The Pitcher’s thistle (Cirsium pitcheri) is a native of the shorelines of the western Great Lakes, one of the upper Midwest’s most extensive linear ecosystems and an important landmark for founding the concept of succession and the science of ecology (e.g. Cowles, 1899). It is a short-lived monocarpic species (i.e. the plant flowers, set seeds and then dies) and does not spread vegetatively, hence colonization, establishment and persistence is through seedling recruitment. Its preferred habitat is the upper beaches, foredunes and blowouts maintained by cyclic natural disturbance processes (Loveless, 1984; McEachern et al., 1994). Succession or disturbance eventually eliminates populations; thus persistence is through colonization. As a result, this species serves as an important bioindicator of natural shoreline processes that maintain dynamic sand dune ecosystems.

In the early 20th century, pitcher’s thistle was found along the entire coast of Lake Michigan. Currently, it is extinct from Illinois and ninety percent of the remaining population (173 occurrences) are found in Michigan. The factor that has contributed the most to endangerment of C. pitcheri is recreational beach use and human-caused shoreline erosion that prevents the natural disturbances associated with sand dunes, thereby eliminating C. pitcheri’s preferred habitat. It was listed as a federally threatened species under the U.S. Endangered Species Act in July of 19881.

Whether a population contains enough individuals and genetic diversity to withstand environmental fluctuation, demographic stochasticity, selective pressures, and catastrophic events over evolutionary time is a fundamental question in population biology. Many approaches, from molecular and quantitative genetic studies to demographic studies, have been used to predict whether or not a population is likely to persist, but few studies, if any, have incorporated all three of these approaches in a plant population study.