Stories tagged colors

Jan
14
2009

Conolophus rosada: Research scientist Gabriele Gentile holding the elusive pink iguana.
Conolophus rosada: Research scientist Gabriele Gentile holding the elusive pink iguana.Courtesy Photograph settings by Gabriele Gentile, photo shot by an assistant
A pink lizard that eluded Charles Darwin when he visited the Galapagos Islands nearly 175 years ago has been recognized as a new species of land iguana. Conolophus rosada is found only in the region of Volcan Wolf volcano on the island of Isabela.

"That Darwin might have missed this form is not surprising, because he stayed in the Galápagos only five weeks, and he did not visit Volcan Wolf [volcano], which to our knowledge is the only place on the archipelago where the pink form occurs," said lead researcher Gabriele Gentile of the University Tor Vergata in Rome, Italy. "What is surprising is that several other scientists visited in the last century Volcan Wolf and missed this form."

Two genera of iguana populate the Galapagos – land iguanas (Conolophus) and marine iguanas (Amblyrhynchus). The two branches split off from a common ancestor about 8-10 million years ago while still on the mainland. The pink iguana, which branched off the Colonophus line, can reach a length of more than 3 feet, and weigh up to 15 pounds. Park rangers first stumbled upon it in 1986 but not until now has it been recognized as a new, separate species.

Darwin spent only five weeks exploring the Galapagos when the HMS Beagle stopped at the archipelago to gather food for the voyage back to England. He investigated the island of Isabela but not around the Volcan Wolf volcano, the only area where rosada has been found. Overall, the naturalist wasn’t too impressed by the land iguanas he encountered on the Galapagos, He described them as “ugly animals, of a yellowish orange beneath, and of a brownish-red color above: from their low facial angle they have a singularly stupid appearance."

Good looks aside, the pink iguana presents other problems for modern scientists. Recent genetic analysis shows the rosada species diverged from other lines of land iguana about 5.7 million years ago. The trouble with that is the island of Isabela is only about one million years old and the oldest extant island in the chain, Espanola, is only 3-4 million years old. That means the split must have taken place somewhere else. But rosada hasn’t been found anywhere else in the Galapagos. How can this be?

One possibility is the split took place on the mainland before iguanas arrived on the islands, possibly floating there on rafts of vegetation. That would have been a long, miserable trip over 600 miles of open water. More likely rosada developed on an earlier island in the chain that no longer exists above sea level. Plate tectonics provide an explanation for this. Ocean crusts spread out from mid-ocean ridges located along the edges of plates moving away from each other. The Galapagos are part of the Nazca plate which is moving east-southeast (at about 7 cm/year) toward the continent of South America. The island chain was created (and is still being created) as the plate moved over a hotspot where a mantle plume is pushing up into the lithosphere and crust. Magma from the plume forms undersea volcanoes that build and sometimes break the ocean’s surface as islands. The Hawaiian Islands were created the same way but on a plate moving in a north-northwest direction.

As it moves toward the South American coastline, the heavier Nazca plate sinks beneath the lighter continental plate in a process called subduction. This means the earliest formed islands in the chain also sink and there is evidence of underwater seamounts between the archipelago and South America. Some of these have been dated to as much as 11 million years old, which means the pink iguanas could have split off from the land iguana line when older, earlier islands were still above sea level.

"This event is one of the oldest events of diversification among species in the Galápagos overall," Gentile said. "The Darwin finches are thought to have differentiated later than the split between the pink and yellow iguana lineages."

Despite rosada's evolutionary ranking, fewer than 100 pink iguanas are known to exist today and the species could be in danger of extinction.

It is, however, fitting that news of the pink iguana comes now. 2009 has been proclaimed the Year of Darwin marking the 200th anniversary of his birth and the 150th anniversary of the publication of his most famous work On the Origin of Species by Means of Natural Selection.

LINKS
Story on LiveScience
Year of Darwin info
Discovery.com story
Geology of the Galapagos Islands

Oct
31
2008

Tuesday, October 31, 2028

Purple. Why is it always purple? Or blue. All the foods that taste terrible but are good for you, always seem to come from the long end of the visible spectrum. Eggplants. Prunes. Now this.

Well, no use whining. Remember what grandma always used to say. Eat your tomatoes, live forever. Or, at least until a truck hits you. She didn’t see that one coming. Literally.

I’d give ‘em to the trick-or-treaters, except they just throw them at my windows. Ungrateful brats. Don’t they know I’m trying to save their lives?

The US Forest Service has a neat page with up-to-date information about fall foliage hotspots and peak dates, plus information about why leaves change color in the fall. Check it out, and maybe plan an outing to take advantage of the colors before they're gone.