As with all of the most interesting discoveries in science, what she discovered was not what she had initially set out to find. Dr. Pfennig researches the process of speciation, the splitting of one species into two or more different species over a long period of time. The following diagram shows how a population of fruit flies can be forced to speciate by separating them into two distinct groups with different sources of food.
She first became interested in research in spadefoot toads when she read an unpublished thesis (a research paper written by a PhD student) that claimed that toads that were a hybrid of two species (Spea bombifrons and Spea multiplicata, or Plains and New Mexico spadefoot toads) were able to develop more quickly than non-hybrids. This means that they would change from a tadpole to a land-dwelling toad very quickly. Dr. Pfennig decided to run her own experiment to verify this and found that it was true.
Meanwhile, she read a journal article about how New Mexico spadefoot toad females (Spea multiplicata)will purposely avoid mating with their close relative, the Plains spadefoot toad (Spea bombifrons). This result was not too surprising since everyone knows that hybridization is a bad thing to do. However, remembering the results of the thesis-writer, Dr. Pfennig decided to do the same experiment with the other species, Plains spadefoot toads. If hybrid toads have an advantage in certain situations, maybe species can evolve to hybridize on purpose!
There was a small problem with this: Dr. Pfennig was in North Carolina, and all of the toads were at a field station in Arizona! Plane tickets are expensive, so she sent the instructions for the experiment to researchers who already worked there. Here there was another problem; none of them spoke English. Luckily, Dr. Pfennig had a graduate student in the lab with a basic understanding of Spanish. He translated the instructions, and the experiment began.
When the tapes that had recorded the results were mailed back to NC, there was a problem with the results. According to the tapes, the Plains toads greatly preferred the New Mexico toads over their own species. Assuming there had to have been a mistake with the translation of the instructions, Dr. Pfennig threw out the tapes and gave up on the experiment.
Years later, she had some free time in the lab and decided to pick up the experiment again. Unexpectedly, she found the same results as those that had been recorded at the field station years earlier! She is still trying to find those old tapes.
Because her results went against what most people have learned about speciation, the results had to be replicated many times before other scientists would accept them. But now researchers are working to build on her research to find out why animals will sometimes behave in a way that seems to be maladaptive.
Dr. Pfennig's research focuses on animal behavior and evolution, but every topic that you explore in school has hundreds or thousands of researchers who are working every day to expand human understanding of that process or idea.
While research can sometimes be frustrating and tedious when your experiments don't work, the end goal is always very exciting. Imagine yourself as a science researcher. You are working to discover something that no one else in the world knows. You have learned everything there is to know about a certain topic, and for a little while, you will know more about it than anyone else in the world! Then when you publish this information, you will expand the base of human knowledge just a little bit more.
While the lab toads are essential to this endeavor, they are less than enthusiastic.
Dr. Sabrina Burmeister is another researcher at UNC. One of her main interests in research is the evolution of the brain. She also looks closely at how sensory information (what an animal sees, hears, and feels) changes their hormones and behavior. Because a sensory input (water levels) changes a toad's behavior, she wants to find out if the change in water levels causes a change in the toad's hormones. This could be what causes the toad to decide to hybridize.
Nick Garcia is a graduate student in Dr. Burmeister's lab. This module will be looking at how he does his research. His goal is to find out how a hormone called leptin affects mate choice in spadefoot toads. He knows why toads will sometimes choose to mate with a different species (their tadpoles need to metamorphose quickly), but what he wants to find out is how the toads make that decision. For example, you might know why you chose to wear that particular shirt this morning. Maybe you chose it because it is your favorite color. But you probably don't know what hormones or what parts of your brain were responsible for making that decision. Those in-between steps are mostly unknown, so a lot of research is being done to understand the process of decision-making.
Image courtesy of Daniel Flather
Nick is looking at the in-between steps of how toads choose a mate. This requires designing experiments to test both their behaviors and their hormones. Animal behavior is a very broad field of study, so let us take a moment to examine it.