Collaborative Research: LTREB: Feedbacks between evolution and demography in severely fragmented prairie populations of the purple coneflower, Echinacea angustifolia

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

This project will continue a long-term study of natural selection in the purple coneflower, Echinacea angustifolia. At the beginning of the 1800s, prairie covered a great swath of North America. Since then, about 99% of the tallgrass prairie has been destroyed. The small, isolated patches of prairie that remain harbor great biodiversity, yet rates of local plant extinctions are alarmingly high in remnant prairies. This project will advance scientific understanding of why some populations go extinct and others persist. Threats to prairie populations include fire suppression, declines of pollinators, inbreeding, loss of genetic diversity, and a reduced capacity to evolve by natural selection. This project builds on a long-term investigation of these ecological and genetic processes and feedbacks between them affecting a model prairie plant species. The purple coneflower typifies prairie plants in its long lifespan, often decades, and in other attributes. This study is the first of its kind to illustrate a population's capacity to adapt. In addition to advancing scientific knowledge and disseminating information to scientists and land stewards, this project will provide research experience and training to diverse participants at a level appropriate for their interests and career stage: high school, college, and graduate students, teachers, and citizen scientists in Minnesota and at the Chicago Botanic Garden. The project uses formal quantitative genetic approaches and common garden experimental designs to quantify additive genetic variance for fitness, population differentiation, and inbreeding depression. Researchers will estimate the amount of genetic variation in Darwinian fitness of individuals planted in 2003, many of which flowered for the first time in 2015 using aster statistical models to analyze fitness data. Other experiments will estimate the reduction in mean fitness due to mating between siblings. Together with demographic censuses of remnant populations, started in 1996, these studies will yield comprehensive assessments of population growth rates and the potential for evolutionary rescue. A key strength of the research is that experiments are conducted in a realistic habitat, including interactions of the coneflower with its pollinators and herbivores. The core datasets comprise continuous individual fitness records, including annual survival and reproduction of over 17,000 plants in ten experiments and in 27 natural prairie remnants in Minnesota. These datasets, which will extend up to 30 years by the end of the project, offer a rare window into the interplay of evolutionary and ecological processes of a long-lived species.