Parity effects in rock-paper-scissors type models with a number of species N S < 12

We investigate the impact of parity on the abundance of weak species in the context of the simplest generalization of the rock-paper-scissors model to an arbitrary number of species - we consider models with a total number of species (N-S) between 3 and 12, having one or more (weak) species characterized by a reduced predation probability (by a factor of Pw with respect to the other species). We show, using lattice based spatial stochastic simulations with random initial conditions, large enough for coexistence to prevail, that parity effects are significant. We find that the performance of weak species is dependent on whether the total number of species is even or odd, especially for N-S <= 8 , with odd numbers of species being on average more favourable to weak species than even ones. We further show that, despite the significant dispersion observed among individual models, a weak species has on average a higher abundance than a strong one if P-w is sufficiently smaller than unity - the notable exception being the four species case. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study investigates the impact of parity on the abundance of weak species. Through modeling and simulation experiments, it is found that parity has a significant effect on the performance of weak species, especially when the total number of species is less than or equal to 8, with odd numbers of species being more favorable to weak species.