Recombination and Bistability in Finite Populations

In this paper we analyse the phenomenon of \bistability" in nite population evolutionary dynamics, especially with regard to recombination. Bistability, where the steady-state population distribution depends on the initial state of the population, has recently been observed in an (innnite population) quasi-species model of viral recombination Boerlijst et al., 1996]. We analyse a comparable nite-population model using a birth and death process due to Moran, 1958]. Bistability (or its stochastic analogue) is revealed in the bimodality of the stationary probability distribution of the birth and death process and long mean transition times between the modes. These eeects are demonstrated to be exaggerated by recombination.