Pitcher's thistle (Cirsium pitcheri) is a federal threatened monocarpic herbaceous perennial of the western Great Lakes shoreline dune habitats. The plant is self-compatible, with little allozyme variation across its range. Population maintenance of this species depends on cohort replacement and recolonization of successional habitat maintained by shoreline processes. Succession also eliminates populations, while disturbances can either eliminate or create new habitat for populations. These dynamics require metapopulation persistence, in which local populations avoid simultaneous extinction by reacting independently to landscape-scale disturbances and colonizing newly formed habitats. Our population restoration in former Illinois habitat along Lake Michigan comprises Wisconsin, Indiana and Michigan seed sources. Because this species is monocarpic, annual translocation of greenhouse propagated plants was used to build up large cohort numbers. Spontaneous seedlings from flowering plants are now replacing these artificial cohorts, and the first flowering of these plants occurred in 1998. Morphological, demographic, and genetic (as shown by RAPDs) differences occur between geographically different seed sources, with Indiana plants having larger cotyledons and greater growth, survivorship and reproduction in the restoration. The restored Illinois population is now in its seventh year with nearly 150 plants, but population growth rate (lambda) is less than 1. Stage structured demographic analysis projects cohort sizes, number of spontaneous seedlings and, or, translocations, and amount of flowering needed to sustain population viability. For example, the minimum number of translocated seedlings needed to achieve a positive growth rate is twice the number of currently observed spontaneous seedlings.

Key words: Cirsium pitcheri, demography, dune habitat, population viability analysis, restoration, threatened