This project will extend a study of genetics and ecology of Echinacea angustifolia, a long-lived perennial plant native to the plains and prairie of the United States. Land-use changes over the past century have eliminated prairie habitat, confining populations of this typical prairie plant to small remnants. Previous work has revealed feedbacks between the genetics and demography of E. angustifolia. To clarify the effects of these feedbacks on the persistence and ongoing evolution of this plant, this project will continue the annual census of all flowering plants of E. angustifolia growing in 23 prairie remnants within a 6400 hectare study area in MN. It will include intensive searches for seedlings and subsequent monitoring of their survival to evaluate recruitment rates among remnant populations. This research will also continue monitoring plants in three experiments designed to 1) characterize divergence among remnant populations in the health, survival, and reproduction of individuals, 2) determine how inbreeding and inter-remnant mating affect progeny fitness and 3) assess genetic variation in the fragmented populations. This project contributes substantively to understanding of the population biology of long-lived herbaceous plants. Results from this project will inform the conservation and management of perennial populations in fragmented habitat.
The tallgrass prairie was once a vast, continuous expanse of habitat harboring many different species of plants and animals. Now prairie habitat is limited to small and isolated patches. How long will small remnant populations persist and what can we do to conserve them? To answer this central question in conservation biology requires better understanding of some basic biological processes and how they interact. Traditionally, researchers have taken either of two distinct approaches to understanding population persistence in fragmented habitat. One approach investigates ecological dynamics focusing on environmental factors such as fire suppression, disrupted interactions between species (e.g. plant-pollinators), colonization of sites from other remnants, and competition with invasive weeds. Another approach investigates genetic processes in fragmented populations, such as loss of genetic diversity by drift, inbreeding depression, genetic swamping from nearby reintroductions, and outbreeding depression in restorations. Bringing the two approaches together. Our overall research approach is to simultaneously investigate ecological and evolutionary processes and feedbacks between them. We use experiments, observational studies, and modeling approaches. We focus on a common plant native to the prairie and plains, Echinacea angustifolia (Asteraceae), growing in remnant populations within an agricultural landscape in western Minnesota. This widespread purple coneflower isn't rare or endangered, but it serves as a good model for diverse prairie plants because it has many traits in common with them like self-incompatibility and a long lifespan. Our contributions. During the term of this award, we have evaluated how ecological and evolutionary processes interact and affect the persistence and ongoing evolution of fragmented Echinacea populations. We shared our findings with other scientists, land stewards, managers, practitioners, and policymakers through publications in scientific journals, at scientific meetings, and in workshops. Among our key findings (you can read all the details in published articles, posted on our website): 1. Establishing Echinacea in existing prairie restorations requires more than 20 seeds for each plant that germinates and survives to eventually flower about 10 years later. Also, burning the prairie before broadcasting seeds helps. 2. When sibling Echinacea individuals mate, their offspring are generally weaker than those from matings between distant relatives. This inbreeding depression severely reduces their survival and reproduction by about 60% over their first 8 years. 3. About 30 species of native bees pollinate Echinacea. Remarkably, these bees visit isolated plants in small patches just as frequently as plants in clusters and in big patches, nevertheless, reproduction is much lower in isolated and small patches of Echinacea. 4. We found a species of aphid that feeds exclusively on Echinacea angustifolia, and this aphid has been found to be a previously unknown species. Early in the season, these aphids are particularly frequent and abundant on inbred plants and plants with parents that originate from different sites. All season long, large plants having more than average nitrogen and little phosphorus in their leaves tend to harbor the most aphids. In the process of making our major findings, we developed a new statistical approach for rigorously quantifying lifetime Darwinian fitness of long-lived organisms, including perennial plants. We made a software package, called "aster" in the open-source and free statistics programs "R," that is available for use by other research scientists. Aster is proving to be invaluable as a tool for analyzing demographic and genetic processes in diverse populations. Another aspect of this project is training scientists and educators. We engaged many people in our activities, including many graduate, undergraduate, and high school students, two post-doctoral researchers, a high-school biology teacher, a college professor, and many volunteers. They all learned science by doing it, and they all helped advance understanding of population biology of long-lived herbaceous plants. We have a website (http://echinaceaProject.org/) that helps disseminate results, organize datasets, and curate collections, such as our frozen seed bank, our insect specimens, and microscope images of pollen from prairie plants. The website facilitates our research activities and collaborations; we have links to aster software, details about experimental plots, information on the newly discovered aphid, and descriptions of our long-term data sets. The website provides information on how to improve the conservation and management of perennial populations in fragmented habitat. In addition, the website furthers our educational goals with links to lesson plans, educational materials, and postings about internship and employment opportunities. We also keep project members, collaborators, and the public up-to-date on our activities with a blog and twitter feed (during the summer field season) and a page on facebook. This report covers the first five years of a ten-year award, so there will be much more to come. Please visit our website to keep up to date on our current activities and learn about our latest exciting findings!
