Darwin's finches
Different beaks in Darwin's finches
- Ground finches ( Geospiza )
- Tree finches ( Camarhynchus )
- Certhidea
- Pinaroloxias
The Darwin's finches or Galapagos finches ( Geospizinae ) are a group of passerine species that are endemic to the Galapagos Islands, and with a kind, the coconut finches ( Pinaroloxias inornata ) on the Cocos Island. These are 14 very closely related species, all descended from a common ancestor. Their closest relatives are not, as the name suggests, the finches, finches but similar songbirds that today among the tanagers ( Thraupidae ), sometimes to the Buntings ( Emberizidae ) are expected.
Appearance
Darwin's finches are about 20 inches tall and differ mainly by the shape and size of their beak and their different life, especially diets. Their songs are different.
Genera and species
- Ground finches ( Geospiza ) Large - ground finch (G. magnirostris )
- Medium ground finch (G. fortis )
- Small ground finch (G. fuliginosa )
- Sharp-beaked ground finch (G. difficilis )
- Cactus ground finch (G. scandens )
- Opuntia - ground finch (G. conirostris )
- Thick -billed Darwin finch ( Camarhynchus crassirostris )
- Mangrove Darwin finch ( Camarhynchus heliobates )
- Parrot beak -Darwin finch ( Camarhynchus psittacula )
- Branch -Darwin finch ( Camarhynchus parvulus )
- Small -billed Darwin finch ( Camarhynchus pauper )
- Woodpecker Finch ( Camarhynchus pallidus )
- Warbler Finch ( Certhidea olivacea )
- Cocos Island finch ( Pinaroloxias inornata )
Evolution of Darwin's finches
The Galapagos Islands are volcanic in origin and have been gradually colonized by different organisms. By storms or other causes few finches a founder population have been cast upon the island group. For this reason, there was initially no Opponenz and no competition between the executed arrived there by chance Darwin's finches (possibly only one pregnant female ). However, not a robber, a large supply of food and plenty of room to spread and to brood care was available. Due to the favorable conditions, the growth rate was very high. This resulted after an extended period to over- population, which increased the selection pressure and the intraspecific competition of the finches. Presumably through random geographical separation, the finches were gradually colonize other islands of the Galápagos archipelago and occupy new, empty ecological niches. After this divergence, some individuals were sold back to the island's output type. There they lived with the ancestral species together in co-existence, as they were now genetically and reproductively isolated from each other by isolation mechanisms. This process was repeated several times, which led to the 14 species of finches of the Galapagos Islands. This process is called adaptive radiation. This speciation is also an example of the formation of species evolution.
Zoological history
During her nearly five -year marine survey, the HMS Beagle held on until October 20, 1835 in the territory of the Galápagos Islands on 15 September. Charles Darwin, who took part as a young man at the ride, explored during this time, the islands of San Cristobal, Floreana, Isabela and San Salvador. Among the shot birds on these islands, which he presented to the Zoological Society on January 4, 1837 there were 31 specimens of Galapagos finches.
Curator of the museum of the Zoological Society at this time was John Gould, who examined the unknown birds and discovered that these specimens represented a completely new group. A few days later, on January 10, 1838, presented Gould before its findings to the Zoological Society. The person designated by him as a new genus Geospiza he divided initially into the subgenera Camarhynchus and Cactornis and described 12 species. In the further work of Darwin brought back from the Galapagos birds Gould realized that even the warbler finch ( Certhidea olivacea ) belonged to this group and set the type to the third subgenus Certhidea. In the final version of his lecture, which appeared at the end of the year, the new group comprised a total of 13 species.
The conformity of the number of species with the species now known from the Galapagos Islands described in 1838 by John Gould is a coincidence. The Opuntia - ground finch (G. conirostris ), the Mangrove Darwin finch ( Camarhynchus heliobates ), the small -billed Darwin finch ( Camarhynchus pauper ) and the woodpecker finch ( Camarhynchus pallidus ) were only 1868-1899 discovered. The Cocos Island finch ( Pinaroloxias inornata ), the only belonging to the group of Darwin's finches kind that does not come from the Galápagos Islands, was during the journey of the HMS Sulphur discovered on Cocos Island and described in 1843 by Gould.
That Darwin the shot of him Darwin's finches not then assigned each of the islands, has repeatedly taxonomic difficulties. The inclusion of the specimens collected by Robert FitzRoy, whose personal steward Harry Fuller and Darwin's assistant Syms Covington but this could be solved. The commonly encountered representation that the observation of the " finches " has led to the Galápagos Islands by Darwin to his theory of evolution is incorrect. In the first edition of The Origin of Species, the Galapagos finches are not mentioned. However, Darwin noted in his diary during the Beagle voyage - first held in 1835 - and in his travelogue, in which he brings the stepped shape with variety of geographical separation in conjunction. According to some authors are occurring on the Galapagos islands four species of mockingbirds, namely Hood Mockingbird, San Cristobal Mockingbird, Galapagos Mockingbird and Charles Mockingbird, have been important for Darwin's contributions to the theory of evolution as Darwin's finches. During the stay in the Galapagos Islands, these four mockingbirds caught the attention of Darwin, because on the one hand, resembled those he knew from the South American mainland, at the same time, however, showed significant deviations. He found it so striking that he, unlike the Darwin finches for each collected on the islands copy the locality held exactly.
The term " Darwin's finches " in 1936 by Percy Roycroft Lowe ( 1870-1948 ) coined and popularized by the 1947 book called Darwin's Finches by David Lack.