Towards a population ecology of stressed environments: the effects of zinc on the springtail Folsomia candida
Article first published online: 31 MAR 2006
Journal of Applied Ecology
Volume 43, Issue 2, pages 325–332, April 2006
How to Cite
NOËL, H. L., HOPKIN, S. P., HUTCHINSON, T. H., WILLIAMS, T. D. and SIBLY, R. M. (2006), Towards a population ecology of stressed environments: the effects of zinc on the springtail Folsomia candida. Journal of Applied Ecology, 43: 325–332. doi: 10.1111/j.1365-2664.2006.01133.x
- Issue published online: 31 MAR 2006
- Article first published online: 31 MAR 2006
- Received 7 June 2005; final copy received 4 November 2005 Editor: Rob Freckleton
- Allee effect;
- 1To understand population dynamics in stressed environments it is necessary to join together two classical lines of research. Population responses to environmental stress have been studied at low density in life table response experiments. These show how the population's growth rate (pgr) at low density varies in relation to levels of stress. Population responses to density, on the other hand, are based on examination of the relationship between pgr and population density.
- 2The joint effects of stress and density on pgr can be pictured as a contour map in which pgr varies with stress and density in the same way that the height of land above sea level varies with latitude and longitude. Here a microcosm experiment is reported that compared the joint effects of zinc and population density on the pgr of the springtail Folsomia candida (Collembola).
- 3Our experiments allowed the plotting of a complete map of the effects of density and a stressor on pgr. Particularly important was the position of the pgr= 0 contour, which suggested that carrying capacity varied little with zinc concentration until toxic levels were reached.
- 4This prediction accords well with observations of population abundance in the field. The method also allowed us to demonstrate, simultaneously, hormesis, toxicity, an Allee effect and density dependence.
- 5The mechanisms responsible for these phenomena are discussed. As zinc is an essential trace element the initial increase in pgr is probably a consequence of dietary zinc deficiency. The Allee effect may be attributed to productivity of the environment increasing with density at low density. Density dependence is a result of food limitation.
- 6Synthesis and applications. We illustrate a novel solution based on mapping a population's growth rate in relation to stress and population density. Our method allows us to demonstrate, simultaneously, hormesis, toxicity, an Allee effect and density dependence in an important ecological indicator species. We hope that the approach followed here will prove to have general applicability enabling predictions of field abundance to be made from estimates of the joint effects of the stressors and density on population growth rate.