Individual‐based Models in Population Ecology

Abstract

Abstract The individual‐based approach is a concept of population ecology that rests on the premise that population properties should be derived from properties of individuals. It was developed due to conceptual advances in evolutionary biology in the second half of the twentieth century and as a consequence of access to computers. The advances in biology have allowed the rejection of the notion of adaptations of units of natural selection other than individuals whereas the computers made possible the simulations of very complex phenomena in many fields of science, engineering and economy. Investigations of individual variation have shown its origin and its impact on population dynamics. Computer simulations of particular ecological systems, especially those of economic and conservation importance, have proven to be very useful and able to discover relations that cannot be found out by analytical inquiries. It seems that in the future the individual‐based approach will be fully integrated into theoretical and applied ecology. Key Concepts: Individual plants and animals differ not only in their sex and age but also in other phenotypic features. Individual differences affect resource partitioning by individuals within the population, explain the mechanisms of scramble or contest competition and consequently the conditions for population stability and persistence. Absolutely equal resource partitioning by population members makes population stability and persistence impossible. By itself, individual variation in resource partitioning is not sufficient for population persistence and its ability to survive sudden drop in the availability of resources; some degree of resource monopolisation is required. The best examples of situation in which we can observe monopolisation of resources are populations of plants competing for light and birds or other animals defending individual territories. The important ecological phenomenon – despotic distribution which forces some individuals to move into worse habitat where their fitness is lower is possible only with some degree of monopolisation of available resources. Another ecological phenomenon – the existence of the source and sink system, which is important in population dynamics, can be maintained due to resource monopolisation by some population members. Individual variability and individual properties, as well as spatial population structure are difficult to describe by general models with analytical solutions but computer simulations make their description much easier and the exploration of their consequences much more effective. Computer simulation of ecological phenomena uses methods and concepts developed in other fields of science and technology, like agent‐based models or complex adaptive systems. Agent‐based models are used not only for the study of population dynamics but also to explain collective animal behaviour and other population or community‐level phenomena.