“…The expected payoff of an individual is a linear function of the frequencies of all strategies; the coefficients of this function are the entries of the payoff matrix. For detailed reviews of the replicator equation and other approaches to evolutionary game dynamics, see Fudenberg and Tirole (1991), Weibull (1995), Samuelson (1997), Cressman (2003), Sigmund (1998, 2003), Gintis (2000) and Nowak and Sigmund (2004). in finite populations Imhof and Nowak, 2006;Taylor et al, 2004;Fudenberg et al, 2006;Traulsen et al, 2006a,b), in spatially extended systems (Nowak and May, 1992;Nakamaru et al, 1998;Killingback and Doebeli, 1996;van Baalen and Rand, 1998;Irwin and Taylor, 2001;Hauert and Doebeli, 2004;Ifti et al, 2004;Nakamaru and Iwasa, 2005;Jansen and van Baalen, 2006) or on graphs (Lieberman et al, 2005;Santos et al, , 2006a.…”