Lucky for them: These lizards are in danger of being saved by nature conservation.

That was a close call. The Mexican government had already decided to eradicate the West Mexican black iguana on a remote island in the Pacific. The lizard species, with its keel-shaped scales on its long tail, was considered an invasive species on Clarión – an alien that disrupted the delicate balance of native flora and fauna and therefore had to be removed. But then, at the last minute, help arrived.

A research team led by Daniel Mulcahy from the Museum of Natural History in Berlin has now determined in a study : The reptile with the somewhat cumbersome scientific name Ctenosaura pectinata is by no means out of place on the small island of just under 20 square kilometers, 1000 kilometers off the coast of the state of Colima.

While humans first settled in the Americas around 16,000 years ago and only established a permanent presence in Clarión in 1979 with a small Mexican naval base, the black iguana has lived there for over 400,000 years. It's just that nobody had really noticed. "The idea that it was introduced was pure speculation; nobody ever investigated it," Mulcahy recently explained in the New York Times .

In 2013, the evolutionary biologist traveled to Clarión with a few colleagues in search of a rumored snake. During this trip, they discovered several specimens of the black iguana. They captured one animal and took it with them for later genetic analysis.

The study revealed that the genetic makeup of the black iguana from Clarión Island differs significantly from that of specimens on the Mexican mainland. Furthermore, increasing evidence suggests that the reptiles on either side of the border are also less similar in appearance than previously thought.

However, if the reptiles on Clarión had evolved independently and had never been introduced there by the Mexican military, then they would not need to be – and should not be – eradicated now!

Daniel Mulcahy and his colleagues therefore decided to take action and have now published the results of their genetic analysis in the aforementioned study. They focused on examining DNA in the cell's powerhouses, the mitochondria. These cell organelles are inherited only maternally and are particularly well-suited for reconstructing phylogenetic relationships over long periods.

The result: The black iguanas on Clarión and those on the mainland in western Mexico show a difference of about 1.5 percent in their DNA. That's enough to say: The supposedly foreign island inhabitants were not introduced in recent decades, but have formed a genetically distinct population there for an estimated 425,600 years.

"The iguanas are native to Clarión and should be considered part of the natural fauna – and preserved rather than eradicated," concludes the researchers in their study, which is clearly intended as an appeal. One can only hope that the message reaches the Mexican government in time.