An object-oriented simulation framework for individual-based simulations (OSIRIS): Daphnia population dynamics as an example

A general framework for the implementation of ecological models directed towards the falsification of knowledge, as opposed to models directed at making predictions, is proposed. The framework is constructed by defining a set of classes, with their interrelationships, in an object-oriented programming language. The classes represent the major levels of the so-called levels-of-integration hierarchy: individual, population and system. The abiotic physical and chemical environment is implemented by the classes condition and resource, respectively. Class habitat is used to represent the spatial structure of an ecosystem. The simulation is controlled by a class called analyser. The simulation mechanism is implemented by deriving all these real-life objects from a more abstract class simobject. The engine of the simulation is formed by a dynamic list of references to simobjects, sorted according to the time each simobject should be activated next, The data of each object are implemented in class dataobject, from which simobject is derived. The applicability of this framework, called OSIRIS (object-oriented simulation framework for individual-based simulations), is shown for a population dynamical study on daphnids, The effects of variation among individual daphnids on the growth rate and structure of a population of daphnids are studied by comparing the results of the individual-based model with those of a life table. Moreover, variation in population growth rate over time, which parameter cannot be derived from a life table, is calculated. Finally, the sensitivity of the model for the number of modelled individuals and the sampling interval is analysed.