In search of evolutionary change: Part 1 – An interview with Rosemary Grant

Rosemary Grant

I first met Rosemary Grant back when  I was at the University of British Columbia finishing up my PhD.  The last year and half of a PhD is a slog (well, it was for me) and it was really important to see and hear from scientists, who after decades of studying the same system, were still excited by their work.  One of these scientists was Rosemary Grant.  It was clear in their seminar and the discussion afterwards that despite four decades of studying the Galapagos finches, Rosemary and her partner Peter, had this infectious enthusiasm about their work.  So it made perfect sense  that Rosemary Grant be included in this series.
Recently, the Grants were awarded the 2009 Kyoto Prize for their work “Demonstrating Rapid Evolution Caused by Natural Selection in Response to Environmental Changes” in the basic sciences category.  The two have also co-authored a book called, “How and why species multiply:  The radiation of Darwin’s finches, which narrates their observations about speciation in the Galapagos finches.  And although Rosemary Grant is a professor emeritus at Princeton University, she and her husband Peter continue to travel to and from the Galapogos Islands to do research.  I caught Rosemary after she had returned from a month on the unhabited Daphne Island.

Me:  Describe a little bit about your background.  What was some of the first science you did?

Rosemary:   My interest in Biology began early in life. I grow up in a small village in the English Lake District, where as a child I was able to roam the surrounding fells and fossil-rich carboniferous limestone cliffs, finding wild flowers, butterflies and fossils. My parents encouraged this interest and when I was about 12 years old my Father suggested I should read Darwin’s “Origin of Species”.
I thought that genetics would provide a fundamental approach to understanding the variety of organisms, and I was fortunate to study genetics at Edinburgh University in Professor Conrad Waddington’s department. My first project was an undergraduate thesis on soil amoebae. Among many identical looking amoebae living in the soil one was thought to be pathogenic because it had been found in association with mammals. My genetics training had introduced me to the possible importance of cell surface protein differences, and I was able to unravel the differences between 12 strains of amoeba using what today would be considered rather primitive immunological techniques.
Me: What  led you to work on the evolutionary dynamics of the Galapagos finches?
Rosemary:  Spurred on by this small success I wanted to ask the bigger question: how do populations of organisms maintain such a large amount of genetic and morphological variation and how do they diverge to the point of becoming different species?  When I met Peter, I found he was interested in similar questions but more from an ecologist’s point of view. It was trying to shed light on these questions that led us to our research in the Galapagos.
My PhD project on the Large Cactus Finch on Genovesa Island in the Galápagos explored some of these questions. Staffan Ulfstrand at the University of Uppsala in Sweden was my supervisor. He was invaluable; allowing me flexibility in pursuing my own research interests, but at the same time was immensely stimulating with his provocative questions.
Me:  During your time on the Galapagos, what were some important and perhaps surprising aspects that you learned about speciation?
Rosemary: Phenotypic and genetic changes in populations occurring through the process of natural selection and evolutionary responses to selection events was more rapid than expected.  Furthermore, oscillations in the direction of selection did not cancel out but resulted in long-term evolutionary changes.
Rare episodic introgressive hybridization, particularly when it is between species with different allometries, has important evolutionary implications. It increases the phenotypic and genetic characteristics of a population on which selection acts, and allows populations to track environmental changes in climatically varying or new environments.
Our two most exciting and certainly unanticipated recent findings have been first, a character displacement event in both morphology and song as a result of the colonization of the island by a large, dominant species of ground finch, G. magnirostris; and second, the origin of a new genetic, endogamously breeding, lineage of finches, which we followed from its inception through six generations.
Me:  Six generations of finches is a long time.  It’s so rare that a scientist has a chance to conduct long term studies and yet they can influence our understanding of ecological and evolutionary principals.
Rosemary:  Long-term studies are rare for a variety of reasons, but probably the most germane is the length of funding. Three-year periods constrain studies to short-term projects or to quick testing of pre-existing hypotheses. The results of these can sometimes be difficult to interpret because the preceding conditions are often unknown.
Most long-term studies start out as short-term studies, including our own. For example our hypotheses at the outset were conditioned by our reading of the literature. But all our major findings have stemmed from our observations in the field, and then from distinguishing between the hypotheses that these observations generated.
Me:  Field systems like your own can be a risky business, in that catastrophic events occur.  In the case of the finches, I believe it was a 1977 drought that led almost 80% mortality of the medium ground finch.  Yet despite that you were able to obtain some very interesting results.

Rosemary:  It was these extraordinarily severe droughts that have revealed some of our most important results.
Me: What advice can you give a field biologist about planning their experiments?
The advice I would give to young biologists faced with a biological catastrophe would be to observe carefully what is happening, be constantly alert, observant and flexible in thinking. Never go searching by expectation, but to think of several hypotheses that might explain your observations. It is often the unexpected that gives you the greatest insight and reward.
Me:  These events also led to some very cool studies on song and its role in reproductive isolation. Does one experiment always lead to another and is this how you get new ideas?
Rosemary: Peter and I start from a question generated from an observation, and then tried to examine several hypotheses that could explain the observation or observations. Yes, the results do indeed generate new questions and new hypotheses.
Me: Do you think that there are any important questions left to answer in about the finches?
Rosemary: There are some major questions. We know rather little about the underlying genetics of phenotypic differences between individuals that have been important in selection episodes. Our collaborators have made an important first step in the search for the key genetic factors. Arkhat Abzhanov and Cliff Tabin at Harvard found at least two signaling molecules associated with beak length and depth differences between species of Darwin’s Finches. There must be many more such factors awaiting discovery.
Another major area where very little is known is in physiological differences between individuals, and the underlying genetics responsible for these physiological differences. Some of these we know to be important. For example the varying length of male plumage maturation, the differences between birds of the same species living and breeding in the cool cloud forest on the tops of islands and those in the arid lowlands. Other physiological differences are involved in the triggering of breeding. Darwin’s finches, unlike birds at higher latitudes, cannot use increasing daylight for triggering breeding, but breed in response to sufficient rainfall to activate a vegetative and arthropod response. Michaela Hau in Germany has done and is doing interesting work on Darwin’s finches in this area.
Next Time –> Part 2: Interview with Rosemary Grant

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