The Population Dynamics of Erigeron Canadensis, A Successional Winter Annual

Abstract

E. canadensis is one of several annual colonizing species in the eastern USA that typically germinate under a crop canopy during summer and autumn, overwinter as vegetative rosettes, then bolt and flower the following summer. Populations of E. canadensis were monitored over a 2 yr period for seed input and germination, seedling survival, and flower and seed production. Seedlings in 2 field populations in Illinois growing at low densities suffered only 1% mortality prior to the 1st frost in Nov. However, the populations suffered severe mortality in winter (16-86%), due to frost heaving. Winter survival correlated closely with rosette size, and ranged from 0% for small rosettes up to 100% survival of rosettes in large diameter-classes (> 5 cm). At maturity, 80% of the E. canadensis individuals exhibited symptoms of aster yellows, a mycoplasma disease transmitted by the aster leaf hopper (Macrosteles fascifrons). As a result, seed production was reduced by 53%.