PARENT SESSION
Contributed Oral Session 85: Mutualism: Pollination
Wednesday, August 10, 8:00 AM - 11:30 AM, Meeting Room 520 C, Level 5, Palais des congrès de Montréal

Does reduced reproduction at low density lead to Allee effects in a perennial plant?

Feldman, Tracy^*,1, ¹ Duke University, Durham, NC, USA

ABSTRACT- Plants growing at low densities may produce fewer seeds than plants at higher densities, due to reduced pollinator visits or reduced compatible pollen receipt. This reduction in seed production at low densities will lead to Allee effects where the population will become extinct if seeds produced do not adequately replace dying individuals. In contrast, plants growing at low density may grow and survive better than those at high densities, due to release from competitive effects. However, few studies have examined the combined effects of density-dependence in fecundity and growth on plant population dynamics. I constructed a matrix model of population growth for Piriqueta cristoides caroliniana, a common sandhill plant, combining demographic data from natural populations with data from separate field experiments testing for effects of density on fecundity and plant growth. I then use the matrix model to test for strong Allee effects (population decline at low density) and weak Allee effects (slower population growth at low densities), and to determine whether (population growth rate) is more sensitive to changes in fecundity terms at low densities. The model shows that P. c. caroliniana populations exhibit weak (but not strong) Allee effects, and that is more sensitive to changes in fecundity terms at low densities.

Key words: Allee effects, matrix population model, mutualism, pollination