Adaptive radiation of Darwins finches: consequences for parasite diversification and susceptibility to emerging diseases

University of Exeter - College of Life and Environmental Science

Main supervisor: Dr Camille Bonneaud (Centre for Ecology and Conservation, University of Exeter)

Title: Adaptive radiation of Darwin’s finches: consequences for parasite diversification and susceptibility to emerging diseases

The Darwin’s finches of the Galapagos archipelago represent a rare example of evolution-in-action, and so are amongst the most iconic animals in evolutionary biology. While our understanding of the adaptive radiation of Darwin’s finches has been massively furthered by whole genome sequencing approaches (1), the consequences of rapid evolutionary diversification on their endemic parasites are unknown. Intriguingly, repeated bouts of introgressive hybridization between sympatric Darwin’s finch species has led to genome-scale secondary assimilation, with several species clustering phylogenetically more closely to heterospecifics in sympatry than to conspecifics in allopatry (1). This widespread pattern of reticulate evolution is likely to complicate patterns of co-speciation between Darwin’s finches and their parasites. Furthermore, human activities are increasing the exposure of finches to novel pathogens, but whether more closely related species of Darwin’s finches exhibit similar levels of susceptibility to emerging diseases remains to be tested. 

Here we propose to test: 

(1) The extent to which endemic parasites have co-speciated with their Darwin’s finch hosts; 

(2) Whether more closely related Darwin’s finch species display similar levels of susceptibility to a recently introduced pathogen; 

(3) The ecological and evolutionary implications of pathogen speciation and host susceptibility.

Previous work on other avian species has shown that, while directly transmitted parasites tend to co-speciate with their hosts (2), vector-borne parasites can shift between distantly-related hosts before undergoing rapid speciation (3). To test for patterns of co-speciation, we will screen Darwin’s finches for blood parasites (vector-borne) and gut coccidiae parasites (directly transmitted). In addition, to test whether the phylogenetic relationship between Darwin’s finch species predicts their susceptibility to novel diseases, we will screen these species for a recently arrived viral pox pathogen (direct and vector borne transmission). This project will be conducted with our CASE partner Dr Jaime Chaves (University San Francisco Quito, Ecuador), who has been working in the Galapagos for >10 years and holds all the necessary collection permits (4). We are also in the unusual position to have access to a unique repository of blood samples collected over >10 years from 7 Darwin’s finch species and 12 islands (4). Screening this repository, along with samples collected over the course of this study, will greatly improve our understanding on host-parasite co-evolutionary relationships in an emblematic system. 

Literature cited:

(1) S. Lamichhaney et al. Evolution of Darwin’s finches and their beaks revealed by genome sequencing. Nature 518, 371–5 (2015).

(2) D. Clayton et al. Host defense reinforces host–parasite cospeciation. Proc Natl Acad Sci USA 100, 15694 (2003).

(3) R. E. Ricklefs et al. Species formation by host shifting in avian malaria parasites. Proc Natl Acad Sci USA 111, 14816–14821 (2014)

(4) J. A. Chaves et al. Genomic variation at the tips of the adaptive radiation of Darwin's finches. Mol Ecol doi: 10.1111/mec.13743 (2016).

Please see for full details regarding applications.

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