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Genomic differentiation in small- and large-beaked Nesospiza finches

Duntsch, Laura (2018) BIOM02 20172
Degree Projects in Biology
Popular Abstract
It was in the early 1980s when Peter Ryan from the University of Cape Town started investigating ecological and conservational factors surrounding the endemic Nesospiza finches in the Tristan da Cunha archipelago, a curious case of resource-driven bird diversification in the Southern Atlantic. Ryan and others suggests for the radiation of Tristan finches to have happened around 400,000 years ago, where the finches on Inaccessible Island and Nightingale Island radiated into small-beaked feeding generalists on the one hand-side and rarer large-beaked feeding specialists on the other. What is more, researchers were able to identify two areas associated with beak and body size in the Inaccessible finch genome, but have been as yet unsure about... (More)
It was in the early 1980s when Peter Ryan from the University of Cape Town started investigating ecological and conservational factors surrounding the endemic Nesospiza finches in the Tristan da Cunha archipelago, a curious case of resource-driven bird diversification in the Southern Atlantic. Ryan and others suggests for the radiation of Tristan finches to have happened around 400,000 years ago, where the finches on Inaccessible Island and Nightingale Island radiated into small-beaked feeding generalists on the one hand-side and rarer large-beaked feeding specialists on the other. What is more, researchers were able to identify two areas associated with beak and body size in the Inaccessible finch genome, but have been as yet unsure about those same regions in the Nightingale Island finch.
In my project I wanted to shed more light on the evolution of the two distinct beak sizes in Nesospiza finches by using high-quality re-sequencing data. Did the different beak sizes evolve in allopatry? Has the differentiation event within the beak-size-associated plateau regions happened before or after the colonization of the Tristan da Cunha archipelago?
On Inaccessible Island, I was able to confirm the previously identified plateau regions (FST=1) on both the autosomal chromosome 1 and the sex chromosome Z when comparing finch individuals with small and large beak sizes. On Nightingale Island, where the populations mate assortatively, the differentiation analysis showed a lot more fixed differences small- and large-beaked individuals and confirm a generally more divergent genomic landscape.
Furthermore, a simplified haplotype analysis based on the plateau regions suggests that the small-beak/large-beak differentiation on Inaccessible Island occurred some 80,000 years ago, well after the colonization of the islands (similar on Nightingale Island). At the same, a look into fixed and polymorphic sites within the genomic plateau region in all four finch populations revealed a lot more within-island differences than between islands. Considering that the taxa on both islands seem to have the same genotype, this could be seen as an indication that the divergence process from small-beaked to large-beaked finches happened only once.
Phylogenetic approaches confirm the previously established relationships between the Nesospiza clade on Tristan, the neighbouring Gough Island finches and mainland South America taxa. More elaborate dating and nucleotide diversity analysis are the follow-up steps. (Less)
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author
Duntsch, Laura
supervisor
organization
course
BIOM02 20172
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
8937986
date added to LUP
2018-03-23 15:13:11
date last changed
2018-03-23 15:13:11
@misc{8937986,
  author       = {Duntsch, Laura},
  language     = {eng},
  note         = {Student Paper},
  title        = {Genomic differentiation in small- and large-beaked Nesospiza finches},
  year         = {2018},
}