TY  - JOUR
A1  - Fussmann, Gregor F.
A1  - Weithoff, Guntram
A1  - Yoshida, Takehito
T1  - A direct, experimental test of resource versus consumer dependence : reply
Y1  - 2007
UR  - http://esapubs.org/esapubs/journals/ecology.htm
U6  - https://doi.org/10.1890/06-1692
SN  - 0012-9658
ER  - 
TY  - JOUR
A1  - Yoshida, Takehito
A1  - Jones, Laura E.
A1  - Ellner, Stephen P.
A1  - Fussmann, Gregor F.
A1  - Hairston, Jr.
A1  - Nelson, G.
T1  - Rapid evolution drives ecological dynamics in a predator-prey system
N2  - Ecological and evolutionary dynamics can occur on similar timescales. However, theoretical predictions of how rapid evolution can affect ecological dynamics are inconclusive and often depend on untested model assumptions. Here we report that rapid prey evolution in response to oscillating predator density affects predator-prey (rotifer-algal) cycles in laboratory microcosms. Our experiments tested explicit predictions from a model for our system that allows prey evolution. We verified the predicted existence of an evolutionary tradeoff between algal competitive ability and defence against consumption, and examined its effects on cycle dynamics by manipulating the evolutionary potential of the prey population. Single-clone algal cultures (lacking genetic variability) produced short cycle periods and typical quarter-period phase lags between prey and predator densities, whereas multi-clonal (genetically variable) algal cultures produced long cycles with prey and predator densities nearly out of phase, exactly as predicted. These results confirm that prey evolution can substantially alter predator-prey dynamics, and therefore that attempts to understand population oscillations in nature cannot neglect potential effects from ongoing rapid evolution.
Y1  - 2003
UR  - http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v424/n6946/full/nature01767_fs.html
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  -