Reptiles
Desert Grassland Whiptail
Aspidoscelis uniparens · also called little striped whiptail
Every single desert grassland whiptail alive today, scattered across desert grassland from Arizona to central Mexico, traces back to one hybrid female born generations ago who discovered she did not need a mate at all, and passed that same ability down to every daughter since.
Overview
The desert grassland whiptail, Aspidoscelis uniparens, is an entirely female lizard species native to desert grassland and scrubland habitat across parts of the southwestern United States and northern Mexico. Its origin from a single ancient hybridisation event, complete reliance on parthenogenesis, and retained mating-like ritual despite having no males make it one of the most striking natural experiments in reproduction found in any vertebrate.
A species built from one founding mother
Unlike almost any other vertebrate, every individual of this species can trace an unbroken maternal line back to a single hybrid founder, an entire population descended not from countless generations of mixed parentage but from one original genome copied forward ever since.
Status
Least Concern — widespread and stable across suitable desert grassland habitat throughout the southwestern United States and northern Mexico.
Desert Grassland Whiptail: common questions
How can a species with no males reproduce?
This species reproduces through parthenogenesis, in which a female produces fertile eggs without any genetic contribution from a male, doubling her own chromosomes before egg formation and then dividing them in a way that restores the full set, so each resulting egg develops into another female that is essentially a genetic clone of her mother.
Where did the desert grassland whiptail come from?
This species traces back to a single ancient hybridisation event between two separate, normally sexually reproducing whiptail lizard species; while most such hybrids are sterile, the resulting hybrid female in this case was able to reproduce on her own through parthenogenesis, and every desert grassland whiptail alive today descends from that one founding individual.
Why does the desert grassland whiptail perform a mating-like ritual if there are no males?
Individuals of this species periodically mount and grip one another in a courtship and pseudocopulation ritual left over from their sexually reproducing ancestors, with the hormonal state of each individual determining which one takes the male-like role, and this behaviour appears to help stimulate ovulation and increase overall egg output even though no actual mating or gene mixing occurs.
How can you identify a desert grassland whiptail?
Look for a slender, fast-moving lizard marked with several pale longitudinal stripes running down a darker body, a general pattern typical of whiptail lizards broadly, found actively foraging by digging and probing through soil and leaf litter in desert grassland and scrubland habitat of the southwestern United States and northern Mexico.