ecological information that we get from studying these interactions between plants and other organisms and being able to use that to help us find novel chemical compounds that could be used for medicinal purposes”, Beckman said.
“Nature doesn't do nothing for nothing, you are doing something because something is happening. What is happening?”, Rios explained.
The researchers of this project suspect that seed dispersal may be a driving force to the rise of such diverse chemical evolution. This is the crux of the mystery they are trying to solve, and they believe the answer lies in chemistry.
The key aim in this is to understand the role these complex chemicals play within the different seed dispersal strategies. This project is studying 50 different species of fruiting trees where these strategies are well documented. There are actually over 400species of trees on this six square mile island.
That is Joseph Wright, Senior Scientist at the Smithsonian Tropical Research Institute in Panama and Co-PI of the project. He is an expert in forest ecology, plant phenology, and conservation biology.
“It's just astonishing...Over half of all plant species live in tropical forests...we have to come here to understand nature. The big question is how can all these species coexist? 450 tree species? How can there be 450 trees, on a six square mile island”, Wright said.
This is part two in the series of Secret Beyond the Seed. Welcome back to Barro Colorado Island (BCI)!
In the natural world, plants evolve various mechanisms to spread their seeds. They may rely on the wind or tempt hungry mammals and birds with their succulent and colorful fruits.
“Fruits interact with a diversity of organisms that both consume and kill the seeds, such as plant diseases and insects that can kill the seed, but they also interact with a lot of organisms that are beneficial for the plant like seed dispersers, such as monkeys and birds and bats that move the seed away from the plant that can increase the survival. And we think, because of these diversity of interactions that can be driving the diversity of chemical compounds the plant has... being able to mediate those different interactions”, Beckman described.
Susan Whitehead, associate professor in the department of biological sciences at Virginia Tech is co-PI on this project.
Whitehead explained: “Fruits are in a really tough place ecologically, they need to be attractive to their seed dispersers, and still defend against insects, and fungal pathogens that would attack roots, and damage the seeds. We think that chemistry might be really key to mediating these really complex interactions”.
Being such a well-studied island, this project builds off of research conducted from previous scientists who too have spent their career collecting and analyzing data while walking along the same trails.
“BCI is a dream location for a project like this because we have so much existing data, right, we know the main seed dispersers for all the plants. And that's not a trivial thing to figure out, like whether the seeds are dispersed mainly by birds, or bats, or abiotically” Whitehead said.
They also know the phenology of the plants- when they fruit and flower, when they should collect plants, their genetic information and how they are all related to one another.
“So that type of background is just incredible to have because it provides so much context for the data that we're collecting on the chemical traits of plants. Now we can really ask how those chemical traits relate to all of these other ecological and evolutionary factors for each of those different species”, Whitehead said.
“And so we can use this comparative approach to see how the chemistry changes across these these species that have very different dispersal modes” Beckman elaborated.
Not only do they have all of this existing data but they are able to process the samples in the field.
Postdoctoral researcher at USU, Jerry Schneider, and key chemistry ecologist took us on a tour of the lab space they use when preparing the plant samples for chemical extractions from the field. His expertise comes in handy when trying to tease apart the role the thousands of chemicals play within the dozens of species of plants this project is investigating.
“A big part of what makes BCI unique as a field station is the laboratory facilities inside so you can go collect samples and half an hour later be grinding them up to do extractions and here's the centrifuge. Here's the microbalance, here's a rotary evaporator…” Schneider pointed out the lab equipment used while preparing the samples.
Residential scientist Joe Wright explained: “Analytical chemistry has just taken off in the last decade, you can now take an extract of plant tissue and determine the structure of every compound... In this method, analytical chemistry allows you to see the structure of those thousand compounds... we're at a cusp of chemists, not the ecologists, the chemists have gotten us to this point where we can suddenly deal with 1000s of compounds...”
Teasing apart the roles that these metabolites play will shed light on the mystery of why there is such a rich diversity of chemicals in plants. Through the lens of seed dispersal strategies, it can also provide the discovery of novel chemical compounds with potential medicinal applications.
Listen for UPR’s continuing coverage from Barro Colorado Island. This ongoing series is made possible by the support of the National Science Foundation.
