Darwin’s finches of the Galápagos are classic example of adaptive radiation, having split from a common ancestor into 14 recognized species in the space of a few million years. The different species have beak sizes and shapes that are best suited for feeding on different food types, such as insects, plants, or different seeds sizes. An example of this diversity can be seen here. I have also created a video explaining the radiation:
Our work focuses on the early stages of adaptive radiation. Specifically, some populations of finches within a species have bimodal beak size distributions, with one mode composed of a small-beaked morph (left side of the photo) and the other of a large-beaked morph (right side of the photo). These two morphs have probably arisen because two different resources are available: hard seeds, for which large beaks are most appropriate, and soft seeds, for which small beaks are most appropriate. These sympatric beak-size morphs within species are thus a small-scale version of the differences among established species, suggesting that the morphs can be used to understand the early stages of adaptive radiation. Part of our work is focused on determining whether large- and small-beaked morphs do indeed specialize on different foods (i.e., divergent selection). We are also asking whether this adaptive split has led to assortative mating, reductions in gene flow, and the onset of speciation.
We have also found that a formerly bimodal population of finches has lost this property in concert with an increase in human population size at Academy Bay on Santa Cruz Island (Hendry et al. 2006; De León et al. 2011). This suggests that humans alter food resource distributions in ways that reverse the process of speciation and cause incipient species to fuse back together. We suggest that this change is the result of the introduction of plants and the feeding of finches, both of which may reduce selection against intermediate beak sizes. This improved fitness of intermediate forms thus breaks one of the barriers keeping different beak sizes as separate gene pools – in essence halting or reversing speciation. This research was featured on the CBC radio programs Quirks and Quarks and, more recently, All-In-A-Weekend.
1. Carvajal-Endara, S., A.P. Hendry, N. Emery, and T.J. Davies. 2017. Habitat filtering not dispersal limitation shapes oceanic island floras: species assembly of the Galápagos archipelago. Ecology Letters. In press.
2. Chaves, J.A., E.A. Cooper, A.P. Hendry, J. Podos, L.F. De León, J.A.M. Raeymaekers, W. O. McMillan, and J. A. C. Uy. 2016. Genomic variation at the tips of the adaptive radiation of Darwin’s finches. Molecular Ecology 25:5282-5295. PDF
3. De León, L. F., J. Podos, T. Gardezi, A. Herrel, and A.P. Hendry. 2014. Darwin’s finches and their diet niches: the sympatric co-existence of imperfect generalists. Journal of Evolutionary Biology 27:1093-1104. PDF
4. De León, L. F., G. Rolshausen, E. Bermingham, J. Podos, and A. P. Hendry. 2012. Individual specialization and the seeds of adaptive radiation in Darwin’s finches. Evolutionary Ecology Research 14:365-380. PDF
5. De León, L.F., J.A.M. Raeymaekers, E. Bermingham, J. Podos, A. Herrel, and A.P. Hendry. 2011. Exploring possible human influences on the evolution of Darwin’s finches. Evolution 65:2258-2272. PDF
6. De León, L.F., E. Bermingham, J. Podos, and A.P. Hendry. 2010. 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 365:1041–1052. PDF
7. Hendry, A.P., S.K. Huber, L. De León, A. Herrel, and J. Podos. 2009. Disruptive selection in a bimodal population of Darwin’s finches. Proceedings of the Royal Society B. Biological Sciences 276:753-759. PDF
8. Herrel, A., J. Podos, B. Vanhooydonck, and A.P. Hendry. 2009. Force-velocity trade-off in Darwin’s finch jaw function: a biomechanical basis for ecological speciation? Functional Ecology 23:119-125. PDF
9. Foster, D., J. Podos, and A.P. Hendry. 2008. A geometric morphometric appraisal of beak shape in Darwin’s finches. Journal of Evolutionary Biology 21:263-275. PDF
10. Huber, S.K., L.F. De Leon, A.P. Hendry, E. Bermingham, and J. Podos. 2007. Reproductive isolation of sympatric morphs in a population of Darwin’s finches. Proceedings of the Royal Society B. Biological Sciences 274:1709-1714. PDF
11. Hendry, A.P., P.R. Grant, B.R. Grant, H.A. Ford, M.J. Brewer, and J. Podos. 2006. Possible human impacts on adaptive radiation: beak size bimodality in Darwin’s finches. Proceedings of the Royal Society B. Biological Sciences. 273:1887-1894. PDF.
12. Herrell, J. Podos, S.K. Huber, and A.P. Hendry. 2005. Evolution of bite force in Darwin’s finches: a key role for head width. Journal of Evolutionary Biology 18:669-675. PDF
13. Herrel, A., J. Podos, S.K. Huber, and A.P. Hendry. 2005. Bite performance and morphology in a population of Darwin’s finches: implications for the evolution of beak shape. Functional Ecology. 19:43-48. PDF
“Darwin’s finches are dull to look at, not only in their orderly ranks in museum trays, but also when they hop about the ground or perch in the trees of the Galapagos, making dull unmusical noises.” (Lack 1947)
Back to Hendry lab page.