Simulation of fig wasp inclusive fitness outcomes under
differential hybrid embryo mortalities
We again used Python programming to model our ‘oviposition
trade-off’ hypothesis
(https://github.com/ctdarwell/wolPredictor/ciFitnessModel.py) and
investigate how offspring fitness might benefit from preferential
oviposition facilitated by reduced foundress egg load (or via selective
oviposition) despite losses in fecundity resulting from the post-zygotic
mechanism of CI. Our model allocates each foundress 1000 eggs whose
fitness is determined by three variables: (i) the proportion of
conspecifics in the population that the foundress can breed with; (ii)
fitness of offspring of conspecific matings (between 0-1); and (iii)
fitness of offspring of heterospecific matings (between 0-1). Further,
we divide a syconium into five layers - at the centre, all eggs survive,
while zero survive at the syconium edge (with 0.75, 0.5, 0.25 survival
in the intermediate layers). We compare a ’CI ’ and a ‘no
CI ’ model across variation in our three variables. See Fig. 4 for a
schematic outline of the parameters.
For example, for the no CI model at 75% conspecifics mating
opportunities: 75% of eggs get conspecific relative mating fitness
(e.g., ω = 0.8) and 25% of eggs get heterospecific relative mating
fitness (e.g., ω = 0.2). Each egg gets randomly assigned into a layer of
the syconium and each egg’s relative mating fitness is multiplied by its
oviposition site fitness (i.e., randomly assigned: 1.0, 0.75, 0.5, 0.25,
0). Finally, all 1000 eggs’ scores are summed to obtain inclusive
fitness for the foundress. For the CI model (at 75% conspecifics
mating opportunities) we lose 25% of the egg load but all eggs get the
conspecific relative mating fitness (i.e., 0.8) - then they are randomly
placed into the best remaining 750 oviposition site positions (mimicking
that fig wasps preferentially lay in optimum sites). Scores are again
multiplied and summed across 10 replicates. The key modeling assumption
here is that unviable eggs are not oviposited and thus do not waste
premium oviposition sites (this is also equitable to a scenario where
egg oviposition order is prioritised). Results are obtained by
subtracting realised CI versus no CI fitness across all
combinations of conspecific-heterospecific relative mating fitness
(i.e., 0-1 for both) surfaces. We display individual heat maps for
outcomes at different percentages of conspecific mating opportunities.