Isocline Analysis

The user first decides if an existing model is to be used or a new one created.

• If a new model is to be built, the user provides names for the two organisms and the kinds of effects they have on each other so that P2a can recognize the interaction as competition, cooperation, or exploitation (see figure). The use of the LV or RD model is then specified, and values for the parameters input (figure). Once the parameters have been set, the isoclines are calculated from the appropriate equations and displayed in the graphics window (see figure).
• If an existing P2a model is to be evaluated, the user supplies the path on which the data files reside and then the names of the two data files. P2b then calculates and displays the isoclines in the graphics window (see figure). Subsequent P2b operations are controlled by function keys:
• [F1] for help and information.
• [F2] to reset parameters to their original values.
• [F3] to plot data on the current graph. Data can be plotted on the isoclines or on the time series graph.
• [F4] to speed up the graph trace.
• [F5] to slow down the graph trace.
• [F6] to save a hard copy of simulated data and models to printer or disk.
• [F7] to change the values of the parameters or to rescale the graph axes. The parameters are described in pop-up windows as each decision is made. All parameters, except the alternate food parameter, F, are the same as those described in P2a. The alternate food option allows the user to model a general predator that feeds on other species.
• [F8] to run simulations with the current model. Simulated trajectories are calculated as in P2a, and are first plotted on the isocline graph (see figure). The simulated traces can then be displayed as a time series (see figure).
• [Alt]+[X] to terminate execution.