Peter Raymond GrantFRSFRSC (born October 26, 1936) and Barbara Rosemary GrantFRSFRSC (born October 8, 1936) are a British married couple who are evolutionary biologists at Princeton University. Each currently holds the position of emeritus professor. They are known for their work with Darwin's finches on Daphne Major, one of the Galápagos Islands. Since 1973, the Grants have spent six months of every year capturing, tagging, and taking blood samples from finches on the island. They have worked to show that natural selection can be seen within a single lifetime, or even within a couple of years. Charles Darwin originally thought that natural selection was a long, drawn out process but the Grants have shown that these changes in populations can happen very quickly.
Peter and Rosemary Grant are distinguished for their remarkable long-term studies demonstrating evolution in action in Galápagos finches. They have demonstrated how very rapid changes in body and beak size in response to changes in the food supply are driven by natural selection. They have also elucidated the mechanisms by which new species arise and how genetic diversity is maintained in natural populations. The work of the Grants has had a seminal influence in the fields of population biology, evolution, and ecology.[2]
The Grants are both Fellows of the Royal Society, Peter in 1987, and Rosemary in 2007. In 2008, the Grants were among the thirteen recipients of the Darwin-Wallace Medal, which is bestowed every fifty years by the Linnean Society of London. In 2009, they were recipients of the annual Kyoto Prize in basic sciences, an international award honouring significant contributions to the scientific, cultural and spiritual betterment of mankind.[3] In 2017, they received the Royal Medal in Biology "for their research on the ecology and evolution of Darwin’s finches on the Galapagos, demonstrating that natural selection occurs frequently and that evolution is rapid as a result".[4]
Early years
Barbara Rosemary Grant was born in Arnside, England in 1936. In her youth, she collected plant fossils and compared them to living look-alikes. At the age of 12, she read Darwin's On the Origin of Species. Despite being told by her headmistress that pursuing an education in a male-dominated field of study would be foolish, in addition to contracting a serious case of mumps that temporarily stalled her academic activity, she decided to continue forth with her education.[5] In 1960, she graduated from the University of Edinburgh with a degree in Zoology. For the next year, she studied genetics under Conrad Waddington and later devised a dissertation to study isolated populations of fish. This project was put on hold when she accepted a biology teaching job at the University of British Columbia,[5] where she met Peter Grant.[6]
Peter Raymond Grant was born in 1936 in London, but relocated to the English countryside to avoid encroaching bombings during World War II. He attended school at the Surrey-Hampshire border, where he collected botanical samples, as well as insects.[6] He attended the University of Cambridge and later moved to Vancouver, British Columbia, Canada, and began work on a doctoral degree in Zoology at the University of British Columbia. Peter met Rosemary after beginning his research there, and after a year, the two wedded.[6]
Research Associate, University of Michigan, 1977[3]
Research Scholar and lecturer, Princeton University, 1985[3]
Senior Research Scholar with rank of Professor, Princeton University, 1997[3]
Senior Research Scholar with rank of Professor Emeritus, Princeton University, 2008[3]
Research
For his doctoral degree, Peter Grant studied the relationship between ecology and evolution and how they were interrelated. The Grants travelled to the Tres Marias Islands off Mexico to conduct field studies of the birds that inhabited the island.[6] They compared the differences of bill length to body size between populations living on the Islands and the nearby mainland. Of the birds studied, eleven species were not significantly different between the mainland and the islands; four species were significantly less variable on the islands, and one species was significantly more variable.[7] On average, the birds on the islands had larger beaks. The Grants attributed these differences to what foods were available, and what was available was dependent on competitors. The bigger beaks indicated a greater range of foods present in the environment.[6]
In 1965, Peter Grant accepted tenure at McGill University in Montreal. He created a method to test the Competition Hypothesis to see if it worked today as it did in the past.[6] This research was done on grassland voles and woodland mice. The study looked at the competitiveness between populations of rodents and among rodent species.[8] In his article "Interspecific Competition Among Rodents", he concluded that competitive interaction for space is common among many rodent species, not just the species that have been studied in detail.[8] Grant also states that there are many causes for increased competition: reproduction, resources, amount of space, and invasion of other species.[8]
Daphne Major, in the Galápagos Islands, was a perfect place to perform experiments and study changes within birds. It was isolated and uninhabited; any changes that were to occur to the land and environment would be due to natural forces with no human destruction.[9] The island provided the best environment to study natural selection; seasons of heavy rain switched to seasons of extended drought. With these environmental changes brought changes in the types of foods available to the birds. The Grants would study this for the next few decades of their lives.
In 1973, the Grants headed out on what they thought would be a two-year study on the island of Daphne Major. There they would study evolution and ultimately determine what drives the formation of new species.[9] There are thirteen species of finch that live on the island; five of these are tree finch, one warbler finch, one vegetarian finch, and six species of ground finch. These birds provide a great way to study adaptive radiation. Their beaks are specific to the type of diet they eat, which in turn is reflective of the food available. The finches are easy to catch and provide a good animal to study. The Grants tagged, labelled, measured, and took blood samples of the birds they were studying. The two-year study continued through 2012.[9]
During the rainy season of 1977 only 24 millimetres of rain fell. Two of the main finch species were hit exceptionally hard and many of them died.[10] The lack of rain caused major food sources to become scarce, causing the need to find alternative food sources. The smaller, softer seeds ran out, leaving only the larger, tougher seeds. The finch species with smaller beaks struggled to find alternate seeds to eat.[10] The following two years suggested that natural selection could happen very rapidly. Because the smaller finch species could not eat the large seeds, they died off. Finches with larger beaks were able to eat the seeds and reproduce. The population in the years following the drought in 1977 had "measurably larger" beaks than had the previous birds.
In 1981, the Grants came across a bird they had never seen before. It was heavier than the other ground finches by more than five grams.[11][12][13] They called this bird Big Bird. It had many different characteristics than those of the native finches: a strange call, extra glossy feathers, it could eat both large and small seeds, and could also eat the nectar, pollen, and seeds of the cacti that grow on the island.[9] Although hybrids do happen, many of the birds living on the island tend to stick within their own species.[14] Big Bird lived for thirteen years, initially interbreeding with local species. His descendants have only mated within themselves for the past thirty years, a total of seven generations.[14]
Big Bird was originally assumed to be an immigrant from the island of Santa Cruz. However, in 2015, whole genome analysis linked its descent to a bird that originated on Española Island, more than 100 kilometers from Daphne Major, the Española cactus finch (G. conirostris). Descendants of G. conirostris and local finches (G. fortis) have become a distinct species, the first example of speciation to be directly observed by scientists in the field.[15] Whole genome studies have enabled scientists to trace changes in the genome as the species became distinct. Genes for beak shape (ALX1) and beak size (HMGA2) have been determined to be crucial in separating the hybridized species from local finches. Genes relating to the finches' song may also be involved.[11][16]
Over the course of 1982–1983, El Niño brought a steady eight months of rain. In a normal rainy season Daphne Major usually gets two months of rain.[17] The excessive rain brought a turnover in the types of vegetation growing on the island. The seeds shifted from large, hard to crack seeds to many different types of small, softer seeds. This gave birds with smaller beaks an advantage when another drought hit the following year.[17] Small-beaked finch could eat all of the small seeds faster than the larger beaked birds could get to them.
In 2003, a drought similar in severity to the 1977 drought occurred on the island. However, in the time between the droughts (beginning in late 1982), the large ground finch (Geospiza magnirostris) had established a breeding population on the island. This species has diet overlap with the medium ground finch (G. fortis), so they are potential competitors. The 2003 drought and resulting decrease in food supply may have increased these species' competition with each other, particularly for the larger seeds in the medium ground finches' diet. Following the drought, the medium ground finch population had a decline in average beak size, in contrast to the increase in size found following the 1977 drought. This was hypothesized to be due to the presence of the large ground finch; the smaller-beaked individuals of the medium ground finch may have been able to survive better due to a lack of competition over large seeds with the large ground finch. This is an example of character displacement.[18]
Significant findings
In Evolution: Making Sense of Life, the takeaway from the Grants' 40-year study can be broken down into three major lessons. The first is that natural selection is a variable, constantly changing process. The fact that they studied the island in both times of excessive rain and drought provides a better picture of what happens to populations over time. The next lesson learned is that evolution can actually be a fairly rapid process. It does not take millions of years; these processes can be seen in as little as two years. Lastly, and as the author states, most importantly, selection can change over time. During some years, selection will favour those birds with larger beaks. Other years with substantial amounts of smaller seeds, selection will favour the birds with the smaller beaks.[19]
In their 2003 paper, the Grants wrap up their decades-long study by stating that selection oscillates in a direction. For this reason, neither the medium ground finch nor the cactus finch has stayed morphologically the same over the course of the experiment. The average beak and body size are not the same today for either species as they were when the study first began.[20] The Grants also state that these changes in morphology and phenotypes could not have been predicted at the beginning.[21] They were able to witness the evolution of the finch species as a result of the inconsistent and harsh environment of Daphne Major directly.
Honorary citizen of Puerto Bacquerizo, I. San Cristobal, Galapagos- 2005–
Since 2010, she has been honoured annually by the Society for the Study of Evolution with the Rosemary Grant Graduate Student Research Award competition, which supports "students in the early stages of their PhD programs by enabling them to collect preliminary data... or to enhance the scope of their research beyond current funding limits".[23]
Evolutionary Dynamics of a Natural Population: Large Cactus Finch of the Galapagos – Rosemary & Peter Grant – (University of Chicago Press, 1989) ISBN978-0-226-30590-5 (Received the Wildlife Publication Award, Wildlife Society, 1991)
How and Why Species Multiply: The Radiation of Darwin’s Finches – Peter & Rosemary Grant – (Princeton University Press, 2008/2011) ISBN978-0-691-14999-8
40 Years of Evolution: Darwin's Finches on Daphne Major Island – Peter & Rosemary Grant – (Princeton University Press,2014) ISBN978-0-691-16046-7
In evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, alters biotic interactions or opens new environmental niches. Starting with a single ancestor, this process results in the speciation and phenotypic adaptation of an array of species exhibiting different morphological and physiological traits. The prototypical example of adaptive radiation is finch speciation on the Galapagos, but examples are known from around the world.
The Beak of the Finch: A Story of Evolution in Our Time (ISBN 0-679-40003-6) is a 1994 nonfiction book about evolutionary biology, written by Jonathan Weiner. It won the 1995 Pulitzer Prize for General Non-Fiction. In 2014, a substantially unchanged 20th-anniversary edition e-book was issued with a preface by the author.
Darwin's finches are a group of about 18 species of passerine birds. They are well known for their remarkable diversity in beak form and function. They are often classified as the subfamily Geospizinae or tribe Geospizini. They belong to the tanager family and are not closely related to the true finches. The closest known relative of the Galápagos finches is the South American dull-coloured grassquit. They were first collected when the second voyage of the Beagle visited the Galápagos Islands, with Charles Darwin on board as a gentleman naturalist. Apart from the Cocos finch, which is from Cocos Island, the others are found only on the Galápagos Islands.
David Lambert Lack FRS was a British evolutionary biologist who made contributions to ornithology, ecology, and ethology. His 1947 book, Darwin's Finches, on the finches of the Galapagos Islands was a landmark work as were his other popular science books on Life of the Robin and Swifts in a Tower. He developed what is now known as Lack's Principle which explained the evolution of avian clutch sizes in terms of individual selection as opposed to the competing contemporary idea that they had evolved for the benefit of species. His pioneering life-history studies of the living bird helped in changing the nature of ornithology from what was then a collection-oriented field. He was a longtime director of the Edward Grey Institute of Field Ornithology at the University of Oxford.
Character displacement is the phenomenon where differences among similar species whose distributions overlap geographically are accentuated in regions where the species co-occur, but are minimized or lost where the species' distributions do not overlap. This pattern results from evolutionary change driven by biological competition among species for a limited resource. The rationale for character displacement stems from the competitive exclusion principle, also called Gause's Law, which contends that to coexist in a stable environment two competing species must differ in their respective ecological niche; without differentiation, one species will eliminate or exclude the other through competition.
The vampire ground finch is a small bird native to the Galápagos Islands. It was considered a very distinct subspecies of the sharp-beaked ground finch endemic to Wolf and Darwin Islands. The International Ornithologists' Union has split the species supported by strong genetic evidence that they are not closely related, and divergences in morphology and song. Other taxonomic authorities still consider it conspecific.
Daphne Major is a volcanic island just north of Santa Cruz Island and just west of the Baltra Airport in the Archipelago of Colón, commonly known as the Galápagos Islands. It consists of a tuff crater, devoid of trees, whose rim rises 120 m (394 ft) above the sea.
The Cocos finch or Cocos Island finch is the only one of the Darwin's finches not native to the Galápagos Islands, and the only member of the genus Pinaroloxias. Sometimes classified in the family Emberizidae, more recent studies have shown it to belongs in the tanager family, Thraupidae. It is endemic to Cocos Island, a Pacific island which is approximately 360 miles (580 km) south of Costa Rica.
Geospiza is a genus of bird in the tanager family Thraupidae. All species in the genus are endemic to the Galápagos Islands. Together with related genera, they are collectively known as Darwin's finches. Although in the past, they were classified in the bunting and American sparrow family Emberizidae, more recent studies have shown they belong in the tanager family.
The medium ground finch is a species of bird in the family Thraupidae. It is endemic to the Galapagos Islands. Its primary natural habitat is tropical shrubland. One of Darwin's finches, the species was the first which scientists have observed evolving in real-time.
The small ground finch is a species of bird in the tanager family Thraupidae. Endemic to the Galápagos Islands, it is common and widespread in shrubland, woodland, and other habitats on most islands in the archipelago. It commonly feeds on small seeds and parasites from the skins of Galápagos land and marine iguanas and Galápagos tortoises.
The Hood mockingbird, also known as the Española mockingbird, is a species of bird in the family Mimidae. It is endemic to Española Island in the Galápagos Islands, Ecuador, and it is one of four closely related mockingbird species endemic to the Galápagos archipelago. It is found in dry forests and is omnivorous, though it primarily is a carnivore or scavenger. The species has a highly territorial social structure and has no fear of humans. It is the only species of Galápagos mockingbird that Charles Darwin did not see or collect on the voyage of HMS Beagle.
The Galápagos mockingbird is a species of bird in the family Mimidae. It is endemic to the Galápagos Islands, Ecuador.
The vegetarian finch is a species of bird in the Darwin's finch group of the tanager family Thraupidae endemic to the Galápagos Islands. It is the only member of the genus Platyspiza.
Why Evolution is True is a popular science book by American biologist Jerry Coyne. It was published in 2009, dubbed "Darwin Year" as it marked the bicentennial of Charles Darwin and the hundred and fiftieth anniversary of the publication of his On the Origin of Species By Means of Natural Selection. Coyne examines the evidence for evolution, some of which was known to Darwin (biogeography) and some of which has emerged in recent years. The book was a New York Times bestseller, and reviewers praised the logic of Coyne's arguments and the clarity of his prose. It was reprinted as part of the Oxford Landmark Science series.
The Genovesa cactus finch is a species of bird in the tanager family Thraupidae. It is one of Darwin's finches, and is endemic to the Galápagos islands, Ecuador, where it is restricted to Genovesa Island.
The Española cactus finch, is a species of bird in the tanager family Thraupidae. It is one of Darwin's finches, and is endemic to the Galápagos islands, where it is restricted to Española, Genovesa, and the Darwin and Wolf Islands. This rather dark bird resembles the smaller and finer-beaked common cactus finch, but the two species do not co-inhabit any island.
The Daphne Major finches are a group of Darwin's finches that inhabit Daphne Major island of the Galápagos. The common cactus finch and the medium ground finch are the main species; while the large ground finch and the Española cactus finch are regular immigrants. Most extensively studied by Peter and Rosemary Grant of Princeton University since 1973, the birds are one of the sources of the understanding of bird behaviour, adaptation, and evolution.
A selection gradient describes the relationship between a character trait and a species' relative fitness. A trait may be a physical characteristic, such as height or eye color, or behavioral, such as flying or vocalizing. Changes in a trait, such as the amount of seeds a plant produces or the length of a bird's beak, may improve or reduce their relative fitness. Changes in traits may accumulate in a population under an ongoing process of natural selection. Understanding how changes in a trait affect fitness helps evolutionary biologists understand the nature of evolutionary pressures on a population.
Big Bird, also known as the Big Bird lineage, is one of the species of Darwin's finches that is exclusively present on Daphne Major of the Galápagos islands. It originated from a mixed-breed (hybrid) of the Española cactus finch and the medium ground finch that immigrated to Daphne Major in 1981. It resembles the medium ground finch but is relatively larger, hence, the name. The original Big Bird bred with a female medium ground finch and the offspring tend to breed only with their own family members, thereby giving rise to reproductive isolation and undergoing speciation. Discovered by the research team of Peter and Rosemary Grant, the formation of Big Birds as a distinct species is considered as an instance of observed speciation and as a process of evolution by natural selection.
↑ Grant, P. R. (1967). "Bill length variability in birds of the Tres Marías Islands, Mexico". Canadian Journal of Zoology. 45 (5): 805–815. doi:10.1139/z67-092.
↑ Zimmer, Carl, and Douglas John Emlen. "Natural Selection: Empirical Studies in the Wild." Evolution: Making Sense of Life. Greenwood Village, CO: Roberts, 2013. 220-23. Print.
↑ "1995 Pulitzer Prize Winners". pulitzer.org. The Pulitzer Prizes — Columbia University. Archived from the original on 15 June 2017. Retrieved 23 August 2017.
Education, accolades, joint awards, and publishing were cited from the International Balzan Prize Foundation bibliography (13)
External links
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