Terrestrial Native Species and Habitat Restoration: Pitcher’s Thistle (Cirsium pitcheri)

Science Center Objects

Pitcher’s thistle (Cirsium pitcher) is a native thistle that grows on beaches and grassland dunes along the shorelines of Lakes Michigan, Superior, and Huron. It has been listed as a threatened species likely to become endangered in the foreseeable future due to loss of critical dune habitat. Shoreline development and destructive recreational activities have fragmented remaining populations of Pitcher’s thistle.

In 2018, the USGS evaluated existing populations of the thistle in three National Parks including the southern limit of its range at Indiana Dunes and in the central portion of its range at Sleeping Bear Dunes and Pictured Rocks. Current monitoring was compared to vegetation surveys conducted at all three parks in 1991. Analysis of vegetation changes between 1991 and 2018 are ongoing. USGS continues to work with the National Park Service (NPS) at Indiana Dunes to augment current thistle populations by collecting seeds from the NPS common garden.

Pitcher's Thistle

Sampling a demography plot at Sleeping Bear Dunes in 2017.

(Public domain.)

In addition to fragmentation of habitat, Pitcher’s thistle populations are under pressure from the invasive Thistle Bud Weevil (Larinus carlinae). Weevil populations were observed along the coastal dunes in the Manistee National Forest (along the Lake Michigan shoreline). No evidence of the weevil was observed at the Nordhouse Dune site (inland and upland from the coastal site) or Sleeping Bear Point (also an upland dune). It is unclear if coastal dune populations are more vulnerable to weevil infestations than perched dunes or if the lack of weevils in upland dunes is due to delayed invasion. Further investigation will help better understand the vulnerabilities of specific thistle populations to the weevil.

Contributions

  • This initiative is part of the Great Lakes Restoration Initiative, Oak Savanna ground layer restoration

Partners

  • National Park Service (NPS)