Caribbean anole lizards and trade

This video is called Convergent evolution of anole lizards.

Study shows human impact on biodiversity on islands based on amount of trade

19 hours ago

(Phys.org) — A trio of researchers looking to test the idea of island biogeography have found a real world example that seems to both upend the traditional tenets upon which the science is based and confirm them at the same time. In their paper published in the journal Nature, Matthew Helmus of Vrije Universiteit in the Netherlands, Luke Mahler of the University of California and Jonathan Losos of Harvard University describe their study of anoles (a type of lizard) in the Caribbean Islands and how new data shows the ways humans have impacted the means by which the tiny color changing creatures migrate.

The science of island biogeography took off back in 1969, when ecologists Robert MacArthur and E. O. Wilson essentially sterilized a few very small islands and then monitored them to see how long and in which ways they would recover. Their study cemented the idea that island biodiversity is based on two major principles. The first is that the bigger an island is the more diversity it can support. The second is that the more remote an island is the less diverse it will be because other species have so much difficulty getting to it.

If humans weren’t around, it’s likely the original model would persist, but because they do, the principles have to be modified. That’s because people engage in shipping which living creatures can use to migrate. In this new study, the researchers looked at anoles as a barometer of sorts—traditional theory suggests there should be more species of them on larger islands, and more of them in general. Smaller islands on the other hand should have less, or none at all if they are too far away for migrants to reach.

This new study entailed cataloguing anoles by number and species throughout the Caribbean Islands and then comparing what they found to the traditional model. Doing so showed the original model failed miserably—but it also showed why. Because distance is no longer a factor in the equation (due to so much shipping), anoles are free to migrate to wherever they wish. The researchers found that in the newly updated model, island size still dictates population density, but now economic isolation is more of a factor. As one example, they note that diversity is limited on the Cuban islands, due to the trade embargo imposed by the United States. Much smaller Trinidad, on the other hand, which has a robust trade association with other nations throughout the area, has as many of the lizards and species as the island seems capable of supporting.