geitonogamia

Geitonogamia is a form of pollination in which pollen is transferred from the anther of one flower to the stigma of another flower on the same individual plant. In this sense, it is a type of self-pollination, because the pollen and the recipient belong to the same genetic individual, though the fertilization occurs between different flowers rather than within a single flower. It is distinct from autogamy, which occurs when self-pollination happens within the same flower, and from xenogamy, which involves pollen transfer between different plants.

Geitonogamy is typically mediated by pollinators that visit multiple flowers on the same plant, such as insects or birds, or by abiotic vectors like wind or water. It can be particularly common in plants with many flowers per individual or with dense inflorescences where pollinators move pollen from one flower to another on the same plant.

Genetic and evolutionary consequences of geitonogamy resemble those of selfing more than outcrossing. Because the pollen comes from the same genetic individual, geitonogamy increases homozygosity and can expose recessive deleterious alleles, leading to inbreeding depression relative to xenogamy. However, it can provide reproductive assurance when flowers on nearby plants are scarce or when pollinator activity is unreliable.

Plants employ various adaptations to reduce geitonogamy and promote outcrossing. These include self-incompatibility systems, protandry or protogyny (temporal separation of male and female function), dichogamy, and herkogamy (spatial separation of reproductive structures). The balance between geitonogamy and xenogamy varies among species and ecological contexts.