Breeding systems in flowering plants and the control of variability

Plants have three basic means of reproduction, by outcrossing, by selfing, and asexually. In most plant populations, at least two and often all three of these options are everpresent, so that individuals adopt mixed mating strategies at evolutionarily stable strategy (ESS) thresholds. Because mating systems are genetically controlled and affect genotype structure, they are liable to feedback. Productive habitats with a large standing crop are more likely to favour outcrossing, while unproductive habitats may favour asexuality or selfing, so that mating systems may change through seral development, even within the same species. Outcrossing tends to break up linkage disequilibria, but may also favour the creation of adaptive linkage groups. Mechanisms whereby male sexual selection, small population size and selfing can influence the genetic structure of populations are examined.