Tuesday, 21 January 2014

Evolution in action: plants resistant to herbicides.

plants resistant to herbicides.

Evolution in action: plants resistant to herbicides.

Powles SB, Yu Q.

Author information

Abstract

Modern herbicides make major contributions to global food production by easily removing weeds and substituting for destructive soil cultivation. However, persistent herbicide selection of huge weed numbers across vast areas can result in the rapid evolution of herbicide resistance. Herbicides target specific enzymes, and mutations are selected that confer resistance-endowing amino acid substitutions, decreasing herbicide binding. Where herbicides bind within an enzyme catalytic site very few mutations give resistance while conserving enzyme functionality. Where herbicides bind away from a catalytic site many resistance-endowing mutations may evolve. Increasingly, resistance evolves due to mechanisms limiting herbicide reaching target sites. Especially threatening are herbicide-degrading cytochrome P450 enzymes able to detoxify existing, new, and even herbicides yet to be discovered. Global weed species are accumulating resistance mechanisms, displaying multiple resistance across many herbicides and posing a great challenge to herbicide sustainability in world agriculture. Fascinating genetic issues associated with resistance evolution remain to be investigated, especially the possibility of herbicide stress unleashing epigenetic gene expression. Understanding resistance and building sustainable solutions to herbicide resistance evolution are necessary and worthy challenges.
PMID:
20192743
[PubMed - indexed for MEDLINE]
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Gene change in cannibals reveals evolution in action

Gene change link


Gene change in cannibals reveals evolution in action

It's a snapshot of human evolution in progress. A genetic mutation protecting against kuru – a brain disease passed on by eating human brains – only emerged and spread in the last 200 years.
When members of the Fore people in Papua New Guinea died, others would eat the dead person's brain during funeral rituals as a mark of respect. Kuru passed on in this way killed at least 2500 Fore in the 20th century until the cause was identified in the late 1950s and the practice halted.
Identification of kuru and how it was spread helped researchers identify how BSE – mad cow disease – spread through the feeding of infected cattle brains to other animals, and how this eventually led to variant Creutzfeldt-Jakob disease (vCJD), which has killed 166 people so far in the UK.
Simon Mead of the British prion research centre at University College London says the discovery of an "anti-kuru" gene is the most clear-cut evidence yet of human evolution in action.
"I hope it will become a textbook example of how evolution happens," he says. "It's a striking and timely example, given the 150th anniversary of the publication of Darwin's Origin of Species," he says.

Good mutations

Mead and his colleagues discovered the mutation after comparing stored DNA from 152 dead Fore victims of the disease with DNA from more than 3000 living Fore, including almost 560 who participated in the ritual eating of brains before it was banned.
In 51 survivors and their descendants, they discovered a hitherto-unknown variant of PRNP, the gene which makes prions, the proteins that spread the disease. These prions become malformed and in turn make all healthy prions they encounter malformed as well, in a chain reaction that ultimately destroys brains by turning them into a spongy mush.
The change in the gene comes at a position called codon 127. Throughout the animal kingdom, the codon contains the same amino acid, called glycine or "G", from each parent, giving the form G127G. To their astonishment, Mead and his colleagues found a variant of the codon never seen in nature before, in which one of the glycines has been swapped for a valine amino acid, giving the new variant the name G127V.
Initially, Mead and his colleagues thought that because the variant had never been seen before, it must have damaging rather than beneficial effects. "We thought we'd found the trigger for how kuru happens, that someone ate the brain of someone with the mutation and that's how the disease started spreading through the cannibalistic funeral feasts," he said.
"Instead, we found the complete opposite, which is that it was protective."

Inherited health

The mutation first arose about 200 years ago by accident in a single individual, who then passed it down to his or her descendants. "When the kuru epidemic peaked about 100 years back, there were maybe a couple of families who found that they and their children survived while all their neighbours were dying, and so on to today's generation, who still carry the gene," says Mead. "So it was a very sudden genetic change under intense selection pressure from the disease," he says.
None of the 152 victims of kuru had the protective gene, suggesting that it provides almost complete resistance to the disease. But it's not yet known whether the variant protects against other prion diseases. Mead said that experiments are already under way in mice deliberately given the new mutation, to see if they are protected against both kuru and vCJD.
Mead says that the team has evidence that the prion protein made by the new variant might prevent the abnormal version of the prion from multiplying, giving clues to how to treat or prevent vCJD with drugs.
In 2003, Mead and his colleagues discovered a much more common variant of the prion gene that provides protection against prion diseases. The variant's position in the gene, at codon 129, is just two units away from the new one.
The protective variant at codon 129 is called "MV", standing for the amino acids methionine and valine. All deaths except one from vCJD have so far been in people with the "MM" variant, suggesting that they are specially at risk.
Jose Ordovas, who studies genetics and nutrition at Tufts University, Boston, said the finding "really supports the concept of very rapid adaptation of humans to the environment".
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Salamanders Spell out Evolution in Action

Salamander link


Salamanders Spell out Evolution in Action

July 11, 2011 — Lungless salamanders (Ensatina eschscholtzii) live in a horseshoe-shape region in California (a 'ring') which circles around the central valley. The species is an example of evolution in action because, while neighboring populations may be able to breed, the two populations at the ends of the arms of the horseshoe are effectively unable to reproduce.
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New research published in BioMed Central's open access journal BMC Evolutionary Biology showed that this reproductive isolation was driven by genetic divergence rather than adaption to different ecological habitats.
Researchers used genetic variation to determine 20 distinct populations of salamanders and focused in detail at 13 zones where the populations were able to cross breed. Results showed that the diversification of salamander populations was associated with significant genetic divergence, both nuclear and mitochondrial, and also with strong ecological divergence, in the plants and climate within their habitats.
However the ability to cross-breed was only associated with nuclear divergence. At contact zones around the ring up to 75% of the salamanders were hybrids, including second generation and back crosses to the parental populations but at the ends of the ring only 5.7% were hybrids and all of these were first generation F1 hybrids which rarely reproduced.
Dr Pereira said, "Evidence from E. eschscholtzii shows that the ecological environment, which may drive species formation, does not necessarily drive reproductive isolation. Instead, reproductive isolation of this 'ring' species of salamanders appears to be due to processes such as length of time in geographic isolation which are related to overall genetic divergence."
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Domesticated silver fox

http://en.wikipedia.org/wiki/Domesticated_silver_fox


The domesticated silver fox (marketed as the Siberian fox) is a domesticated form of the silver morph of the red fox. As a result of selective breeding, the new foxes became tamer and more dog-like.
The result of over 50 years of experiments in the Soviet Union and Russia, the breeding project was set up in 1959[1] by Soviet scientist Dmitri Belyaev. It continues today at The Institute of Cytology and Genetics at Novosibirsk, under the supervision of Lyudmila Trut.

Initial experimentation

The experiment was initiated by scientists who were interested in the topic of domestication and the process by which wolves became tame domesticated dogs. They saw some retention of juvenile traits by adult dogs, both morphological ones, such as skulls that were unusually broad for their length, and behavioral ones, such as whining, barking, and submission.
In a time when centralized political control exercised over genetics and agriculture was an official state doctrine, known as Lysenkoism, Belyaev's commitment to classical genetics had cost him his job as head of the Department of Fur Animal Breeding at the Central Research Laboratory of Fur Breeding in Moscow in 1948.[2] During the 1950s, he continued to conduct genetic research under the guise of studying animal physiology.
Belyaev believed that the key factor selected for in the domestication of dogs was not size or reproduction, but behavior; specifically, tameability. Since behavior is rooted in biology, selecting for tameness and against aggression, means selecting for physiological changes in the systems that govern the body's hormones and neurochemicals. Belyaev decided to test his theory by domesticating foxes; in particular, the silver fox, a dark color form of the red fox. He placed a population of them under strong selection pressure for inherent tameness.[3]
As Lyudmilla Trut says in her 1999 American Scientist article [1], The least domesticated foxes, those that flee from experimenters or bite when stroked or handled, are assigned to Class III. Foxes in Class II let themselves be petted and handled but show no emotionally friendly response to experimenters. Foxes in Class I are friendly toward experimenters, wagging their tails and whining. In the sixth generation bred for tameness we had to add an even higher-scoring category. Members of Class IE, the "domesticated elite," are eager to establish human contact, whimpering to attract attention and sniffing and licking experimenters like dogs. They start displaying this kind of behavior before they are one month old. By the tenth generation, 18 percent of fox pups were elite; by the 20th, the figure had reached 35 percent. Today elite foxes make up 70 to 80 percent of our experimentally selected population.
Belyaev and Trut believe that selecting for tameness mimics the natural selection that must have occurred in the ancestral past of dogs, and more than any other quality, must have determined how well an animal would adapt to life among humans.
The result is that Russian scientists now have a number of domesticated foxes that are fundamentally different in temperament and behavior from their wild forebearers. Some important changes in physiology and morphology are now visible, such as mottled or spotted colored fur. Many scientists believe that these changes related to selection for tameness are caused by lower adrenaline production in the new breed, causing physiological changes in very few generations and thus yielding genetic combinations not present in the original species. This indicates that selection for tameness (i.e. low flight distance) produces changes that are also influential on the emergence of other "dog-like" traits, such as raised tail and coming into heat every six months rather than annually.
The project also investigated breeding vicious foxes to study aggressive behavior. These foxes snap at humans and otherwise show no fear.
Similar research was carried out in Denmark with mink (Neovison vison).[4]

Current project status

Following the demise of the Soviet Union, the project has run into serious financial problems. In 1996, there were 700 domesticated foxes, but in 1998, without enough funds for food and salaries, the number had to be reduced to 100. Most of the project expenses are covered by selling the foxes as pets, but the project remains in a difficult situation and is looking for new sources of revenue from outside sources.
In an article published in Current Biology about the genetic differences between the two fox populations,[5] an experiment was reported in which DNA microarrays were used to detect differential gene expression between domesticated foxes, non-domesticated foxes raised at the same farm as the tame foxes, and wild foxes. Forty genes were found to differ between the domesticated and non-domesticated farm-raised foxes, although about 2,700 genes differed between the wild foxes and either set of farm-raised foxes. The authors did not analyze the functional implications of the gene expression differences they observed.
In another study published in Behavior Genetics,[6] a system of measuring fox behavior was described that is expected to be useful in QTL mapping to explore the genetic basis of tame and aggressive behavior in foxes.
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Blind Mole Rats Show Evolution in Action

news.sciencemag.org/plants-animals/2013/01/blind-mole-rats-show-evolution-action

Blind Mole Rats Show Evolution in Action

28 January 2013 3:00 pm
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Blind mole rats could be a real eye-opener for evolutionary science. According to a new study, the burrowing rodents are key to answering a controversial question about how new species arise.
Sex is a near-universal fact of life that helps spread genes through a population. When a mountain chain or some other physical barrier blocks that spread, a population may evolve into two genetically distinct groups that are no longer able to interbreed successfully. This process is known as allopatric speciation.
In theory, though, new species can form even without a physical barrier to force the issue. Natural variation means that some individuals in a population may behave differently from their peers, for instance, and over time the differences can become great enough to prevent gene flow. Exactly how often this so-called sympatric speciation occurs in nature remains a topic of hot debate.
Eviatar Nevo, an evolutionary biologist at the University of Haifa in Israel, thinks that sympatric speciation could be much more common than is generally believed—and he says that he has found a method to help prove it. His team has been studying the Upper Galilee Mountains blind mole rat ( Spalax galili) in a small area of northern Israel where geological activity has pushed igneous basalt rock against the chalk bedrock. The sharp geological boundary is reflected at the surface: Some plants living above the chalk are not seen above the basalt, and vice versa. Blind mole rats are found in both the basalt-derived and chalk-derived soils, and Nevo's team studied their mitochondrial DNA. Although in some places mole rats in the two soil types are separated by just a few meters of easily dug dirt, the researchers found clear genetic differences.
"The populations differ by up to 40% of their mitochondrial DNA," says Nevo, who reports his findings online today in the Proceedings of the National Academy of Sciences. Despite the lack of any physical barrier "the gene flow between the different soil-dwelling populations is very low." He has preliminary evidence that female and male mole rats taken from one soil type prefer to mate with each other even in the presence of mole rats from the other soil type—although he says more work must be done to show that this preference is strong enough to explain the genetic differences.
Nevo says that given enough time, the basalt mole rats may become so genetically distinct that they are no longer able to breed with chalk mole rats at all—in other words, he thinks his results show sympatric speciation in action. What's more, he says ecologists could find many more examples of sympatric speciation by studying the numerous localities around the world with similarly sharp ecological boundaries. Nevo predicts that populations on either side of the boundary will show unique adaptations that leave them unable to interbreed, even though individuals from the two populations come into regular contact because the boundary is not a physical barrier.
Jerry Coyne, an evolutionary biologist at the University of Chicago in Illinois, is unconvinced. He identifies a clear problem: Only time will tell if the two mole rat populations truly become incapable of interbreeding—until they do, it's too soon to add this to the small pile of confirmed sympatric speciation events. "We plan to conduct additional habitat and mate-choice experiments, which are the decisive demonstration of the origin of a new species," Nevo retorts.
Sergey Gavrilets, an evolutionary biologist at the University of Tennessee, Knoxville, is more comfortable with the idea that the mole rats may be undergoing speciation. But is it sympatric speciation? "I don't know," he says. The two populations certainly live side-by-side today, but it's challenging to prove that the genetic differences between them were not locked in place at an earlier date when the two were physically separated. That said, Gavrilets agrees with Nevo that sharp ecological boundaries may be "especially promising" locations to search for examples of sympatric speciation—examples that could settle the controversy about how common the process really is.
But Coyne thinks this search is better focused on oceanic islands that are small enough to rule out earlier episodes of physical separation. "Sympatric speciation could be more common than we think," he says. "But you need a propitious set of circumstances to show that."
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Shorter-winged swallows evolve around highways

https://www.sciencenews.org/article/shorter-winged-swallows-evolve-around-highways

Shorter-winged swallows evolve around highways

In survey along Nebraska roads, number of birds killed by cars has plummeted over 30 years
by Meghan Rosen
12:48pm, March 18, 2013
Magazine issue: 
April 20, 2013
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Crossing the road has gotten easier for cliff swallows. Over generations, the mortal threat of speeding cars may have shortened their wings.
TRAFFIC DODGERS Cliff swallows build small mud nests under bridges and highway overpasses, placing them at serious risk of becoming roadkill. Dodging cars may have favored a shift toward short, maneuverable wings.
C.R. Brown and M.B. Brown/Current Biology 2013
Cliff swallow colonies can include thousands of nests like the ones pictured here on an interstate highway bridge in Nebraska. The birds’ roadkill rates have dropped over the last 30 years; shorter wings that help the swallows evade traffic may explain why.
C.R. Brown and M.B. Brown/Current Biology 2013
Over the last 30 years, the number of cliff swallows killed along roads in southwestern Nebraska has plunged, and the birds’ average wing length has shrunk, researchers report March 18 in Current Biology.
The data are “jaw dropping,” says animal behaviorist Colleen Cassady St. Clair of the University of Alberta in Edmonton, who was not involved with the work. The results suggest that years of smacking into SUVs forced swallows to adapt to the road.
In the absence of roads, cliff swallows — sparrow-sized birds with orange rumps and white foreheads — tuck their nests under overhangs on cliff faces. But in the last few decades, many birds have traded ancestral homes for modern real estate — highway bridges and overpasses.
Cliff swallows can plaster thousands of cantaloupe-sized mud nests to the undersides of these structures, says study author Charles Brown of the University of Tulsa in Oklahoma. These colonies are less likely than cliff nests to be washed away in storms but come with a different risk: They perch near roads — and fast-moving traffic.
As graduate students in the 1980s, Brown and study coauthor Mary Bomberger Brown didn’t set out to study swallows’ adaptations to cars. They were interested in the birds’ social behavior. But because the team drove thousands of kilometers among colonies, they saw a lot of roadkill.
Every summer for the next 29 years, the team trekked to the colonies, counted nests and picked up dead birds. In total, the Browns gathered more than 2,000 swallows.
Starting in 1983, the researchers collected fewer birds killed by cars each year, until they found only four in 2012. And when Charles Brown measured preserved specimens’ wing lengths, he saw that, compared with the rest of the population, swallows that died on the road had wings that were a few millimeters longer.
A few millimeters — about the width of a Tic Tac — might seem like a small change, but for birds’ wings, “a little bit can make a big difference,” says evolutionary biologist Ronald Mumme of Allegheny College in Meadville, Pa.
Petite wings let birds take off quickly and maneuver deftly through the air. Like quail, which have short, rounded wings and can explode off the ground almost vertically, Brown says, swallows might be better served by short wings that help them whiz up and out of harm’s way.
He thinks the population’s shorter average wing lengths could help explain why roadkill numbers are going down. “It’s amazing what natural selection can do,” he says. 
The team ruled out other potential explanations, such as declining swallow populations or an increase in avian scavengers stealing carcasses. Still, Charles Brown says, factors other than wing length may also be involved. Cars may have killed off daredevil swallows, for example, leaving more cautious birds behind.
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E. coli long-term evolution experiment

 http://en.wikipedia.org/wiki/E._coli_long-term_evolution_experiment

 

E. coli long-term evolution experiment

From Wikipedia, the free encyclopedia

The 12 evolving E. coli populations on June 25, 2008
The E. coli long-term evolution experiment is an ongoing study in experimental evolution led by Richard Lenski that has been tracking genetic changes in 12 initially identical populations of asexual Escherichia coli bacteria since 24 February 1988.[1] The populations reached the milestone of 50,000 generations in February 2010.
Since the experiment's inception, Lenski and his colleagues have reported a wide array of genetic changes; some evolutionary adaptations have occurred in all 12 populations, while others have only appeared in one or a few populations. One particularly striking adaption was the evolution of a strain of E. coli that was able to use citric acid as a carbon source in an aerobic environment.[2]

Experimental approach

The long-term evolution experiment was intended to provide experimental evidence for several of the central questions of evolutionary biology: how rates of evolution vary over time; the extent to which evolutionary changes are repeatable in separate populations with identical environments; and the relationship between evolution at the phenotypic and genomic levels.[3]
The use of E. coli as the experimental organism has allowed many generations and large populations to be studied in a relatively short period of time, and has made experimental procedures (refined over decades of E. coli use in molecular biology) fairly simple. The bacteria can also be frozen and preserved, creating what Lenski has described as a "frozen fossil record" that can be revived at any time (and can be used to restart recent populations in cases of contamination or other disruption of the experiment). Lenski chose an E. coli strain that reproduces only asexually, without bacterial conjugation; this limits the study to evolution based on new mutations and also allows genetic markers to persist without spreading except by common descent.[3]

Methods

Each of the 12 populations is kept in an incubator in Lenski's laboratory at Michigan State University in a minimal growth medium. Each day, 1% of each population is transferred to a flask of fresh growth medium. Under these conditions, each population experiences 6.64 generations, or doublings, each day. Large, representative samples of each population are frozen with glycerol as a cryoprotectant at 500-generation (75 day) intervals. The bacteria in these samples remain viable, and can be revived at any time. This collection of samples is referred to as the "frozen fossil record", and provides a history of the evolution of each population through the entire experiment. The populations are also regularly screened for changes in mean fitness, and supplemental experiments are regularly performed to study interesting developments in the populations.[4] As of October 2012, the E. coli populations have been under study for over 56,000 generations, and are thought to have undergone enough spontaneous mutations that every possible single point mutation in the E. coli genome has occurred multiple times.[2]
The initial strain of E. coli for Lenski's long-term evolution experiment came from "strain Bc251", as described in a 1966 paper by Seymour Lederberg, via Bruce Levin (who used it in a bacterial ecology experiment in 1972). The defining genetics traits of this strain were: T6r, Strr, r−m−, Ara− (unable to grow on arabinose).[1] Before the beginning of the experiment, Lenski prepared an Ara+ variant (a point mutation in the ara operon that enables growth on arabinose) of the strain; the initial populations consisted of 6 Ara− colonies and 6 Ara+ colonies, which allowed the two sets of strains to be differentiated and tested for fitness against each other. Unique genetic markers have since evolved to allow identification of each strain.

Results


Growth in cell size of bacteria in the Lenski experiment
In the early years of the experiment, several common evolutionary developments were shared by the populations. The mean fitness of each population, as measured against the ancestor strain, increased, rapidly at first, but leveled off after close to 20,000 generations (at which point they grew about 70% faster than the ancestor strain). All populations evolved larger cell volumes and lower maximum population densities, and all became specialized for living on glucose (with declines in fitness relative to the ancestor strain when grown in dissimilar nutrients). Of the 12 populations, four developed defects in their ability to repair DNA, greatly increasing the rate of additional mutations in those strains. Although the bacteria in each population are thought to have generated hundreds of millions of mutations over the first 20,000 generations, Lenski has estimated that within this time frame, only 10 to 20 beneficial mutations achieved fixation in each population, with fewer than 100 total point mutations (including neutral mutations) reaching fixation in each population.[3]

The population designated Ara-3 (center) is more turbid because that population evolved to use the citrate present in the growth medium.

Evolution of aerobic citrate usage in one population

In 2008, Lenski and his collaborators reported on a particularly important adaptation that occurred in the population called Ara-3: the bacteria evolved the ability to grow on citrate under the oxygen-rich conditions of the experiment. Wild-type E. coli cannot grow on citrate when oxygen is present due to the inability during aerobic metabolism to produce an appropriate transporter protein that can bring citrate into the cell, where it could be metabolized via the citric acid cycle. The consequent lack of growth on citrate under oxic conditions, referred to as a Cit- phenotype, is considered a defining characteristic of the species that has been a valuable means of differentiating E. coli from pathogenic Salmonella. Around generation 33,127, the experimenters noticed a dramatically expanded population-size in one of the samples; they found clones in this population could grow on the citrate included in the growth medium to permit iron acquisition. Examination of samples of the population frozen at earlier time points led to the discovery that a citrate-using variant (Cit+) had evolved in the population at some point between generations 31,000 and 31,500. They used a number of genetic markers unique to this population to exclude the possibility that the citrate-using E. coli were contaminants. They also found the ability to use citrate could spontaneously re-evolve in a subset of genetically pure clones isolated from earlier time points in the population's history. Such re-evolution of citrate use was never observed in clones isolated from before generation 20,000. Even in those clones that were able to re-evolve citrate use, the function showed a rate of occurrence on the order of one occurrence per trillion cell divisions. The authors interpret these results as indicating that the evolution of citrate use in this one population depended on one or more earlier, possibly nonadaptive "potentiating" mutations that had the effect of increasing the rate of mutation to an accessible level. (The data they present further suggests that citrate use required at least two mutations subsequent to this "potentiating" mutation) More generally, the authors suggest these results indicate (following the argument of Stephen Jay Gould) "that historical contingency can have a profound and lasting impact" on the course of evolution.[2]
In 2012, a team of researchers working under Lenski reported the results of a genomic analysis of the Cit+ trait that shed light on the genetic basis and evolutionary history of the trait.[5] The researchers had sequenced the entire genomes of twenty-nine clones isolated from various time points in the Ara-3 population's history. They used these sequences to reconstruct the phylogenetic history of the population, which showed that the population had diversified into three clades by 20,000 generations. The Cit+ variants had evolved in one of these, which they called Clade 3. Clones that had been found to be potentiated in earlier research were distributed among all three clades, but were over-represented in Clade 3. This led the researchers to conclude that there had been at least two potentiating mutations involved in Cit+ evolution. The researchers also found that all Cit+ clones sequenced had in their genomes a duplication mutation of 2933 base pairs that involved the gene for the citrate transporter protein used in anaerobic growth on citrate, citT. The duplication is tandem, resulting in two copies that are head-to-tail with respect to each other. This duplication immediately conferred the Cit+ trait by creating a new regulatory module in which the normally silent citT gene is placed under the control of a promoter for an adjacent gene called rnk. The new promoter activates expression of the citrate transporter when oxygen is present, and thereby enabling aerobic growth on citrate. Movement of this new regulatory module (called the rnk-citT module) into the genome of a potentiated Cit- clone was shown to be sufficient to produce a Cit+ phenotype. However, the initial Cit+ phenotype conferred by the duplication was very weak, and only granted a ~1% fitness benefit. The researchers found that the number of copies of the rnk-citT module had to be increased to strengthen the Cit+ trait sufficiently to permit the bacteria to grow well on the citrate, and that further mutations after the Cit+ bacteria became dominant in the population continued to accumulate that refined and improved growth on citrate. The researchers conclude that the evolution of the Cit+ trait suggests that new traits evolve through three stages: potentiation, in which mutations accumulate over a lineage's history that make a trait accessible; actualization, in which one or more mutations render a new trait manifest; and refinement, in which the trait is improved by further mutations.

Evolution of increased cell size in all twelve populations

All twelve of the experimental populations show an increase in cell size, and in many of the populations, a more rounded cell shape.[6] This change was partly the result of a mutation that changed the expression of a gene for a penicillin binding protein, which allowed the mutant bacteria to outcompete ancestral bacteria under the conditions in the long-term evolution experiment. However, although this mutation increased fitness under these conditions, it also increased the bacteria's sensitivity to osmotic stress and decreased their ability to survive long periods in stationary phase cultures.[6]
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The tropical blue moon butterfly has developed a way of fighting back against parasitic bacteria.

 http://news.bbc.co.uk/1/hi/sci/tech/6896753.stm
Butterfly shows evolution at work
A male Hypolimnas bolina, or blue moon, butterfly
The bacteria selectively kills male blue moons before they can hatch
Scientists say they have seen one of the fastest evolutionary changes ever observed in a species of butterfly. The tropical blue moon butterfly has developed a way of fighting back against parasitic bacteria.
Six years ago, males accounted for just 1% of the blue moon population on two islands in the South Pacific.
But by last year, the butterflies had evolved a gene to keep the bacteria in check and male numbers were up to about 40% of the population.
Scientists believe the comeback is due to "suppressor" genes that control the Wolbachia bacteria that is passed down from the mother and kills the male embryos before they hatch.
"To my knowledge, this is the fastest evolutionary change that has ever been observed," said Sylvain Charlat, of University College London, UK, whose study appears in the journal Science.
Rapid natural selection
Gregory Hurst, a University College researcher who worked with Mr Charlat, added: "We usually think of natural selection as acting slowly, over hundreds of thousands of years.
"But the example in this study happened in the blink of the eye, in terms of evolutionary time, and is a remarkable thing to get to observe."
The team first documented the massive imbalance in the sex ratio of the blue moon butterfly (Hypolimnas bolina) on the Samoan islands of Savaii and Upolu in 2001.
In 2006, they started a new survey after an increase in reports of male sightings at Upolo.
They found that the numbers of male butterflies had either reached or were approaching those of females.
The researchers are not sure whether the gene that suppressed the parasite emerged from a mutation in the local population or whether it was introduced by migratory Southeast Asian butterflies in which the mutation already existed.
But they said that the repopulation of male butterflies illustrates rapid natural selection, a process in which traits that help a species survive become more prominent in a population. "We're witnessing an evolutionary arms race between the parasite and the host. This strengthens the view that parasites can be major drivers in evolution," Mr Charlat said.
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"Instant" Evolution Seen in Darwin's Finches, Study Says

http://news.nationalgeographic.co.uk/news/2006/07/060714-evolution_2.html

"Instant" Evolution Seen in Darwin's Finches, Study Says

Mason Inman
for National Geographic News
July 14, 2006
Evolution may sometimes happen so fast that it's hard to catch in action, a new study of Galápagos finches suggests.
Researchers from New Jersey's Princeton University have observed a species of finch in Ecuador's Galápagos Islands that evolved to have a smaller beak within a mere two decades.
Surprisingly, most of the shift happened within just one generation, the scientists say.
In 1982 the large ground finch arrived on the tiny Galápagos island of Daphne, just east of the island of San Salvador (map of the Galápagos).
Since then the medium ground finch, a long-time Daphne resident, has evolved to have a smaller beak—apparently as a result of direct competition with the larger bird for food.
Evolutionary theory had previously suggested that competition between two similar species can drive the animals to evolve in different directions.
But until now the effect had never been observed in action in the wild.
In the new study Princeton's Peter and Rosemary Grant closely tracked the two related species for decades.
Their results appear in this week's issue of the journal Science.
Changing Beaks, Changing Diet
For both finch species, the researchers note, feeding is a trade-off between effort and payoff.
The birds generally prefer to eat larger seeds, which are harder for their nutcracker-like beaks to break open but hold a bigger reward inside.
 The bigger the bird's beak, the easier it is to crack open the seeds' coatings.
The already smaller-beaked medium ground finch couldn't keep up with the newly arrived large ground finch, which is about twice as big and dominates feeding grounds.
Apparently in response, the medium ground finch evolved to have an even smaller beak, making the species more adept at eating small seeds that didn't interest the larger finch.
"This is a phenomenon known as character displacement," Peter Grant said.
"It is a very important one in studies of evolution, because it shows that species interact for food and undergo evolutionary change which minimizes further competition."
The researchers say they have seen other types of evolution in action in Galápagos finches before.
But this was the strongest shift they've seen in their 33 years of study, the scientists say.
Nutcrackers, Woodpeckers, Vampires, Oh My!
The Galápagos Islands' 14 species of finches all evolved from one ancestral species, which arrived from the South American mainland about two to three million years ago.
That original species branched out into many others, with each one specialized for different roles.
The woodpecker finch, for example, has evolved to the point where it can drill holes in trees, while the vampire finch drinks other birds' blood (watch video of vampire finches).
Ironically, naturalist Charles Darwin missed signs of evolution among these finches during his 1831 visit to the Galápagos.
Only later, with the help of other collectors and scientists, was he able to see how evolution was responsible for the variety of finches. (Read "Was Darwin Wrong?" in National Geographic magazine [November 2004].)
Since then, the 1982 arrival of the large ground finch on Daphne is the first known instance of a new finch arriving in the Galápagos.
"The event we observed is the only one that we know about, the only establishment of a new breeding population anywhere in the archipelago," Peter Grant says.
"Once this happened before our eyes, we realized we had a very unusual and potentially very important event to follow."
The two bird species immediately began competing for larger seeds.
The situation reached a tipping point when a severe drought hit the island in 2003 and 2004.
Both finches suffered, since there were far fewer seeds overall. The dominant large ground finch ate most of the available large seeds.
"With the near removal of the supply of large seeds, the large-beaked birds [among] the medium ground finches did not have enough food to survive," Peter Grant said.
"They died at a faster rate than the small-beaked members of the population."
The effects of competition are apparent when this event is compared to a drought in 1977, before the large ground finch arrived on the island, the researchers argue.
During the earlier drought the medium ground finches' average beak size actually increased.
Textbook Classic
Jonathan Losos is an evolutionary ecologist at Harvard University in Boston, Massachusetts, who was not involved with the Grants' work.
"This study will be an instant textbook classic," he said.
"The most intriguing aspect of the study is its nuanced understanding of how and when character displacement occurs," Losos added.
"It supports suggestions by the Grants and others that [natural] selection will be most intense during crunch times."
David Pfennig at the University of North Carolina at Chapel Hill agrees that the study has important implications.
For Pfennig, the study's greatest surprise was "the apparent speed with which the character displacement occurs—within a single year!"
Usually we think of evolution as being a slow grind, he says.
But, Pfennig added, the study suggests that evolution due to competition between closely related species "paradoxically may often occur so rapidly that we may actually miss the process taking place."
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EVOLUTION CAUSED BY CANE TOADS

 

 http://www.canetoadsinoz.com/cane-toads-caused-evolution.html

EVOLUTION CAUSED BY CANE TOADS

Not only have cane toads evolved rapidly; also, they have caused rapid evolution in native animals in the course of their Australian invasion.
We know that toads kill lots of native predators that try to eat the toxic invaders, but cannot tolerate the toads’ poisons. Animals that try to eat big toads, like quolls and goannas, are in the biggest trouble (because big toads have a lot more poison than small toads. However, not every predator is equally vulnerable. Some are reluctant to try to eat toads; others are a bit more tolerant than usual of the toads’ poison, and so forth. In evolutionary biology jargon, this means that cane toads in Australia are a “selective pressure”. That is, the arrival of toads removes some genetic traits from the predator population (genes that make predators vulnerable to toads) but other traits (e.g., genes that tell the predator not to eat toads) are not affected. So, the toads cause a change in genetic composition of the predators: the only ones that survive are the ones that are able to live side-by-side with toads.


Goanna

Large goannas, like this Lace Monitor, are in big trouble when cane toads invade their territory
(photo by Terri Shine).

What kinds of characteristics would help a predator to survive after the cane toads arrive? The obvious characteristics would be genes that help predators ignore toads as food, and that allow predators to survive a dose of toad poison. But probably lots of characteristics might play a role … for example, any gene affecting where and when a predator is active (if it’s best not to overlap too much with toads) might help the predator to survive. Another “toad-smart” characteristic would be any gene that reduced the size of toads that a predator could eat – because smaller toads have much less poison than larger animals.

The best evidence on this evolutionary process comes from Dr Ben Phillips’ studies on red-bellied blacksnakes, a venomous snake species from eastern Australia. Ben looked at animals from Queensland (where the snakes lived in toad-infested areas) and New South Wales (where there are large areas where the snakes occur but toads do not – or at least, not yet). Ben found exactly the kinds of differences between snakes from toad-infested and non-infested areas that we would expect from evolutionary change. First, the snakes that lived with toads wouldn’t eat toads when we offered them to snakes in captivity, whereas when given the chance, about half of the snakes from toad-free areas readily grabbed a toad – and usually died as a result. Second, the toad-exposed snakes were more able to deal with the toads’ poison. Third, the snakes from toad areas had smaller heads compared to their body size – so they were not able to eat really big (and thus, more dangerous) toads.


Red Bellied Black Snake

The Red-bellied Black Snake has evolved rapdily to help it deal with toxic cane toads
(photo by Ben Phillips).

The ability of native animals to evolve rapidly to deal with toads is a really encouraging result in terms of biodiversity and conservation. Toads haven’t driven any species to extinction – instead, they reduce predator numbers and change their characteristics. After some time (and we really don’t know how long), the predators are able to coexist with toads, and so their numbers begin to recover.

Understanding exactly how native predators adapt to toads is a big part of TEAM BUFO’s program of research. We’re looking not only at Fogg Dam – for example, Matt Greenlees has examined how frog behaviour changes after toad invasion – but also in areas that were colonized by cane toads many years ago. John Llewelyn is based in Townsville, and he has worked out how the local snakes and marsuplials react to toads, and how they can deal with the presence of this toxic frog-mimicking invader.

Adder

Research on Death Adders by Dr. Ben Phillips has measured the evolutinary pressures that cane toad invasion imposes on these predators
(photo by Ben Phillips).

One consequence of all of this research by TEAM BUFO is that cane toads in Australia have proved to be one of the best biological systems, anywhere in the world, for studies on rapid evolutionary change. Australian cane toads are now turning up in lots of textbooks of evolutionary biology!
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Lizards Rapidly Evolve After Introduction to Island

 http://news.nationalgeographic.co.uk/news/2008/04/080421-lizard-evolution_2.html

 

Lizards Rapidly Evolve After Introduction to Island

Kimberly Johnson
for National Geographic News
April 21, 2008
Italian wall lizards introduced to a tiny island off the coast of Croatia are evolving in ways that would normally take millions of years to play out, new research shows.
In just a few decades the 5-inch-long (13-centimeter-long) lizards have developed a completely new gut structure, larger heads, and a harder bite, researchers say.
In 1971, scientists transplanted five adult pairs of the reptiles from their original island home in Pod Kopiste to the tiny neighboring island of Pod Mrcaru, both in the south Adriatic Sea.
Genetic testing on the Pod Mrcaru lizards confirmed that the modern population of more than 5,000 Italian wall lizards are all descendants of the original ten lizards left behind in the 1970s.
(Related: "Evolution's 'Driving Force' Shifts Based on Behavior, Study Says" [November 16, 2006].)
Lizard Swarm
While the experiment was more than 30 years in the making, it was not by design, according to Duncan Irschick, a study author and biology professor at the University of Massachusetts, Amherst.
After scientists transplanted the reptiles, the Croatian War of Independence erupted, ending in the mid-1990s. The researchers couldn't get back to island because of the war, Irschick said.
In 2004, however, tourism began to open back up, allowing researchers access to the island laboratory.
(Read: "Kayaking the New Croatia" in National Geographic Adventure Magazine.)
"We didn't know if we would find a lizard there. We had no idea if the original introductions were successful," Irschick said.
What they found, however, was shocking.

 "The island was swarming with lizards," he said.
The findings were published in March in the journal Proceedings of the National Academy of Sciences.
Fast-Track Evolution
The new habitat once had its own healthy population of lizards, which were less aggressive than the new implants, Irschick said.
The new species wiped out the indigenous lizard populations, although how it happened is unknown, he said.
The transplanted lizards adapted to their new environment in ways that expedited their evolution physically, Irschick explained.
Pod Mrcaru, for example, had an abundance of plants for the primarily insect-eating lizards to munch on. Physically, however, the lizards were not built to digest a vegetarian diet.
Researchers found that the lizards developed cecal valves—muscles between the large and small intestine—that slowed down food digestion in fermenting chambers, which allowed their bodies to process the vegetation's cellulose into volatile fatty acids.
"They evolved an expanded gut to allow them to process these leaves," Irschick said, adding it was something that had not been documented before. "This was a brand-new structure."
Along with the ability to digest plants came the ability to bite harder, powered by a head that had grown longer and wider.
(Related news: "Komodo Dragon's Bite Is 'Weaker Than a House Cat's'" [April 18, 2008].)
The rapid physical evolution also sparked changes in the lizard's social and behavioral structure, he said. For one, the plentiful food sources allowed for easier reproduction and a denser population.
The lizard also dropped some of its territorial defenses, the authors concluded.
Such physical transformation in just 30 lizard generations takes evolution to a whole new level, Irschick said.
It would be akin to humans evolving and growing a new appendix in several hundred years, he said.
"That's unparalleled. What's most important is how fast this is," he said.
While researchers do know the invader's impact on its reptile brethren, they do not know how the species impacts local vegetation or insects, a subject of future study, Irschick said.
Dramatic Changes
The study demonstrates that a lot of change happens in island environments, said Andrew Hendry, a biology professor at Montreal's McGill University.
What could be debated, however, is how those changes are interpreted—whether or not they had a genetic basis and not a "plastic response to the environment," said Hendry, who was not associated with the study.
There's no dispute that major changes to the lizards' digestive tract occurred. "That kind of change is really dramatic," he added.
"All of this might be evolution," Hendry said. "The logical next step would be to confirm the genetic basis for these changes."
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Mussels Evolve Quickly To Defend Against Invasive Crabs

... from universities, journals, and other research organizations

Mussels Evolve Quickly To Defend Against Invasive Crabs

Aug. 11, 2006 — Scientists at the University of New Hampshire (UNH) have found that invasive crab species may precipitate evolutionary change in blue mussels in as little as 15 years. The study, by UNH graduate student Aaren Freeman with associate professor of zoology James Byers and published in the Aug. 11 issue of the journal Science, indicates that such a response can evolve in an evolutionary nanosecond compared to the thousands of years previously assumed. The paper is called "Divergent induced responses to an invasive predator in marine mussel populations."
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"It's the blending of ecological and evolutionary time," says Freeman, a Ph.D. candidate in the department of zoology. "It's an important development in the arms race between these crabs and these mollusks." Crabs prey on blue mussels by crushing their shells.
Freeman looked at the inducible defense -- shell thickening -- of blue mussels (Mytlius edulis) in the presence of two invasive crab species in New England, the Asian shore crab Hemigrapsus sanguineus and the green crab Carcinus maenas. While Carcinus was introduced to New England from Europe between 150 and 200 years ago, Hemigrapsus is a relative newcomer, arriving from Asia to New Jersey in 1988. While previous research had established that mussels recognize Carcinus, it had not be determined if they recognize Hemigrapsus. And, crucial to the design of Freeman's study, Hemigrapsus is not present north of mid-coast Maine.
"This set up a chance to look at populations that had been exposed to the predators for varying lengths of time," says Freeman. "We wanted to know, how is it that these mollusks can recognize a crab that is historically not present in North America?"
Freeman exposed mussels native to the northern -- above mid-coast Maine -- and southern New England to both Carcinus and the Hemigrapsus. Both populations thickened their shells when exposed to waterborne cues of Carcinus, but only the southern mussels -- Freeman describes them as "more worldly" -- expressed inducible shell thickening in the presence of Hemigrapsus.
"The mussel's inducible response to H. sanguineus reflects natural selection favoring the recognition of this novel predator through rapid evolution of cue specifity or thresholds," Freeman and Byers write.
Findings were consistent in two experiments over two years, one in a laboratory setting in Nahant, Mass., and one in the field at Woods Hole, Mass. "The consistency over two years and two sites really suggests an underlying robust mechanism," says Byers, who is Freeman's dissertation advisor.
While this sort of rapid evolutionary response to predators has been exhibited in some other species, all have been vertebrates. The blue mussel, which Freeman describes as the lab rat of marine biologists, is an invertebrate "that people assume is not very bright," he says. Yet his findings indicate that within the brief span of 15 years, it has evolved an inducible response to a new predator.
How do mussels evolve so quickly? In southern New England, the scientists say, mussels are prey to many crabs as well as other marine species. "When Hemigrapsus came along the mussels' wheels were well-greased to respond," says Byers. "That's our best guess."
Byers helps put the impact of the research in context. Because extensive data does not exist on invasive ecology, "there's a tendency to extrapolate any data you get on an invasive species. But here we show that the response from the prey differs over just a couple hundred kilometers."
And while its "real world" impact is not immediately obvious, Byers suggests that perhaps northern Maine and Canadian shellfishers might consider "beefing up the worldliness of their naïve mussel populations before the Hemigrapsus arrives," he says, suggesting that this could be done by mixing some of the responsive southern mussels into the naïve northern stocks. "Although 15 years is fast to evolve better defenses to your predator, it can be painfully long if you're a shellfisherman," Byers adds.
This paper is one chapter of Freeman's doctoral dissertation, which also explores how mussels respond to sea stars and to multiple predators. He anticipates completing his doctoral work by October 2006, when he will begin a post-doctoral position with UNH research associate professor Fred Short.
Freeman notes that there's one predator mussels will not need to defend themselves against: him. "I used to like them, before I started working with them for my dissertation," he says. "Not anymore."
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Evolution in Action: Lizard Moving From Eggs to Live Birth


http://news.nationalgeographic.co.uk/news/2010/09/100901-science-animals-evolution-australia-lizard-skink-live-birth-eggs/

 

Evolution in Action: Lizard Moving From Eggs to Live Birth

A yellow-bellied three-toed skink.
A yellow-bellied three-toed skink carrying embryos, visible as light orbs inside its body.
Photograph courtesy Rebecca A. Pyles
Brian Handwerk
for National Geographic News
Published September 1, 2010
Evolution has been caught in the act, according to scientists who are decoding how a species of Australian lizard is abandoning egg-laying in favor of live birth.
Along the warm coastal lowlands of New South Wales (map), the yellow-bellied three-toed skink lays eggs to reproduce. But individuals of the same species living in the state's higher, colder mountains are almost all giving birth to live young.
Only two other modern reptiles—another skink species and a European lizard—use both types of reproduction. (Related: "Virgin Birth Expected at Christmas—By Komodo Dragon.")
Evolutionary records shows that nearly a hundred reptile lineages have independently made the transition from egg-laying to live birth in the past, and today about 20 percent of all living snakes and lizards give birth to live young only.
(See "Oldest Live-Birth Fossil Found; Fish Had Umbilical Cord.")
But modern reptiles that have live young provide only a single snapshot on a long evolutionary time line, said study co-author James Stewart, a biologist at East Tennessee State University. The dual behavior of the yellow-bellied three-toed skink therefore offers scientists a rare opportunity.
"By studying differences among populations that are in different stages of this process, you can begin to put together what looks like the transition from one [birth style] to the other."
Eggs-to-Baby Switch Creates Nutrient Problem
One of the mysteries of how reptiles switch from eggs to live babies is how the young get their nourishment before birth.
In mammals a highly specialized placenta connects the fetus to the uterus wall, allowing the baby to take up oxygen and nutrients from the mother's blood and pass back waste. (See related pictures of "extreme" animals in the womb.)
In egg-laying species, the embryo gets nourishment from the yolk, but calcium absorbed from the porous shell is also an important nutrient source.
Some fish and reptiles, meanwhile, use a mix of both birthing styles. The mother forms eggs, but then retains them inside her body until the very last stages of embryonic development. (Related: "Dinosaur Eggs Discovered Inside Mother—A First.")
The shells of these eggs thin dramatically so that the embryos can breathe, until live babies are born covered with only thin membranes—all that remains of the shells.
This adaptation presents a potential nourishment problem: A thinner shell has less calcium, which could cause deficiencies for the young reptiles.
Stewart and colleagues, who have studied skinks for years, decided to look for clues to the nutrient problem in the structure and chemistry of the yellow-bellied three-toed skink's uterus.
"Now we can see that the uterus secretes calcium that becomes incorporated into the embryo—it's basically the early stages of the evolution of a placenta in reptiles," Stewart explained.
Evolutionary Transition Surprisingly Simple
Both birthing styles come with evolutionary tradeoffs: Eggs are more vulnerable to external threats, such as extreme weather and predators, but internal fetuses can be more taxing for the mother.
(Related: "Human Sperm Gene Traced to Dawn of Animal Evolution.")
For the skinks, moms in balmier climates may opt to conserve their own bodies' resources by depositing eggs on the ground for the final week or so of development. Moms in harsh mountain climates, by contrast, might find that it's more efficient to protect their young by keeping them longer inside their bodies.
In general, the results suggest the move from egg-laying to live birth in reptiles is fairly common—at least in historic terms—because it's relatively easy to make the switch, Stewart said.
"We tend to think of this as a very complex transition," he said, "but it's looking like it might be much simpler in some cases than we thought."
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