Genovesa Island
The Galápagos Islands are a remote archipelago situated in the Pacific Ocean, straddling the equator and over 700 miles from the nearest mainland. They are the tips of giant submerged volcanoes that eventually broke through the surface of the sea as bare, sterile stretches of lava. The cool waters that bathe the coastlines bring drought-like conditions most of the year, adding to the inhospitality of the place. “A group rather of extinct volcanoes than of Isles; looking much as the world at large might, after a penal conflagration. It is to be doubted whether any spot on Earth can, in desolateness, furnish a parallel to this group.” Thus wrote Herman Melville, after having visited what he termed “The Encantadas” (or Enchanted Isles), captivated by a nature he found both charmingly fascinating and horrifying.
The inhabitants of the islands arrived and established against all odds, surviving the difficulties of crossing such a large distance of sea and sky and eking out a living once here. As such, it really is an odd assortment of both plants and animals that make up the flora and fauna of the islands, with major animal and plant groups completely missing and others, such as reptiles and members of the aster family, markedly over-represented – a phenomenon common to remote oceanic islands, known as “disharmonic distribution”. Those who did manage to survive constituted just a tiny sampling of the gene pool of the parent population, with many of the genetic variations present in the mainland population thus absent. This particular phenomenon, know as the “Founder Effect”, will rapidly give rise to a genetic drift, whereupon the tiny founding population will rapidly diverge from the original stock. Add to this the pressures of adapting to a brand new environment and you rapidly have completely new species arising from the original ancestor. In an archipelago situation like Galápagos, where one has a group of islands relatively close together yet far enough to be isolated, the new species might happen to spread to other islands and undergo the same process; soon several closely related species arise, all descended from one common ancestor.
Phenomena such as these are everywhere to be seen on an expedition to the Galápagos, which have hence earned the nickname “Laboratory of Evolution”. It is small wonder indeed that these islands played such an important role in the elaboration of Charles Darwin’s theory of Natural Selection, when he came across many of the same species that we have this week, among which all this is particularly evident. A superb illustration is the mockingbird group, of which one of four species is pictured here – the one found among a few of the central and northern islands, such as today’s visitor site on Genovesa Island.
The Galápagos Islands are a remote archipelago situated in the Pacific Ocean, straddling the equator and over 700 miles from the nearest mainland. They are the tips of giant submerged volcanoes that eventually broke through the surface of the sea as bare, sterile stretches of lava. The cool waters that bathe the coastlines bring drought-like conditions most of the year, adding to the inhospitality of the place. “A group rather of extinct volcanoes than of Isles; looking much as the world at large might, after a penal conflagration. It is to be doubted whether any spot on Earth can, in desolateness, furnish a parallel to this group.” Thus wrote Herman Melville, after having visited what he termed “The Encantadas” (or Enchanted Isles), captivated by a nature he found both charmingly fascinating and horrifying.
The inhabitants of the islands arrived and established against all odds, surviving the difficulties of crossing such a large distance of sea and sky and eking out a living once here. As such, it really is an odd assortment of both plants and animals that make up the flora and fauna of the islands, with major animal and plant groups completely missing and others, such as reptiles and members of the aster family, markedly over-represented – a phenomenon common to remote oceanic islands, known as “disharmonic distribution”. Those who did manage to survive constituted just a tiny sampling of the gene pool of the parent population, with many of the genetic variations present in the mainland population thus absent. This particular phenomenon, know as the “Founder Effect”, will rapidly give rise to a genetic drift, whereupon the tiny founding population will rapidly diverge from the original stock. Add to this the pressures of adapting to a brand new environment and you rapidly have completely new species arising from the original ancestor. In an archipelago situation like Galápagos, where one has a group of islands relatively close together yet far enough to be isolated, the new species might happen to spread to other islands and undergo the same process; soon several closely related species arise, all descended from one common ancestor.
Phenomena such as these are everywhere to be seen on an expedition to the Galápagos, which have hence earned the nickname “Laboratory of Evolution”. It is small wonder indeed that these islands played such an important role in the elaboration of Charles Darwin’s theory of Natural Selection, when he came across many of the same species that we have this week, among which all this is particularly evident. A superb illustration is the mockingbird group, of which one of four species is pictured here – the one found among a few of the central and northern islands, such as today’s visitor site on Genovesa Island.
