The thousands-of-years existence of coqui frogs have influenced the evolution of many adaptive traits. Photo credit Karen Beard.
By Kelsen Kitchen
The state of Hawaii is popularly depicted as an island paradise and an ideal vacation destination for those looking to relax on the beach. However, it is also home to one of the most unique ecological systems in the world, made up of thousands of both native and invasive species of flora and fauna.
One such species is the small coqui frog. Originally native to Puerto Rico, the species has since found its way to the Hawaiian Islands and is now considered by some to be a pest. In the June 20, 2012 online edition of “Biology Letters,”USU faculty member Karen Beard, USU alumnus Eric O’Neill and former USU faculty member Mike Pfrender published a paper on the adaptive traits of the coqui frogs in Hawaii, which may shed light on how traits are established in different populations.
Karen Beard, an associate professor at Utah State University, has been working with coqui frogs for fifteen years, which has included studying them in their native habitat of Puerto Rico for her PhD dissertation research. While conducting these studies, a paper was published announcing the presence of the coqui frogs in Hawaii. “I couldn’t wait to go there and start figuring out what this non-native species was doing in this new range,” she said.
Having studied other invasive species, including plants, Beard offered some insight as to what can be gained by studying invasive species. “[They] give us an opportunity to understand the ecological and evolutionary role of single species,” she said. They can also help ecologists understand the impact of the species, especially in the case of the coqui frog, which spread of the species researchers are currently trying to control and eradicate.
Beard, O’Neill and Pfrender’s manuscript on Hawaii details the effect of changing environments on the evolutionary traits of a species. Mainly, the team was trying to determine whether the allele frequencies of the coqui frogs in Hawaii were changing because of genetic drift—which occurs through random sampling or adaptation—resulting from non-random selection, such as predation or mate choice.
“Selection tends to shift allele frequencies in particular directions, whereas drift randomly shuffles them,” said O’Neill, who studied the evolutionary implications of the invasion of the coqui frog as part of his PhD. “Selection is therefore more effective in larger populations than in smaller populations, in part because of the relationship between population size and drift.”
In Puerto Rico, the coqui frog population has probably existed for thousands of years, which has allowed selection to be a major driver of evolution for many adaptive traits. However, in Hawaii, populations have started out small, and their evolution has been driven by strong genetic drift. Because there are no natural predators for the island frogs, the researchers believe that selection in general may be more relaxed, though it is hard to be sure.
“Selection on color patterns may actually be happening in Hawaii, but if it is, the effects were undetectable by our study because of strong drift,” O’Neill said. “Theory predicts that if drift remains the dominant driver of evolution in Hawaii, different populations will eventually become fixed for one stripe pattern or another.” While researchers often believe that selection plays the largest role in the evolution of differences between populations, this study shows that these patterns in introduced populations may often be the result of drift.
Field research such as this isn’t all glamour and discovery, even in Hawaii, since fieldwork is always challenging, O’Neill said. It requires permits, equipment, assistants, and money to pay for everything—and flying to Hawaii is not cheap. “(The experience) was quite challenging, but also very rewarding,” O’Neill said.
Beard said the publishing process is also quite a hurdle. “Writing a publishable manuscript is a lot of work,” he said. “It requires a lot of revision and research into how to put the research in perspective.” In the end, however, the potential positive impact of their research is significant, as the paper “put a new spin” on the invasion. “It showed that (the frogs) are experiencing evolutionary processes differently in Hawaii and Puerto Rico,” he added.
Choose your own adventure
For scientifically-inclined Aggies who are interested in getting involved in fieldwork such as the coqui frog, O’Neill advises finding a good advisor to work with and keeping an open mind about studying organisms and research questions. While he initially was only interested in working with amphibians and reptiles, he is currently studying lady beetles as well. Before O’Neill decided to go to graduate school, he was involved in projects in Puerto Rico and Florida, and also took a field course in tropical herpetology in Costa Rica.
Beard said that for interested USU students could get involved in research, they need to decide generally what types of questions really interested them, whether that be animal behavior, evolution, invasive species, or physiology. Then, it is important to identify labs of students who are doing the types of projects that interest them.
While it may require volunteering time or working in a lab for class credit, Beard asserted that each experience is helpful in figuring where you want to go in the future. “If you know exactly what you want to continue studying, I would suggest going to graduate school,” Beard said. “If you don’t, I’d suggest spending a couple of years working on different projects around the world. This will open your eyes to so many possibilities.”