CAREER: Habitat Specialization and the Evolution of Dispersal

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This project evaluates the evolution of dispersal in annual herbs called 'goldfields' that grow in vernal pools in California, to understand the evolutionary feedbacks between the dispersal traits of organisms and their habitat specialization. Organisms rely on dispersal to remain in suitable habitat when their environments vary in space and time. The tendency for an organism to disperse, and the distance it will travel, is influenced by traits that can evolve by natural selection. In turn, the costs and benefits of dispersing will depend on the availability and distribution of suitable habitat in the organism's environment. This work will provide important insights into the mechanisms by which organisms navigate complex environments, and how these mechanisms change over time as both a cause and consequence of adaptation to specific habitat types. An understanding of the causes of dispersal is particularly critical in this time of rapid environmental change, in which natural dispersal patterns for many species are severely modified by human activities, and dispersing organisms experience unprecedented levels of change in the size and distribution of suitable habitat. This research will be largely conducted in undergraduate courses, senior design projects, and high school internships to provide students with authentic research experiences that integrate biology, mathematics, and engineering. This project also will support the development of a bilingual outreach program for elementary school students that explores the diversity of plant dispersal strategies through field trips and classroom-based experiments. In addition, results will be communicated to the general public through guided tours that take place at the primary field site, and shared with agencies and organizations involved in the conservation, management and creation of vernal pool habitats.This research will use experimental and modeling approaches to evaluate how dispersal evolves in response to spatial and temporal variation in an organism's habitat. The system consists of three plant species in the genus Lasthenia that co-occur in vernal pool landscapes of the California Floristic Province. Lasthenia species occupy different habitats within vernal pool landscapes and exhibit extensive variation in traits that influence seed dispersal propensity and distance. The first step of this project will be to conduct a functional analysis of dispersal phenotypes in Lasthenia under controlled wind conditions in wind tunnels, and in collaboration with engineering students. Next, field experiments will quantify selection on dispersal strategies in populations of three different Lasthenia species that occupy different habitats within a common vernal pool landscape. Environmental components of dispersal trait variation (i.e., dispersal plasticity) will be measured across a range of experimental treatments that will be imposed under controlled greenhouse conditions in the context of CURE (course-based undergraduate research experience) classes. Finally, mathematical models will evaluate the joint evolutionary dynamics of dispersal traits and habitat specialization in Lasthenia, and more generally across a broader range of parameter values.