MateSim: Monte Carlo simulation for the generation of mating tables.

In species with sexual reproduction, the mating pattern is an important element for understanding evolutionary and speciation processes. Given a mating pool where individuals can encounter each other randomly, the individual mating preferences define the mating frequencies in the population. However, in every mating process we can distinguish two different steps. First, the encounter between partners, and second, the actual mating once the encounter has occurred. Yet, we cannot always assume that the observed population patterns accurately reflect the individuals' preferences. In some scenarios, individuals may have difficulties to achieve their preferred matings, such as in monogamous species with low population size, where the mating process is similar to a sampling without replacement. In this case, the encounter process will introduce some noise that may disconnect the individual preferences from the obtained mating pattern. Such a difference between mating patterns and mating preferences has previously been shown by different modeling scenarios. Here I present a program that simulates the mating process for both discrete and continuous traits, under different encounter models and individual preference functions, and including effects such as time dependence and aging. The utility of the software is demonstrated by replicating and extending a recent study that showed how patterns of positive assortative mating, or marriage in human societies, may arise from non-assortative individual preferences. The previous result is confirmed and is shown to be caused by the marriage among the "ugliest" and oldest individuals, who after many attempts were finally able to mate among themselves. In fact, I show that the assortative pattern vanishes if an aging process prevents these individuals from mating altogether. The software MateSim is available jointly with the user's manual, at http://acraaj.webs.uvigo.es/MateSim/matesim.htm.