There are few population viability analyses of restored endangered species populations. This analysis was used to determine optimal strategies for establishing restored populations of the federal threatened Pitcher's thistle (Cirsium pitcheri). This herbaceous perennial of western Great Lakes shoreline dune habitats went extinct from its Illinois habitat before 1920. It is self-compatible, with little allozyme variation across its range. As part of federal and state recovery planning, suitable restoration habitat was identified at Illinois Beach Nature Preserve and population restoration began in 1991 using 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. 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 growth rate (l) is > 1. Stage structured demographic analysis indicates that extinction risk is lowest when populations are initiated by transplanting juveniles rather than seedlings or flowering plants or by sowing seeds. Relatively high variation in transition frequencies for non-fecundity stages indicates that, due to environmental stochasticity, a relatively high minimum population size is required to reduce extinction probability to < 5% for 100 years. Elasticity analysis indicates that Cirsium pitcheri matrices with l > 1 have greater proportional contribution of growth and reproduction elasticities to population growth rate.

Key words: Cirsium pitcheri, endangered species, restored population, viability analysis