BELL, TIMOTHY J.1*, MARLIN BOWLES2, JENNY MCBRIDE2, KARYI HAVENS3, and PATI VITT3. 1Chicago State University, Chicago IL; 2Morton Arboretum, Lisle, IL; 3Chicago Botanic Garden, Glencoe, IL. - Viability Analysis of a Restored Illinois Population of the Federal Threatened Pitcher's Thistle (Cirsium pitcheri).
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