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The Galápagos Islands have received international acclaim as a natural laboratory, where the 19 th century naturalist Charles Darwin gathered important scientific evidence that set in motion his theory of evolution by natural selection—the idea that organisms best suited to changes in the environment are most likely to survive and pass successful genetic traits to their offspring. Scientists and conservationists have been flocking to the Galápagos ever since to observe the incredible plant and animal species variety and endemism concentrated in the islands and to make sense of the evolutionary processes that have subjected these individuals to biological development.
Colonizing plant and animal species arrived to the Galápagos via wind and water dispersal across a seemingly insurmountable 1000km-wide oceanic barrier separating the South American continent from the islands. As a result, these organisms were effectively isolated from their mainland ancestors, becoming independent biological units subject to different environmental factors and evolutionary patterns. This same segregation process occurred on a smaller scale within the archipelago, with individual islands harboring unique species.
Geographic and/or ecological isolation is a main force driving speciation, a phenomenon idyllically represented by the little brown symbols of evolution in action also known as Darwin's finches. Although all finches originated from a single ancestor, competition for resources over time has caused individuals to select specific ecological niches. As a result, individual species have developed differences in beak structure and food preferences that are acute enough to prevent interbreeding. This specialization on food resources becomes especially valuable—and evolutionarily interesting—during climatically different El Niño years, when limited food availability triggers a more severe natural selection.
Besides the archipelago's distance from major land masses, it counts on a unique combination of abiotic and biotic factors—moisture, temperature, light, food, nutrients, predation, competition, etc—to drive the evolutionary formation of endemic species found nowhere else on earth. Nearly one in four total species is endemic to the Galápagos, including the flightless cormorant, Galápagos hawk, Galápagos fur seal, and Galápagos penguin. Certain environmental factors are also responsible for certain animal behaviors. For example, the islands provide the perfect conditions—cool waters, warm terrain, and few predators—for marine iguanas.
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