TY  - JOUR
A1  - Fussmann, Gregor F.
A1  - Blasius, Bernd
T1  - Community response to enrichment is highly sensitive to model structure
N2  - Biologists use mathematical functions to model, understand, and predict nature. For most biological processes, however, the exact analytical form is not known. This is also true for one of the most basic life processes, the uptake of food or resources. We show that the use of a number of nearly indistinguishable functions, which can serve as phenomenological descriptors of resource uptake, may lead to alarmingly different dynamical behaviour in a simple community model. More specifically, we demonstrate that the degree of resource enrichment needed to destabilize the community dynamics depends critically on the mathematical nature of the uptake function.
Y1  - 2005
UR  - http://www.agnld.uni-potsdam.de/~bernd/papers/BiolLett1.pdf
ER  - 
TY  - JOUR
A1  - Fussmann, Gregor F.
A1  - Weithoff, Guntram
A1  - Yoshida, Takehito
T1  - A direct, experimental test of resource vs. consumer dependence
N2  - The uptake of resources from the environment is a vital process for all organisms. Many experimental studies have revealed that the rate at which this process occurs depends critically on the resource concentration, a relationship called "functional response." However, whether the concentration of the consumer normally affects the functional response has been the subject of a long-standing, predominantly theoretical, debate in ecology. Here we present an experimental test between the alternative hypotheses that food uptake depends either only on the resource concentration or on both the resource and the consumer concentrations. In short-term laboratory experiments, we measured the uptake of radioactively labeled, unicellular green algae (Monoraphidium minutum, resource) by the rotifer Brachionus calyciflorus (a consumer) for varying combinations of resource and consumer concentrations. We found that the food uptake by Brachionus depended on the algal concentration with the relationship best described by a Holling type 3 functional response. We detected significant consumer effects on the functional response only at an extraordinarily high Brachionus density (similar to 125 rotifers/mL), which by far exceeds concentrations normally encountered in the field. We conclude that con sumer-dependent food uptake by planktonic rotifers is a phenomenon that can occur under extreme conditions, but probably plays a minor role in natural environments
Y1  - 2005
ER  -