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Directional and disruptive selection in populations structured by class and continuous ontogeny under incomplete plasticity
Fig 4
Evolutionary branching of male growth generates male life-history polymorphism.
Each panel shows results from individual-based simulations (appendix B.3 in S1 Text). The top part shows the expressed trait values in females (red) and males (blue): randomly sampled allelic values (dots; 10 copies every 10 time units), population mean (solid lines), and analytically predicted convergence stable trait values (dashed lines). Reported values give: the male-specific component 
(eq 14); its size-mediated component 
(see eqs 37 and A-37, with 
for diploidy); and the leading eigenvalue of 
. As expected, when this eigenvalue is negative, the population remains monomorphic (panels A–C). When it is positive, evolutionary branching occurs in males (panel D, split in blue lines). The bottom part of each panel shows male and female size distributions at equilibrium as histograms (averaged between time steps 
and 
), along with the analytically predicted distribution at 
(solid lines, eq 26). The Kullback–Leibler divergence between male and female distributions is also reported. A–B: Male and female distributions are similar in shape as both sexes have the same demographic parameters (see left-hand side of panels for parameter values). However, females grow larger on average due to direct selection on size whereas males only track female size via selection for compatibility. C–D: Sex-specific demography generates asymmetries in size distributions with a higher frequency of small females. When sexual selection is strong enough, this leads to evolutionary branching (panel D) with one morph specialising on mating with smaller females. The smaller allele is seldom found at a homozygous state and the smaller large size mode is composed of heterozygotes. Other parameters: 
, 
, 
.
doi: https://doi.org/10.1371/journal.pcbi.1013591.g004