Variable carrying capacity.
(a): A community where the carrying capacity is an increasing function of altruist number, varying from Ni when the population is composed only of selfish individuals to Nf (Nf > Ni) when only altruists are present. (b) Two examples of random walks describing the stochastic behavior a such a system (transition probabilities 4–7), where m,n are the number of selfish and altruistic individuals. Red line: loss of S’s; Blue line: loss of A. A Moran process in this scheme corresponds to a random walk constrained to remain on an anti-diagonal line.
Houchmandzadeh and Vallade BMC Evolutionary Biology 2012 12:61 doi:10.1186/1471-2148-12-61