other individuals. Approximately one half of angiosperm species are SI, the remainder being SC. Mutations that disable SI (resulting in SC) may become common or entirely dominate in natural populations. Pollinator decline, variability in pollinator service, the so-called "automatic advantage" of self-fertilisation, among other factors, may favor the loss of SI. Many cultivated plants are SC, although there are notable exceptions, such as apples and Brassica oleracea. Human-mediated artificial selection through selective breeding is often responsible for SC these agricultural crops. SC enables more efficient breeding techniques to be employed for crop improvement. However, when genetically similar SI cultivars are bred, inbreeding depression can cause a cross-incompatible form of SC to arise, such as in apricots and almonds. In this rare, intraspecific, cross-incompatible mechanism, individuals have more reproductive success when self-pollinated rather than when cross-pollinated with other individuals of the same species. In wild populations, intraspecific cross-incompatibility has been observed in Nothoscordum bivalve. See also Allogamy Dichogamy Dimorphous flower Dioecy Heterosis Monocotyledon reproduction Outcrossing Plant sexuality Pollination Protandry References Further reading External links Self-Incompatibility: How Plants Avoid Inbreeding Heterostyly in cowslip Pollination Plant reproduction Population genetics Plant sexuality