Processes of Pair Formation Leading to Assortative Mating in Biological Populations: Encounter-Mating Model

A model dealing with mating as a process of pair formation is considered. The model explicitly postulates two steps in the process: an encounter between individuals available for mating, and the end of the encounter in mating or not mating depending on the individual mating preferences. Two types of encounters, "individual" and "mass" encounters, are introduced, and the restrictions imposed by previously formed pairs on the availability of individuals for future matings are discussed. It is demonstrated that not only the mating preferences of individuals but also the type of encounters between individuals affect the distribution of characters in mating pairs (mating pattern of the population). It is also shown that the mating pattern of a population is not a direct reflection of the individual mating preferences; for example, panmixia does not necessarily mean that individuals do not have mating preferences, and positive (negative) assortment in mating pairs does not necessarily indicate homotypic (heterotypic) mating preferences. The importance of distinguishing between the pattern of mating preferences and the mating pattern of a population is emphasized.