Cayman’s island-hopping lizards provide evolutionary insight

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This article highlights anoles such as the Maynard’s anole in Cayman Brac and the Brown anole in Grand Cayman. Biologists are getting a better idea of how invasive species adapt and populate new territories.

Most visitors to Cayman Brac will likely not have noticed one of the island’s now established transplants: the Maynard’s anole. This non-native lizard spends much of its time just out of eyesight, perched in the tree branches where its bright green colour blends with the foliage. The elusive anole, originally from Little Cayman, has captured the interest of researchers, intrigued by the insight the species can offer about evolution in island ecosystems.

And the Maynard’s anole is not the only island-hopping lizard on the minds of Cayman Islands researchers these days. While far from the invasive status of the prolific green iguana, the brown anole is also creating questions about the potential impact on Grand Cayman’s native blue anole.

Through separate studies – one carried out by Caymanian researcher Vaughn Bodden and another by National Geographic Society grantee Inbar Maayan – biologists are getting a better idea of how invasive species adapt and populate new territories.

Maynard’s anole in Cayman Brac

While the Maynard’s anoles in Cayman Brac are not far from their native home, Little Cayman, the lizard sheds light on how invasive species colonise new habitat.

Fortunately for Cayman Brac, the Maynard’s anole does not appear to pose a threat to the native Cayman Brac anole and has not shown potential for hybridisation.

“Based on similar invasions on other Caribbean islands, we expect the potential for a negative impact to be low. The native anole in Cayman Brac is found low on tree trunks and on the forest floor, while the introduced anole is predominantly found on upper tree trunks and in the canopy so direct interaction between the two species should be limited,” said Bodden, who studied the species while completing his bachelor’s in conservation biology at the University of Plymouth. He is now completing his master’s in biodiveristy and conservation at the University of Glasgow.

“Any impacts on the native anole are more likely to be indirect, such as a shift in habitat use to further avoid interacting with the introduced anole,” he added.

Through fieldwork capturing and analysing the anoles in both Sister Islands, Bodden’s team, assisted by University of Plymouth lecturer Robert Puschendorf, found some interesting differences in their morphology and ecology. While the team hypothesised that the introduced anole might have developed longer hind legs – a trait that can aid dispersal and movement – their findings did not support this. In fact, they found much the opposite. The anole had instead developed longer forelimbs.

“Potential explanations for the rapid divergence could be that the founding individuals of the introduced population had a unique phenotype and these characteristics became exaggerated over time through the process of genetic drift, or that some habitat use characteristics that we did not measure on Cayman Brac are driving the morphological adaptation,” Bodden said.

Another interesting discovery about the introduced anole population was the presence of a parasite not previously recorded in the Sister Islands. [. . .]

[Photo: Inbar Maayan. The Grand Cayman blue anole stands out for its distinctive colour, seen most prominantly in males. Excluding the tail, this blue anole measures 2.5 inches.]

For full article, see https://www.caymancompass.com/2019/04/25/caymans-island-hopping-lizards-offer-evolutionary-insight/

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