TY  - JOUR
A1  - Shertzer, Kyle W.
A1  - Ellner, Stephen P.
A1  - Fussmann, Gregor F.
A1  - Hairston, Nelson G.
T1  - Predator-prey cycles in an aquatic microcosm : testing hypotheses of mechanism
N2  - 1. Fussmann et al. (2000) presented a simple mechanistic model to explore predator-prey dynamics of a rotifer species feeding on green algae. Predictions were tested against experimental data from a chemostat system housing the planktonic rotifer Brachionus calyciflorus and the green alga Chlorella vulgaris. 2. The model accurately predicted qualitative behaviour of the system (extinction, equilibria and limit cycles), but poorly described features of population cycles such as the period and predator-prey phase relationship. These discrepancies indicate that the model lacked some biological mechanism(s) crucial to population cycles. 3. Here candidate hypotheses for the 'missing biology' are quantified as modifications to the existing model and are evaluated for consistency with the chemostat data. The hypotheses are: (1) viability of eggs produced by rotifers increases with food concentration, (2) nutritional value of algae increases with nitrogen availability, (3) algal physiological state varies with the accumulation of toxins in the chemostat and (4) algae evolve in response to predation. 4. Only Hypothesis 4 is compatible with empirical observations and thus may provide important insight into how prey evolution affects predator- prey dynamics.
Y1  - 2002
UR  - http://www.blackwell-synergy.com/Journals/issuelist.asp?journal=jae
ER  - 
TY  - JOUR
A1  - Hairston, Nelson G.
A1  - Holtmeier, C. L.
A1  - Lampert, W.
A1  - Weider, L. J.
A1  - Post, D. M.
A1  - Fischer, J. M.
A1  - Caceres, C. E.
A1  - Fox, J. A.
A1  - Gaedke, Ursula
T1  - Natural selection for grazer resistance to toxic cyanobacteria: Evolution of phenotypic plasticity?
Y1  - 2001
ER  - 
TY  - JOUR
A1  - Hairston, Nelson G.
A1  - Fussmann, Gregor F.
T1  - Lake ecosystems
N2  - Lakes are discrete, largely isolated ecosystems in which the interplay between physical, biogeochemical and organismal processes can be studied, understood, and put to use in effective management.
Y1  - 2002
ER  - 
TY  - JOUR
A1  - Fussmann, Gregor F.
A1  - Ellner, Stephen P.
A1  - Shertzer, Kyle W.
A1  - Hairston, Nelson G.
T1  - Crossing the Hopf bifurcation in a live predator-prey system
N2  - Population biologists have long been interested in the oscillations in population size displayed by many organisms in the field and Laboratory. A wide range of deterministic mathematical models predict that these fluctuations can be generated internally by nonlinear interactions among species and, if correct, would provide important insights for understanding and predicting the dynamics of interacting populations. We studied the dynamical behavior of a two- species aquatic Laboratory community encompassing the interactions between a demographically structured herbivore population, a primary producer, and a mineral resource, yet still amenable to description and parameterization using a mathematical model. The qualitative dynamical behavior of our experimental system, that is, cycles, equilibria, and extinction, is highly predictable by a simple nonlinear model.
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Fussmann, Gregor F.
A1  - Ellner, Stephen P.
A1  - Hairston, Nelson G.
T1  - Evolution as a critical component of plankton dynamics
N2  - Microevolution is typically ignored as a factor directly affecting on-going population dynamics. We show here that density-dependent natural selection has a direct and measurable effect on a planktonic predator-prey interaction. We kept populations of Brachionus calyciflorus, a monogonont rotifer that exhibits cyclical parthenogenesis, in continuous flow-through cultures (chemostats) for > 900 days. Initially, females frequently produced male offspring, especially at high population densities. We observed rapid evolution, however, towards low propensity to reproduce sexually, and by 750 days, reproduction had become entirely asexual. There was strong selection favouring asexual reproduction because, under the turbulent chemostat regime, males were unable to mate with females, produced no offspring, and so had zero fitness. In replicated chemostat experiments we found that this evolutionary process directly influenced the population dynamics. We observed very specific yet reproducible plankton dynamics that are explained well by a mathematical model that explicitly includes evolution. This model accounts for both asexual and sexual reproduction and treats the propensity to reproduce sexually as a quantitative trait under selection. We suggest that a similar amalgam of ecological and evolutionary mechanisms may drive the dynamics of rapidly reproducing organisms in the wild.
Y1  - 2003
ER  -