Scientists have sequenced the genome of one of the Galápagos finches that inspired Charles Darwin's theory of evolution by natural selection. The genome of the medium ground finch (Geospiza fortis) was sequenced by an international collaboration between the Genome 10K Project and BGI (Beijing Genomics Institute, Shenzhen) and is available through the UCSC Genome Browser.
I recently asked Dr. Peter Grant, AAAS fellow and emeritus professor of ecology and evolutionary biology at Princeton University, about this exciting development. Grant has studied the finches on Daphne Major, an island in the Galápagos archipelago, for nearly four decades. With his wife and fellow evolutionary biologist Rosemary, he has observed and documented evolution in action in the birds known as Darwin's finches.
AAAS MC: The genome of the medium ground finch (Geospiza fortis) is among the first of a planned 100 genomes of vertebrate species to be sequenced and released by an international collaboration between the Genome 10K project and BGI. Tell me a little bit about this particular finch, and why it is so interesting to evolutionary biologists.
Dr. Peter Grant, AAAS fellow and emeritus professor of ecology and evolutionary biology at Princeton University: The medium ground finch is one of the most abundant species that visitors to the Galápagos see. Scientists, including ourselves, have taken advantage of this and have studied their feeding ecology and breeding biology to increase our understanding of how evolution occurs, and the reasons why 14 species of finches have evolved from a common ancestor in the last two to three million years. It has also provided some tantalizing hints that human activity on one of the islands alters the food supply in such a way as to steer further evolution in a different direction.
AAAS MC: You, along with your wife Rosemary Grant, have studied these finches for nearly forty years and documented evolution by natural selection occurring in real time. What makes this long-term, detailed field research approach to questions of evolution so fruitful?
Grant: Studying finches on a small, uninhabited island for a long time reveals the natural forces that cause evolution. Small islands have relatively small populations, so that most if not all individuals can be captured, measured and genotyped, admittedly after a lot of hard work. These benefits have enabled us to witness evolutionary change and put our fingers on the causes. Two major results stand out. First, natural selection occurs when the environment changes, and food becomes scarce. Sometimes this is caused by competition for food with members of the same species, and at other times with other species. Second, species evolve through introgressive hybridization; they exchange genes and undergo changes in beak shape as a result. Neither of these discoveries could be made easily in other settings, or studied in such a direct way.
AAAS MC: How do you think the available sequenced genome of the finch will affect research on these birds going forward?
Grant: I see two immediate benefits from the genome sequence of the medium ground finch. First, it will provide the foundations for a comparative study of genome diversity among the 14 species of Darwin's finches. In fact, part of the foundation has already been laid: The genome of a second species, the large ground finch Geospiza magnirostris, was sequenced last year through the efforts of our colleagues Jonathan Eisen and Arkhat Abzhanov, and the data have been posted. Second, the genome sequence will supply information about individual genes that have known or suspected effects upon the structure and function of adult finches. I am thinking of such things as genes already known to be involved in the development of finch beaks, of genes known more broadly to affect growth patterns of vertebrates, and then genes that have been studied in the brains of zebra finches in connection with neurobiological research on song learning and reception. In the future, many other genes will be identified that will be useful in fields such as immunology and metabolic physiology, to name just two.
AAAS MC: More generally, how do see you the rise of genome sequencing affecting the study of evolutionary biology and ecology?
Grant: We have entered a new era of research into population biology. Genome sequencing is placing information and tools in the hands of biologists that can now be used to understand how populations evolve by undergoing genetic change. The ecological performance of populations—their rise and fall in numbers, their spread and contraction in large-scale distribution, changes in diets, etc.—will be better understood. An obvious subfield that will benefit is disease ecology. The availability of genome sequences will lead to a closer integration of evolution and ecology, with effects ramifying through ecological disciplines from the behavior of individuals within populations, to the nutrient and energy properties of ecosystems, and even to conservation of endangered organisms.
AAAS MC: Do you still travel to the Galápagos to observe the finches? What new research are you working on?
Grant: Yes, we are continuing with research on the finches, and our main focus currently is on the long-term consequences of hybridization, because we think that an exchange of genes between species before they become very different from each other provides them with enhanced potential for further evolution under favorable environmental conditions.