Giant tortoise under threat
Courtesy sly06 (adapted by Mark Ryan)Evolution of mosquitoes on the Galapagos Islands could endanger the islands’ famous giant tortoises and other reptile wildlife. On the mainland the black marsh mosquito Aedes taeniorhynchus normally feeds on mammals and birds, but scientists from the University of Leeds, the Zoological Society of London (ZSL), the University of Guayaquil and the Galapagos National Park have discovered that the island version of the blood-sucking insect has evolved a craving for reptilian blood, particularly that of the Galapagos tortoises and marine iguanas.

Genetic studies show the mosquitoes arrived on the archipelago about 200,000 years ago, giving them plenty of time to adapt to the island environment. Unlike its mainland counterpart which lives and breeds mainly in the lowlands and coastline salt marshes, the island mosquito can also breed as much as 15 miles inland and at altitudes up to 2000 feet above sea-level.

“The genetic differences of the Galapagos mosquitoes from their mainland relatives are as large as those between different species, suggesting that the mosquito in Galapagos may be in the process of evolving into a new species,” said Arnaud Bataille, PhD student at the University of Leeds and ZSL.

Mosquitoes can carry diseases such as West Nile and avian malaria that could potentially devastate the island fauna. Although none of these diseases have been detected in the Galapagos mosquitoes the researchers fear an infected mosquito brought in from the mainland via such modes as tourist transportation could potentially infect the island mosquitoes. If that happens the islands’ wildlife population could be at risk, because the long isolated Galapagos fauna wouldn’t have built up immunities to such an invasion.

But as a countermeasure, the Ecuadorian government has introduced a requirement for planes flying to Galapagos to be treated with insecticide before each flight, although similar controls have yet to be implemented for ships traveling to the islands.

“It is absolutely vital that these control measures are maintained and carried out rigorously, otherwise the consequences could be very serious indeed,” said Dr Simon Goodman, of Leeds’ Faculty of Biological Sciences and Co-author of the study which is published online in the US journal Proceedings of the National Academy of Sciences.

BBC story
Physorg.com story

Tags : mosquitoes, Galapagos Islands, evolution, diseases

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Conolophus rosada: Research scientist Gabriele Gentile holding the elusive pink iguana.
Courtesy Photograph settings by Gabriele Gentile, photo shot by an assistantA 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

Tags : pink iguana, iguanas, Galapagos Islands, evolution, colors, Charles Darwin

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The great race: Satellite technology is keeping tabs on the progress of 11 leatherback turtles as they migrate from Costa Rica to the Galapagos Islands in the Great Turtle Race.The Kentucky Derby is still a few weeks away, but there’s another big animal race taking place right now deep in the waters of the Pacific Ocean.

The Great Turtle Race started on Monday as 11 leatherback turtles left the shores of Costa Rica on their spring migration to the Galapagos Islands. They should complete the 1,200-mile journey within the next couple weeks. Satellite tracking equipment is strapped to each turtle and their progress is being monitored on the website www.greatturtlerace.com. The tracking information measures their progress toward the island and also how deep they’re diving into the ocean.

Leatherback turtles are an endangered species that some environmentalists fear could be wiped off the Earth in the next 10 years. The female populations of the turtles have dropped from 115,000 in 1980 to less than 43,000 today.

Tags : migration, Galapagos Islands, turtles, leatherneck turtles, Costa Rica, Great Turtle Race

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Satellite technology is keeping tabs on the progress of 11 leatherback turtles as they migrate from Costa Rica to the Galapagos Islands in the Great Turtle Race.

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Charles Darwin, c. 1881: Source: Wikipedia (Public Domain)A group of Galapagos Island birds known as Darwin’s Finches continue to do what they’re best known for: evolving. A recent study published in the the journal Science, details how new competition for food has resulted in some rather quick adaptations in the beaks of some of the famous finches that were instrumental in Charles Darwin formulating his theory of evolution.

Finch: US Fish and Wildlife photo courtesy Wikimedia CommonsPeter Grant of Princeton University has been studying the finches for decades. Early on he noticed that a medium sized ground finch, Geospiza fortis, living on the Galapagos island of Daphne, faced no competition for food and ate both small and large seeds. Then, in 1982, competition arrived in the form of a larger ground finch, Geospiza magnirostris, setting in motion a classic case of microevolution.

The new species was able to break open the larger seeds of the Tribulus plants three times faster than G. fortis and soon depleted the island’s large seed supply.

Over the next twenty years the population of G. fortis finches with larger beaks declined dramatically due to the competition, leaving only a population of smaller beaked G. fortis which didn’t compete for the larger seeds favored by G. magnirostris.

What makes this unusual is that it’s given scientists a rare opportunity to actually observe first hand a change in an animal’s appearance caused by the arrival of a new food competitor.

SOURCES AND LINKS

Minneapolis Star Tribune story
Darwin’s Finches
More on Darwins’s Finches
Charles Darwin
The Galapagos Islands
Charles Darwin Foundation

Tags : evolution, Darwin, micro-evolution, Galapagos Islands

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