Figure 4.
Model II (mixed brood): the evolution of paternal care in the face of extra-pair offspring in the brood. The figure represents the maximal fraction of extra-pair offspring in brood, Pe, that allows for the evolution of paternal care induced by either genes or microbes. The solid lines represent the genetic case and the dashed and dotted lines represent the microbial cases. Generally, in the microbial case, paternal care evolves under wider conditions. The range narrows with an increase in extra-pair paternity in both the genetic and microbial cases. However, the effect is reduced when the transmission probability through paternal care (Tc) is high. The different plots (a), (b) and (c) represent different values of transmission through mating (Tm). In both the microbial and the genetic cases, as s increases, this allows for paternal care under higher degrees of extra-pair paternity. Other parameters: b = 0.5, Tn = 0, Tv = 0.8, C = 0.9; (a) Tm = 0.01, (b) Tm = 0.1 and (c) Tm = 0.2.