The long road to ecology

Doctoral student awarded $144,000 NSF grant after beginning his career as a diesel mechanic and welder

David Defilippis was earning great pay at a large mining machinery manufacturer in Milwaukee.

But, the former diesel mechanic turned metal fabricator saw the physical toll his co-workers faced once they reached their 40s and 50s. Many had significant and chronic knee, hip and shoulder injuries.

Unwilling to follow in their footsteps, Defilippis decided to make a change. At the age of 24, he gave up his previous career, enrolled in college and started studying biology.

“My friends and family were confused as to why I would leave a well-paying job with benefits and stability to go to college,” he said. “However, my goal was to learn more about hypothesis testing and experimental design, and my interest was in ecology.”

That key decision paid off for the doctoral student in Marquette University’s Department of Biological Sciences.

Defilippis this spring was awarded a three-year, $144,000 National Science Foundation Graduate Research Fellowship, becoming only one of a handful of graduate students at Marquette to receive it. The money includes a stipend and education expenses.

A total of 17,000 applications were received by the NSF and Defilippis was one of only 2,000 winners.

“This fellowship will enable me to focus my time on my doctoral thesis research and will help jumpstart my graduate career,” he said.

The problem of the woody vines

In tropical forests, the number of woody vines — called lianas — are increasing. These vines are winding their way up and over the tree canopy, and their leaves are blotting out the sunlight that the trees need. This could have a profoundly negative effect on tropical forests as the lianas continue to grow in numbers.

Scientists are unsure why the number of lianas is increasing, but they suspect that climate change may play a significant role. Many studies have been completed and others currently are underway in order to understand how the increasing number of lianas are affecting the environment for humans, animals and plants.

Defilippis’ work is extremely important in helping this research. He has invented a novel sensor system that has the capacity to measure plant growth and response to environmental conditions over very short time periods. The sensors will be placed on 500 tropical tree and lianas species in sites ranging from an ever-wet forest, Ft. San Lorenzo, on the Caribbean side of Panama, to a highly-seasonal dry forest in Parque National Metropolitano on the Pacific coast of the Central America country.

Many tropical plants tolerate the conditions during the dry season, but other plants still thrive. Defilippis hypothesizes that trees and lianas that can grow during the dry season will have an advantage over species that can tolerate — but not thrive — during drought conditions.

“Some species may actually thrive and become dominant in seasonal forests because they can grow more than other species during seasonal droughts,” Defilippis said.

The dry seasons have lasted longer and have been more pronounced in recent years, likely due to a rapidly changing climate change. If Defilippis finds that the lianas tolerate the dry conditions better than most species of trees, it could point to a possible cause of the increased number of these woody vines.

The study is possible due to the novel sensor he invented, which is extremely sensitive to measuring plant diameter growth. The sensor is a band that is paired with an inexpensive yet robust microprocessor. It sends the data wirelessly to be recorded.

The data will be both stored and transmitted hourly to a storage server through cellular networks.

“This project is the culmination of the unique skills that I have developed over the past decade,” Defilippis said.

“I am leveraging my knowledge of electronics, microprocessors, software development and problem-solving skills that I learned as a mechanic and metal fabricator together with my knowledge of ecology to address important ecological questions.”

Previously, people would have to manually check each plant’s sensor to get the data.

“Due to the relatively low cost and ease of producing the sensor system, I can test the dry season growth and tolerance hypotheses on a much larger number of tree and liana species than was previously possible,” he said. “I predict that the tree and liana species that are most abundant will be the ones that can maintain diameter growth throughout the dry season.”

The journey to Marquette (goes through Panama)

After leaving his job as a metal fabricator, Defilippis enrolled at the University of Wisconsin-Milwaukee, where he quickly became a standout undergraduate. He presented work on autonomously detecting aquatic phosphorous levels and algal blooms at the National Conference for Undergraduate Research in Utah, and again to Wisconsin legislators at the State Capital.

He traveled to Copenhagen, Denmark, to present a poster at the International Society of Microbial Ecology symposium, and was the honorary guest speaker for the UW System Board of Regents Annual Review in 2015.

He was awarded a McNair Fellowship and received a Research Experience for Undergraduates Fellowship from the Smithsonian Tropical Research Institute in Panama.

That’s where he met Dr. Stefan Schnitzer, then a professor at UW-Milwaukee and now a professor of biological sciences at Marquette. Schnitzer also is a research associate at the Smithsonian Tropical Research Institute, which runs many studies in Panama, and has led many groundbreaking studies on the effects of lianas in tropical forests.

Upon graduation, Defilippis took a job with a local software development company. Within a year, he realized he was more interested in ecology, and last year was accepted as a doctoral student in Schnitzer’s lab at Marquette.

In addition to his research in Panama, Defilippis will use his doctoral project to continue to teach elementary school students in Milwaukee Public Schools about science and technology and how the two disciplines can be combined. Three years ago, he worked with a teacher at Fratney Elementary School to develop a teaching unit called “Ecology & Electronics” for fifth grade students.

The students created sensors to measure and test environmental conditions, and they won first and third places in the citywide STEM competition in 2014. Defilippis plans to continue working with MPS students this year.

Ultimately, he would like to become a university professor where he can conduct original research and teach students about how to test ecological theory using novel sensor networks.