Periodicity in population dynamics is one of the fundamental issues in ecology. In addition to species-specific analyses, allometric studies facilitate understanding of limit cycles amongst different species. So far, body-size regressions have been derived for the oscillation period of warm-blooded species, in particular herbivores. Here, oscillations expected from a one-species (delayed logistic) and a two-species (Rosenzweig-MacArthur) model were compared to cycles observed in laboratory experiments and field surveys for a wide range of invertebrates and vertebrates. Supplemented by historical original studies, 759 oscillation periods were derived from the 'Global Population Dynamics Database' (GPDD) to cover a broad range of species and environmental conditions. The parameters in the equations were linked to body mass, using a consistent set of allometric relationships that was calibrated on 230log-log linear regressions. Oscillation period and amplitude predicted by the models were validated with available data. The one-species model produced cycle times that increase with species' body mass to the power 1/4 if the delay was set equal to the size-dependent age at maturity. If the delay was set on 1 year, the delayed logistic model yielded oscillations with a size-independent period of 4.7 years. Cycle times calculated by the two-species model scaled less than expected to the 1/4 power of mass m. The intercepts expected from the two-species were generally higher than those for the one-species model and increased with decreasing consumer-resource mass mi/mi-1ratios. Amplitudes turned out to be size-independent according to both models. With exception of aquatic herbi-detritivores, intercepts were observed at the level calculated by the two-species model. Remarkably, oscillation periods were size-independent for predatory metazoans. Average cycles were of 4-5 years, similar to those predicted by the one-species model with a size-independent delay of one year. The consistent difference between lower trophic levels (i.e. herbivores) and higher trophic levels (i.e. carnivores) could be explained by the models from the small parameter space for consumer-resource cycles in generalist predators. Amplitudes recorded in the field did not scale to size and observed oscillation periods were about a factor of 2. This demonstrates that one allometric setting for age and density applicable to a wide range of species at lower trophic levels allows a reasonable estimate of independently measured cycles. Â© 2011 Elsevier B.V.
|Titolo:||Delayed logistic and Rosenzweig-MacArthur models with allometric parameter setting estimate population cycles at lower trophic levels well|
MULDER, Christian [Writing – Original Draft Preparation] (Corresponding)
|Data di pubblicazione:||2012|
|Appare nelle tipologie:||1.1 Articolo in rivista|