Different beak shapes in Darwin's finches
|Swarth , 1929|
The Darwin's finches or Galápagos finches (Geospizini) are a group of songbird species that are only found on the Galápagos Islands and with one species, the Coconut Island Darwin's finch ( Pinaroloxias inornata ), on the Coconut Island . There are 18 very closely related species that all descend from a common ancestor. Their closest relatives are not, as the name suggests, the finches , but finch-like songbirds, which used to be part of the bunting (Emberizidae), but are now counted as the tangars (Thraupidae).
Darwin's finches are about 20 centimeters tall and differ mainly in the shape and size of their beak as well as in their different ways of life, especially diet. Their chants are also different.
For a long time, the Darwin's finches were classified in the family of the Ammern (Emberizidae), which at that time still included many North and South American species, among others. a. also the New World chambers (Passerellidae). Within this family, the Darwin's finches were sometimes assigned the rank of subfamily (Geospizinae). Since the 1990s, however, molecular genetic studies have shown that the classifications were phylogenetically not tenable, so that the family of the Ammern now only contains the ancient genus Emberiza . For the Darwin's finches it was particularly evident that they belong to the tangar family. Within this family they are recently in the subfamily Coerebinae, which contains many "island species" that are characterized by the construction of covered nests or spherical nests. The group of Darwin's finches is accordingly led under the name Geospizini. Although the ending "-ini" suggests the rank of a tribe, no division of the subfamily into different tribes is recognized.
The internal systematics of Darwin's finches has also been examined in detail in recent years. This confirmed that the group was forming a clade . The assignment of species to genera was changed to ensure monophyletic taxa. The current World Bird List of the IOU has the following list:
Genera and species
- Tree finches ( Camarhynchus )
Ground finches ( Geospiza )
- Genovese finch ( Geospiza acutirostris )
- Españolagrundfink ( Geospiza conirostris )
- Middle ground finch ( Geospiza fortis )
- Small ground finch ( Geospiza fuliginosa )
- Great Ground Finch ( Geospiza magnirostris )
- Opuntia ground finch ( Geospiza propinqua )
- Cactus ground finch ( Geospiza scandens )
- Vampire ground finch ( Geospiza septentrionalis )
- Pointed-billed ground finch ( Geospiza difficilis ) - may not belong in this genus
- Coconut Island Darwin's Finch ( Pinaroloxias inornata )
- Thick -billed Darwin's finch ( Platyspiza crassirostris )
According to Ferrington et al. (2014) can be represented by the following cladogram:
|Geospizini (Darwin's Finches)||
Evolution of the Darwin's finches
The Galápagos Islands belong to Ecuador and are located around 1000 kilometers off the west coast of South America . They are of volcanic origin, never had a direct connection to the mainland and were therefore only gradually colonized by different organisms. Storms or other causes also brought “finches” to the archipelago; possibly the founder population consisted of only a single pregnant female. Nevertheless, a population of these immigrants was able to establish itself, and as a result all islands of the archipelago were settled by them. Geographical separation and intraspecific competition led to the fact that on the various islands, several descendent species emerged from the parent species.
After this diversification, some individuals of the subsequent species returned to the island of the parent species and lived in coexistence with the parent species, since both were genetically and reproductively isolated from one another by isolation mechanisms. This speciation process through adaptive radiation was repeated several times, resulting in the 14 Darwinian finch species of the Galapagos Islands; it is regarded as exemplary for the formation of species in the course of the ancestral history of life.
During its survey journey, which lasted almost five years, the HMS Beagle stayed in the Galápagos Islands from September 15 to October 20, 1835 . Charles Darwin , who took part in the ride as a young man, explored the islands of San Cristóbal , Floreana , Isabela and San Salvador during this time . Among the birds shot on these islands, which he donated to the Zoological Society on January 4, 1837 , were 31 specimens of the Galápagos finches.
The curator of the Museum of the Zoological Society at the time was John Gould , who examined the unknown birds and discovered that these specimens represented an entirely new group. Only a few days later, on January 10, 1837, Gould presented his findings to the Zoological Society. He first subdivided the new genus, named by him as Geospiza , into the subgenus Camarhynchus and Cactornis and described 12 species. During the further processing of the birds brought by Darwin from the Galápagos Islands, Gould recognized that the wood warbler finch ( Certhidea olivacea ) also belonged to this group and placed the species in 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 Opuntiengrundfink ( Geospiza conirostris ), the Mangrovedarwinfink ( Camarhynchus heliobates ), the small beak Darwinfink ( Camarhynchus pauper ) and Specht Fink (Camarhynchus pallidus) were discovered 1868-1899. The coconut finch ( Pinaroloxias inornata ), the only species belonging to the group of Darwin's finches that does not come from the Galápagos Islands, was discovered during the cruise of the HMS Sulfur on the Coconut Island and described by Gould in 1843.
The fact that Darwin did not assign the Darwin finches he shot to the individual islands repeatedly caused taxonomic difficulties. By including the copies collected by Robert FitzRoy , his personal steward Harry Fuller and Darwin's assistant Syms Covington , this could be resolved. The frequently encountered statement that Darwin's observation of the “finches” on the Galápagos Islands contributed to his theory of evolution is incorrect. The Galápagos Finches are not mentioned in the first edition of The Origin of Species . However, Darwin mentions them in his diary notes during the Beagle trip - for the first time in 1835 - and in his travel report, in which he connects the graduated variety of forms with geographical separation. According to some authors, the four species of mockingbird found in the Galapagos Islands , namely the Hood mockingbird , San Cristobal mockingbird , Galapagos mockingbird, and Charles mockingbird , were more important to Darwin's contributions to evolutionary theory than the Darwin's finches. During his stay in the Galapagos Islands, these four mockingbirds caught Darwin's attention because, on the one hand, they were similar to those he knew from mainland South America, but at the same time had noticeable differences. He found this so conspicuous that, unlike the Darwin's finches, he recorded the exact location for every specimen collected on the islands. As a taxon, the Darwin's finches were set up in 1929 by Harry S. Swarth as the family Geospizidae. Charles Eduard Hellmayr, downgraded them to a subfamily in 1938. Today the group is within the subfamily Coerebinae within the family Tangaren (Thraupidae). The name " Darwin's Finches " was coined in 1936 by Percy Roycroft Lowe (1870–1948) and made popular by David Lack 's book Darwin's Finches , published in 1947 .
- Charles E. Hellmayr: Catalog of birds of the Americas and the adjacent islands in the Field Museum of Natural History. Part XI. Ploceida - Catamblyrhynchidae - Fringillidae. In: Zoological Series of the Field Museum of Natural History 8 (11). Pp. 1-662. ( Full text )
- Frank D. Steinheimer: Charles Darwin's bird collection and ornithological knowledge during the voyage of HMS Beagle, 1831-1836. In: Journal of Ornithology. Volume 145, 2004, pp. 300-320; on-line
- Frank J. Sulloway: Darwin and His Finches: The Evolution of a Legend. In: Journal of the History of Biology. Vol. 15, 1982, pp. 1-53; Online PDF
- Frank J. Sulloway: Darwin's Conversion: The Beagle Voyage and Its Aftermath. In: Journal of the History of Biology. Vol. 15, 1982, pp. 325-96; Online PDF
- Frank J. Sulloway: The Beagle collections of Darwin's finches (Geospizinae). In: Bulletin of the British Museum (Natural History) Historical Series. Volume 43, No. 2, 1982, pp. 49-94 ( PDF ).
- J. Zrzavý, D. Storch, S. Mihulka, H. Burda, S. Begall : Evolution. A reading textbook. Spektrum Akademischer Verlag, 2009, doi: 10.1007 / 978-3-8274-2233-0_6 , ISBN 978-3-8274-2233-0
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- Frank Gill & David Donsker, IOC World Bird List v 8.2 : Tanagers and allies
- Heather Farrington, Lucinda Lawson, Courtney Clark, Kenneth Petren: The evolutionary history of Darwin's finches: speciation, gene flow, and introgression in a fragmented landscape . In: evolution . tape 68 , no. 10 , 2014, p. 2932-2944 , doi : 10.1111 / evo.12484 ( wiley.com ).
- Reports of the council and auditors of the Zoological Society of London. 1837, p. 15.
- Frank J. Sulloway: The Beagle collections of Darwin's finches (Geospizinae) , p. 62.
- J. Gould: Remarks on a Group of Ground Finches from Mr. Darwin's Collection, with Characters of the New Species. In: Proceedings of the Zoological Society of London. Volume 5, 1838, pp. 4-7. (filed October 3, 1838); (on-line)
- Richard Darwin Keynes: From Bryozoans to Tsunami: Charles Darwin's Findings on the Beagle. In: Proceedings of the American Philosophical Society. Volume 147, No. 2, 2003, pp. 125-127.
- Narrative of the surveying voyages of His Majesty's Ships Adventure and Beagle between the years 1826 and 1836, describing their examination of the southern shores of South America, and the Beagle's circumnavigation of the globe. Journal and Remarks. 1832-1836. Henry Colburn, London 1839, p. 475.
- Dominic Couzens: Rare Birds - Survivors, Evolution Losers and the Lost. Haupt Verlag, Bern 2011, ISBN 978-3-258-07629-4 , p. 42.
- Harry S. Swarth: A new bird family (Geospizidae) from the Galapagos Islands. In: Proceedings of the California Academy of Sciences. Volume 18, No. 2, 1929, pp. 29-43 (  digitized version).
- Hellmayr 1938, p. 130.
- Percy Roycroft Lowe: The Finches of the Galapagos in Relation to Darwin's Conception of Species . In: Ibis. Volume 6, 1936, pp. 310-321.
- David Lack: Darwin's Finches . Cambridge University Press, 1947.
- Peter R. Grant, Jonathan Weiner : Ecology and Evolution of Darwin's Finches. Princeton University Press, 1999, ISBN 0-691-04866-5
- Peter R. Grant, B. Rosemary Grant: Genetics and the Origin of Bird Species. In: Proceedings of the National Academy of Sciences. Volume 94, No. 15, 1997, pp. 7768-7775; Full text (PDF)
- B. Rosemary Grant, Peter R. Grant: Fission and fusion of Darwin's finches populations. In: Philosophical Transactions of the Royal Societey B. Volume 363, No. 1505, 2008 pp. 2821-2829; doi : 10.1098 / rstb.2008.0051
- Peter R. Grant, B. Rosemary Grant: Pedigrees, assortative mating and speciation in Darwin's finches. In: Philosophical Transactions of the Royal Societey B. Volume 275, No. 1635, 2008, pp. 661-668, doi : 10.1098 / rspb.2007.0898
- A. Sato, C. O'Huigin, F. Figuera, PR Grant, BR Grant, H. Tichy, J-Klein: Phylogeny of Darwin's finches as revealed by mtDNA sequences. In: Proceedings of the National Academy of Sciences. Volume 96, No. 9, 1999, pp. 5101-5106; Full text (PDF)
- Jeffrey Podos: Correlated evolution of morphology and vocal signal structure in Darwin's finches. In: Nature. Volume 409, 2001, pp. 185-188, doi : 10.1038 / 35051570 ; Illustration of the beak shapes