PARENT SESSION
IP08 - Population Modeling Ecological Risk Assessment
Chair: Kapustka, Lawrence¹, ¹ 5010 SW Hout Street, Corvallis, WA, USA
Co-chair: Landis, Wayne², ² 516 High Street, Bellingham, WA, USA
8:00 AM to 12:00 PM - Tuesday, 19 November 2002
Room Room 150 G

(IP65) Modeling multiple stressors to plant populations in ecological risk assessment.

Johnson, Alan^*,1, Turner, Sandra², ¹ Clemson University, Pendleton, SC, USA² St. Cloud State University, St. Cloud, MN, USA

ABSTRACT- Native plant populations are subject to multiple impacts affecting local population dynamics and persistence. Significant stressors may include: (1) fragmentation or loss of habitat due to human activity and changing land use; (2) direct toxicity of chemicals in the environment to sensitive stages in the life-history of the plant; (3) toxicity of environmental chemicals to pollinators or other mutualists, which indirectly affect native plant populations. A metapopulation model that incorporates these categories of effect in an ecological risk assessment framework is presented. The model is structured to represent a metapopulation of terrestrial orchids (Platanthera sp.) and lepidopteran pollinators in an agricultural landscape, but the approach is readily generalizable to a wide range of vascular plants and animal pollinators. Habitat fragmentation and loss is represented by changes in the number, size, and spatial arrangement of habitat patches. Direct phytotoxicity is represented by changes in the demographic parameters of the stage-transition matrix. The indirect effect of loss of pollinators is represented by changes in the Allee parameter, which determines density-dependent pollination rates for local populations. Multiple iterations of a stochastic model are used to estimate risk of metapopulation extinction.

Key words: metapopulation, pollination, Allee effect, fragmentation