By Ines Fournon Berodia & Andrea Fernandes
When Darwin arrived at the Galápagos Islands he realised the immense diversity of Finches that coexisted and he could only asked himself, how? We will explore a paper by Lamichhaney et al (2015) that gives an insight to the genomics behind the phenomena that Darwin first discovered, evolution.
“One species has been taken and modified for different ends.”
These are the famous words of Charles Darwin written in the second edition of his journal ‘The Voyage’, in which he described one of the most captivating discoveries in evolutionary history, his finches. Darwin’s finches are a group of birds discovered on the Galápagos Islands during his world voyage from 1831 to 1836. He established that these birds had beaks of varying shapes and sizes that were all adapted to their own individual niche. These observations improved the understanding of the origin of species, providing a greater insight to how and why speciation occurs. Darwin’s research played a major role in the development of the modern day theory of evolution. His work on finches can perhaps be described as one of his most significant discoveries, so much so, that research in this field is still being presented today.
Figure 1 (National Geographic, 2015): The varying morphologies of Darwin’s finches.
A study conducted by Lamichhaney et al (2015) sequenced the autosomal genome of 120 individuals, representing all species of Darwin’s finches. They aimed to investigate how the species evolved, the formation of new species and adaptive evolution, to understand the evolvement of an individual to adapt to specific surroundings. As well as providing evidence of hybridisation of two species, that gave rise to a new species of mixed ancestry. Finally, the researchers explore which gene or genes are linked to the vast diversity of beak shapes.
Gene flow, hybrids and one gene only
In this study, morphological and mitochondrial data supported the phylogenies proposed by Darwin. Consequently, this showed that there was a consistency in the data, however by looking at the distribution and morphological differences of 3 different populations of Geospiza species they found conflicts in data, showing evidence of gene flow. Therefore, gene flow was investigated by looking at the population of G. conirostris on the islands of Española and Genovesa.
There was evidence of gene flow between the most closely related populations in Española and Genovesa and therefore a genome wide scan was performed. They obtained 15 significant regions in the genome related to beak morphology, 6 of them craniofacial genes. However, the largest region with most significant values corresponded to the ALX1 gene. The ALX1 gene, which can be found in other vertebrates, has been established as the gene controlling the different beak morphologies.
The study was able to pinpoint the different polymorphic alleles caused by the ALX1 gene. They revealed that PP homozygous correspond mostly to long pointed beaks, BB homozygous to blunt beaks and the BP heterozygous to a hybrid form of the two. Moreover, this pattern was also observed on the populations in Santa Cruz and Daphne Major islands, showing that this phenomenon occurred parallel in other locations. This gives evidence that recent introgressive hybridisationoccurred, giving path to new beak morphologies.
Will there be more beaks and finches?
The evidence of hybrid beak morphologies could be explained by the existence of a niche allowing these new morphologies to thrive in the environment. Further and continuous study of these species would allow a better understanding and the ability to follow the diversification of the species as the food resources and ecosystems are being affected by current climate change.
- Darwin, C. “Narrative of the Surveying Voyages of His Majesty’s Ships Adventure and Beagle”, Henry Colburn, London, 1839
- Lamichhaney, S., Berglund, J. “Evolution of Darwin’s finches and their beaks revealed by genome sequencing” Nature 2015: 518; 371–375 doi: 10.1038/nature14181
- Figure: NatGeo Education, One Of ‘Darwin’s Finches’ Struggles To Survive, 05/12/2015
Reviewers: Patrick Hennessey, Tudor Aniculaesei, Zanna Johansen & Lina Holmstrom
Editors: Tom Lillie & Nathalie Bacardi Santa Cruz
Web Editors: Ines Fournon Berodia & Patrick Hennessey
Senior Editor: Dr Yannick Wurm