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This New Lizard Species Evolved in a Lab

The novel reptile shows that hybrids can indeed lead to viable species, but not by the normal reproductive route

Aspidoscelis neavesi, a species unlike any other. (Photo: Peter Baumann)
smithsonian.com

Aspidoscelis neavesi, a new lizard that looks a bit like the anoles that hang out on Florida porches, isn't just any old recently discovered species. Rather than evolving in nature, A. neavesi was created in a lab by breeding two related species of lizards. Normally, hybrid animals are sterile, but as Carl Zimmer reports for the New York Times, A. neavesi defied that biological expectation and began reproducing in the lab—not by mating, but by cloning itself. 

New species typically evolve over thousands of generations, Zimmer explains, although in recent years scientists have begun to realize that, in some rare cases, hybridization might represent a viable route toward establishing a novel animal. Some whiptail lizards (a species found in the southern U.S.) possess genes that appear to come from two different species, and they only produce female offspring. Females give rise to females—a process called parthenogenesis—by duplicating their chromosomes. Scientists, Zimmer writes, concluded that "sometimes individuals from two different species of whiptail lizards interbreed, and their hybrid offspring carry two different sets of chromosomes." Zimmer:

Somehow, this triggers a switch to parthenogenesis. The female hybrids start to produce clones distinct from either parental species. In other words, they instantly become a new species of their own.

But it gets even more bizarre. Some species of whiptail lizards carry three sets of genes, rather than two....The strangeness doesn’t end there. In 1967, a Harvard graduate student named William B. Neaves was searching for whiptails around Alamogordo, N.M., when he found one with four sets of chromosomes.

To try to recreate this natural experiment, researchers collected parthenogenic females with three sets of genes from the field in New Mexico and introduced them to closely related males in the lab. As Zimmer reports, the scientists found that the offspring of those lizards did indeed possess four sets of chromosomes. The females with four sets of genes then began cloning themselves, eventually producing a colony of 200 lizards, which is still growing. 

After confirming that they had created a new species, the scientists named it Aspidoscelis neavesi, after William B. Neaves, who led the study and who first discovered the four-chromosome lizards back in 1967. Some scientists, however, think that biology needs a brand new term to describe A. neavesi, since the entire species consists of clones. Something like "hybrid clones," one researcher told Zimmer, would be a more accurate descriptor. 

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