Re-introduction of Pitcher’s thistle at Illinois Beach State Park, Illinois State, USA

Summary

Pitcher's thistle (Cirsium pitcheri), a federally Threatened, short-lived monocarpic dune plant that depends entirely on repeated seedling recruitment since it cannot spread vegetatively, was extirpated from Illinois by the early 1900s before researchers from the Morton Arboretum and Chicago Botanic Garden began the state's oldest reintroduction attempt at Illinois Beach State Park, the last protected dune system in Illinois. Because the species naturally persists as metapopulations across multiple interconnected habitat patches, secondary dunes south of the park's Dead River, found through detailed habitat surveys to closely replicate natural conditions and to be relatively free from shoreline erosion and recreational disturbance, were recommended as the primary reintroduction site, with additional dunefield habitat north of the river also proposed despite its greater erosion exposure to satisfy metapopulation requirements. Long-term monitoring spanning up to 18 years compared demographic and genetic dynamics between this restored population and natural populations elsewhere in the species' range, revealing that vital rates of transplanted versus naturally recruited plants differ and that natural recruitment requires long time periods with slow overall population growth. Major difficulties included securing sufficient funding, collecting adequate propagule numbers, developing effective propagation and restoration techniques from scratch, and coping with altered natural shoreline erosion and sediment-transport processes that limit available habitat. The project rates itself Partially Successful, citing demographic instability from large annual variation in population numbers and recruitment as the central unresolved concern.