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The Floreana mockingbird, which inspired Darwin’s
The Origin of Species,
A mockingbird that sowed the seeds of evolution in the mind of Charles Darwin stands on the precipice of extinction, with no more than about 100 breeding pairs left alive in its home on the enchanted Pacific islands of the Galapagos archipelago. The Floreana mockingbird is the unsung hero in the story of evolution. It played a pivotal role by making Darwin realise that species were not stable units, but changing entities subject to the vagaries of competition and the forces of natural selection. It went extinct on its home island of Floreana in the Galapagos within a few decades of it being discovered by Darwin, thanks to the introduction of rats, pigs and feral cats, and now survives in two small, isolated populations on the nearby satellite islets of Champion and Gardner-by-Floreana. Scientists believe that these remnant colonies are so small and inbred that they could soon disappear with the next drought or famine, which is why the species was this year placed on the critically endangered "red list" of the International Union for the Conservation of Nature. But now a team of researchers and conservationists has devised a bold plan to reintroduce the blackbird-sized birds back to the bigger island of Floreana in the hope of building up the population to the many thousands of individuals that cheekily greeted Darwin on his arrival there in 1835 — one of them audaciously drank from a cup of water he was holding in his hand. Intriguingly, an essential element of this reintroduction initiative has centred on a dried museum specimen of the Floreana mockingbird, as well as one from the nearby island of San Cristobal that Darwin himself brought back to Britain from his five-year voyage on HMS Beagle, during which he collected the thousands of biological specimens that inspired his 1859 book, The Origin of Species. Scientists have extracted DNA from the fleshy footpad of the Floreana specimen, which went on display at the Natural History Museum in London recently, to gauge the level of genetic diversity that may have existed within the original population on the island. They are using the results to compare the genetic makeup of the specimen against the DNA extracted from blood samples taken from individuals living on the islands of Champion and Gardner. The hope is to identify those birds that will be best suited to act as breeding pairs when building up a new colony on Floreana. "For most projects involving the reintroduction of animals, it is important to maximise the genetic diversity in order to prevent or limit inbreeding," said Karen James, a researcher at the Natural History Museum who is involved in the reintroduction programme. The importance of the Galapagos mockingbirds to the story of evolution cannot be overestimated. Darwin had travelled about 4,000 miles along the South American coast and had seen just three species of mockingbird during that time. And yet, when he journeyed from the Galapagos island of San Cristobal to Floreana, just 50 miles away, he found two quite different mockingbirds with as many distinct differences between them as there were with the mockingbird species he had seen on the mainland of Chile. When he had left the Galapagos on his three-week voyage to Tahiti he had time to inspect his specimens more closely. It was, then, that it dawned on him that the two mockingbirds of San Cristobal and Floreana, separated by just 50 miles of water, were probably separate species unique to each island. "Each variety is constant in its own island," Darwin wrote in his notes prepared during that part of the voyage in October 1835. Later on in his life, Darwin was to note that the four different species of mockingbird on the islands of the Galapagos illustrated how competition and natural selection could result in the evolution of one species into another. — By arrangement with The Independent
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