title: Simplifying a physiologically structured population model to a stage-structured biomass model.
abstract: We formulate and analyze an archetypal consumer-resource model in terms of ordinary differential equations that consistently translates individual life history processes, in particular food-dependent growth in body size and stage-specific differences between juveniles and adults in resource use and mortality, to the population level. This stage-structured model is derived as an approximation to a physiologically structured population model, which accounts for a complete size-distribution of the consumer population and which is based on assumptions about the energy budget and size-dependent life history of individual consumers. The approximation ensures that under equilibrium conditions predictions of both models are completely identical. In addition we find that under non-equilibrium conditions the stage-structured model gives rise to dynamics that closely approximate the dynamics exhibited by the size-structured model, as long as adult consumers are superior foragers than juveniles with a higher mass-specific ingestion rate. When the mass-specific intake rate of juvenile consumers is higher, the size-structured model exhibits single-generation cycles, in which a single cohort of consumers dominates population dynamics throughout its life time and the population composition varies over time between a dominance by juveniles and adults, respectively. The stage-structured model does not capture these dynamics because it incorporates a distributed time delay between the birth and maturation of an individual organism in contrast to the size-structured model, in which maturation is a discrete event in individual life history. We investigate model dynamics with both semi-chemostat and logistic resource growth.
authors.affiliation: Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O.Box 94084, 1090 GB Amsterdam, The Netherlands. A.M.deRoos@uva.nl
authors.forename: André M
authors.initials: AM
authors.lastname: De Roos
authors.forename: Tim
authors.initials: T
authors.lastname: Schellekens
authors.forename: Tobias
authors.initials: T
authors.lastname: Van Kooten
authors.forename: Karen
authors.initials: K
authors.lastname: Van De Wolfshaar
authors.forename: David
authors.initials: D
authors.lastname: Claessen
authors.forename: Lennart
authors.initials: L
authors.lastname: Persson
mesh_terms: D018533:Biomass; D049628:Body Size; D005502:Food; D006801:Humans; D008954:Models, Biological; D015233:Models, Statistical; D009026:Mortality; D011157:Population Dynamics; D012098:Reproduction