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Showing posts with label hybridization. Show all posts
Showing posts with label hybridization. Show all posts

Tuesday, January 10, 2012

Extinct Giant Tortoise May Still Be Alive in Galapagos

A hybrid C. becki tortoise. Photo: Claudio Ciofi
by Brandon Keim

Genetic traces of a supposedly extinct giant tortoise species have been found in living hybrids on the Galapagos island of Isabela.

A few pure Chelonoidis elephantopus almost certainly still exist, hidden in the island’s volcanic redoubts. The hybrids have so much C. elephantopus DNA that scientists say careful breeding could resurrect the tragically vanished behemoths.

“To our knowledge, this is the first rediscovery of a species by way of tracking the genetic footprints left in the genomes of its hybrid offspring,” wrote researchers led by Yale University biologists Ryan Garrick and Edgar Benavides in a Jan. 9 Current Biology paper.

At the beginning of the 16th century, before humans arrived, an estimated 250,000 giant tortoises representing 15 different species lived in the Galapagos. Once fully grown, the tortoises had no natural predators — except people.

For whalers and pirates, the slow-moving animals were like walking grocery stores. They weighed up to 900 pounds; their flesh was tasty and rich in oil. They could survive for months, even years, without eating or drinking, and sailors stored tortoises alive in the hulls of their ships for future consumption.

By the time a young Charles Darwin surveyed the tortoises, they were being indiscriminately slaughtered. (“The inhabitants believe that these animals are absolutely deaf; certainly they do not overhear a person walking close behind them,” he wrote.) Five species, including C. elephantopus, would eventually go extinct. But the tortoises’ long-term storage convenience had one unexpected benefit.

“If a ship was under siege, sailors would unload it by throwing things overboard,” said Garrick. “The first thing to go was stuff stored in the hull. Tortoises don’t swim, but they float like wine corks, and it so happens that the prevailing current runs northeast through the islands. The last place a tortoise might catch land before being swept into the ocean was the northern part of Isabela island. This is where they would have washed up.”

Three years ago, Garrick and Colleagues sequenced the genomes of museum specimens of C. elephantopus and Chelonoidis becki, a closely related tortoise found on the northern part of Isabela island. They found C. elephantopus genes in a few C. becki, suggesting that some castaway tortoises historically made landfall and mated with the locals.

For the new study, the researchers traveled to Isabela island. On the island’s northern tip, on the slopes of Volcano Wolf, they took genetic samples from 1,600 C. becki individuals. Of these, 84 contained so much C. elephantopus DNA that at least one recent ancestor must have been a purebred C. elephantopus.

None of the purebreds was spotted, but because of the genetic signals’ strength and the hybrids’ youth — many were juveniles — the researchers estimate that about 40 purebreds still survive. Given that individual tortoises from other giant Galapagos species have lived for 170 years in captivity, some of the survivors could conceivably have been thrown from ships themselves.

Later this year the researchers will return to Isabela, where they hope to establish a captive breeding program using hybrids and, if they can find them, a few true C. elephantopus. The tortoises could roam again, their slaughter an evolutionary chapter rather than an end.

“The way they were moved around creates a rare opportunity to resuscitate a species that we thought we’d lost,” said Garrick.

Citation: “Genetic rediscovery of an ‘extinct’ Galápagos giant tortoise species.” By Ryan C. Garrick, Edgar Benavides, Michael A. Russello, James P. Gibbs, Nikos Poulakakis, Kirstin B. Dion, Chaz Hyseni, Brittney Kajdacsi, Lady Márquez, Sarah Bahan, Claudio Ciofi, Washington Tapia, and Adalgisa Caccone. Current Biology, January 9, 2012.

Monday, November 7, 2011

Friday, January 7, 2011

Mitochondrial Genome Sequences Effectively Reveal the Phylogeny of Hylobates Gibbons

Chan Y-C, Roos C, Inoue-Murayama M, Inoue E, Shih C-C, et al. (2010) Mitochondrial Genome Sequences Effectively Reveal the Phylogeny of Hylobates Gibbons. PLoS ONE 5(12): e14419. doi:10.1371/journal.pone.0014419

Uniquely among hominoids, gibbons exist as multiple geographically contiguous taxa exhibiting distinctive behavioral, morphological, and karyotypic characteristics. However, our understanding of the evolutionary relationships of the various gibbons, especially among Hylobates species, is still limited because previous studies used limited taxon sampling or short mitochondrial DNA (mtDNA) sequences. Here we use mtDNA genome sequences to reconstruct gibbon phylogenetic relationships and reveal the pattern and timing of divergence events in gibbon evolutionary history.

Methodology/Principal Findings
We sequenced the mitochondrial genomes of 51 individuals representing 11 species belonging to three genera (Hylobates, Nomascus and Symphalangus) using the high-throughput 454 sequencing system with the parallel tagged sequencing approach. Three phylogenetic analyses (maximum likelihood, Bayesian analysis and neighbor-joining) depicted the gibbon phylogenetic relationships congruently and with strong support values. Most notably, we recover a well-supported phylogeny of the Hylobates gibbons. The estimation of divergence times using Bayesian analysis with relaxed clock model suggests a much more rapid speciation process in Hylobates than in Nomascus.


Use of more than 15 kb sequences of the mitochondrial genome provided more informative and robust data than previous studies of short mitochondrial segments (e.g., control region or cytochrome b) as shown by the reliable reconstruction of divergence patterns among Hylobates gibbons. Moreover, molecular dating of the mitogenomic divergence times implied that biogeographic change during the last five million years may be a factor promoting the speciation of Sundaland animals, including Hylobates species.

Tuesday, September 14, 2010

Hybridization is a normal part of speciation (and so freakin' cool!)

I ♥ hybridization. Thanks to Vanessa Van D for the link! -MA

from the

Hybrids May Thrive Where Parents Fear to Tread

On May 15, 1985, trainers at Hawaii Sea Life Park were stunned when a 400- pound gray female bottlenose dolphin named Punahele gave birth to a dark-skinned calf that partly resembled the 2,000-pound male false killer whale with whom she shared a pool. The calf was a wholphin, a hybrid that was intermediate to its parents in some characteristics, like having 66 teeth compared with the bottlenose’s 44 and the 88 of the false killer whale, a much larger member of the dolphin family.

In 2006, a hunter in the Canadian Arctic shot a bear that had white fur like a polar bear’s but had brown patches, long claws and a hump like a grizzly bear’s. DNA analysis confirmed the animal was a hybrid of the two species.

While one might think that these oddities are examples of some kind of moral breakdown in the animal kingdom, it turns out that hybridization among distinct species is not so rare. Some biologists estimate that as many as 10 percent of animal species and up to 25 percent of plant species may occasionally breed with another species. The more important issue is not whether such liaisons occasionally produce offspring, but the vitality of the hybrid and whether two species might combine to give rise to a third, distinct species.

While several examples of human-bred animal hybrids are well known and can thrive in captivity including zorses (zebra-horse), beefalo (bison-beef cattle) and, of course, mules (donkey-horse), naturally occurring animal hybrids have many factors working against their longer-term success.

One of the main obstacles is that, even if members of different species might mate, when the two species are too distant genetically or carry different numbers of chromosomes, the offspring are usually inviable or infertile (like zorses and mules), and are therefore evolutionary dead ends. A second problem is that any hybrid will usually be vastly outnumbered and outcompeted by one or both parent species.

But because species hybrids create new combinations of genes, it is possible that some combinations might enable hybrids to adapt to conditions in which neither parent may fare as well. Several such examples are now known from nature. Furthermore, DNA analysis is now allowing biologists to better decipher the histories of species and to detect past hybridization events that have contributed new genes and capabilities to various kinds of organisms including, it now appears, ourselves.

The familiar sunflower has provided great examples of adaptation by hybrids. Loren H. Rieseberg of the University of British Columbia and colleagues have found that two widespread species, the common sunflower and prairie sunflower, have combined at least three times to give rise to three hybrid species: the sand sunflower, the desert sunflower, and the puzzle sunflower.

The parental species thrive on moist soils in the central and Western states, but the hybrids are restricted to more extreme habitats. The sand sunflower, for instance, is limited to sand dunes in Utah and northern Arizona and the puzzle sunflower to brackish salt marshes in West Texas and New Mexico.

The species distributions suggest that the hybrids thrive where the parents cannot. Indeed, recent field tests that examined the relative ability of the parental species to thrive in the hybrids’ habitat, and vice versa, found that the sand sunflower was better able than its parents to germinate, grow and survive in its dune habitat but fared relatively poorly in parental habitats. Similarly, the puzzle sunflower was much better at growing in salty conditions than its parents.

One lesson from the sunflowers appears to be that hybrids may succeed if they can exploit a different niche from their parents. The same phenomenon has been discovered in animal hybrids.

In the past 250 years, various forms of honeysuckle have been introduced to the Northeastern states. In the late 1990s, researchers led by Bruce McPheron of Pennsylvania State University discovered that this invasive honeysuckle was infested by a particular fruit fly species they called the Lonicera fly. When they analyzed DNA to determine its relationship to others, they were stunned to find that it was a hybrid of two closely related flies, the blueberry maggot and the snowberry maggot.

In laboratory experiments, the researchers found that the Lonicera hybrid preferred its honeysuckle host plant over its parent species’ host plants and that each parent species preferred its own host plant over the other’s. However, both parents also accepted honeysuckle. The researchers suggest that since the two parental species were thus more likely to encounter each other on honeysuckle in the wild, the newly invasive weed served as a catalyst for matings between the species and the formation of the hybrid species that now prefers honeysuckle.

The sunflower and Lonicera fly examples raise the question of whether hybridization between species has been more frequent than biologists once assumed. The most provocative report of possible hybridization came from the recent analysis of more than 60 percent of the Neanderthal genome sequence, which raised the specter of our ancestors commingling their genes with a long-diverged cousin.

Analyses of the overall genetic distance between Neanderthals and modern humans reveal that our DNA is 99.84 percent identical to that of Neanderthals. This small divergence indicates that the two lines split off from each other about 270,000 to 440,000 years ago. The fossil evidence shows that Neanderthals were restricted to Europe and Asia, whereas Homo sapiens originated in Africa. Various kinds of evidence indicate that modern humans migrated out of Africa and reached the Middle East more than 100,000 years ago and Europe by about 45,000 years ago, and would have or could have encountered Neanderthals for some time in each locale. The crucial question for paleontology, archaeology, and paleogenetics has been what transpired between the two species. To put it a little more crudely, did we date them or kill them, or perhaps both?

If the former, then there could be a bit of Neanderthal in some or all of us. The first comparisons of small sections of Neanderthal DNA did not indicate any hybridization, and the lack of interbreeding became a widely accepted conclusion. That remained the case until this year, when a much greater portion of the Neanderthal genome was obtained by Svante Paabo and colleagues at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. It now appears that 1 percent to 4 percent of the DNA sequence of Europeans and Asians, but not Africans, was contributed by Neanderthals mixing with Homo sapiens, perhaps in the Middle East 50,000 to 80,000 years ago. It is possible that some Neanderthal versions of genes enabled modern humans to adapt to new climates and habitats.

The discovery of hybrid species and the detection of past hybridizations are forcing biologists to reshape their picture of species as independent units. The barriers between species are not necessarily vast, unbridgeable chasms; sometimes they get crossed with marvelous results.

Sean B. Carroll is a molecular biologist and geneticist at the University of Wisconsin.

Wednesday, May 26, 2010

Introducing the Grolar Bear. Let's discuss implications.

Let's discuss this - if the grolar bear persists and the polar bear goes extinct, could we maybe be happy about that? In the same way that people seem thrilled that neanderthals "live on" as part of some of us? Hybridization is a natural phenomenon and part of species evolution, I think its sad if the polar bear goes extinct but this maybe the silver lining as the ice melts....well of course, provided that people stop poaching them and selling their pelts to the highest bidder-MA

From Scientific American
Polar-grizzly bear hybrid found in Canada
By John Platt

An extremely rare "grolar bear"—a polar-grizzly bear hybrid—was shot and killed by an Inuit hunter in Canada's Northwest Territories last month.

Global warming has reportedly been driving grizzly bears (Ursus arctos horribilis) farther north in search of food, bringing them into polar bear (U. maritimus) territory. Polar bears, meanwhile, are finding themselves stranded on land instead of their usual sea ice, bringing them into contact with the grizzlies.

This is only the second time that a grolar bear has been encountered in the wild and confirmed, but even with its rarity, it is more distinctive than expected. DNA tests released by the N.W.T. Environment and Natural Resources Department reveal that this was actually a second-generation grolar bear—meaning one of its parents (its mother) was already a polar-grizzly hybrid. The father was a purebred grizzly, the tests found.

The hunter knew he had something unusual, which is why he asked to have it identified. The bear had the polar bear's white fur but a bigger head, brown paws and longer claws more typical of a grizzly bear.

The first grolar bear confirmed in the wild was killed by a hunter in 2006. A few others have been born in zoos.


Bear shot in N.W.T. was grizzly-polar hybrid, could be first 2nd generation hybrid found in wild

Biologists in the Northwest Territories have confirmed that an unusual-looking bear shot earlier this month near Ulukhaktok, N.W.T., was a rare hybrid grizzly-polar bear.

The unusual-looking bear caught the attention of biologists after David Kuptana, an Inuvialuit hunter, shot and killed it on April 8 on the sea ice just west of the Arctic community, formerly known as Holman. The bear had thick white fur like a polar bear, but it also had a wide head, brown legs and brown paws like a grizzly. Kuptana said he shot the bear from a distance after it scavenged through five unoccupied cabins near Ulukhaktok, then tried running toward the community.

Wildlife DNA analysis shows the bear was a second-generation hybrid, officials with the N.W.T. Environment and Natural Resources Department said in a news release Friday. The bear was the result of a female grizzly-polar hybrid mating with a male grizzly bear, according to the department. "This confirms the existence of at least one female polar-grizzly hybrid near Banks Island," the release said. "This may be the first recorded second-generation polar-grizzly bear hybrid found in the wild."

Kuptana told CBC News he is currently selling the bear pelt to the highest bidder and has received calls from across Canada for the unique pelt. "Right now, we're already at $15,000, and we're going to see how far we can go," Kuptana said Friday. "If we can do better, we'll be happy."

The N.W.T.'s first confirmed "grolar bear" was shot by a U.S. hunter in Sachs Harbour, N.W.T., located on Banks Island, in April 2006. More DNA tests are planned to determine whether the bear shot this month was related to the one from 2006.

Hybrid bears will likely become more common in the North, as the direct consequence of climate change, predicts Brendan Kelly, a marine biologist with the International Arctic Research Center at the University of Alaska Fairbanks. In the absence of summer Arctic sea ice, polar bears are stranded on land and come into more contact with grizzly bears, he said. "We're taking this continent-sized barrier to animal movement, and in a few generations, it's going to disappear, at least in summer months," Kelly said. "That's going to give a lot of organisms — a lot of marine mammals in particular — who've been separated for at least 10,000 years the opportunity to interbreed again, and we're predicting we're going to see a lot more of that." Kelly said he has seen reports of harp seals and hooded seals interbreeding, as well as beluga whales and narwhal. Interbreeding helps species adapt to major shifts in their environments, he said.

more info: Grolar Bear/Pizzly Bear/Prizzly Bear on Wikipedia

Thanks to Chrissie E for the link

Sunday, August 16, 2009

Meet the coywolf: a coyote wolf hybrid in Ontario

The "discovery" of the coywolf has settled a debate between me and one of my colleagues from western Canada here at the MPI-EVA. We were discussing coyote behaviour and he insisted they were solitary (he is correct by the way) but i was SURE that the coyotes in the suburbs of Toronto traveled in packs as I had seen and heard them many times while walking my dogs (and i knew they wern't wolves since I have seen those too). Well, I was sorta correct too - its the coywolf. -MA

From the Toronto Star

A newly emerging species is behind the brazen attacks in Durham

Is it a coyote? Is it a wolf?

Yes and yes. It's a "coywolf."

The predators that are plaguing Durham Region and showing up in urban areas appear to be an emerging species resulting from wolves and coyotes interbreeding.

The larger, highly adaptable animals "have the wolf characteristics of pack hunting and aggression and the coyote characteristics of lack of fear of human-developed areas," says Trent University geneticist Bradley White, who's been studying the hybrids for 12 years.

We're seeing "evolution in action," he says.

But that combination of genetic material from both species has spelled trouble for farmers, who are losing a growing number of livestock to predators.

They report attacks by animals that are bigger, bolder and smarter than regular coyotes. They say hunting in packs to prey on sheep and cattle in broad daylight is becoming a common behaviour.

Durham Region farmers have suffered the most damage to livestock in the province. Last year the food and agriculture ministry paid out a total compensation of $168,000 in the region for 545 dead or injured animals.

Commonly called eastern coyotes, the creatures are actually a mixture of western coyote and eastern wolf that comes from a constantly evolving gene pool, says White, chair and professor of biology in Peterborough.

Going back 100 years, deforestation, wolf control programs and changing habitat, ecosystems and prey conspired to drive down the wolf population. Meanwhile, the number of coyotes – whose original range was in western North America – grew, thanks to their ability to adapt and reproduce with ease. The two species started to interbreed, White explains.

"In many ways, this animal is a creation of human impact on the planet," says White.

Although the coywolf hybrid has only recently been verified through genetic research, White believes they started appearing in southern Algonquin Park back in the 1920s.

Colleague Paul Wilson, a wildlife genetics specialist, says the genetic gumbo from which coywolves emerge produces some that are more wolf-like, while others have more coyote characteristics. But they're definitely bigger.

"Some of these are 80-pound animals, double the size of a typical coyote that used to be 40 pounds."

But there's no cause for alarm, says John Pisapio, a wildlife biologist with the Ministry of Natural Resources, which is studying the role of coyotes and wolves in the ecosystem.

Hybrids may be larger but there's no evidence the population as a whole is more aggressive or prone to aberrant behaviour, he says.

He agrees predation on livestock is a concern – they do kill sheep and smaller animals – but insists attacks on cattle are unusual.

"As a biologist I find it hard to explain how a coyote brings down a 900-pound steer."

In some cases, coyotes might just be feeding on an animal that died from other causes, he says.

The population growth is a natural upswing following a mange epidemic that wiped out big numbers eight or nine years ago, he adds.

Pisapio says instances of fearlessness or brazen attacks are usually the result of coyotes that have come to associate food with people and lose their natural fear of humans.

That belief is echoed by Johnny, "The Critter Gitter," who didn't want his last name used because people don't like that he kills problem wildlife for a living.

"I kill coyotes. I don't sugarcoat it," he says.

But he feels sympathy for them.

"Humans are to blame for making monsters of them," he says. Coyotes are attracted by pet food and garbage left lying around in urban areas, and deadstock on farms.

They're not all bad and often get the blame when dogs kill livestock, he says. Johnny also doubts they're making a regular meal of cattle. During the 30 years he's worked in the province, he's seen only a few cases of "large, healthy animals taken down by coyotes."

But as coywolves become more urbanized and their relationship with people continues to evolve, city dwellers can expect problems, says White, suggesting a control program may be needed at some point.

"They will clearly bump into human activities, and there will be pets eaten in Rouge Valley."