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. Author manuscript; available in PMC: 2013 Aug 1.
Published in final edited form as: Evolution. 2012 Apr 10;66(8):2498–2513. doi: 10.1111/j.1558-5646.2012.01629.x

Figure 3. Facilitation effect: coexistence of the complementary altruism type selects for increased ESS of the focal type.

Figure 3

In these figures only the focal trait is allowed to evolve; the complementary trait is fixed at a static value indicated by the horizontal axis, while the focal trait evolves to an ESS indicated by the vertical axis. A) Survival/fecundity altruism evolves against a fixed value of resource-based altruism (Equation 12 in main text); B) resource-based altruism evolves against a fixed value of survival/fecundity altruism (Equation 13). In both cases, increasing the trait value of the complementary altruism type always increases the predicted ESS of the focal trait. This suggests that the each altruism type creates positive selection promoting the evolution of other. Parameter values are: S0 = 1, f0= 1, y = 1, αS = 0.1, αf = 0.1.