Figure 2.

The outcome of selection for genes experiencing directional selection or caste-antagonistic selection. (a) The probability of fixation of newly arising additive alleles as a function of the strength of selection is identical under direct selection (DS) on queens or kin selection (KS) on workers when queens are singly mated (KS-single). However, when queens are multiply mated, beneficial alleles (s > 0) fix at lower rates and deleterious alleles (s < 0) fix at higher rates, when they are subjected to KS in workers (KS-multiple). (b,c) Regions in which antagonistic selection results in fixation of the queen-favoured a allele, the worker-favoured A allele or polymorphism. Solid lines and dashed lines delineate regions for singly and multiply mated queens, respectively. sQ and sW represent the strength of selection on performance against alleles A and a in queens and workers, respectively. In (b), all possible combinations of selection coefficients are shown, whereas panel (c) expands the region with more realistic, weaker selection. (Online version in colour.)