Darwin’s Finches and Natural Selection in the Galapagos
simple intervention can help Galapagos finches to stave off an insidious parasite. Offered insecticide-soaked cotton, birds from four finch species wove it into their nests and effectively stamped out an invasive nest fly, researchers report today in Current Biology. The fly Philornis downsi represents a serious threat to the iconic birds, whose speciation patterns were key to Charles Darwin’s theory of evolution. Its larvae feed on blood from newly-hatched finches and have been known to kill all a year’s nestlings at a given field site.
What did Darwin hypothesize about the finches ..
The species on these islands - birds, plants, insects and reptiles - resembled those on the South American mainland, but they were also different in many subtle ways. After his journey back to England, Darwin began to develop the idea that the species from the mainland had reached the Galápagos, and then changed, adapting to their new environment. Until this point it was universally accepted that species did not change yet Darwin's emerging theory was about to challenge this in a radical way.
The larvae were found to be killing off nestlings in Ecuador’s Galapagos Islands in the 1990s, spurring conservation ecologists and others to seek a way to eliminate the flies without harming the birds. Now, with funding scarce and the finch population declining, it turns out that the answer might be as simple as giving the birds the means to conduct their own pest extermination.
How Do Darwin's Finches Respond So Quickly To ..
One of the classic examples of adaptive radiation under natural selection is the evolution of 15 closely related species of Darwin's finches (Passeriformes), whose primary diversity lies in the size and shape of their beaks. Since Charles Darwin and other members of the Beagle expedition collected these birds on the Galápagos Islands in 1835 and introduced them to science, they have been the subjects of intense research. Many biology textbooks use Darwin's finches to illustrate a variety of topics of evolutionary theory, such as speciation, natural selection and niche partitioning. Today, as this Theme Issue illustrates, Darwin's finches continue to be a very valuable source of biological discovery. Certain advantages of studying this group allow further breakthroughs in our understanding of changes in recent island biodiversity, mechanisms of speciation and hybridization, evolution of cognitive behaviours, principles of beak/jaw biomechanics as well as the underlying developmental genetic mechanisms in generating morphological diversity. Our objective was to bring together some of the key workers in the field of ecology and evolutionary biology who study Darwin's finches or whose studies were inspired by research on Darwin's finches. Insights provided by papers collected in this Theme Issue will be of interest to a wide audience.
Searching for the ancestor of Darwin’s finches
High above the cliffs of the Darwin Bay on Isla Genovésa (Tower Island), one of the Galápagos archipelago islands in the Pacific Ocean, jumping around the sharp lava rocks on the ground, perched on the branches of the yellow geiger (Cordia lutea) and croton (Croton scouleri) bushes and flying around large yellow flowers of prickly pear cactuses (Opuntia helleri), are small black and brown birds. These birds look similar to each other in plumage and song, yet closer observation reveals that they all differ from one another in how their beaks look and work. One of them is called a warbler finch (Certhidea fusca) and, as its name suggests, it looks and behaves like a warbler from the mainland. It has a very thin and pointed beak, which is used to probe leaves of the palo santo trees (Bursera graveolens) to catch small insects and their larvae. Another species feeding nearby on a small bush is the sharp-beaked finch (Geospiza difficilis), which has a slightly larger and more cone-shaped beak that is used to collect a more varied diet of both insects and small seeds. On the neighbouring small island of Wolf, members of the same species (G. difficilis septentrionalis) use their sharp arrowhead-shaped beaks to cut wounds on large sea birds, such as the Nazca and blue-footed boobies, and drink their blood. These same populations also feed on booby eggs by pushing and rolling them into rocks until they break, revealing remarkable behavioural adaptations that match their beak morphology. Two larger species of finches on Genovésa feed and nest in close proximity to the warbler and sharp-beaked finches. One of them, the large ground finch (G. magnirostris), has a massive, extremely deep and broad bullfinch-shaped beak that can be deployed to crush the large and hard seeds that no other bird on the island can handle. Lastly, there is the large cactus finch (G. conirostris) that has a more elongated yet still robust beak adapted for penetrating the firm covers of cactus fruits and closed cactus flower buds that contain protein- and sugar-rich parts inside (). All these species and 10 more across other islands of the Galápagos archipelago and Cocos Island do not belong to different families, as their extreme differences in beak morphology and specializations would suggest, but are all part of a tightly linked and relatively recent group that diverged within the last 2–3 Myr called Darwin's finches (formerly known as the Galápagos finches) (Grant , ; ; ). How was such morphological and behavioural diversity generated and how is it being maintained?
The First Hypothesis: Darwin’s Finches - Frank Jochem
It was during Darwin's journeys on the British survey ship HMS Beagle that he saw the variations in different species that led him to develop the idea of natural selection. Darwin's experiences on The Galápagos Islands were a catalyst for his thinking about evolution.