Ecosim: A Proposal for Null Models Software

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EcoSim is a set of stand-alone software modules for Windows 95 personal computers that will satisfy the needs of biologists for null models. "Null models" are simulations that deliberately exclude a mechanism of interest, and provide benchmark tests for patterns in nature. Initial funding from an NSF SGER grant resulted in the development of a graphical user interface and the prototypes for two modules of EcoSim. This project will expand EcoSim and develop nine software modules to answer broad questions in community ecology. Each module will contain a number of simulations and statistical tests that are most appropriate for addressing the question. The modules will test patterns of (1) species diversity, (2) niche overlap, (3) body size ratios, (4) co-occurrence, (5) incidence functions, (6) species-area relationships, (7) range overlap, (8) shared species, and (9) cluster formation. A tenth module will allow the user to construct customized null model tests with a minimum of programming. This tenth user-module will greatly expand the utility of EcoSim for problems in population genetics, demography, and behavior. EcoSim is written in Delphi, a high-level programming environment for Object Pascal. Data can be easily imported and exported, provided full compatibility with other graphics and statistics software. Pull-down menus, checkboxes, and a powerful data editor allow users to select a variety of simulation options. Output is fully documented and can be exported to text files. An extensive online Help system, which includes a tutorial and sample data sets, guides users through the steps of null model analysis. The expanded EcoSim will be demonstrated in seminars, presentations, and workshops. As with the current version of the program, the expanded EcoSim will be distributed free via the Internet.