It is assumed that self-pollination is beneficial, in spite of potential fitness costs, when there is insufficient pollinator services or outcross pollen from other individuals to accomplish full seed set..
[2] As plants pursue reproductive assurance through self-fertilization, there is an increase in homozygosity, and inbreeding depression, due to genetic load, which results in reduced fitness of selfed offspring.
[3] Solely outcrossing plants may not be successful colonizers of new regions due to lack of other plants to outcross with, so colonizing species are expected to have mechanisms of reproductive assurance - an idea first proposed by Herbert G. Baker and referred to as Baker's "law" or "rule".
[2] Reproductive assurance is thought to be a driver for the evolution of selfing because it would promote purging of genetic load[4][2] and it contributes to the occurrence of mixed mating systems.
Reproduction assurance occurs when there is insufficient outcross pollen present to attain fertilization of all of the ovules.