selffertilization

Self-fertilization, or selfing, is a form of sexual reproduction in which the male gamete fertilizes the female gamete produced by the same individual. It is common among hermaphroditic plants and animals and contrasts with outcrossing, in which fertilization involves gametes from different individuals. In plants, self-fertilization typically occurs by self-pollination, where pollen from the same flower or plant fertilizes its own ovules (autogamy or geitonogamy).

Many species have mechanisms to prevent selfing, including self-incompatibility systems that reject self-pollen and physical or developmental barriers such as herkogamy (spatial separation of sex organs) and dichogamy (temporal separation). Some plants are capable of selfing when cross-pollination fails, ensuring reproduction in sparse populations.

Genetic consequences of selfing include reduced heterozygosity and increased homozygosity, which can reveal deleterious recessive alleles and cause inbreeding depression. Over longer timescales, selfing can purge weak alleles and favor lineages adapted to selfing, but it generally reduces adaptive potential and genetic diversity. Ecologically, selfing is favored when mates or pollinators are scarce or unreliable, or when rapid seed production is advantageous.

Examples and relevance: many crop species such as wheat, rice, barley, and beans rely heavily on self-fertilization, facilitating seed production with limited pollinators. In animals, some hermaphroditic species such as certain nematodes and mollusks can self-fertilize. The balance between selfing and outcrossing remains a central topic in reproductive biology.