Androgenesis is a system of asexual reproduction that requires the presence of eggs and occurs when a zygote is produced with only paternal nuclear genes.
However, it is also not strictly a form of sexual reproduction because the offspring have uniparental nuclear DNA that has not undergone recombination, and the proliferation of androgenesis can lead to exclusively asexually reproducing species.
A male allele promoting the elimination of the female gametic nucleus therefore has a high fitness advantage and can spread through a population and even reach fixation.
Upon fertilization with pollen or sperm, there is no maternal nucleus to expel, and a zygote is produced that derives its nuclear genome entirely from its paternal parent.
There are also clonal species that reproduce through vegetative reproduction such as Lomatia tasmanica,[20] Lagarostrobos franklinii,[20] and Pando,[21] where the genetic material is exclusively male.
[2] This method of reproduction is relatively rare and has been found in several species of clams of the genus Corbicula,[3] some plants like Elodea canadensis,[18] Cupressus dupreziana,[14] Lomatia tasmanica,[20] Lagarostrobos franklinii,[20] and Pando,[21] algae of the genus Phaeophyceae,[17] and recently in the all male fish species Squalius alburnoides.
[13] Androgenesis is more likely to persist in hermaphrodites than in species with two distinct sexes (gonochorists) because all individuals have the ability to produce ova, so the spread of androgenesis-promoting alleles causing egg-producers to become scarce is not an issue.
[13] Humans sometimes induce androgenesis to create clonal lines in plants (specifically crops), fish, and silkworms.
Egg cells can have their nuclei inactivated by gamma ray, UV, or X-ray radiation before being fertilized with sperm or pollen.