The Amazon molly (Poecilia formosa) is a freshwater fish native to warm, fresh waters between Tuxpan River in northeastern Mexico and the Rio Grande and the Nueces River in the southern parts of the U.S. state of Texas. It reproduces through gynogenesis, and essentially all individuals are females. The common name acknowledges this trait as a reference to the Amazon warriors, a female-run society in Greek mythology.
Reproduction is through gynogenesis, which is sperm-dependent parthenogenesis. This means that females must mate with a male of a closely related species, but the sperm only triggers reproduction and is not incorporated into the already diploid egg cells the mother is carrying (except in extraordinary circumstances). This results in clones of the mother being produced en masse. This characteristic has led to the Amazon molly becoming an all-female species. Other all-female species include the New Mexico whiptail, desert grassland whiptail lizard, and blue-spotted salamander.
In nature, the Amazon molly typically mates with a male from one of four different species, either P. latipinna, P. mexicana, P. latipunctata, or occasionally P. sphenops. One other male that could possibly exist in the Amazon molly's natural range that could induce parthenogenesis in Amazon molly females is the triploid Amazon molly males. These triploid males are very rare in nature and are not necessary in the reproduction of the species, which is why the species is considered to be all female.