Even on remote islands, busy ports mean more invasives

In the Caribbean, trade trumps geographic isolation in the spread of nonnative lizards

brown anole lizard

SCALY STOWAWAY  Islands with thriving trade networks are more likely to be colonized by opportunistic species such as this brown anole (Anolis sagrei), a new study of the distribution of native and nonnative anoles shows. 

Neil Losin

When it comes to invasive species, the number of ships an island welcomes may be more important than how remote it is. Islands with more trading ties end up with more species of invasive lizard, concludes a study in the Sept. 25 Nature.

Without human intervention, secluded islands are rarely colonized by new species. “Trade now trumps geography,” says Matthew Helmus, an ecologist at VU University Amsterdam and lead author of the study. “Islands aren’t isolated the way that they used to be.”

Helmus and colleagues studied anoles, a group of lizards that includes about 150 species in the Caribbean. The lizards island hop by hiding in shipments of ornamental plants bound for hotel and resort gardens, concealed among leaves, trunks and soil, he says.

Helmus put together databases of native and exotic anole distribution on the Caribbean islands. He then calculated the islands’ economic isolation from a United Nations log of shipping activity. Islands with a large number of ships docking have gained multiple anole species since the 1950s. Trinidad, for instance, has gained four new species, while Cuba, which trades less, has gained none.

Anoles are not responsible for any economic or ecological mayhem so far. But the brightly colored lizards indicate the potential for dangerous species such as venomous snakes, crop pests and disease-carrying insects to reach remote shores. 

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