Darwin's finches
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{{Taxobox
| name = Darwin's Finches
| image = Darwin's finches.jpeg
| image_width = 220px
| image_caption = [[Large Ground-finch]], [[Medium Ground-finch]]<br/>[[Small Tree-finch]], [[Warbler Finch]]
| regnum = [[Animal]]ia
| phylum = [[Chordata]]
| classis = [[Aves]]
| ordo = [[Passeriformes]]
| familia = [[Emberizidae]]
| subdivision_ranks = [[Genus|Genera]]
| subdivision =
''[[Geospiza]]''<br>
''[[Camarhynchus]]''<br>
<!-- ''[[Platyspiza]]''<br> validity of distinction from Camarhynchus to be determined before inclusion-->
''[[Certhidea]]''<br>
''[[Pinaroloxias]]''
}}
'''Darwin's finches''' (also known as the '''Galápagos Finches''') are 13 or 14 different closely related [[species]] of [[finch]]es that [[Charles Darwin]] collected on the [[Galápagos Islands]] during [[Second voyage of HMS Beagle|the voyage of the ''Beagle'']]. Thirteen reside on the Galápagos Islands and one on [[Cocos Island]].
The birds are all about the same size (10–20 cm). The most important differences between species are in the size and shape of their beaks, and the beaks are highly adapted to different food sources. The birds are all brownish or black. Their behaviour differs, and they have different song melodies.
==Darwin's theory==
Although these birds were to play an important part in the [[inception of Darwin's theory]] of [[evolution]] by [[natural selection]], at the time of [[Second voyage of HMS Beagle|the survey voyage of]] [[HMS Beagle|HMS ''Beagle'']] Darwin had no idea of their significance. It is often assumed that when he saw the finches on the islands this inspired the theory, but this is not true: Darwin believed that they were not closely related when he encountered them; indeed he thought that most of these birds were not finches at all (Sulloway 1982). He collected various birds, and noted that [[mockingbird]]s differed depending on which island they came from. When organising his notes on the last stage of the return journey, Darwin wrote that if his growing suspicions about the mockingbirds and tortoises were correct, “such facts undermine the stability of Species”, then cautiously added “would” before “undermine”. He later wrote that such facts “seemed to me to throw some light on the origin of species”.<ref>{{Harvnb|Eldredge|2006}}</ref>
Following his return from the voyage, Darwin presented the finches to the [[Geological Society of London]] at their meeting on [[4 January]] [[1837]], along with other mammal and bird specimens he had collected. The bird specimens, including the finches, were given to [[John Gould]], the famous English [[ornithologist]], for identification. Gould set aside his paying work and at the next meeting on [[10 January]] reported that birds from the [[Galápagos Islands]] which Darwin had thought were [[Icterid|blackbirds]], "[[Grosbeak|gross-beaks]]" and [[finch]]es were in fact ''"a series of ground Finches which are so peculiar"'' as to form ''"an entirely new group, containing 12 species."'' This story made the newspapers.<ref>{{harvnb|Desmond|Moore|1991|p=209}}</ref>
In March Darwin met Gould again, learning that his Galápagos "[[wren]]" was another species of finch and the [[mockingbird]]s he had labelled by island were separate species rather than just varieties, with relatives on the [[South America]]n mainland. By mid March he realised that the original immigrants had somehow become altered to produce an array of new species. Darwin had not bothered to label his finches by island, but others on the expedition had taken more care. He now sought specimens collected by Captain [[Robert FitzRoy]] and crewmen. From them he was able to establish that the species were uniquely related to individual islands, giving him the idea that somehow in this geographical isolation these different species could have been formed from a small number of common ancestors so that each was modified to suit "different ends" as Darwin comments in his ''[[The Voyage of the Beagle|Journal and Remarks]]''.<ref>{{harvnb|Desmond|Moore|1991|p=220, 228}}</ref> He again commented on this divergence of species of birds in the Galápagos in ''[[On the Origin of Species]]''.<ref>{{harvnb|Darwin|1859|p=[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F373&pageseq=408 390].}}</ref>
The term ''Darwin's Finches'' was first applied in 1936, and popularized in 1947 by [[David Lack]]. Later, [[Peter and Rosemary Grant]] conducted extensive research in documenting evolutionary change among the finches. Beginning in 1973, the pair spent many years tracking thousands of individual finches across several generations, showing how individual species changed in response to environmental changes. ''[[The Beak of the Finch]]'' by [[Jonathan Weiner]] is a book about the finches, highlighting the Grants' research.
==Taxonomy==
===Family===
For some decades taxonomists have placed these birds in the family [[Emberizidae]] with the New World sparrows and Old World buntings (Sulloway 1982). However, the [[Sibley-Ahlquist taxonomy]] puts Darwin's finches with the [[tanager]]s (Monroe and Sibley 1993), and at least one recent work follows that example (Burns and Skutch 2003). The [[American Ornithologists' Union]], in its [[North America]]n check-list, places the Cocos Island Finch in the Emberizidae but with an asterisk indicating that the placement is probably wrong (AOU 1998–2006); in its tentative [[South America]]n check-list, the Galápagos species are ''incertae sedis'', of uncertain place (Remsen et al. 2007).
===Species===
*Genus ''[[Geospiza]]''
**[[Large Cactus-finch]], ''Geospiza conirostris''
**[[Sharp-beaked Ground-finch]], ''Geospiza difficilis''
***[[Vampire Finch]], ''Geospiza difficilis septentrionalis''
**[[Medium Ground-finch]], ''Geospiza fortis''
**[[Small Ground-finch]], ''Geospiza fuliginosa''
**[[Large Ground-finch]], ''Geospiza magnirostris''
***Darwin's Large Ground-finch, ''Geospiza magnirostris magnirostris'' - possibly [[extinct]] ([[1957]]?)
**[[Common Cactus-finch]], ''Geospiza scandens''
*Genus ''[[Camarhynchus]]''
**[[Vegetarian Finch]], ''Camarhynchus crassirostris'' - sometimes separated in ''Platyspiza''
**[[Large Tree-finch]], ''Camarhynchus psittacula''
**[[Medium Tree-finch]], ''Camarhynchus pauper''
**[[Small Tree-finch]], ''Camarhynchus parvulus''
**[[Woodpecker Finch]], ''Camarhynchus pallidus'' - sometimes separated in ''Cactospiza''
**[[Mangrove Finch]], ''Camarhynchus heliobates''
*Genus ''Certhidea''
**[[Warbler Finch]], ''Certhidea olivacea''
*Genus ''Pinaroloxias''
**[[Cocos Island Finch]], ''Pinaroloxias inornata''
== Text from the ''Voyage of the Beagle'' ==
In the first edition of ''[[The Voyage of the Beagle]]'' Darwin simply described the finches without mentioning his thoughts at that time, merely stating that "It is very remarkable that a nearly perfect gradation of structure in this one group can be traced in the form of the beak, from one exceeding in dimensions that of the largest gros-beak, to another differing but little from that of a warbler."<ref>{{harvnb|Darwin|1839|p=[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F10.3&pageseq=481 462].}}</ref> The book was written in the months after [[John Gould]] had revealed that the birds which Darwin had thought to be unrelated were different species of finches.<ref>{{harvnb|Desmond|Moore|1991|p=248}}</ref> The proofs were finished later that year, but the book did not go into print until 1839. By the time of the second edition in 1845 Darwin had brought together his theory, and he cautiously added two closing sentences hinting at his ideas.<ref>{{harvnb|Darwin|1887}}</ref>
{{quotation|The remaining land-birds form a most singular group of finches, related to each other in the structure of their beaks, short tails, form of body and plumage: there are thirteen species, which Mr. Gould has divided into four subgroups. All these species are peculiar to this archipelago; and so is the whole group, with the exception of one species of the sub-group ''Cactornis'', lately brought from Bow Island, in the Low Archipelago. Of ''Cactornis'', the two species may be often seen climbing about the flowers of the great cactus- trees; but all the other species of this group of finches, mingled together in flocks, feed on the dry and sterile ground of the lower districts. The males of all, or certainly of the greater number, are jet black; and the females (with perhaps one or two exceptions) are brown. The most curious fact is the perfect gradation in the size of the beaks in the different species of ''Geospiza'', from one as large as that of a hawfinch to that of a chaffinch, and (if Mr. Gould is right in including his sub-group, ''Certhidea'', in the main group) even to that of a warbler. The largest beak in the genus ''Geospiza'' is shown in Fig. 1, and the smallest in Fig. 3; but instead of there being only one intermediate species, with a beak of the size shown in Fig. 2, there are no less than six species with insensibly graduated beaks. The beak of the sub-group ''Certhidea'', is shown in Fig. 4. The beak of ''Cactornis'' is somewhat like that of a starling, and that of the fourth subgroup, ''Camarhynchus'', is slightly parrot-shaped. Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends. In a like manner it might be fancied that [[Galapagos Hawk|a bird originally a buzzard]], had been induced here to undertake the office of the carrion-feeding [[Caracara|Polybori]] of the American continent.<ref>{{harvnb|Darwin|1845|p=[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F14&pageseq=393 380].}}</ref>}}
==Real-time evolution==
One of Darwin's finches (''Geospiza fortis'') helped prove their namesake's theory of [[evolution]] when scientists observed a shift in the species to birds with smaller beaks after competition was introduced by the arrival of another species with larger beaks. This happened over a twenty year span and was the first instance where scientists were able to document the type of evolutionary change known as character displacement from the start to completion of the process.<ref>{{Citation |last=Goudarzi |first=Sara |title=Scientists watch Darwin’s finches evolve |url=http://www.msnbc.msn.com/id/13845002/ |accessdate=2007-11-07}}</ref>
==Molecular basis of beak evolution==
In 2004 a group led by Harvard biologist Dr.Cliff Tabin proposed that the bone morphogenetic protein 4 (BMP4) and its differential expression during development was responsible for the variation in beaks' size and shape among finches. BMP4 acts in the developing embryo to lay down skeletal features (including the beak). They supported their in situ hybridization data by functional experiments in the model organism ''Gallus gallus'', getting the hypothesized transformations. The work was published in [[Science (journal)|Science]].<ref>
{{cite journal
| last = Abzhanov
| first = Arhat
| authorlink =
| coauthors = Meredith Protas, B. Rosemary Grant, Peter R. Grant, Clifford J. Tabin
| date = [[September 3]] [[2004]]
| title = Bmp4 and Morphological Variation of Beaks in Darwin's Finches
| journal = Science
| volume = 305
| issue = 5689
| pages = 1462–1465
| publisher = [[American Association for the Advancement of Science|AAAS]]
| location = USA
| issn = 0036-8075
| pmid = 15353802
| doi = 10.1126/science.1098095
| oclc = 1644869
| url = http://www.sciencemag.org/cgi/content/abstract/sci;305/5689/1462
| accessdate = 2008-03-8
}} </ref> As Published in ''Nature'' in August 2006, the same group showed that the different beak shapes of Darwin's finches develop also due to slightly different timing and spatial expression of a gene called calmodulin (CaM).<ref> {{cite journal
| last = Abzhanov
| first = Arhat
| coauthors = Winston P. Kuo, Christine Hartmann, B. Rosemary Grant, Peter R. Grant and Clifford J. Tabin
| date = [[August 3]],[[2006]]
| title = The calmodulin pathway and evolution of elongated beak morphology in Darwin's finches
| journal = Nature
| volume = 442
| pages = 563–567
| publisher = Nature Publishing Group
| location = UK
| issn = 0028-0836
| pmid = 16885984
| doi = 10.1038/nature04843
| oclc = 1586310
| url = http://www.nature.com/nature/journal/v442/n7102/abs/nature04843.html
| accessdate = 2008-03-8
}}</ref> Calmodulin acts in a similar way to BMP4, affecting some of the features of beak growth. Using microarray data and early embryo staining from each of the species, this group could show how the different beak shapes were obtained. Additionally, they got similar but partial transformations of the developing beak by providing elevated calmodulin in chick (''G.gallus'') embryos. The authors propose changes in the temporal and spatial expression of these two factors as possible ways of obtaining the beak diversity observed but do not explain how this may have happened.
==Notes==
{{reflist}}
== References ==<!-- AmNat166:56; BiolJLinnSoc74:267; BullBritMusNatHistZool43:49; PNAS96:5101; ProcRSocLondB266:321; ZoolJLinnSoc118:119 -->
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*{{cite web |url=http://www.vqronline.org/articles/2006/spring/eldredge-confessions-darwinist/ |title=VQR - Confessions of a Darwinist |accessdate=2007-12-26 |author=Niles Eldredge |authorlink=Niles Eldredge |date= Spring 2006 |publisher=The Virginia Quarterly Review |pages=32–53 }}
*{{cite web | title = Check-list of North American Birds | year = 1998–2006 | url = http://www.aou.org/checklist/index.php3 | accessdate = 2007-04-09 | publisher = [[American Ornithologists' Union]]}}
*{{cite book | author = Kevin J. Burns and [[Alexander Skutch|Alexander F. Skutch]] | year = 2003 | title = The Firefly Encyclopedia of Birds | chapter = Tanagers and Tanager-Finches | editor = [[Christopher Perrins]], ed. | pages = 629–631 | publisher = Firefly Books | id = ISBN 1-55297-777-3 | url = http://www.amazon.com/Firefly-Encyclopedia-Birds-Christopher-Perrins/dp/1552977773/ref=si3_rdr_bb_product/103-5704731-0011011 | accessdate = 2007-04-09}} It is not clear whether this placement was made by Burns and Skutch or by Perrins.
*Burt L. Monroe and Charles G. Sibley, ''[http://books.google.com/books?vid=ISBN0300070837 A World Checklist of Birds]''. New Haven, Conn.: Yale University Press (1993). ISBN 0-300-07083-7. Accessed 2007-04-09. Monroe and Sibley consider the tanagers to be a tribe (Thraupini) of a big family [[Fringillidae]] rather than a family of their own ([[Thraupidae]]).
*J. V. Remsen, Jr., C. D. Cadena, A. Jaramillo, M. Nores, J. F. Pacheco, M. B. Robbins, T. S. Schulenberg, F. G. Stiles, D. F. Stotz, and K. J. Zimmer. [Version 2007-04-05.] ''[http://www.museum.lsu.edu/~Remsen/SACCBaseline.html A classification of the bird species of South America]''. American Ornithologists' Union. Accessed 2007-04-09.
*Frank J. Sulloway, [http://darwin-online.org.uk/content/frameset?itemID=A86&viewtype=image&pageseq=3 The ''Beagle'' collections of Darwin's finches (Geospizinae)] (1982), ''Bulletin of the British Museum (Natural History) Historical Series'' 43, No. 2: pp 49-94
==External links==
{{Commonscat|Geospizinae}}
* Sulloway, F.J. (1982): "Darwin and his finches: the evolution of a legend". ''J. Hist. Biol. 15: p.1–53
* [http://www.nature.com/nature/journal/v409/n6817/fig_tab/409185a0_F1.html Different bills and song melodies]
*''Genetics and the Origin of Birds Species'', Grant and Grant in [http://www.pnas.org/cgi/reprint/94/15/7768 PNAS]
*[http://www.pnas.org/cgi/content/full/96/9/5101?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&author1=Sato&andorexactfulltext=and&searchid=1081449482400_6822&stored_search=&FIRSTINDEX=0&sortspec=relevance&volume=96&firstpage=5101&resourcetype=1 Sato ''et al'' Phylogeny of Darwin's finches as revealed by mtDNA sequences in PNAS]
*[http://www.galapagosonline.com/Galapagos_Natural_History/Birds_and_Animals/Birds/Darwins_Finches.html Galápagos Online. Darwin's Finches.]
*[http://www.galapagosonline.com/Galapagos_Natural_History/Birds_and_Animals/Birds/Bird_List.html#Mimidae Galapagos Online. List of birds of the Galapagos Islands.]
*[http://www.livescience.com/animalworld/060713_darwin_finch.html Darwin's Finches Evolve Before Scientists' Eyes]: new developments reported [[13 July]] [[2006]]
*[http://fink.sourceforge.net/faq/general.php?phpLang=en#what Fink F.A.Q.] Darwin's finches inspired the naming of the [[Fink]] project, a collaborative initiative for porting open source software to the Darwin platform to enable its use and evolution in the Apple Mac OS X environment. "Fink" is the German name for "finch."
*[http://www.nature.com/nature/journal/v442/n7102/abs/nature04843.html Aug 2006 Nature Article] that shows how modulation of a certain gene during development can account for the differences seen in beak shape.
*[http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/Speciation.html Speciation] Kimball's Biology Pages
[[Category:Charles Darwin|Finches]]
[[Category:History of evolutionary biology]]
[[Category:Evolution by taxon|Finches]]
[[Category:Geospizini| ]]
[[Category:Tribes of birds]]
[[Category:Endemic birds of the Galápagos Islands]]
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