Punishment of polygyny

We investigated the evolution of monogamy (one male, one female) and polygy ny (one male, more than one female). In particular, we studied whether it i s possible for a mutant polygynous mating strategy to invade a resident pop ulation of monogamous breeders and, alternatively, whether a mutant monogam y can invade resident polygyny. Our population obeys discrete-time Ricker d ynamics. The role of males and females in the breeding system is incorporat ed via the harmonic birth function. The results of the invasability analysi s are straightforward. Polygyny is an evolutionary stable strategy mating s ystem; this holds throughout the examined range of numbers of offspring pro duced per female. So that the two strategies can coexist, polygyny has to b e punished. The coexistence of monogamy and polygyny is achieved by reducin g the offspring number for polygyny relative to monogamy. This yields long- term persistence of the strategies for all offspring numbers studied. An al ternative punishment is to increase the sensitivity of polygynous breeders to population density. The coexistence is possible only with a limited rang e of offspring produced. The third way to achieve coexistence of the two ma ting strategies is to assume that individuals live in a spatially structure d population, where dispersal links population subunits to a network. Reduc ing the dispersal rate of polygynous breeders relative to that of monogamou s individuals makes the coexistence feasible. However, for monogamy to pers ist, the number of offspring produced has to be relatively high.