1. The Evolution of Self-Fertilization When Inbreeding Depression is Frequency-Dependent Pierre-Olivier Cheptou and Ulf Dieckmann Proc. R. Soc. Lond. B, in press

2. Primary Questions n What factors can drive the evolution of selfing rates in hermaphrodites? Cost of outcrossing: only 50% relatedness with offspring Cost of selfing: inbreeding depression n Does it matter if inbreeding depression has frequency-dependent components? n What are the demographic conditions that lead to intermediate selfing rates?

3. Resident Dynamics and Inbreeding Depression n Resident population dynamics n Resultant inbreeding depression with and Total number of seeds Fixed cost of selfing Variable cost of selfing Ricker-type density regulation

4. Mutant Dynamics and Evolutionary Singularity n Mutant population dynamics n Resultant evolutionary singularity Three components:  selfed zygotes  outcrossed zygotes  zygotes of other individuals produced by fertilization with exported male gametes Selfed zygotes receive two gametes from their mother, whereas outcrossed zygotes receive only one. The number of male gametes used for self-fertilization is assumed to be negligible so that the selfing rate does not influence the export of male gametes.  with

5. Equilibrium Population Dynamics n General case The singular selfing rate is evolutionarily stable. n Density- and frequency-independent case a=b=c=d: No intermediate selfing rates. n Density-dependent case a=c, b=d: Intermediate selfing rates, but only if inbreeding depression decreases with density. n Frequency-dependent case E.g., b<a=d<c: Intermediate selfing rates, even if inbreeding depression increases with density.

6. Nonequilibrium Population Dynamics n Deterministic demographic fluctuations n Stochastic environmental fluctuations

7. Conclusions n Considering frequency-dependent components of inbreeding depression drastically alters the predictions for the evolution of selfing rates. n In particular, intermediate selfing rates become evolutionarily feasible under equilibrium population dynamics. n Nonequilibrium population dynamics (deterministic demographic fluctuations and/or stochastic environmental fluctuations) resulting in fluctuating inbreeding depression further enhance the range of conditions that lead to intermediate selfing rates.