Leach's Anole - my, how geographic isolation facilitates speciation.

Leach's Anole (Anolis leachii), photographed on Antigua in 2016.

Also called the panther anole, Leach's anole is a common lizard native to the island of Antigua in the Caribbean.  The interesting thing about endemic island life is that the various species didn't just magically appear; they would have travelled there on some flotsam from some distant point of origin, most likely the nearest continent.

We don't know when the first anoles showed up, but the chances are very good that they didn't look anything like they do today, other than that they were anoles.  Separated from the original gene pool, the now-isolated lizards would breed and lay eggs, producing new generations.  If they survived, the population would grow.

Two things would happen over the millennia that would produce the new species of anole.  Natural selection, where the environment would weed out less well-adapted individuals, and random mutation, where existing genes would experience small changes due to base-pair alterations.  These two factors would work in tandem to mould the now-established population into whatever form was to come.

Take a small population of any creature, isolate it for hundreds of thousands of years, especially in a totally new environment, and wait to see what happens.  Genes that favour survival will begin to dominate.  New genes, created through random mutation, will produce new characteristics that will be selected through environmental factors.  There is also a process known as gene drift, where natural selection doesn't play a role in a species' development, but rather random chance does.  

Leach's anole has several characteristics that differ from its forebears.  They are bigger (especially the males, which can grow up to 14 inches), more colourful, and very arboreal.  Google AI summed it up like this:

Google AI listing differences between Leach's anole and ancestors

The genetics of the two species have been separated for so long that they are no longer capable of producing viable offspring.  The long geographic isolation has produced a new species.

Thanks for reading.

Eric Svendsen     www.ericspix.com