Behavior has often been argued to be the first level of response of animal populations to new environments, changing before other traits. A great deal of previous research has documented existing geographic and environmental variation in behavior, but there have been relatively few opportunities to examine the role of behavior changes during contemporary shifts of populations to new environments. This project will take advantage of an unprecedented opportunity to monitor changes in reproductive behavior during an experimental introduction of Trinidadian guppies (Poecilia reticulata) from one ecological environment where predation pressure is relatively high to another environment where predation pressure is relatively low. There is a deep comparative literature exploring the way that reproductive traits of guppies, such as male color patterns, male mating tactics and female preferences for male traits, vary with predation pressure across streams, setting up a predictive framework for this work. The results of this project are expected to highlight the way that behavioral changes, through both flexible modification and genetic evolution, allow animals to adapt to new environmental conditions. The findings of this research will have implications for biological invasions and conservation biology as animal populations respond behaviorally to increasingly modified environments caused by human disturbance and global change. This work will have broader implications for the participation of minorities in science, not only through the involvement of a Hispanic principle investigator, but more importantly through graduate advising, undergraduate mentoring and education at the K-12 level. This project will help to increase the participation of minority students in the biological sciences at Colorado State University and will include the development of a workshop program to bring guppy behavior and experimental biology to K-12 classrooms in Colorado.
In the face of climate change, habitat loss, and species invasion, it is becoming increasingly important to understand how animals adapt to new and changing environments. When experiencing a new environment, it is often thought that behavior changes first, before other traits. This can happen rapidly during the lifetime of an individual, if the new environment directly influences its behavior; or this can happen across generations, if the new environment selects for genetic changes in behavior in the population over time. Few studies have documented the way that behavior changes in the early stages of adapting to a new environment. The goal of this project was to take advantage of a rare opportunity to monitor changes in behavioral traits following an experimental translocation of Trinidadian guppies (Poecilia reticulata) from one environment where predation risk was relatively high to another environment where predation risk was relatively low. Trinidadian guppies are freshwater fish that live in a range of environments that differ in predation risk; some guppies, known as high predation guppies, live in streams with many larger fish predators. In contrast, low predation guppies live in streams that lack major predators. Guppies in these distinct environments differ in many traits, including mating behavior, foraging behavior, social behavior, and male coloration. Because they are relatively free from predation risk, low predation males tend to be more colorful and perform more courtship displays to attract females. In contrast, high predation males are less colorful and court females less, because their displays can also attract the attention of predators; instead, they tend to pursue females to sneak matings with them. Further, high predation guppies invest more time in predator avoidance, leaving less time for foraging, and are more likely to be in large groups to defend against predation; thus they tend to be less aggressive socially to maintain cohesion in those groups. As part of a separate project, guppies were taken from a high predation site and introduced to four low predation sites that previously lacked guppies. We took advantage of this experiment to monitor changes in behavior in the new environment. We found that males in the introduced populations shifted certain aspects of their behavior very rapidly. They became more like low predation guppies and less like high predation guppies in aspects of their mating, foraging, and social behavior. This suggests that these kinds of behavior are relatively sensitive to the environment and can change rapidly. We also collected guppies from the source population and the introduced populations at several time points, one, two, and three years post-introduction, and we reared their offspring and grand-offspring in a common lab environment. To find out if their traits were sensitive to the environment, we reared a subset of each family in different treatments, so that they were either reared with or without predator odor cues, and under high or low food levels. Interestingly, we found that being reared with predator cues and low food levels caused males to develop their color more slowly; predator cues also caused males to be less colorful as adults compared to their brothers reared without predator cues. To our knowledge, this is the first evidence that the presence of predator cues in the rearing environment can affect the development of a sexual trait that is used for attracting mates. We also found that the rearing environment influenced mating and social behavior. Thus, we established that several traits are sensitive to the environment, allowing individuals to adjust rapidly within their lifetime to new conditions. We are continuing to monitor the introduced guppy populations to determine whether their behavior is also evolving genetically across generations. In addition to our research goals, this project also had broader educational goals to provide training to students. Two PhD students were supported by this project, and one of them based her dissertation on this project. Four undergraduate students conducted honors theses on components of this project, and thirteen additional undergraduates gained research experience by helping with our lab experiments. Most of the students involved in the project gained experience presenting their results at research conferences. We also developed a new outreach program to introduce inquiry-based science at several local elementary and middle schools. Students in the 4th and 7th grades learned about science and the guppy system and developed hypotheses about guppy behavior. Then they conducted behavioral experiments, entered their data, interpreted their results, and participated in a discussion about their findings. Several of the classes produced a scientific poster that could be displayed at the school, and two of the 4th-grade classes also presented their posters at a local ecology conference. Overall this was a rewarding and educational experience for everyone involved.
