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Tuesday, January 6, 2009

Pink Iguana That Darwin Missed Holds Evolutionary Surprise

By Alexis Madrigal Email


For iguanas, it turns out that it's not easy being pink, either.

Biologists report that a rare type of pink iguana found on a single volcano in the Galapagos Islands is a genetically-distinct species from its green cousins — and that it's probably critically endangered.

"This form, which we recognize as a good species, is very important because it carries substantial evolutionary legacy," the authors of a new paper in the journal Proceedings of the National Academy of Sciences wrote. "Thus far the rosada form is the only evidence of deep diversification along the Galapagos land iguana lineage."

Charles Darwin visited the Galapagos islands in 1835 but didn't make it to the northernmost volcano, Volcan Wolf, which is the lone habitat for these pink lizards. Later travelers and scholars also seem to have missed or failed to report the curiously striped creature until 1986 when some Galapagos National Park rangers spotted the animals. Still, no scientists had looked into whether they represented a distinct species until now.

What they found was surprising. Instead of being some slight variation on the Galapagos iguana theme, the pink lizards represent a distinct and early branch of the genetic tree. The genomic analysis of the species suggests that they broke from other iguanas about five million years ago, much deeper in history than most other Galapagos species, like Darwin's finches. In addition to the genetic differences, the pink iguanas also perform the characteristic mating ritual "head-bob" differently.

The iguana and other animals on Volcan Wolf are threatened by an "invasion of feral goats" that are devastating the area's natural flora.

In the interest of preserving this genetic diversity, the biologists wrote that "a conservation program aimed at evaluating the risk of extinction of this newly recognized species," should be initiated. They estimate that the iguana could already by termed "critically endangered."

Citation: "An overlooked pink species of land iguana in the Galapagos" by Gabriele Gentile, Anna Fabiani, Cruz Marquez, Howard L. Snell, Heidi M. Snell, Washington Tapia, and Valerio Sbordonia in the Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.0806339106