A form of parthenogenesis in which the male gamete is required to activate development of the egg but fertilization does not occur. Generally, the sperm or pollen is from a member of the same species, although in some cases, for example in the fish Poeciliopsis, egg development is triggered by the sperm of a closely related species. Pseudogamous plants require pollination, and the endosperm undergoes fertilization even though the diploid embryo develops without it.