Posts Tagged ‘evolution’
If Charles Darwin returned to the Galapagos Islands today, he would find all but one of the finch species that lived there during his visit in the 1830s. But he would also find birds that look and sound different.
Peter and Rosemary Grant, husband-and-wife evolutionary biologists at Princeton University, have written about a medium ground finch that is heavier, has a broader beak and sings a different song than its closest relative.
The Grants have documented the emergence of this medium ground finch lineage since 1981, when they caught what they believe was an immigrant bird on Daphne Major, a tiny Galapagos island where they’ve measured, weighed and tagged ground finches several months every year since 1973.
The new lineage, which nobody has dared to call a new species yet, has been molded by droughts, above average rainfall and competition for food – factors that also affected other finches living on Daphne Major.
“In the 2000s, the birds are not the same as the ones that were on the island when we started,” Peter Grand told a crowd of more than 200 who had come to his and his wife’s presentation April 11 at the N.C. Museum of Natural Sciences in Raleigh.
That evolution can happen as researchers watch was unexpected. That the Grants documented the making of what might be a new species in 20 years has turned them into legends.Their research has won multiple awards and is featured prominently in biology textbooks and one Pulitzer-Prize-winning book.
The couple’s visit to North Carolina’s Research Triangle was the result of a collaboration of the museum, N.C. State University and the National Evolutionary Synthesis Center.
Thirteen species of ground finches live on the Galapagos archipelago, a cluster of more than a dozen islands located in the Pacific Ocean about 600 miles west of Equador. They are plain birds with brown, gray or black plumage that have been famous since they helped Darwin develop the theory of evolution.
All descend from one species that lived on the South American mainland.
The smallest finch species on the Galapagos Islands weighs about one-fourth of the largest species and each species has developed a specific beak to eat a special diet.
The Warbler finch has a slender beak to probe for insects. Ground finches have broad beaks to crush seeds of various sizes. Cactus finches have long, curved beaks to probe flowers for nectar. The large tree finch has a powerful, curved beak to strip bark and extract insects and termites.
The diet has a lot to do with where a species lives. The medium tree finch, for example, can only be found on Floreana Island. The common cactus finch lives on all but the five Galapagos Islands that are inhabited by the large cactus finch.
Daphne Major is home to four species, the Grants reported. The couple caught small, medium and large ground finches and cactus finches, including some that had immigrated from neighboring islands.
The males of each species sing a different song, which male and female birds learn as nestlings listening to their fathers. Males and females of a species recognize each other by that song. Interbreeding can occur, Rosemary Grant said, for example, when the fatherly lesson gets garbled because the nest is close to the nest of another species in the same cactus bush.
In 1981, the Grants caught a medium ground finch immigrant whose plumage was particularly glossy and black. The male bird was about 20 percent bigger than the biggest medium ground finch captured on Daphne Major and had a wider beak. It also sang an unusual song and a blood test determined that it carried cactus finch genes.
The immigrant hybrid male mated with a female hybrid that also carried genes of both species. Three generations of offspring – finches live up to 16 years – bred with local medium ground finches and other hybrids.
Then, all but two of the birds in the lineage died during a severe drought in 2003 and 2004. The remaining two birds, a sister and a brother, mated and their offspring has mated, but only with each other.
This has led to two distinct groups of medium ground finches on Daphne Major that do not mix, the Grants reported. They differ in weight, beak shape and song and breed in two different areas on the island.
(More in the Grants’ inaugural article in the 2009 Proceedings of the National Academy of Sciences.)
I didn’t feel kinship with female lizards until I listened to Ryan Calsbeek talk about women having a say in whether their children will be boys or girls.
Calsbeek has studied natural selection among lizards and spoke about his research Thursday at N.C. State University’s biology department. He is an assistant professor of biological sciences at Dartmouth College and a visitor at the National Evolutionary Synthesis Center in Durham where he is working on a book.
Experiments he and his team have run with brown anoles, lizards native to Cuba and the Bahamas, suggest that the female lizards sort sperm to have the fittest males father more male offspring. It’s unclear how female brown anoles do that, Calsbeek said, but they’re not the only ones doing it.
“It’s even true in humans,” he said.
The remark generated quips from the audience about the exclusively female offspring of three consecutive U.S. presidents and the girl that Calsbeek’s pregnant wife is expecting. But Calsbeek argued that statistically four examples don’t mean much. Throughout history, women whose mates were presidents and kings tended to overproduce sons, he said.
Still, why should I care about sperm sorting among reptiles the size of my finger? Because brown anoles are, as Calsbeek put it, “the drosophila of lizards.” Both are model organisms. Just as the drosophila fruit fly has been extensively used to understand genetics, brown anoles can tell us something about the role female choice plays in the evolution of organisms, including ours, Calsbeek said.
More than 150 years ago, Charles Darwin picked up on female behavior patterns that ensure reproductive fitness down the generations.
Nature is full of examples. To a peacock hen lustrous tail feathers on a male signal he’s not parasite-ridden. Size and strength help male elephant seals drive away competitors and attract harems of up to 100 cows. Size is also important for female brown anoles to determine male fitness.
After World War II, another Brit, Angus Bateman, determined through drosophila experiments that female choice makes sense, because the number of offspring a female fruit flies can produce is limited more by how many eggs she generates than by how many mates she has. Bateman concluded that eggs are more precious than sperm, Calsbeek said.
Calsbeek and his team conducted breeding experiments with brown anoles to learn more about the choices the female lizards made. The findings they reported last year suggested the dams were very sophisticated.
The experiments showed that the size of the father only played a role in the number of male offspring that hatched.
Males are either losers or winners while females do pretty well regardless, Calsbeek said. “If you’re a loser in the animal kingdom, you’re probably a male. Sorry guys.”
What Brian Hare says might rub people who quibble about evolution the wrong way.
Hare, an assistant professor of evolutionary anthropology at the Duke Institute for Brain Sciences, says humans are apes.
Indeed, on the timeline that tracks the evolution of hominids, we are between chimpanzees and bonobos on the left and gorillas and orangutans on the right.
“Humans are slap dab in the middle of the great ape clade,” Hare said during a talk he gave Friday at N.C. State University’s biology department.
But wait a minute. We may share 98.7 percent of our genetic material with apes, but we’ve accomplished a lot more than they have. We speak and write books. We pray. We build cities and pay with money that’s part of a global financial system. We join different groups. We depose dictators. Apes live in trees. They grunt and scream. Their allegiances tend to be with one group only and they usually follow a strict ranking system.
To figure out how we humans got to be that way, researchers have begun to set up experiments with chimpanzees and bonobos, the apes most closely related to us. Hare’s research is based on these experiments. At Duke, for example, he has access to two sanctuaries, the Tchimpounga Natural Reserve in the Republic of Congo and Lola y Bonobo in the neighboring Democratic Republic of Congo, a country formerly known as Zaire. Read more…
Vanessa Woods (website, old blog, new blog, Twitter) will be reading from her new book “Bonobo Handshake” (comes out May 27th – you can pre-order on amazon.com) at the Regulator in Durham on May 27th at 7pm, at Quail Ridge Books on June 9th at 7:30pm, and at Chapel Hill Borders on June 12th at 2pm.
I have interviewed Vanessa last year so you can learn more about her there.
I received a review copy recently and am halfway through. Once I finish I will post my book review here.
From Publishers Weekly:
Devoted to learning more about bonobos, a smaller, more peaceable species of primate than chimpanzees, and lesser known, Australian journalist Woods and her fiancé, scientist Brian Hare, conducted research in the bonobos’ only known habitat—civil war–torn Congo. Woods’s plainspoken, unadorned account traces the couple’s work at Lola Ya Bonobo Sanctuary, located outside “Kinshasa in the 75-acre forested grounds of what was once Congo dictator Mobutu Sese Seko’s weekend retreat. The sanctuary, founded in 1994 and run by French activist Claudine André, served as an orphanage for baby bonobos, left for dead after their parents had been hunted for bush meat; the sanctuary healed and nurtured them (assigning each a human caretaker called a mama), with the aim of reintroducing the animals to the wild. Hare had only previously conducted research on the more warlike, male-dominated chimpanzee, and needed Woods because she spoke French and won the animals’ trust; through their daily work, the couple witnessed with astonishment how the matriarchal bonobo society cooperated nicely using frequent sex, and could even inspire human behavior. When Woods describes her daily interaction with the bonobos, her account takes on a warm charm. Woods’s personable, accessible work about bonobos elucidates the marvelous intelligence and tolerance of this gentle cousin to humans.”
NESCent Catalysis Meeting, coorganized by the Evolution Institute was on November 13-15, 2009 and several of the participants remained another day and came to NESCent on the 16th to report on the meeting in a form of a panel. The meeting and the panel were organized by David Sloan Wilson, professor of evolution at Binghamton University and one of my newest SciBlings. The other panelists were Dennis Embry, John Gowdy, Douglas Kenrick, Joel Peck, Harvey Whitehouse and Peter Turchin.
It hit me when my mind wandered through a blog post by Robert Lee Hotz, a Wall Street Journal science writer, about research that explores the brain during sudden Eureka moments. Also a contributing factor was a book, that, as I’m reading it, makes me wonder whether it’s smarter to be a nematode or a human.