Bell, Timothy , Bowles, Marlin .
Vital rates differ between transplants and their naturally recruited descendants in a reintroduction of the federally threatened Pitcher.
PITCHER'S thistle (Cirsium pitcheri) is a short-lived herb endemic to western Great Lakes sand dunes where it colonizes successional habitats and requires frequent cohort replacement to maintain populations. This federally threatened plant became extinct in Illinois before 1920. As part of federal and state recovery planning, suitable reintroduction habitat was identified at a former site in Illinois Beach Nature Preserve and reintroduction began in 1991. Because this species is monocarpic, we used annual translocation of greenhouse-propagated plants from 1991 to 2000 to build up large cohort numbers. We monitored all transplants and their naturally recruited descendants since reintroduction began. Natural recruitment began in the 5th year of reintroduction, and the number of naturally recruited plants surpassed the number of transplants in the 11th year. The last transplant died in 2005. Mean population size from 1991 to 2005 was 150 and population size in 2005 was 168. Transplants and their naturally recruited descendants differed in survival, growth and fecundity. Survival, growth and fecundity significantly increased with plant size, decreased with drought severity and was related to location. Naturally recruited seedlings had lower survival rates than first year transplants. Naturally recruited seedlings had significantly higher survival in a relatively undisturbed area with steeper dune slopes, while survival of transplants did not differ between habitats. Conversely, fecundity did not differ between sites for naturally recruited plants but was significantly lower for transplants in disturbed habitats. Understanding these relationships will provide more realistic stochastic models for projecting the future of this reintroduction.
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1 - Chicago State University, Biological Sciences, 9501 South King Drive, Chicago, Illinois, 60628, USA
2 - The Morton Arboretum, 4100 Illinois Route 53, Lisle, Illinois, 60532, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Wednesday, August 2nd, 2006
Time: 8:30 AM