Does Promiscuity Prevent Extinction?

(Feb. 26, 2010) — Promiscuous females may be the key to a species' survival, according to new research by the Universities of Exeter and Liverpool. Published February 25 in Current Biology, the study could solve the mystery of why females of most species have multiple mates, despite this being more risky for the individual.

These are Drosophila pseudoobscura mating. A new study by the Universities of Exeter and Liverpool, UK, on these fruitfly suggests promiscuous females may be the key to a species' survival. (Credit: University of Exeter)

Known as 'polyandry' among scientists, the phenomenon of females having multiple mates is shared across most animal species, from insects to mammals. This study suggests that polyandry reduces the risk of populations becoming extinct because of all-female broods being born. This can sometimes occur as a result of a sex-ratio distortion (SR) chromosome, which results in all of the Y chromosome 'male' sperm being killed before fertilisation. The all-female offspring will carry the SR chromosome, which will be passed on to their sons in turn resulting in more all-female broods. Eventually there will be no males and the population will die out.

For this study, the scientists worked with the fruitfly Drosophila pseudoobscura. They gave some populations the opportunity to mate naturally, meaning that the females had multiple partners. The others were restricted to having one mate each. They bred several generations of these populations, so they could see how each fared over time.

Over fifteen generations, five of the twelve populations that had been monogamous became extinct as a result of males dying out. The SR chromosome was far less prevalent in the populations in which females had the opportunity to have multiple mates and none of these populations became extinct.

The study shows how having multiple mates can suppress the spread of the SR chromosome, making all-female broods a rarity. This is because males that carry the SR chromosome produce only half as many sperm as normal males. When a female mates with multiple males, their sperm will compete to fertilise her eggs. The few sperm produced by males carrying the SR chromosome are out-competed by the sperm from normal males, and the SR chromosome cannot spread.

Lead author Professor Nina Wedell of the University of Exeter said: "We were surprised by how quickly -- within nine generations -- a population could die out as a result of females only mating with one partner. Polyandry is such a widespread phenomenon in nature but it remains something of an enigma for scientists. This study is the first to suggest that it could actually save a population from extinction."

This study was funded by the Natural Environment Research Council.

.First Brain Recordings from Flying Fruit Flies

(Feb. 15, 2010) — Researchers at the California Institute of Technology (Caltech) have obtained the first recordings of brain-cell activity in an actively flying fruit fly.

The work -- by Michael Dickinson, the Esther M. and Abe M. Zarem Professor of Bioengineering, with postdoctoral scholars Gaby Maimon and Andrew Straw -- suggests that at least part of the brain of the fruit fly (Drosophila melanogaster) "is in a different and more sensitive state during flight than when the fly is quiescent," Dickinson says.

A paper describing the research appears February 14 in the advance online edition of Nature Neuroscience.

A dye-filled glass electrode (pink) is inserted into a fruit fly's brain. The electrode and the brain are immersed in saline (colored blue in this image). The fly is flapping its wings in tethered flight. (Credit: Gaby Maimon and Michael Dickinson/Caltech

"Prior work on fruit flies has led to many important breakthroughs in biology. For example, the fact that genes reside on chromosomes and our understanding of how genes control development both emerged from experiments on fruit flies," Maimon says. "New research hopes to use these tiny insects to help determine how neurons give rise to complex behavior. This effort is helped by the fact that it is easy to manipulate the genes of fruit flies, but one problem remains: These insects are really, really tiny, which means it is very difficult to record from their brain during active behaviors such as flight."

"Researchers have recorded the neural-cell activity of fruit flies before, but only in restrained preparations -- animals that had been stuck or glued down," Dickinson explains. "Gaby was able to develop a preparation where the animal is tethered" -- its head clamped into place -- "but free to flap its wings." By slicing off a patch of the hard cuticle covering the brain, "we were able to target our electrodes onto genetically marked neurons," he says.

A puff of air was used to spur the flies into flapping their wings, while electrodes measured the activity of the marked neurons and high-speed digital cameras simultaneously recorded the flies' behavior.

In particular, the researchers focused on those neurons in the fly's visual system that keep the animal flying stably during flight. "These cells basically help the fly detect when its body posture changes," Dickinson says. "The signals from these cells are thought to control tiny steering muscles that then change the pattern of wing motion and bring the animal back into equilibrium."
In their experiments, the researchers discovered that when the animals began to fly, the visual cells immediately ramped up their activity. "The neurons' responses to visual motion roughly double when the flies begin to fly, which suggests that the system is more sensitive during flight," Dickinson says. "The increase is very abrupt. It's not at all a subtle change, and so we suspect that there is a neurochemical quickly released during flight that sets the animal's brain in this different state."

Previous studies in locusts -- which are far bigger and thus far easier to study -- had suggested the existence of this effect. However, the genetics of locusts are not nearly as well understood as those of Drosophila, which has made it impossible to pinpoint the genetic basis for the phenomenon.
In Drosophila, Dickinson says, it now should be possible to " out specifically what causes the change in sensitivity. Is the system turned off when the fly is on the ground? What neurochemicals are involved? Now we can start to use the genetic tricks that are available in fruit flies to get a better idea of what is going on."

Maimon adds: "Our work on Drosophila is of general interest because sensory neurons in many species -- including birds, rodents, and primates -- change their response strength depending on the behavioral state of the animal, but why these changes in sensitivity take place is not entirely clear."

In addition, the researchers plan to use their tethered-flight system to record the activity of other types of cells, including olfactory and motor cells, to determine if these also behave differently during flight and when flies are at rest.
"The question is, 'Is the entire brain completely different in flight?'" Dickinson says. "We suspect that this phenomenon is not unique to the visual cells we have studied. Most cells care whether the animal is flying or not."

This work was supported by the National Science Foundation and a Caltech Della Martin Fellowship.

Sex Life May Hold Key To Honeybee Survival

 (Jan. 11, 2010) — The number and diversity of male partners a queen honeybee has could help to protect her children from disease, say University of Leeds scientists, who are investigating possible causes of the widespread increase in bee deaths seen around the world.
The researchers are working on the theory that the reason some colonies are wiped out while others remain healthy could be down the genetic diversities of the hives.

Dr Bill Hughes, from the Faculty of Biological Sciences at the University of Leeds, says: “By making sure queens mate with enough genetically variable males, we may be able to boost resistance levels and so protect our Bee populations from disease attacks like the ones we have seen hitting the US.”

One possibility is that the loss of honeybees means that the number and variety of potential mates for a queen is becoming too low to maintain genetic diversity and therefore disease resistant populations.

Says Dr Hughes: “Given the choice, queen honeybees will typically mate with up to 12 different male partners in a matter of minutes and some with over 20. The record is the giant Asian honeybee whose queens normally mate with well over 40 males - and in one case was found to have mated with over a hundred.”

The Leeds scientists will be examining the question of genetic resistance by studying honeybee reactions to a common fungus parasite called Chalkbrood, under carefully controlled laboratory conditions.

The fungus, already found in the majority of UK hives, infects and ‘eats’ larvae, giving them a chalky appearance. Individual larvae die but the parasite rarely kills the whole colony.

In 2008, US average losses of honeybee colonies were 35%, with some beekeepers losing 90% of their colonies. A contributing factor to these high levels of bee may have been a virus. However the same virus has been found in other countries yet does not seem to cause the same problems.

Dr Hughes and his team think infections by hidden parasites in genetically susceptible bees may be combining with other factors to produce a lethal ‘perfect storm’ which overwhelms their defences.

Honeybee survival is vital to the protection of our food supplies because they pollinate up to a third of the food we grow in the UK.

The project, which has received just under £500,000 in funding from the Natural Environment Research Council, is due last for three years. Collaborators include the UK Government’s National Bee Unit based near York and the University of Copenhagen.

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To a Mosquito, Matchmaking Means 'Singing' in Perfect Harmony

 (Jan. 4, 2010) — Researchers have new insight into the sex lives of the much-maligned mosquitoes that are responsible for the vast majority of malaria deaths, according to a report published online on December 31st in Current Biology, a Cell Press publication.
                                                                                 A new study shows that in finding a partner of the right species type, male and female mosquitoes depend on their ability to "sing" in perfect harmony.
In finding a partner of the right species type, male and female mosquitoes depend on their ability to "sing" in perfect harmony. Those tones are produced and varied based on the frequency of their wing beats in flight.
"Everyone must be familiar with the maddening whine a mosquito makes as it hones in for a bite," said Gabriella Gibson of the University of Greenwich at Medway. "There's no doubt many of us have wondered why it makes its presence so obvious -- surely, after all of these centuries of blood-feeding, selection should have favored a more stealthy approach that would leave mosquitoes less vulnerable to the defensive attacks of its unsettled host. Our findings suggest that mosquitoes rely on the sounds they make to attract a mate of the right species, a behavior that is far more vulnerable to selection than avoiding the risk of being squashed by the rare host that is still awake at feeding time."

The Anopheles gambiae mosquitoes in fact include a considerable amount of genetic diversity, representing a complex of seven species and several chromosomal forms. And that diversity comes with real consequences for humans, explained Gibson and Ian Russell of the University of Sussex. The complexity of malaria epidemiology and control is due in part to the mosquito's remarkable genetic plasticity, enabling its adaptation to a widening range of human-influenced habitats.
The new results help to explain how those different mosquito forms manage to reproductively isolate themselves and maintain that genetic diversity, even while some, including the "M" and "S" forms found in Burkina Faso that were the subject of the current study, can be found traveling together in the very same swarms.
Gibson and Russell's team first discovered that male and female mosquitoes harmonize with each other. Gibson said that this is analogous to two partially deaf singers -- one alto and the other soprano -- who can hear low frequencies, but perhaps not their own or each other's songs. Instead, they listen to the terrible dissonance if one or the other goes a bit sharp or flat, which they can get rid of by adjusting their respective tones until the dissonance diminishes to nothing.

"They can do this even if they each sing a different note, say a 'middle C' and a 'G' four tones higher," Russell said. "By listening and subtly altering their pitch to minimize the dissonance, they achieve their goal of 'singing' in a perfect harmony that we, but not they, can hear."
The researchers have now shown that two mosquitoes don't harmonize successfully if they are of the same sex or if they are not the same type of mosquito. They might try for a while, Gibson explained, but they never find that harmony and eventually give up trying.
And that leads Gibson to another take-home of the study. "Even the most 'lowly creatures,' such as mosquitoes, have highly evolved neurosensory systems that can process relatively simple auditory inputs to produce motor outputs enabling them to distinguish between other types of mosquito that are so closely related we need to analyze their DNA to tell them apart."

The researchers include C. Pennetier, University of Sussex, U.K., University of Greenwich at Medway, Kent, U.K., B. Warren, University of Sussex, U.K.; R. Dabire, Institut de Recherche en Science de la Sante/Centre Muraz, Burkina Faso; I.J. Russell, University of Sussex, U.K.; and G. Gibson, University of Sussex, U.K., University of Greenwich at Medway, Kent, U.K.

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Final Moments of Bee Landing Tactics Revealed

(Jan. 2, 2010) — Landing is tricky: hit the ground too fast and you will crash and burn; too slow and you may stall and fall. Bees manage their approach by monitoring the speed of images moving across their eyes. By slowing so that the speed of the looming landing pad's image on the retina remains constant, bees manage to control their approach. But what happens in the final few moments before touch down? And how do bees adapt to landing on surfaces ranging from the horizontal to upside-down ceilings?

Bees manage their approach by monitoring the speed of images moving across their eyes. By slowing so that the speed of the looming landing pad's image on the retina remains constant, bees manage to control their approach. (Credit: iStockphoto/Amit Erez)

Flies land on a ceiling by simply grabbing hold with their front legs and somersaulting up as they zip along, but a bee's approach is more sedate. Mandyam Srinivasan, an electrical engineer from the Queensland Brain Institute, The University of Queensland and the Australian Research Council's Vision Centre, knew that bees must be doing something different from daredevil flies. Curious to know more about bee landing strategies Srinivasan teamed up with Carla Evangelista, Peter Kraft, and Judith Reinhard from the University of Queensland, and Marie Dacke, visiting from Lund University.

The team used a high-speed camera to film the instant of touch down on surfaces at various inclinations and publish their discoveries about bee landing tactics in The Journal of Experimental Biology on December 28 2009 at http://jeb.biologists.org/.
First the scientists built a bee-landing platform that could be inclined at any angle from horizontal to inverted (like a ceiling), then they trained bees to land on it and began filming. Having collected movies of the bees landing on surfaces ranging from 0deg. to 180deg., and every 10deg. inclination between, Evangelista began the painstaking task of manually analysing the bees landing strategies, and saw that the bees' approach could be broken down into 3 phases.
Initially the bees approached from almost any direction and at any speed, however, as they got closer to the platforms, they slowed dramatically, almost hovering, until they were 16mm from the platform when they ground to a complete halt, hovering for anything ranging from 50ms to over 140ms. When the surface was horizontal or inclined slightly, the bees' hind legs were almost within touching distance of the surface, so it was simply a matter of the bee gently lowering itself and grabbing hold with its rear feet before lowering the rest of the body.

However, when the insects were landing on surfaces ranging from vertical to 'ceilings', their antennae were closest to the surface during the hover phase. The team saw that the antennae grazed the surface and this contact triggered the bees to reach up with the front legs, grasp hold of the surface and then slowly heave their middle and hind legs up too. 'We had not expected the antennae to play a role and the fact that there is a mechanical aspect of this is something that we hadn't thought about,' admits Srinivasan.

Looking at the antennae's positions, the team realised that in the final stages as the insects approached inverted surfaces, they held their antennae roughly perpendicular to the surface. 'The bee is able to estimate the slope of the surface to orient correctly the antennae, so it is using its visual system,' explains Srinivasan. But this is surprising, because the insects are almost completely stationary while hovering and unable to use image movement across the eye to estimate distances. Srinivasan suspects that the bees could be using stereovision over such a short distance, and is keen to test the idea.
Finally the team realised that bees are almost tailor made to land on surfaces inclined at angles of 60deg. to the horizontal. 'When bees are flying fast their bodies are horizontal, but when they are flying slowly or hovering their abdomen tilts down so that the tips of the legs and antennae lie in a plane that makes an angle of 60deg.' explains Srinivasan: so the legs and antennae all touch down simultaneously on surfaces inclined at 60deg. 'It seems like they are adapted to land on surfaces tilted to 60deg. and we are keen to find out whether many flowers have this natural tilt,' says Srinivasan.
Srinivasan is optimistic that he will eventually be able to use his discoveries in the design of novel flight control systems.

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Dominant Chemical That Attracts Mosquitoes To Humans Identified

(Dec. 30, 2009) — Scientists at the University of California, Davis, have identified the dominant odor naturally produced in humans and birds that attracts the blood-feeding Culex mosquitoes, which transmit West Nile virus and other life-threatening diseases.

The groundbreaking research, published this week in the early online edition of the Proceedings of the A side view of a Culex mosquito, an important vector in West Nile Virus transmission.

National Academy of Sciences, explains why mosquitoes shifted hosts from birds to humans and paves the way for key developments in mosquito and disease control.

Entomology professor Walter Leal and postdoctoral researcher Zain Syed found that nonanal (sounds like NAWN-uh-nawl) is the powerful semiochemical that triggers the mosquitoes' keen sense of smell, directing them toward a blood meal. A semiochemical is a chemical substance or mixture that carries a message.
"Nonanal is how they find us," Leal said. "The antennae of the Culex quinquefasciatus are highly developed to detect even extremely low concentrations of nonanal." Mosquitoes detect smells with the olfactory receptor neurons of their antennae.
Birds, the main hosts of mosquitoes, serve as the reservoir for the West Nile virus, Leal said. When infected mosquitoes take a blood meal, they transmit the virus to their hosts, which include birds, humans, horses, dogs, cats, bats, chipmunks, skunks, squirrels and domestic rabbits. Since 1999, the U.S. Centers for Disease Control and Prevention have recorded 29,397 human cases and 1,147 fatalities in the United States alone.
The UC Davis researchers tested hundreds of naturally occurring compounds emitted by people and birds. They collected chemical odors from 16 adult human subjects, representing multiple races and ethnic groups.
"We then determined the specificity and sensitivity of the olfactory receptor neurons to the isolated compounds on the antennae of the mosquitoes," Syed said.
Leal and Syed found that nonanal acts synergistically with carbon dioxide, a known mosquito attractant. "We baited mosquito traps with a combination of nonanal and carbon dioxide and we were drawing in as many as 2,000 a night in Yolo County, near Davis," Syed said. "Nonanal, in combination with carbon dioxide, increased trap captures by more than 50 percent, compared to traps baited with carbon dioxide alone."
The UC Davis research was funded in part by the National Institutes of Health; a cooperative research agreement with Bedoukian Research, a supplier of specialty aroma and flavor ingredients headquartered in Connecticut; and the National Science Foundation.

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Cockroaches Offer Inspiration for Running Robots

(Dec. 29, 2009) — The sight of a cockroach scurrying for cover may be nauseating, but the insect is also a biological and engineering marvel, and is providing researchers at Oregon State University with what they call "bioinspiration" in a quest to build the world's first legged robot that is capable of running effortlessly over rough terrain.

Researchers at Oregon State University are using studies of guinea hens and other animals such as cockroaches to learn more about the mechanics of their running ability, with the goal of developing robots that can run easily over rough terrain. (Credit: Image courtesy of Oregon State University)
If the engineers succeed, they may owe their success to what's being learned from these insects and other animals, such as the guinea hen, that have their own remarkable abilities.
The latest findings -- just published in the professional journal Bioinspiration and Biomimetics -- outline how animals use their legs to manage energy storage and expenditure, and why this is so important for running stability. The work is being supported by the National Science Foundation.
"Humans can run, but frankly our capabilities are nothing compared to what insects and some other animals can do," said John Schmitt, an assistant professor in the School of Mechanical, Industrial and Manufacturing Engineering at OSU. "Cockroaches are incredible. They can run fast, turn on a dime, move easily over rough terrain, and react to perturbations faster than a nerve impulse can travel."
Within certain limitations, Schmitt said, cockroaches don't even have to think about running -- they just do it, with muscle action that is instinctive and doesn't require reflex control. That, in fact, is part of what the engineers are trying to achieve. Right now some robots have been built that can walk, but none of them can run as well as their animal counterparts. Even walking robots absorb far too much energy and computing power to be very useful.
"If we ever develop robots that can really run over rough ground, they can't afford to use so much of their computing abilities and energy demand to accomplish it," Schmitt said. "A cockroach doesn't think much about running, it just runs. And it only slows down about 20 percent when going over blocks that are three times higher than its hips. That's just remarkable, and an indication that their stability has to do with how they are built, rather than how they react."
If successful, Schmitt said, running robots could serve valuable roles in difficult jobs, such as military operations, law enforcement or space exploration. Related technology might also be applied to improve the function of prosthetic limbs for amputees, or serve other needs.
The OSU researchers are trying to identify some of the basic biological and mechanical principles that allow certain animals to run so well and effortlessly. A guinea hen, for instance, can change the length and angle of its spring-like legs to almost automatically adjust to an unexpected change in a ground surface as much as 40 percent of its hip height. That would be like a human running at full speed, stepping into a 16-inch-deep hole and never missing a beat.
Researchers are getting closer to their goal.
In a computer model, they've created a concept that would allow a running robot to recover from a change in ground surface almost as well as a guinea hen. They are studying how the interplay of concepts such as energy storage and expenditure, sensor and feedback requirements, and leg angles can produce recovery from such perturbations. Ultimately, a team of OSU engineers hopes to use knowledge such as this to actually build robots that can efficiently run over rough terrain without using significant computing power.
And some day, a robot -- instead of a human -- might be used to run into a dangerous area, check things out and report back for further instructions.

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Spider Mite Predators Serve As Biological Control

(Dec. 28, 2009) — The control of spider mites, which damage tree leaves, reduce fruit quality and cost growers millions of dollars in the use of pesticide and oil spraying, is being biologically controlled in Pennsylvania apple orchards with two tiny insects known to be natural predators, according to Penn State researchers.

"Predator mite attacking a spider mite."

"Spider mites feed on the chlorophyll in the cells of leaves, damaging their ability to use photosynthesis," said David Biddinger, tree fruit entomologist and biocontrol specialist at the Penn State Fruit Research and Extension Center in Biglerville.
 "When the numbers of mites per leaf reaches 25 to 30, the tree becomes stressed and the leaves start to bronze. This affects the quality of its fruit and in two to three seasons can actually kill small trees."

The two most popular insect specialists used to control
spider mites are a lady bug named Stethorus punctum and a predatory mite named T. pyri. These insects prey on two types of spider mites, the European red mites and the two-spotted spider mites, which are agricultural pests worldwide. Much of Biddinger's work is in Pennsylvania apple orchards, a prime target for both types of pest mites.
Although the lady bug and the predatory mite both hunt spider mites, their ways of tracking them down are different.
"It turns out the predatory mite sort of roams around and bumps into them," said Biddinger. "The lady bug on the other hand is a selective killer, hunting using visual and olfactory cues to prey on spider mites."
The lady bug is tiny, oval, and black and it is a natural killer of pest mites. It is attracted to specific volatile chemical signals given off by the damage the spider mites cause to leaves. It is not just the smell that drives the lady bugs wild; this insect cannot resist the yellowing of the leaves damaged by spider mites. Adult lady bugs can live for over a year and eat up to nine mites an hour or 75 to 100 a day.
The predatory mite is much smaller than the lady bug. It is pear-shaped and is usually creamy-white in color. Young mites develop into adults in a very short time and their voracious appetites make them a formidable enemy to spider mites. Adults have a lifespan of about 75 days and can eat 350 mites during this time.
Reducing pest mite numbers and controlling outbreaks with the aid of mite predators is an important task. The biological control of spider mites reduces the need for mite-controlling chemicals and saves growers millions in integrated pest management costs.

"Biological control is basically using the good bugs to control the bad bugs," said Biddinger.
Growers chose lady bugs as their biological control agent until U.S. Environmental Protection Agency regulations prompted growers to switch to new pesticides that kill lady bugs. The predatory mite, however, was resistant and could live through sprayings. So predatory mites are now the hunter of choice for spider mites.
Biddinger, working with Donald C. Weber, research entomologist, U.S. Department of Agriculture, Agricultural Research Service Invasive Insect Biocontrol and Behavior Laboratory, Maryland, and Larry Hull, professor of entomology, Penn State, published their work in a special issue of Biological Control devoted to ladybugs in agriculture.
"With the pesticides we are using now it is very hard for the lady bug to survive," said Biddinger. "The predatory mite could never exist here before because they could not stand the old pesticides, but they are resistant to the new pesticides. With the predatory mite being more effective than the lady bug, we are probably going to exceed the savings for growers that we had with the lady bug in the past. So far we have reduced miticide use by over 90 percent since we switched. This is saving growers about a million dollars a year and is reducing oil spraying by 45,000 gallons a year."
The State Horticultural Association of Pennsylvania supported this work.

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How the Daisy Got Its Spot: Insect Mimicry

(Dec. 26, 2009) — Dark spots on flower petals are common across many angiosperm plant families and occur on flowers such as some lilies, orchids, and daisies. Much research has been done on the physiological and behavioral mechanisms for how these spots attract pollinators. But have you ever wondered what these spots are composed of, how they develop, or how they only appear on some but not all of the ray florets?

This is the Nieuw morphotype of Gorteria diffusa, which exhibits striking dark petal spots at the bases of some ray florets. Scale bar = 1 cm. (Credit: Courtesy Meredith Murphy Thomas.)


Dr. Meredith Thomas from the University of Cambridge and associates from England and South Africa were interested in exploring these questions and published their findings in the December issue of the American Journal of Botany. They focused on the South African endemic beetle daisy Gorteria diffusa (Asteraceae), which has a unique, raised, dark spot at the base of some of its ray florets.
"I find this plant/pollinator system very exciting to study because of the amazing morphological variation in the flowers between populations," Thomas said. "The spots on the flowers mimic the plant's pollinator, a small fly, which is attracted to the plant because of the spots. The plant is dependent on the pollinator for reproductive success, so it's incredibly important that the plant attracts the flies.
"What we found surprising," Thomas continued, "was how complex the petal spots are in a few populations, when other populations seem to get by with a very simple spot or even no petal spot at all."
By peeling away layers of the tissues that make up the spots on mature ray florets and examining them under a simple dissecting scope, Thomas and associates found that the spots of G. diffusa are more complex than most. These spots are composed of three different types of specialized epidermal cells: the central highlight cells that reflect UV and lack pigment; the interior cells that are shorter, rounder, variously pigmented, and raised above the highlight cells; and, surrounding the spot, a circle of multicellular papillae that are swollen, shiny, and filled with anthocyanin. Moreover, each spot spans four congenitally fused petal lobes, meaning that each lobe contained only part of the spot (and only some cell types) in its genetic makeup.

So what attracts the pollinators? Because there is a lot of spot variation in this species, the authors hypothesize that the elements that are found in common among the various populations, such as the presence of anthocyanin pigment or UV reflectivity, might do the trick.
The authors also wanted to know how only a subset of the floral rays develops a spot. Using scanning electron microscopy the authors looked at how the spot developed, or its ontogeny, over time. They found that only the first few ray florets that develop contain the spots, whereas the rest do not. Thomas noted that "the plant has evolved a very clever way of distributing the pollinator-mimicking spots around the inflorescence so that they appear random, as if a few flies had just landed on the inflorescence, when in fact the position of the spots is mathematically pre-determined according to the plant's phyllotaxy [or the order and location in which new floral organs are initiated]." The authors hypothesize that the genes that control the appearance of the spot are turned on initially and then fade with time, such that only the first, and oldest, rays to develop have the spots. Thus, the development of the spots is complex not only at the cellular level, but at the organismal level as well.
"What we now plan to investigate," concludes Thomas, "is whether the development of this adaptive floral trait is regulated by a similarly complex genetic regulatory pathway, or if this plant has simply co-opted and modified a pathway commonly used in plants to produce other types of specialized surface structures, like hairs.$395. Termite Treatments Termite Bonds Pest Control Termite Real Estate Inspections.
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Microscopic Flower Petal Ridges Flash to Attract Pollinating Insects; Scientists Now Know How Ridges Form

 (Dec. 25, 2009) — Microscopic ridges contouring the surface of flower petals might play a role in flashing that come-hither look pollinating insects can't resist. Michigan State University scientists and colleagues now have figured out how those form.

The result could help researchers learn to enhance plants' pollination success and even could lead to high-grip nanomaterials and "green chemical" feedstocks.
"Surprisingly, our work on plant surface biochemistry became a birds and bees and flowers story," said John Ohlrogge, MSU University Distinguished Professor of plant biology. "It's a fundamental property of plant flowers, and we've discovered a basis of how these ridges are made."
Known for 75 years, the exact biological function and nature of the flower nanoridges still eludes scientists. They might help pollinating insects grip petals, and retain glistening water droplets that could attract the visitors. Because the ridges' spacing is approximately that of visible and ultraviolet light wavelengths, moreover, some recent research suggests they produce an iridescent shimmer that attracts pollinators.

To start, visiting professor Mike Pollard and former Ohlrogge post-doctoral research associates Fred Beisson and Yonghua Li tapped new genetic information to find a mutated strain of the standard research plant Arabidopsis thaliana -- mustard weed. The petals have no such nanoridges because the mutation inhibits production of a polymer that forms the plant cuticle, which separates cell walls from plants' waxy surfaces.
Examining the mutant plants' flowers and comparing them to normal mustard plants under scanning electron microscopes, the researchers found that the ridges form from cutin polyester, not from underlying surfaces as some have speculated. How that occurs -- from surface folding or uneven synthesis of cutin polymer across the cell wall, for example, has yet to be learned.
But the research will open doors to further research based on cuticular nanostructures, the researchers noted in a recent edition of the journal Proceedings of the National Academy of Sciences.
"That could include production of polyesters or related basic chemicals by genetically manipulating plants or microbes" said Beisson, now at Aix Marseille Université in Saint-Paul-lez-Durance, France.

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Female Fruit Flies Can Be 'Too Attractive' to Males, Scientists Show

 (Dec. 14, 2009) — Females can be too attractive to the opposite sex -- too attractive for their own good -- say biologists at UC Santa Barbara. They found that, among fruit flies, too much male attention directed toward attractive females leads to smaller families and, ultimately, to a reduced rate of population-wide adaptive evolution.
In an article published in the December 8 issue of Public Library of Science Biology, the authors described their experiments on the sex lives of fruit flies.

"Can females be too good looking?" asks William Rice, biology professor at UCSB. "Can there be disadvantages to being attractive? The answer is yes: If you are too attractive, you get too much male attention, and that interferes with your ability to function biologically."
The authors explain that the term "good looking," among fruit flies, refers to something, like a large body. From the perspective of a male fly, a desirable mate is a female that is larger and can therefore produce more offspring.
"These larger females are disproportionately courted and harassed by males attempting to obtain matings," said Tristan A. F. Long, the study's first author. "When these males are 'choosy' with their courtship, there may be negative consequences to the species' ability to adaptively evolve."
According to the scientists, too much mating is harmful to the females because seminal fluid from the male has toxic side effects. Too much courtship can also hinder the female's ability to forage effectively.

"When they court the females, the males sing to them; they do this by vibrating their wings," said Rice. "They dance and sing at the same time. This might sound romantic, and it would be if it only happened once. But males are doing it all the time. This courtship is unrelenting -- like mosquitoes on a warm summer night -- as the male fruit flies try to persuade females to mate. The males are so persistent that they get them to mate almost every day."
In many species, females are frequently subject to intense courtship "harassment" from males attempting to obtain additional matings, according to the researchers. These coercive activities can result in attractive females becoming less fit to reproduce -- a factor that has a major effect on the entire population.

"We found that when harmful courtship behaviors were directed predominantly toward larger females of greater fecundity potential -- and away from smaller females, of lesser fecundity potential -- this resulted in an overall reduction in the variation of lifetime reproductive success of females in the population," said Long.

The male-mediated, persistent courtship bias can have important consequences for the ability of a population to adaptively change over time. If, for example, a female acquires a mutation that increases metabolic efficiency, allowing her to grow larger, and produce more offspring over her lifetime, this mutation should rapidly spread through the population. However, if the males get in the way of the biological success of these more attractive females, the mutation won't spread through the population as well as it might if males courted females indiscriminately.
The experiments clearly showed that the evolutionary adaptation of fruit flies is hindered by this mating situation. "This change in the distribution of fitness represents a previously unappreciated aspect of sexual selection -- one with important implications for the ability of beneficial genetic variation to spread through the gene pool, and ultimately for a species' capacity to adaptively evolve," Long explained.

Long was a Natural Sciences and Engineering Research Council of Canada (NSERC) postdoctoral fellow at UCSB at the time that he carried out the experiments designed with Rice. Long is currently a postdoctoral fellow with the University of Toronto in the Department of Ecology and Evolutionary Biology. The other authors are Alison Pischedda, a graduate student, and Andrew D. Stewart, a postdoctoral fellow, both of UCSB.