In the deserts of Mexico and the southwestern United States lives a lizard that broke the rules of reproduction.
Aspidoscelis, known as the whiptail lizard, forms species made up exclusively of females. There isn’t a single male in the entire population and yet they have been reproducing successfully for generations.
Their eggs develop through parthenogenesis, meaning they clone themselves without needing fertilization of any kind.
But these females did not simply appear one day and decide to do without males. The story began with something much stranger: hybridization between species of lizards that did reproduce sexually. The mixing of their genomes gave rise to exclusively female lineages.
But there is one detail that surprises even biologists: although there is not a single male, these lizards need to mount one another to trigger ovulation. One female acts as the male, the other becomes pregnant, and so the species continues generation after generation. Scientists believe this behavior is a direct inheritance from their ancestors with normal sexual reproduction.
And they are not the only ones to have found a way to produce offspring without males. Parthenogenesis has also been observed in other reptiles, such as geckos, snakes, and even Komodo dragons.