Optimal sex allocation under pollen limitation

Authored by Philip H Crowley, William Harris, Evelyn Korn

Date Published: 2017

DOI: 10.1007/s12080-017-0339-y

Sponsors: No sponsors listed

Platforms: MATLAB

Model Documentation: Other Narrative Mathematical description

Model Code URLs: Model code not found

Abstract

Most flowering plants are simultaneous hermaphrodites. Within species and even within local populations, sex allocation is usually highly plastic. Here, we link pollen sufficiency to the size of pollen-exchanging groups (i.e., pollen neighborhoods) and to pollen transfer efficiency, using an individual-based game-theoretic framework to determine the stable distribution of sex allocation that does not require the unrealistic assumption of infinitely large, panmictic populations. In the absence of selfing, we obtain the novel result that pollen limitation destabilizes hermaphroditism and favors separate sexes, whereas hermaphroditism remains stable without pollen limitation. With mixed mating, hermaphroditism is stable except when the fitness value of selfed offspring is less than half that of outcrossed offspring (i.e., strong inbreeding depression). In that case, the size of pollen neighborhoods, pollen transfer efficiencies, and the relative fitness of selfed offspring determine whether separate sexes or hermaphroditism is the stable outcome. The model thus predicts that separate sexes can derive from either of two ancestral states: obligate outcrossing under pollen limitation, or mixed mating (competing self-fertilization) under severe inbreeding depression. It also predicts conditions under which variance in sex-allocation among hermaphrodites within pollen exchanging groups along a gradient of pollen limitation can range from high (dioecy) to near zero (equal proportions of male and female investment).

Tags

game theory Evolution phenotypic plasticity Pollination Reproductive success Individual-based model Plasticity Self-fertilization Inbreeding depression Hermaphroditism Evolution of dioecy Selfing Hermaphroditic plants Cross-fertilization Dioecy Gynodioecy