Two days ago, Ambika Kamath posted an entry in which she observed that the green anoles in her study site in Gainesville are doing just fine, they’re just high up in the trees and harder to spot than the abundant browns. She concluded that, contrary to what many think, brown anoles are not threatening greens in Florida with extinction.
I’d like to add to Ambika’s conclusion by pointing out how browns and greens interact throughout the natural range. Both species evolved in Cuba. There members of the sagrei group coexist widely with carolinensis’s relatives. Where they co-occur, brown anoles are very abundant and are found on the ground and low in vegetation. Greens, primarily A. allisoni and A. porcatus are seemingly less abundant (population estimates are not available) and they occur on tree trunks on up into the canopy.
This mostly peaceful coexistence is repeated in other places the two species co-occur. In the Bahamas, it’s A. smaragdinus and A. sagrei, on Little Cayman, it’s A. maynardi and A. sagrei. In both cases, sagrei is apparently much more abundant, and the two species occupy different parts of the habitat.
Some time ago (possibly several million years, according to genetic data), green anoles colonized Florida from Cuba. In the absence of browns, the greens took the arboreal to increase their habitat use, a phenomenon termed “ecological release.” Then the browns arrived, thanks to us. They have moved into their ancestral niche and the ancient order has been restored. Greens have moved back up in the trees and, yes, their populations are probably now smaller, because some of the resources they were using are now taken by browns. But they’re not going extinct. Greens and browns stably coexist throughout their range. That’s what they’ll do in Florida, too, as long as all the trees aren’t cut down for shopping malls and parking lots.