Scientist at Work Blog: Quest for a Little-Known Suburban Lizard

Jonathan Losos, professor and curator of herpetology at Harvard?s Museum of Comparative Zoology, writes from Colombia, where he is studying the biodiversity of anole lizards, an evolutionarily successful group that has produced 400 species throughout Central and South America and Caribbean islands. For more on anoles, see anoleannals.org.

Feb. 18, 2013

Mired in rush-hour traffic, layered in sweatshirts and long sleeves, it?s hard to imagine a more unlikely start to a tropical reptile hunt. But here we are in Bogot?, perched 8,600 feet high in the chilly Andes, setting out on our first day to find a little-known lizard that is said to be common in suburban parks and roadsides. A far cry from the rain forests where we usually work, the Andean uplands of Colombia are home to the variable-scaled anole, a prehistoric-looking lizard about which we know almost nothing, despite the fact that it lives on the outskirts of a city of nine million people and is, by all accounts, reasonably abundant.

Our team is multinational. I?m a professor and curator at the Museum of Comparative Zoology at Harvard University; Anthony Herrel is a research scientist at the Museum of Natural History in Paris; and Maria del Rosario Casta?eda, though currently a postdoctoral fellow in my laboratory, hails originally from Bogot?. But we all have one thing in common: We?ve each spent our careers studying lizards in the genus Anolis. Recognized by the retractable flap of skin under the throat and enlarged and sticky pads at the end of the toes, anoles have become a textbook case of evolutionary diversification. About 400 species are currently known (with more being discovered every year), and as many as 15 different species can be found at a single locality.

These lizards are particularly renowned for their unusual pattern of evolution on the four large islands of the Caribbean ? Cuba, Hispaniola, Jamaica and Puerto Rico. On each island, the species that co-occur use different parts of the environment ? one high in the canopy, another on narrow twigs, a third in the grass and so on ? and exhibit anatomical features that appear to be adaptations for where they live. Twig anoles, for instance, have short legs that allow them to negotiate narrow and irregular surfaces with agility. Canopy anoles have large toe pads to cling to the smooth surfaces of leaves.

Most remarkably, the same set of habitat specialists occurs on each island (with several exceptions), but they are not closely related evolutionarily.? For example, the twig anoles on each island are extremely similar in appearance, behavior and habitat, but a comparison of their DNA indicates that they are not one another?s closest relatives; rather, they have evolved independently on each island. The same is true of the canopy dwellers, the grass anoles and the other specialist types. Convergent evolution, the phenomenon in which distantly related species living in the same environment adapt by evolving the same features, has been known from the time of Darwin, but convergence of entire communities is a different matter, and anoles are arguably the best-documented example of this phenomenon.

But most anole species occur not only the islands, but on mainland Central and South America (approximately 250 and 150 species, respectively). Given that the same habitat specialist types have evolved repeatedly on the islands, we might also expect them to occur on the mainland. But data are scarce ? the mainland species have been studied much less than their island counterparts, owing in large part to the fact that island species tend to have much larger populations.

And that?s what brings us to South America. If we can understand where the species live, how they behave and what their anatomy is like, we may be able to determine whether the mainland anoles have, in fact, followed the same path as their island brethren, or whether they have blazed their own evolutionary trail.

For the first leg of our three-week trip, we?ve chosen to focus on a species that is supposed to be abundant and easy to find, the variable-scaled anole, Anolis heterodermus; we?re postponing the search for the more difficult species until later. But as I?ve learned many times in my studies, it?s best not to get cocky. Lizards that ?you can?t miss? often turn out to be harder to find than advertised. So, as with the proverbial chickens (which are, after all, just feathered reptiles), I?m not counting these lizards until they?re in focus in my binoculars. And before that can happen, we?ve got to make our way through the traffic. Not exactly the type of field biology I envisioned when I started graduate school, but if you study anoles, you?ve got to go where the lizards are.

Source: http://scientistatwork.blogs.nytimes.com/2013/03/12/quest-for-a-little-known-suburban-lizard/?partner=rss&emc=rss

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