How geitonogamous selfing affects sex allocation in hermaphrodite plants

Does the mode of self-pollination affect the evolutionarily stable allocati on to male vs. female function? We distinguish the following scenarios. (1) An 'autogamous' species, in which selfing occurs within the flower prior t o opening. The pollen used in selfing is a constant fraction of all pollen grains produced. (2) A species with 'abiotic pollination', in which selfing occurs when pollen dispersed in one flower lands on the stigma of a nearby flower on the same plant (geitonogamy). The selfing rate increases with ma le allocation but a higher selfing rate does not mean a reduced export of p ollen. (3) An 'animal-pollinated' species with geitonogamous selfing. Here the selfing rate also increases with male allocation, but pollen export to other plants in the population is a decelerating function of the number of simultaneously open flowers. In all three models selfing selects for increased female allocation. For mo del 3 this contradicts the general opinion that geitonogamous selfing does not affect evolutionarily stable allocations. In all models, the parent ben efits more from a female-biased allocation than any other individual in the population. In addition, in models 2 and 3, greater male allocation result s in more local mate competition. In model 3 and in model 2 with low levels of inbreeding depression, hermaph roditism is evolutionarily stable. In model 2 with high inbreeding depressi on, the population converges to a fitness minimum for the relative allocati on to male function. In this case the fitness set is bowed inwards, corresp onding with accelerating fitness gain curves. If the selfing rate increases with plant size, this is a sufficient conditi on for size-dependent sex allocation (more allocation towards seeds in larg e plants) to evolve. We discuss our results in relation to size-dependent sex allocation in plan ts and in relation to the evolution of dioecy.