How an Asexual Lizard Procreates Alone

How an Asexual Lizard Procreates Alone

All moms and no dads, the whiptail still comes up with genetically diverse offspring.


3 - 12


Biology, Genetics


N. Mexico Whiptail Lizard

Without females, lizards in the Aspidoscelis genus, like this New Mexico Whiptail (Aspidoscelis neomexicana), reproduce asexually. Unlike other animals that produce this way, however, their DNA changes from generation to generation.

Photograph by Bill Gorum/Alamy Stock Photo
Selected text level

In sexual reproduction—the way most life-forms procreate—each parent provides half an offspring's chromosomes. Over generations, this mating and procreating shuffles the DNA deck, giving sexual reproducers a genetic diversity that helps them adapt to changing environments.

By contrast, asexual reproducers—some 70 vertebrate species and many less-complex organisms—"use all the chromosomes they have" to solitarily produce offspring that are genetic clones, molecular biologist Peter Baumann says. Because the organisms are genetically identical, they're more vulnerable: A disease or an environmental shift that kills one could kill all.

But there's a twist in the case of the genus Aspidoscelis, the asexually reproducing whiptail lizards that Baumann and his colleagues have been studying at the United States' Stowers Institute for Medical Research in Kansas City, Missouri. The lizards are all female and parthenogenetic, meaning their eggs develop into embryos without fertilization.

But before the eggs form, Baumann's team discovered, the females' cells gain twice the usual number of chromosomes during meiosis. This results in a standard pair of chromosones derived from two sets of pairs. So the eggs get a full chromosome count and genetic variety and breadth (known as heterozygosity) rivaling that of a sexually reproducing lizard.

Why does this occur? Because long ago, Baumann says, lizards of the genus Aspidoscelis had "a hybridization event"—that is, females of one species broke form and mated with males of another species. Those outlier liaisons gave whiptails robust heterozygosity, which has been preserved by the identical replication—essentially, cloning—that occurs in asexual reproduction. It's a genetic-diversity advantage that today's females still enjoy and propagate.

Media Credits

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Last Updated

June 2, 2022

For information on user permissions, please read our Terms of Service. If you have questions about licensing content on this page, please contact for more information and to obtain a license. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. She or he will best know the preferred format. When you reach out to him or her, you will need the page title, URL, and the date you accessed the resource.


If a media asset is downloadable, a download button appears in the corner of the media viewer. If no button appears, you cannot download or save the media.


Text on this page is printable and can be used according to our Terms of Service.


Any interactives on this page can only be played while you are visiting our website. You cannot download interactives.

Related Resources