MAY RANDOM-PROCESSES EXPLAIN MATING SUCCESS IN LEKS

The object of this paper is to verify whether in specific cases the va riance of mating success among lekking males may be due exclusively to a random mechanism, as opposed to the adaptive mechanisms of mate cho ice which are usually postulated in the literature in the framework of sexual selection theory. In fact, some studies attempted to compare o bserved distributions of male mating success with a Poisson 'null' dis tribution based on the conjecture of random mating; the conjecture is usually rejected. In this paper we construct a plausible model (the 'n ull' hypothesis) for a strictly random non-adaptive pattern of social behaviour of lekking males and females and we perform several simulati ons for reasonable choices of parameter values. It should be observed that some of the simulations based on our random model lead to a distr ibution of male mating success which is Poisson-like. However, contrar y to predictions, in several simulations a random process of mate choi ce lead to non-Poissonian distributions. Accordingly, the fact that, w hen performing a statistical test on several sets of field data, we fi nd both cases which are in agreement with Poisson distribution, or a n ormal one, and cases which are not, does not allow us to reject the as sumption of random male reproductive success. Thus it is legitimate to conjecture that in many cases the inter-individual variability of mal e mating success might indeed be determined by random processes. If th is conjecture were to be confirmed by further studies, the actual sign ificance of sexual selection in the evolution of lekking species shoul d be reassessed, and a novel approach in the analysis of field data wo uld be called for.