In aquatic ecosystems, where organisms typically feed and grow by eating smaller individuals, a characteristic size spectrum emerges, such that large organisms are much more rare than small ones. Here, a stochastic individual-based model for the dynamics of size spectra is described, based on birth, growth, and death of individuals, using simple assumptions about feeding behavior. It is shown that the deterministic limit derived from the stochastic process is a partial differential equation previously used to describe the dynamics of size spectra. The equation has two classes of dynamics in the long term. The first is a steady state. A derivation under simple mass-balance assumptions shows that, at steady state, the linear size spectrum relating log abundance to log mass has a slope of approximately 1, similar to that often observed in natural size spectra. The second class of dynamics, not previously described, is a traveling-wave solution in which waves move along the size spectrum from small to large body size. Traveling waves become more likely when predators prefer prey much smaller than themselves and when they are specialized in the range of prey body sizes consumed. Wavelength depends on the size of prey relative to the size of predator, and wave speed depends on how fast mass moves through the spectrum.

Item Type:	Refereed Article
Keywords:	size spectra, stochastic individual processes
Research Division:	Biological Sciences
Research Group:	Ecology
Research Field:	Community Ecology
Objective Division:	Expanding Knowledge
Objective Group:	Expanding Knowledge
Objective Field:	Expanding Knowledge in the Biological Sciences
UTAS Author:	Blanchard, JL (Dr Julia Blanchard)
ID Code:	100502
Year Published:	2009
Web of Science® Times Cited:	70
Deposited By:	Sustainable Marine Research Collaboration
Deposited On:	2015-05-18
Last Modified:	2015-09-07
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