Faculty Opinions recommendation of Gene flow, ancient polymorphism, and ecological adaptation shape the genomic landscape of divergence among Darwin's finches.

This study addresses the extent and consequences of gene exchange between populations of Darwin's finches. Four species of ground finches ( Geospiza ) inhabit the small island of Daphne Major in the centre of the Galápagos archipelago. We undertook a study of microsatellite DNA variation at 16 loci in order to quantify gene flow within species owing to immigration and between species owing to hybridization. A combination of pedigrees of observed breeders and assignments of individuals to populations by the program S tructure enabled us to determine the frequency of gene exchange and the island of origin of immigrants in some cases. The relatively large populations of Geospiza fortis and G. scandens receive conspecific immigrants at a rate of less than one per generation. They exchange genes more frequently by rare but repeated hybridization. Effects of heterospecific gene flow from hybridization are not counteracted by lower fitness of the offspring. As a result, the standing genetic variation of the two main resident populations on Daphne Major is enhanced to a greater extent by introgressive hybridization than through breeding with conspecific immigrants. Immigrant G. fuliginosa also breeds with G. fortis . Conspecific immigration was highest in the fourth species, G. magnirostris . This species is much larger than the other three and perhaps for this reason it has not bred with any of them. The source island of most immigrants is probably the neighbouring island of Santa Cruz. Evolutionary change may be inhibited in G. magnirostris by continuing gene flow, but enhanced in G. fortis and G. scandens by introgressive hybridization.

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Divergence with gene flow as facilitated by ecological differences: within-island variation in Darwin's finches

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2009.0314 ◽

2010 ◽

Vol 365 (1543) ◽

pp. 1041-1052 ◽

Cited By ~ 61

Author(s):

Luis Fernando de León ◽

Eldredge Bermingham ◽

Jeffrey Podos ◽

Andrew P. Hendry

Keyword(s):

Gene Flow ◽

Allelic Variation ◽

Genetic Differences ◽

Darwin's Finches ◽

Darwin’S Finches ◽

The Face ◽

Beak Size ◽

Additional Support ◽

Divergence With Gene Flow ◽

Ecological Differences

Divergence and speciation can sometimes proceed in the face of, and even be enhanced by, ongoing gene flow. We here study divergence with gene flow in Darwin's finches, focusing on the role of ecological/adaptive differences in maintaining/promoting divergence and reproductive isolation. To this end, we survey allelic variation at 10 microsatellite loci for 989 medium ground finches ( Geospiza fortis ) on Santa Cruz Island, Galápagos. We find only small genetic differences among G. fortis from different sites. We instead find noteworthy genetic differences associated with beak. Moreover, G. fortis at the site with the greatest divergence in beak size also showed the greatest divergence at neutral markers; i.e. the lowest gene flow. Finally, morphological and genetic differentiation between the G. fortis beak-size morphs was intermediate to that between G. fortis and its smaller ( Geospiza fuliginosa ) and larger ( Geospiza magnirostris ) congeners. We conclude that ecological differences associated with beak size (i.e. foraging) influence patterns of gene flow within G. fortis on a single island, providing additional support for ecological speciation in the face of gene flow. Patterns of genetic similarity within and between species also suggest that interspecific hybridization might contribute to the formation of beak-size morphs within G. fortis .

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Genes controlling beak size and shape in Darwin's finches

AccessScience ◽

10.1036/1097-8542.yb170504 ◽

2017 ◽

Keyword(s):

Darwin's Finches ◽

Size And Shape ◽

Darwin’S Finches ◽

Beak Size

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DONOHUE, K. (editor). Darwin's finches: readings in the evolution of a scientific paradigm. University of Chicago Press, Chicago & London: 2011. Pp. xvi, 492; illustrated. Price US$ 45.00, £ 29.00 (paperback). ISBN: 978-0-226-15771-9.

Archives of Natural History ◽

10.3366/anh.2012.0088 ◽

2012 ◽

Vol 39 (1) ◽

pp. 188-189

Author(s):

T. R. Birkhead

Keyword(s):

University Of Chicago ◽

Scientific Paradigm ◽

Darwin's Finches ◽

Darwin’S Finches ◽

University Of Chicago Press

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Isotopic Niche Segregation among Darwin’s Finches on Santa Cruz Island, Galápagos

Diversity ◽

10.3390/d13040147 ◽

2021 ◽

Vol 13 (4) ◽

pp. 147

Author(s):

Mariana Villegas ◽

Catherine Soos ◽

Gustavo Jiménez-Uzcátegui ◽

Shukri Matan ◽

Keith A. Hobson

Keyword(s):

Three Dimensional ◽

Sympatric Species ◽

Isotopic Niche ◽

Museum Specimens ◽

Santa Cruz Island ◽

Santa Cruz ◽

Δ13c And Δ15n ◽

Darwin's Finches ◽

Darwin’S Finches ◽

Foraging Guilds

Darwin’s finches are a classic example of adaptive radiation involving differential use of dietary resources among sympatric species. Here, we apply stable isotope (δ13C, δ15N, and δ2H) analyses of feathers to examine ecological segregation among eight Darwin’s finch species in Santa Cruz Island, Galápagos collected from live birds and museum specimens (1962–2019). We found that δ13C values were higher for the granivorous and herbivorous foraging guilds, and lower for the insectivorous finches. Values of δ15N were similar among foraging guilds but values of δ2H were higher for insectivores, followed by granivores, and lowest for herbivores. The herbivorous guild generally occupied the largest isotopic standard ellipse areas for all isotopic combinations and the insectivorous guild the smallest. Values of δ2H provided better trophic discrimination than those of δ15N possibly due to confounding influences of agricultural inputs of nitrogen. Segregation among guilds was enhanced by portraying guilds in three-dimensional isotope (δ13C, δ15N, and δ2H) space. Values of δ13C and δ15N were higher for feathers of museum specimens than for live birds. We provide evidence that Darwin’s finches on Santa Cruz Island tend to be generalists with overlapping isotopic niches and suggest that dietary overlap may also be more considerable than previously thought.

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