PARENT SESSION
Contributed Oral Session 105: Rare, Threatened, and Endangered Species: Fauna; Management
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 522 A, Level 5, Palais des congrès de Montréal
Management strategies for Boltonia decurrens, a threatened, fugitive plant species in a dynamic environment.
Smith, Marian *,1, Mettler-Cherry, Paige2, Caswell, Hal3, 1 Southern Illinois University, Edwardsville, IL, US2 Lindenwood University, St Charles, MO, US3 Woods Hole Oceanographic Institution, Woods Hole, MA, US
ABSTRACT- The complex life cycle of Boltonia decurrens evolved in response to the historic flood regime of the Illinois River, which has changed in the last century due to the construction of dams and levees. Late floods and/or low precipitation reduce population growth. Early floods and high precipitation lead to explosive growth. Demographic analysis shows that changes in floods and precipitation alter the life history pathways responsible for population growth, from annual to biennial and eventually clonal pathways. Developing a stochastic model in which flood timing and precipitation vary independently, we computed the stochastic growth rate as a function of the same parameters. Using historical flood and rainfall data from 1887 - 2000, we found that stochastic growth rate declined following the regulation of the river. Over that time the contribution of annual life history pathways to the stochastic growth rate has declined as the contributions of biennial and clonal pathways have increased. Application of this understanding to the development of management strategies for the species would require an approach far removed from the usual protection of selected populations from disturbance. It is clear that the annual life cycle must be restored, and that preservation of vegetatively reproducing populations is impossible. The dynamic system in which B. decurrens evolved must either be restored or simulated by appropriate application of carefully timed flooding.
Key words: threatened, plant, fugitive, floodplain