RAPID: Behavioral Plasticity and Hybridization of Young Species

Clark University, Worcester MA

Investigators

Abstract

Biological diversity is decreasing at an exceptionally rapid rate in response to human modification of the environment. One outcome of human activity is increasing productivity in aquatic environments, often leading to changes in growth rates of aquatic organisms including the threespine stickleback fish. This small fish has served as a model for understanding how newly-arisen species have evolved and how they maintain their distinctiveness. The research proposed here will evaluate the threat posed to pairs of species that have arisen in a small number of lakes in the Pacific Northwest, focusing on possible shifts in body size and behavior. The research has significant conservation implications not just for stickleback but also for understanding human-caused environmental changes leading to size and behavioral shifts, and, ultimately, interbreeding between species and loss of biodiversity. The research will include undergraduates and graduate students in field and laboratory research. The findings will be incorporated into teaching at the undergraduate level at Clark University and into outreach activities involving elementary school through high school students in the largely impoverished and minority community in which Clark University is located. The initial stages of speciation are difficult to capture, but the threespine stickleback fish (Gasterosteus aculeatus) from the Pacific Northwest has served as a model system of the speciation process. Replicated pairs of species have revealed in detail the genetic, morphological, and behavioral transitions associated with divergence. Sometimes, the initial stages of speciation are mediated by plastic shifts in behavior and morphology, when populations are exposed to novel environments. Plastic transitions may be followed by genetic accommodation, leading to evolutionary differentiation of the populations, and to stable reproductive isolation. In some instances however, reproductive isolation can be maintained by differential use of habitats in secondary sympatry, without significant genetic differentiation, leading to the possibility that changing environments will facilitate hybridization and loss of closely related species. This is a possibility that has not been explored in the species pairs of G. aculeatus. Differences in body size are important mediators of reproductive isolation between members of the pairs. This research will evaluate the possibility that differences in body size between the species pairs is decreasing due to increasing aquatic productivity and that this could lead to hybridization of the three remaining benthic-limnetic species pairs in southern British Columbia. The timing of the research is critical, as evolution in this system is known to be rapid, as is the environmental change that could cause its demise. These species pairs have offered unparalleled insight into the mechanisms of ecological speciation, and their loss through hybridization will conceal the numerous biological signatures of early divergence they have provided. All data will be archived in the Dryad Digital Repository.