The All-Female Species Of Lizard

By Joshua T. Garcia on Friday, January 10, 2014
1280px-NRCSNM01030_-_New_Mexico_(5251)(NRCS_Photo_Gallery)

In A Nutshell

A small, unassuming lizard roams the deserts of New Mexico and Arizona. But the New Mexico whiptail lizard has developed a unique attribute: The population is entirely female. A hybrid of two related species, the New Mexico whiptail’s ability to reproduce asexually makes the gender-bias sustainable.

The Whole Bushel

New Mexico’s state reptile is a miniscule lizard—around 8 centimeters (3 in) long from snout to base—with a lengthy, blue, curling tail, aptly named the New Mexico whiptail (Aspidoscelis neomexicana). Extant to New Mexico, it has also been spotted in Arizona, Texas, and Mexico.

Whiptails (Teiidae) as a family are found exclusively in the Americas. Successful asexual reproduction has been observed in sharks, turkeys, and komodo dragons, among others, but in whiptails, the practice is more pronounced: Entire populations of whiptails have been observed performing asexual reproduction, also known as parthenogenesis. Practicing parthenogenesis to this degree is practically unheard of among vertebrates.

The New Mexico whiptail also practices parthenogenesis, but what’s more, the species is entirely female. The lizard is a hybrid of the Western whiptail and little striped whiptail; many hybrids, like mules, are not sexually viable—but the New Mexico whiptail found a way. Every single New Mexico whiptail is a genetic clone, a miniature army of stormtroopers in a United States desert.

Cloning occurs in the summer. The New Mexico whiptail will lay around one to four eggs (and may do so twice), with the lizards hatching about two months later. Remember—there are no genetic differences between either the siblings or their mother. All are female, and since all are capable of parthenogenesis, the population is sustainable.

Aside from convenience, parthenogenesis has very few benefits over sexual reproduction. If the New Mexico whiptail had an undesirable genetic deformity, it would be passed on to every member of the population. Sexual reproduction promotes diversification of genes, helping to separate good traits from bad.

That’s not to say the New Mexico whiptail is entirely opposed to sex. Whiptails may engage in “pseudocopulation” with each other to stimulate fertility.

Show Me The Proof

National Geographic: Extra chromosomes allow all-female lizards to reproduce without males
Reptiles of Arizona: New Mexico whiptail
Pseudocopulation in the Gila Spotted Whiptail