Aphids reproducing asexually by parthenogenesis can have genetically identical winged and non-winged female progeny. In plants parthenogenesis is a component process of apomixis. Females of many species are known to be capable of reproducing asexually through thelytokous parthenogenesis. A form of asexual reproduction related to parthenogenesis is gynogenesis. Certain species of gecko also reproduce by parthenogenesis. Lamia informs them their society reproduces without males through parthenogenesis. This species is the only known velvet worm to reproduce via parthenogenesis. No naturally occurring cases of parthenogenesis exist in mammals because of imprinted genes. There are no known cases of naturally occurring mammalian parthenogenesis in the wild. Populations consist only of females, which reproduce by parthenogenesis. The lizard is a female-only species that reproduces by producing an egg through parthenogenesis. The females can produce eggs either as a result of mating or via parthenogenesis. A few species of fish, reptiles, and insects reproduce by parthenogenesis and are female altogether. Many species have been shown to transition to obligate parthenogenesis over evolutionary time. Polyploid lizards are also quite common, but are sterile and must reproduce by parthenogenesis.