OMIA 001992-48881 : Beak size in Geospiza |
By the time of the second edition of this journal, published in 1845, Darwin had more to say on the variation in beak shape and size: "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 sub-group, 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. [pp. 379-380]". The reference to figures relates to a plate in the 1845 journal, illustrating the contrasting beak shapes and sizes of four Galapagos finches.
Interestingly, Darwin makes no mention of Galapagos finches in any edition of Origin of Species, because (despite his earlier surmises above), he never had sufficient information on the available specimens to enable him to draw firm conclusions about evolution. Ironically, it was not until many decades after Darwin's death that sufficient information had been gathered on Galapagos finches (see, e.g., Lack, 1947) to enable them to become a classic textbook example of evolution.
Mapping: Lamichhaney et al. (2016) sequenced 10 each of six Galapagos finch species: small, medium and large ground finches and small, medium and large tree finches. Comparison of large vs small, large vs medium, and medium vs small (pooled across ground and tree species, and separately in each) identified a 525kb region that showed the strongest differentiation in all contrasts. This region contains four genes, the most likely candidate being HMGA2, which is associated with size in mice, humans, horses (see OMIA 001968-9796) and dogs (see OMIA 001968-9615). Molecular basis: Lamichhaney et al. (2016) genotyped a diagnostic SNP for the two HMGA2 haplotypes in 133 medium ground finches and discovered that this locus showed a highly significant additive effect on beak size, accounting for "as much as 27% of the phenotypic variance [in beak size] in this population". Comparison of medium ground finches from the island of Daphne Major that survived or died in the 2004-2005 drought led Lamichhaney et al. (2016) to conclude that HMGA2 caused about 30% of the shift in beak size and "the relationship between HMGA2 and fitness was mediated entirely by the effect of this locus on beak size or associated craniofacial bones or muscles". (with thanks to Leif Andersson for feedback on an earlier version of the text on this page) Associated gene:Symbol | Description | Species | Chr | Location | OMIA gene details page | Other Links |
---|---|---|---|---|---|---|
HMGA2 | high mobility group AT-hook 2 | Geospiza fortis | - | no genomic information (-..-) | HMGA2 | Homologene, Ensembl, NCBI gene |
References
Note: the references are listed in reverse chronological order (from the most recent year to the earliest year), and alphabetically by first author within a year.
2016 | Lamichhaney, S., Han, F., Berglund, J., Wang, C., Almén, M.S., Webster, M.T., Grant, B.R., Grant, P.R., Andersson, L. : | |
A beak size locus in Darwin's finches facilitated character displacement during a drought. Science 352:470-4, 2016. Pubmed reference: 27102486. DOI: 10.1126/science.aad8786. | ||
2010 | Abzhanov, A. : | |
Darwin's Galapagos finches in modern biology. Philos Trans R Soc Lond B Biol Sci 365:1001-7, 2010. Pubmed reference: 20194163. DOI: 10.1098/rstb.2009.0321. | ||
2009 | Hendry, A.P., Huber, S.K., De León, L.F., Herrel, A., Podos, J. : | |
Disruptive selection in a bimodal population of Darwin's finches. Proc Biol Sci 276:753-9, 2009. Pubmed reference: 18986971. DOI: 10.1098/rspb.2008.1321. | ||
2007 | Schneider, R.A. : | |
How to tweak a beak: molecular techniques for studying the evolution of size and shape in Darwin's finches and other birds. Bioessays 29:1-6, 2007. Pubmed reference: 17187350. DOI: 10.1002/bies.20517. | ||
2006 | Abzhanov, A., Kuo, W.P., Hartmann, C., Grant, B.R., Grant, P.R., Tabin, C.J. : | |
The calmodulin pathway and evolution of elongated beak morphology in Darwin's finches. Nature 442:563-7, 2006. Pubmed reference: 16885984. DOI: 10.1038/nature04843. | ||
Hendry, A.P., Grant, P.R., Rosemary Grant, B., Ford, H.A., Brewer, M.J., Podos, J. : | ||
Possible human impacts on adaptive radiation: beak size bimodality in Darwin's finches. Proc Biol Sci 273:1887-94, 2006. Pubmed reference: 16822748. DOI: 10.1098/rspb.2006.3534. | ||
2005 | Herrel, A., Podos, J., Huber, S.K., Hendry, A.P. : | |
Evolution of bite force in Darwin's finches: a key role for head width. J Evol Biol 18:669-75, 2005. Pubmed reference: 15842496. DOI: 10.1111/j.1420-9101.2004.00857.x. | ||
2004 | Podos, J., Southall, J.A., Rossi-Santos, M.R. : | |
Vocal mechanics in Darwin's finches: correlation of beak gape and song frequency. J Exp Biol 207:607-19, 2004. Pubmed reference: 14718504. | ||
2002 | Grant, P.R., Grant, B.R. : | |
Unpredictable evolution in a 30-year study of Darwin's finches. Science 296:707-11, 2002. Pubmed reference: 11976447. DOI: 10.1126/science.1070315. | ||
2001 | Podos, J. : | |
Correlated evolution of morphology and vocal signal structure in Darwin's finches. Nature 409:185-8, 2001. Pubmed reference: 11196640. DOI: 10.1038/35051570. | ||
1984 | Price, T.D., Grant, P.R., Gibbs, H.L., Boag, P.T. : | |
Recurrent patterns of natural selection in a population of Darwin's finches. Nature 309:787-9, 1984. Pubmed reference: 6738694. | ||
1947 | Lack, D. : | |
Darwin's finches: An Essay on the General Biological Theory of Evolution. Cambridge University Press, Cambridge :, 1947. | ||
1859 | Darwin, C.R. : | |
On the Origin of Species by Means of Natural Selection John Murray, London :, 1859. | ||
1845 | Darwin, C.R. : | |
Journal of researches into the natural history and geology of the countries visited during the voyage of H.M.S. Beagle round the world. John Murray, London :, 1845. | ||
1839 | Darwin, C.R. : | |
Journal of researches into the geology and natural history of the various countries visited by H.M.S. Beagle. John Murray, London :, 1839. |
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- Created by Frank Nicholas on 22 Apr 2016
- Changed by Frank Nicholas on 22 Apr 2016
- Changed by Frank Nicholas on 23 Apr 2016