In Promiscuous Antelopes, The 'Battle Of The Sexes' Gets Flipped

In some promiscuous species, sexual conflict runs in reverse, reveals a new study. Among African topi antelopes, females are the ones who aggressively pursue their mates, while males play hard to get.

The classical view of sexual conflict holds that males, for whom reproducing is cheap, will mate as much as possible. On the other hand, females, who must pay a heftier price, are choosier about their mating partners.

Mother nursing baby topi antelope in Serengeti National Park in Tanzania,
East Africa. (Credit: iStockphoto/Bruce Block)

"When biologists talk about the 'Battle of the Sexes,' they often tacitly assume that the battle is between persistent males who always want to mate and females who don't," said Jakob Bro-Jørgensen of University of Jyväskylä in Finland. "However, in topi antelopes, where females are known to prefer to mate with males in the center of mating arenas, we've found a reversal of these stereotypic sex roles."

Such role reversals may occur in species where females benefit from mating multiply, either because it increases their chances of conception with high-quality males or simply because it increases the probability that they conceive at all, Bro-Jørgensen added. He noted that this reversed sexual conflict might not be a rarity in the animal kingdom, as topi are "in many ways a very typical mammalian species characterized by male mate competition and female choice."

In promiscuous species--those in which individuals mate with multiple partners within a short time period--Bro-Jørgensen's group suspected that females might sometimes have higher optimum mating rates than their mating partners. Topi antelope offered an ideal opportunity for studying the dynamics of sex roles in promiscuous mammals, Bro-Jørgensen said, because over a month and a half, individual females become receptive to mating for roughly one day, when they mate several times with each of about four males on average. Females prefer to mate with those males who have succeeded in acquiring territories in the center of "mating arenas," known as leks. But the majority of females also mate with other males as well, resulting in intense sperm competition.

Indeed, they have now shown that aggressive female topis compete with one another for a limited supply of sperm from the most desirable members of the opposite sex, even attacking their fellow mating pairs. Meanwhile, resistant males grow choosier about their mating partners, deliberately selecting the least mated females and launching counterattacks against aggressive females with whom they've already mated.

The bottom-line of the findings, according to Bro-Jørgensen: "We should not regard coyness as the only natural female sex role just as we should not expect that it is always the natural male sex role to mindlessly accept any mating partner," he said. "Nature favors a broader range of sex roles."

This research was published online on November 29th in Current Biology.

The researcher is Jakob Bro-Jørgensen, of the Department of Biological University of Jyva¨ skyla, Jyva¨ skyla¨, Finland; and the Institute of Zoology, Zoological Society, Regent's Park, London, UK.

SOURCE : Cell Press

Protein Translation In Sperm

A new paper in the February 15th issue of Genes & Development lends novel insight into the cellular changes that occur in sperm while they reside in the female reproductive tract -- providing a new understanding of the molecular genetics of successful fertilization.

It had been believed for decades that spermatozoa are translationally silent. However, Dr. Yael Gur and Haim Breitbart (Bar-Ilan University, Israel) now show that, in fact, protein translation does take place in mammalian sperm prior to fertilization.

Their paper has been released online ahead of print at www.genesdev.org.

After ejaculation, sperm reside in the female reproductive tract for several hours. During this time, a number of biochemical changes take place within sperm, collectively known as "capacitation," that render the sperm competent to penetrate and fertilize the female oocyte.

In their new report, Drs. Gur and Breitbart demonstrate that human, rat, bovine and mouse sperm all incorporate labeled amino acids into polypeptides during the capacitation phase. They identify that mitochondrial translation machinery (as opposed to cytoplasmic) directs translation of nuclear-encoded genes in sperm, and that its inhibition leads to a marked decrease in sperm motility, actin polymerization, the acrosome reaction and in vitro fertilization rates.

Thus, protein translation in sperm is essential for sperm functions that directly contribute to fertilization. Dr. Breitbart is confident that "The new findings would give us better understanding for treatment of male infertility and developing new male or female contraceptives."

SOURCE : Cold Spring Harbor Laboratory

Male Deer Are Born To Live Fast, Die Young

In the September issue of The American Naturalist, Juan Carranza (Biology and Ethology Unit, University of Extremadura, Spain) and Javier Pérez-Barbería (Macaulay Institute, United Kingdom) offer a new explanation for why males of ungulate species subjected to intense competition are born with lower survival expectancies than females.

The research reveals that male ungulates have smaller molars relative to their body size -- and hence less durable teeth that will wear out sooner, which might contribute to their shorter lives compared with females.

Natural selection favors reproduction rather than survival; the cost of reproduction compromises survival. Males of species subjected to intense male-male competition for access to females are known to have shorter life expectancies than females. Earlier aging in males might be related to higher reproductive costs, especially when lifetime reproductive success in males takes place within the few years when they can win contests and maintain their dominance.

By comparing body and dental size of males and females of 123 species of ungulates, the authors offer another compelling explanation for why male ungulates lead shorter lives. They estimated the pattern of change of these traits along the evolutionary development of the group and found that for species where a single male has many females and where the males and females are different sizes, the rate of increase of dental size was lower than that of body size.

As a result, smaller teeth (in comparison to body size) are produced in males. It is possible that natural selection did not produce larger, more durable teeth because there was no reproductive return from it, since males in these species do not generally increase their success by living longer after prime age.

"These findings," the authors state, "provide us with interesting insights into how natural and sexual selection design our bodies and their longevity."

Reference: Juan Carranza and F. Javier Pérez-Barbería, "Sexual selection and senescence: male size-dimorphic ungulates evolved relatively smaller molars than females", The American Naturalist (2007) volume 170:370--380. DOI: 10.1086/519852

SOURCE : University of Chicago Press Journals

The Cost Of Keeping Eggs Fresh For Mother Cockroaches

Tiny multiple sperm can be long lived, while large "expensive" eggs degenerate quickly if they are not fertilized. This conundrum -- there should be selection for females to keep their eggs fresh until they are used -- has recently been studied in a cockroach where some choosy females have genes that allow them to maintain eggs while looking for the best mate. Perhaps, however, these genes are limited because they are harmful in some environments.

One of the defining differences between the sexes is in the size of their gametes. Males make many tiny sperm while females make only a few large eggs. This suggests that sperm are cheap while eggs are expensive. Yet sperm can be very long lived, while eggs degenerate quickly after they are made if they are not fertilized.

Why don't females take better care of their expensive eggs? After all, if the females don't use their eggs they have fewer offspring, whereas males make more sperm then they will use anyway. This evolutionary conundrum -- there should be selection for females to keep their eggs fresh until they are used -- has recently been studied by Dr. Trish Moore and her colleagues at the Cornwall Campus of the University of Exeter, with support from NERC, and is published in the March issue of The American Naturalist.

Moore and colleagues examined why females don't keep their eggs fresh in a cockroach where females mate only once during a reproductive cycle, give live birth, and therefore are choosy about the male with which they will mate. Females can't be too choosy, however. If they wait too long to mate they lose good quality oocytes through programmed cell death. But Moore's team finds that some females have genes that would allow them to maintain eggs even if they delay mating. So why aren't all females delaying cell death and holding onto their eggs? Moore speculates that perhaps these genes play a dual role and while they may be beneficial under one environment, when females don't mate, they might be harmful under another, such as when food is limiting. "When females are starving, hanging on to yolky eggs full of nutrients is bad.

Instead a female could recycle those nutrients into her survival. So females face a decision between keeping eggs fresh for producing offspring now, or using those nutrients herself and taking the chance she can reproduce later." The group is currently investigating this trade-off arising from a conflict over food or sex. Although this is a new twist in the conflict over food or sex, the result is a familiar one in evolutionary biology; it is hard to be best at everything.

SOURCE : University of Chicago Press Journals

Male Chimpanzees Prefer Mating With Old Females

Researchers studying chimpanzee mating preferences have found that although male chimpanzees prefer some females over others, they prefer older, not younger, females as mates.

Imoso, the highest-ranking male in the Kanyawara community of Kibale National Park,
Uganda, grooms Outamba, a middle-aged female. Male chimpanzees at Kanyawara consistently prefer the oldest females in their community as mating partners, suggesting that the preference that human men exhibit for youthful women is a recent evolutionary phenomenon. For more information, see the Report by Muller et al. in the November 21 Current Biology. (Credit: Photograph by Jean-Michel Krief)

The findings uncover a stark contrast between chimpanzee behavior and that of humans, their primate cousins. The basis for this difference may lie in the fact that whereas chimpanzees participate in a relatively promiscuous mating system, humans form unusually long-term mating bonds, thereby making young females more valuable as mates with greater reproductive potential. The findings, reported by Martin Muller of Boston University and colleagues at Harvard University, appear in the November 21st issue of Current Biology.

Theoretical explanations for the preference of human males for young females as mates include the facts that humans tend to form long-term mating partnerships, and that female fertility is limited by menopause and, therefore, age. The converse of such an explanation suggests that species that appear to lack long-term pair bonding and menopause (such as chimpanzees) should not exhibit such strong preferences by males for young females.

In the new work, researchers examined this idea by studying male mate preferences within the Kanyawara chimpanzee community in Kibale National Park in Uganda. The researchers found that, in contrast to humans, male chimpanzees prefer older females to younger ones. They found that, compared to younger females, older females were more likely to be approached for copulation, were more often in association with males during estrous periods, copulated more frequently with high-ranking males, and gave rise to higher rates of male-on-male aggression in mating contests.

The findings, in addition to supporting the idea that long-term pair bonding and menopause may contribute to the preference of human males for young females, also suggest that this characteristic may be an evolutionarily derived trait that arose in the human lineage sometime after the lineages giving rise to humans and chimpanzees diverged.

The researchers include Martin N. Muller of Boston University in Boston, MA; Melissa Emery Thompson and Richard W. Wrangham of Harvard University in Cambridge, MA. The research at Kibale was supported by grants from the United States National Science Foundation (grant no. 0416125), the L.S.B. Leakey Foundation, the National Geographic Society, and the Wenner-Gren Foundation.

Muller et al.: "Male Chimpanzees Prefer Mating with Old Females." Publishing in Current Biology 16, 2234--2238, November 21, 2006 DOI 10.1016/j.cub.2006.09.042.


SOURCE : Current Biology

Mouse Ovaries And Testes Age In Unique Ways

Aging leads to large changes in gene activity in the ovaries of mice, but only limited changes in testes, according to new research. A lifespan-extending calorie-restricted diet reversed some of the aging effects -- but, unlike the widespread changes observed in somatic organs, it had an impact only in a small number of gonad-specific genes.

As well as tackling one of the key questions of ageing -- by exploring if reproductive organs age in the same way as other body organs -- this research is important in the light of the trend for some women in developed countries to put off childbearing until later in life.

A research team led by Minoru Ko, MD, PhD, from the National Institute on Aging, Baltimore, USA used whole-genome DNA microarrays to study the effects of age, sex and diet on the global gene expression in mouse ovaries and testes. They found that reproductive organs age in a different way to other body tissues and, furthermore, that ovaries age in a different way from testes.

Age-related changes in gene expression occurred in gonads -- as they are known to in other body tissues -- but these changes tended to be in different classes of genes. Only two of the six categories of genes previously associated with aging in muscle, kidney and brain were associated with aging in the ovary; none were associated with aging in the testis. The changes seen in ovaries could be influenced by changes in the tissue composition of ovaries as females age and ovulation ceases.

The researchers also found that calorie restriction in females reduced the expression of genes involved in metabolism and follicle growth, which seems to be consistent with a popular view that the calorie restriction causes a shift in energy use away from reproduction towards general body maintenance and repair. However, male mice on the same diet did not appear to sacrifice reproductive function, suggesting an evolutionary difference between males and females when coping with a food shortage.

SOURCE : BioMed Central

Alarm Pheromone Causes Aphids To Sprout Wings

Chemical communication within insect species is often much more sophisticated than expected. When aphids are attacked by predators such as ladybird beetles, they release an alarm pheromone, (E)-β-farnesene, that has long been known to cause other aphids to walk around or drop from the plant.

In a paper soon to appear in Ecology Letters, researchers at the University and Max-Planck-Institute in Jena, Germany, now show that exposure to alarm pheromone also causes pea aphids to produce winged offspring that leave their host plant when mature. Because some plants can also release (E)-β-farnesene, they could in theory manipulate aphids into flying away.

However, aphids were shown to react mainly to the frequency of pheromone release and not the actual quantity present, possibly to avoid manipulation by plants. Thus, to reduce damage caused by aphids, the major insect pests in Europe, it may prove effective to apply pulses of alarm pheromone to infested fields.

SOURCE : Blackwell Publishing Ltd.

Men And Women May Need Different Diets

Diet can strongly influence how long you live and your reproductive success, but now scientists have discovered that what works for males can be very different for females.

In the first study of its kind, the researchers have shown that gender plays a major role in determining which diet is better suited to promoting longer life or better reproductive success.

In the evolutionary "battle of the sexes", traits that benefit males are costly when expressed in females and vice versa. This conflict may have implications for human diet, aging and reproduction, says a team of scientists from UNSW, the University of Sydney and Massey University.

"When it comes to choosing the right diet, we need to look more closely to the individual, their sex and their reproductive stage in life," says Associate Professor Rob Brooks, Director of the Evolution and Ecology Research Centre at the University of New South Wales. "It may be, for example, that women in their child-bearing years need a different diet to those who are post-menopausal.

"It also underlines the important lesson that what we want to eat or, if you like, what we're programmed to eat, is not necessarily best for us." The researchers are conducting long-term studies on Australian black field crickets and have discovered that the lifespan of both males and females is maximised on high-carbohydrate, low-protein diets, they say in the latest issue of Current Biology.

But reproductive success differs dramatically between the sexes when the carbohydrate-protein balance is changed: males live longest and have the greatest reproductive success with a diet that favours carbohydrates to protein by eight-to-one, whereas females have greatest success when the ratio is just one-to-one. Given a choice, however, females eat only a small amount more protein than males. The shared ability to sense and choose food dooms both males and females to eat a diet that is a compromise between what is best for each sex.

"Male and female crickets maximise their fitness on different diets," says UNSW's Dr Alexei Maklakov, the study's lead author. "Despite that, the dietary preferences of the sexes are very similar. Instead of selecting foods in a sex-specific manner, males and females select 'intermediate' diets that are less than optimal for both sexes.

The researchers believe the sexes share most of their genes and this fact can constrain the evolution of sex differences in traits such as diet choice, because many of the same genes are likely to be responsible for trait expression in both sexes.

Significance for humans -- "Men and women invest differently in reproduction, a difference that is even more marked than that between male and female crickets," says Rob Brooks. "Think of the tremendous amounts of energy and protein required of a mother in carrying a baby to term and breastfeeding. We also know that men and women need to eat different diets - think of the careful attention we pay to what expectant mothers eat.

"What men and women need to eat might be more dramatically different than we had realised. However, men and women eat very similar diets and our results suggest that our tastes and food preferences could be a shared compromise, as they are in crickets."

SOURCE : University of New South Wales

Rodent Sperm Work Together For Better Results

Individual sperm in promiscuous rodents have learned to work together in order to compete against sperm of rival males, according to new research carried out at the University of Sheffield

Although, sperm are inseminated in millions each sperm goes it alone. However, under some circumstances it might be advantageous for sperm to cooperate with one another. This is especially likely to be the case when females are promiscuous and sperm of one male have to compete against those of rival males. New research by Dr Simone Immler and colleagues from the University's Department of Animal and Plant Sciences shows that in promiscuous rat and mice, where competition is high, individual sperm cooperate with one another in order to out-compete sperm of rival males.

The research shows that this cooperation is possible only because of to the highly specialised design of rat and mouse sperm. Promiscuous species have a particularly well developed 'hook shaped' sperm head which helps individual sperm to hook up to each other and form a 'group'. These groups of sperm contain five to 100 sperm and they swim faster and stronger than individual sperm which makes them better competitors in the race for the fertilisation of the egg.

Dr Simone Immler said: "It was previously believed that sperm not only competed against rival males but that they also competed against each other in order to fertilise the female egg. However, this research shows that when the pressure from rival males is high, individual sperm will cooperate with one another to ensure that at least one of their siblings successfully reaches the female egg."

The results will be published on Wednesday 24th January in the freely available, open-access journal -- online at http://www.plosone.org.

Citation: Immler S, Moore HDM, Breed WG, Birkhead TR (2007) By Hook or by Crook? Morphometry, Competition and Cooperation in Rodent Sperm. PLoS ONE 2(1): e170. doi:10.1371/journal.pone.0000170 (http://dx.doi.org/10.1371/journal.pone.0000170)

SOURCE : Public Library of Science

A Little Bit Of Egg Makes Tracking Aphids Easier

The green peach aphid, despite its name, is a pest of potatoes. Besides siphoning off juices from potato plants, the aphid can infect the plants with viruses that cause an estimated $100 million annually in yield losses.

An alate (winged) green peach aphid, Myzus persicae. (Credit: Photo by Scott Bauer)

Now, tracking where and when the aphid is likely to transmit potato viruses could be easier to do, thanks to a new marker technique devised by Agricultural Research Service (ARS) entomologist Tom Unruh. His approach--which uses egg whites, plastic-mesh screens and an antibody-based test--is still experimental. But, ultimately, information derived from its use could help potato growers improve the timing of insecticide application to deter virus-laden aphids from feeding on plants.

Unruh devised the technique to support studies to determine whether virus-carrying aphids are flying into potato fields from nearby weed patches. Existing methods of capturing and marking the dash-sized pests have been difficult and unreliable, according to Unruh, with the ARS Yakima Agricultural Research Laboratory in Wapato, Wash.

His solution involved mixing egg-white proteins with water to create a solution that can be sprayed onto potato plants or associated weeds like nightshade. Aphids pick up the egg proteins while crawling over treated areas. To track them, Unruh relies on wide-mesh screens secured below a teepee-like scaffold that can be placed in or near potato fields. An adhesive holds the aphids so they can be returned to the laboratory for analysis using an immunological assay, which employs antibodies to detect egg proteins if they're present.

In fields near Wapato, more than 50 percent of green peach aphids that contacted treated potato plants tested positive for egg proteins. More field tests are under way.

SOURCE : US Department of Agriculture

Climate Change And Species Distributions

Scientists have long pointed to physical changes in the Earth and its atmosphere, such as melting polar ice caps, sea level rise and violent storms, as indicators of global climate change.

But changes in climate can wreak havoc in more subtle ways, such as the loss of habitat for plant and animal species. In a series of talks at the Ecological Society of America (ESA) 93rd Annual Meeting, climate change scientists will discuss how temperature-induced habitat loss can spell disaster for many living things.

Climate models project that rising temperatures over time can lead to an increase in dry, desert-like conditions, which will affect not only the survivorship of particular species, but also the natural resources they have adapted to use in their natural environment. Species are thus forced to move elsewhere to find places to live and food to eat.

"Impacts on individual species indicate wider changes at the biome level that will potentially change conditions for many plant and animal species, in addition to ecosystem services to humans," says Patrick Gonzalez, a researcher at The Nature Conservancy and a member of the Intergovernmental Panel on Climate Change (IPCC).

One species whose habitat may be in danger is the Canada lynx, which is listed as threatened in the United States. The feline's main prey, the snowshoe hare, lives in deep snow cover in boreal forest. Because they rely so heavily on hares for food, lynx are adapted to live in areas with snow cover at least four months out of the year. The cats are so specialized to life on snow that their paws are much wider than is required to support their weight; the large paws help them stalk hares over deep snow without falling in.

Gonzalez, who has worked with USDA Forest Service scientists to analyze lynx habitat, projects that a temperature increase of 2.5 to 4 degrees Celsius in the coming century across the U.S. and Canada—the range of warming under the scenarios reported by the IPCC—may diminish snow cover suitable for lynx by 10 to 20 percent and reduce boreal forest cover by half in the contiguous U.S. Together, these changes could shift lynx habitat northward and decrease the area of habitat in the lower 48 states by two-thirds. This potentially extensive loss of habitat signals serious changes in boreal and alpine ecosystems, says Gonzalez.

Climate change can result in animals and plants migrating northward to escape the heat, but in many cases suitable habitat becomes scarce or unavailable farther away from the species' natural range. The Propertius duskywing butterfly lives throughout the West Coast of the U.S., and during its caterpillar stage is specialized to live on oak trees. Shannon Pelini, a graduate student at the University of Notre Dame, conducted experiments revealing that warmer temperatures increased the survivorship and body size of caterpillars in its most northern habitats. A lack of oak trees in more northern climes, however, would preclude them from moving further north. The range shift of oak trees will happen much slower than the shift for the butterflies, leading to a contracted range, says Pelini.

As if the direct effects of rising temperatures weren't enough, climate change also has impacts that could make climate patterns less consistent over time. Michael Notaro, a scientist at the University of Wisconsin-Madison, used climate data from the past century to model vegetation changes over time. He found that large variability in climate causes an increasing number and intensity of fires and droughts, as well as extreme weather events that could kill long-lived trees and allow short-lived grasses to colonize the leftover space. His models predict that year-to-year variability in precipitation and temperature reduces the Earth's total vegetation cover, expanding its relative grass cover and diminishing its relative tree cover.

"The central U.S. is characterized by an ecotone that's the intersection of forest in the East and grassland in the West," says Notaro. "The border between these ecosystems is largely determined by climate variability and it is likely that climate change will shift the location of this and other ecological boundaries worldwide."

Gonzalez agrees that the research results presented at the ESA Annual Meeting indicate serious vulnerabilities of both individual species and global biomes to climate change.

"Climate change threatens to alter extensive areas of habitat," says Gonzalez. "Lynx is one species that is vulnerable, but the potential impacts of climate change on entire ecosystems are even more alarming."

The researchers will present their results in the following oral sessions:

1. Shannon Pelini and Patrick Gonzalez - Climate Change: Range and Phenology, Monday, Aug. 4, Midwest Airlines Center
2. Michael Notaro - Climate Change and Plants I, Tuesday, Aug. 5, Midwest Airlines Center

SOURCE : Ecological Society of America

Prions Show Their Good Side

Prions, the infamous agents behind mad cow disease and its human variation, Creutzfeldt-Jakob Disease, also have a helpful side. According to new findings from Gerald Zamponi and colleagues, normally functioning prions prevent neurons from working themselves to death.

Diseases such as mad cow result when the prion protein adopts an abnormal conformation. This infectious form creates a template that induces normal copies of the protein to misfold as well. Scientists have long assumed that prions must also have a beneficial side but have been unable to pinpoint any such favorable traits.

In the new work, the authors found that mice lacking the prion protein had overactive brain cells. Their neurons responded longer and more vigorously to electrical or drug-induced stimulation than did neurons that had normal prion protein. This hyperactivity eventually led to the neurons' death. The results might help explain why misfolded prions cause dementia: in the wrong conformation, the prion can no longer protect brain cells from deadly overexcitement.

The findings appear in the May 5th issue of the Journal of Cell Biology.

SOURCE : Rockefeller University

In A Bug-eat-bug World, Researchers Use Unique Chinese Wasp To Battle Soybean Aphids

The days of soybean aphids feasting on soybean fields may be numbered, thanks to a unique import from China.

University of Minnesota scientists are field testing a beneficial insect, a stingless wasp from China also known as Binodoxys communis, that kills soybean aphids. A successful field test would be a major breakthrough in controlling a damaging crop pest. The U of M received permission from the federal government to conduct this test and is the leading institution in the testing.

Researchers look for mummies, the darker brown objects on the soybean leaf shown above,
to gauge the effectiveness of the beneficial insect in controlling soybean aphids.
The light green spots on the soybean leaf are soybean aphids.
(Credit: David Hansen, Minnesota Agricultural Experiment Station)

The soybean aphid first appeared in Minnesota fields in 2000 and today costs soybean growers an estimated $200 million annually in lost crop yields and spraying costs in Minnesota alone. The national cost is much higher.

"The soybean aphid was imported without any of its natural enemies, the organisms that keeps aphids in check in China," said Dave Ragsdale, U of M entomologist. "Our researchers and Extension experts are working to provide that check and balance system."

Multiple stages of evaluation and testing have been completed at the Insect Quarantine Facility, a joint effort between the Minnesota Department of Agriculture and the Minnesota Agricultural Experiment Station on the U of M's St. Paul Campus. Special security and air filtration systems ensure the insects being evaluated don't venture out on their own. Field testing will take place in a limited number of grower fields and at Research and Outreach Centers.

Binodoxys communis was approved for release based upon four years of laboratory safety testing. It is an especially promising species for control of soybean aphid, because it comes from a region in China that is a good climate match to Minnesota. The stingless wasp specializes in soybean aphid and has been observed apparently controlling it in China.

A cooperative effort between the U of M, the state and soybean growers, like New Richland farmer Larry Muff, have made this experiment possible.

"The soybean check off is committed to supporting research that will mitigate this devastating pest," said Muff, co-chair of the Minnesota Soybean Research and Tech Transfer Committee. "Organic growers will also benefit from this biological control of aphids."

University researchers and Minnesota Department of Agriculture scientists will monitor the ability of Binodoxys communis to kill soybean aphids this summer and continue the attack this fall when soybean aphids move to buckthorn plants and survive the winter to battle soybean aphids in 2008.

The researchers also have a backup plan. Eleven other species and strains of stingless wasps are under evaluation and some of these that have shown promise from both a safety and efficacy standpoint may be field tested in 2008.

SOURCE : University of Minnesota

Selection On Sex Cells Favors A Recombination Gender Gap

Males and females of the same species can be strikingly different. Peacocks strut around with flashy feathers to attract mates, while peahens blend into their surroundings with more subdued colors. But differences are not always as obvious or easily explainable as in this classic example. Even the amount of genetic reshuffling that goes on during egg and sperm production differs between males and females in most species. An evolutionary reason for this has eluded researchers since the phenomenon was originally discovered in fruitflies, Chinese silk worms, and amphipods almost 100 years ago.

Genetic diversity among organisms is promoted when genetic information is rearranged during meiosis, the cell division process that yields sperm and eggs (generically called gametes). During this genetic reshuffling, chromosome pairs overlap, forming structures called chiasmata (“crosses” in Greek), and physically recombine. This process does not just create diversity, it is also an example of diversity—recombination rates vary across chromosomes, sexes, and species.

An early 20th century hypothesis to explain the sex difference in recombination proposed that recombination is restrained within a pair of unlike sex chromosomes (X and Y, for example) and that the suppression spills over to the rest of the chromosomes. Under this idea, the sex with dissimilar sex chromosomes (XY instead of XX, for example) should be the one with the least amount of recombination in all chromosomes. But that is not always the case. Some hermaphroditic species of flatworms, for example, lack sex chromosomes altogether but still display marked differences in male and female recombination rates. In one salamander genus, more reshuffling unexpectedly occurs in the sex with two different sex chromosomes.

In a new study analyzing an updated dataset of 107 plants and animals, Thomas Lenormand and Julien Dutheil bolster the argument against the recombination suppression hypothesis by showing that in species with sex chromosomes, the sex with two dissimilar sex chromosomes doesn’t necessarily have a reduced recombination rate. Additionally, they found that, as a trait, the sex difference in recombination rate is not a lot more similar between two species in the same genus than between two species in different genera, suggesting that the difference evolves quickly.

An alternative hypothesis suggests that sexual selection might play a role in recombination differences. Reproductive success among males is often highly influenced by selection, so mixing up successful genetic combinations in males could be evolutionarily counterproductive. But in past studies, sexual selection was not related to variation in recombination rates.

Putting a new twist on this hypothesis, Lenormand and Dutheil realized that selection was not necessarily limited to the adult stage and that differences in selection among eggs or sperm might help account for recombination differences between the sexes. The authors reasoned that more opportunity for selection on sperm than egg should correspond to less recombination during sperm than egg production (and vice versa), consistent with the idea that genetic combinations surviving selection should remain more intact in the sex experiencing the strongest selection at the gametic stage.

Though male gametes might be expected to be under stronger selection in many species, in true pines it seems to be the female gametes. The ovules compete with each other for resources over an entire year before being fertilized, and, indeed, from the dataset analysis, ovule production involves low recombination rates compared with male pollen in this group. In males, the opportunity for pollen competition was indirectly estimated using self-fertilization rates. The authors assumed that pollen grains competing for ovules of a self-fertilizing plant would be genetically similar and therefore experience less selection. Again, in the analysis, low selection correlated with less recombination in female gamete production, as predicted.

Is selection among eggs and sperm the evolutionary force generating sex-based variation in genetic shuffling? By demonstrating that differences may be influenced by gamete selection in plants, this work has added clarity to otherwise contradictory observations.


SOURCE : Public Library Of Science

In Bowerbirds, Young Females Go More For Blue, Less For Strutting

ARLINGTON, Va.- When looking for sex partners, younger females prefer males who decorate their place with a little extra blue, be it plastic or feathers. They also prefer males who tone down the intensity of their courtship behavior. At least, that's how it looks for satin bowerbirds, according to research findings published this week in the journal Nature.

The study - conducted in New South Wales, Australia, in 1999-2000 - found that not all females find the same traits attractive in mates. As they choose a mate, females make a series of complex decisions related to male courtship behavior and to the colored decorations males collect and place around the bower, a stick structure that protects females during courtship display. Older females focus more on the male's intense courtship display while younger females are attracted by the blue bower decorations.

The research, funded by the National Science Foundation's Animal Behavior Program, was conducted by biologists Gerald Borgia, Seth Coleman and Gail Patricelli of the University of Maryland. NSF is an independent U.S. federal agency that supports fundamental research and education across all fields of science and engineering.

According to Borgia, learning more about such sophisticated courtship behavior can increase our understanding of mate choice, a fundamental process that affects the genetics of most animal species. Thus, clues to courtship can also aid wildlife conservation and species propagation.

"It's very important," he said, "because it helps us develop a general model of mate choice. We show experimentally that females in a population may choose males for different reasons. This, in turn, explains why males have complex displays - that is to accommodate the different mating preferences of females they engage in courtship."

A male bowerbird's intense performance of "Pick me! Pick me!" involves loud buzzing calls, raising its feathers on end, and running vigorously back and forth, with its wings extended, across its platform stage - the bower. Males build their bowers primarily from sticks, creating a U-shaped chute that they adorn with blue decorations, such as feathers, blue clothespins, and scraps of plastic.

To see if bluer-is-better interior decorating affects females' preferences, the researchers supplemented some bowers with blue plastic tiles and strands. Because male bowerbirds commonly steal from each other, researchers anchored these extra accoutrements with screws and glue.

According to Jane Brockmann of NSF's animal behavior program, "This is an excellent system for studying mate choice. Dr. Borgia watches the bowers by using video cameras that are tripped when a female enters a male's bower, so he has a very accurate record of whether a female just visits a male or mates with him. He has also been studying the same large group of marked birds for years, so he knows when a female's choice changes with age and experience."

Very few studies have this sort of long-term data, and most studies of mate choice treat females as if their decisions do not vary or change, said Brockmann.

"Males of most species show a lot of variation in their behavior," she said. "It is unreasonable to think that females would not similarly show variation. Yet we know very little about variation in how females choose mates. It does matter."

Particularly to males.

Michael Greenfield, who co-directs NSF's animal behavior program with Brockmann, said, "As males are under some pressure to be attractive to and mate with as many females as possible, their display is a means of covering all possibilities in luring potential mates. We still don't really know why female preference varies with age, but one possibility inherent in this study is that learning - which is generally disregarded in studies of sexual selection - plays a role."

As scientists learn more about how females choose mates, biologists will be better able to test various models of how courtship displays evolve among males, Borgia said.

In a previous study, his group found that female satin bowerbirds will return the next year to attractive mates, but "females which fail to encounter very attractive males typically reject their previous mates and search for more attractive males in the following year."

SOURCE : National Science Foundation

Behavioural Ecologists Elucidated How Peahens Choose Their Mates, And Why

Since Darwin, the peacock exhibiting an elongated tail composed of ocelli has been considered a prime example of the strength of sexual selection. Professor Marion Petrie's classical studies have shown that females prefer males with a high number of ocelli. However, a remaining question concerning the role played by ocelli is how peahens value their number. New research published today in Ethology describes that females may actually assess ocelli density.

Since Darwin, the peacock exhibiting an elongated tail
composed of ocelli has been considered a prime example of the strength of sexual selection.
Professor Marion Petrie's classical studies have shown that females prefer males
with a high number of ocelli. (Image courtesy of Blackwell Publishing Ltd.)

Adeline Loyau, Michel Saint Jalme and Gabriele Sorci of the National Museum of Natural History and the Laboratory of Evolutive Parasitology, Paris, have been studying sexual selection on free-ranging common peafowl to elucidate how females choose their mate. They took pictures of displaying peacocks to count the number of ocelli, and captured them to measure tail length. They also made behavioural observations to value male displaying activity and male mating success.

"Preferred males were those exhibiting the higher number of ocelli in the train, but surprisingly females seemed to prefer males with shorter tails. This was unpredictable because we also found that the longer the train, the more dominant the male," they say. The female preference for both high number of ocelli and shorter tail gave the idea that females may actually prefer the visual perception of a dense cluster of ocelli than a diluted number of ocelli over a large surface. "We calculated the ocelli density and found that it did explain female choice."

In the peacock, the ocelli density of the train can only be assessed by females when males spread their trains during the courtship display. "In this species, the expression of the ornament is modulated by the expression of the behaviour. To be chosen, a peacock has to be beautiful but also has to be able to show how beautiful he is. It is not surprising that female preference is also driven by male behaviour." Indeed, they showed that male success was determined by both his ocelli density and his displaying activity. They investigated this preference further and demonstrated that these two cues provide peahens with information about male health. "In other words, it's beneficial for a female to mate with handsome and sportive mates," they conclude with humour, "because these males are in better health."

SOURCE : Blackwell Publishing Ltd.

Researchers Find Resistance To Soybean Fungus

The first soybean line with genetic resistance to charcoal rot has been released by Agricultural Research Service scientists in Mississippi.

Charcoal rot, caused by the soilborne fungus Macrophomina phaseolina, is a major yield-limiting disease of the Mid-South and other soybean-producing regions throughout the world.

The new line, DT97-4290, developed by scientists in the ARS Crop Genetics and Production Research Unit at Stoneville, is a potentially valuable source of resistance to charcoal rot for soybean breeders and producers in areas experiencing yield losses due to the disease.

Charcoal rot symptoms usually appear when weather conditions are hot and dry, causing the soybean plant to lose vigor. In more advanced stages, petioles and leaves may turn yellow and wilt, while remaining attached to the plant. No chemical controls currently exist for charcoal rot, and resistance has been hard to identify.

Field studies were conducted at Stoneville to find charcoal rot resistance among 24 selected soybean genotypes. The researchers identified three breeding lines with genetic resistance, according to Bob Paris, the research geneticist who developed the line with Alemu Mengistu, a soybean pathologist.

The new line was selected for its adaptation to the clay soils of the lower Mississippi River valley, and for its field resistance to charcoal rot, soybean mosaic virus and stem canker, and moderate resistance to frogeye leafspot.

Genetic material of this release will be deposited in the National Plant Germplasm System, where it will be available for soybean researchers and breeders.

ARS is the U.S. Department of Agriculture's chief scientific research agency.

SOURCE : USDA / Agricultural Research Service

Nano-sensor For Better Detection Of Mad Cow Disease Agent

In an advance in food safety, researchers in New York are reporting development of a nano-sized sensor that detects record low levels of the deadly prion proteins that cause Mad Cow Disease and other so-called prion diseases.

Scientists report a new device to detect prion proteins
that cause Mad Cow Disease and other prion diseases.
The finding could lead to a reliable blood test for those illnesses in both animals and humans.
(Credit: Courtesy of USDA-Agricultural Research Service, Photo by Keith Weller)

The sensor, which detects binding of prion proteins by detecting frequency changes of a micromechanical oscillator, could lead to a reliable blood test for prion diseases in both animals and humans, the researchers say.

Prions are infectious proteins that can cause deadly nerve-damaging diseases such as Mad Cow Disease in cattle, scrapie in sheep, and a human form of Mad Cow Disease called variant Creutzfeldt-Jakob Disease. Conventional tests are designed to detect the proteins only upon autopsy and the tests are time-consuming and unreliable.

In the new study, Harold G. Craighead and colleagues describe a high-tech, nano-sized device called a nanomechanical resonator array. The device includes a silicon sensor, which resembles a tiny tuning fork, that changes vibrational resonant frequency when prions bind. Its vibration patterns are then measured by a special detector. In experimental trials, the sensor detected prions at concentrations as low as 2 nanograms per milliliter, the smallest levels measured to date, the researchers say.

The article "Prion Protein Detection Using Nanomechanical Resonator Arrays and Secondary Mass Labeling" is scheduled for the April 1 issue of ACS' Analytical Chemistry.

SOURCE : American Chemical Society

Changing Fashions Govern Mating Success In Lark Buntings, Study Finds

A study of how female lark buntings choose their mates, published in Science, adds a surprising new twist to the evolutionary theory of sexual selection. Researchers at the University of California, Santa Cruz, discovered that female lark buntings show strong preferences for certain traits in the males, but those preferences change from year to year.

Classic examples of sexual selection involve elaborate ornaments, such as the peacock's tail, that evolve as a result of consistent female preferences, so that males with the most exaggerated traits have the most success mating and produce more offspring than less flamboyant competitors. In the case of lark buntings, however, the flexibility shown by females in choosing their mates dampens the trend toward more elaborate ornamentation and may instead maintain variability in male plumage.

"It's counter to the conventional view of female choice as static," said Bruce Lyon, associate professor of ecology and evolutionary biology at UCSC and coauthor of the paper. "These females are capable of very sophisticated behavior, and they appear to benefit from their flexibility in mate choice by gaining enhanced nesting success."

The study suggests that the male's plumage somehow serves as a signal to the female that he possesses certain traits that will affect the pair's nesting success. Shifting environmental conditions may determine which male traits matter most in any given year, said Alexis Chaine, who worked on the study as a UCSC graduate student and is now a postdoctoral researcher at the Centre National de la Recherche Scientifique (National Center for Scientific Research) in France. Chaine is first author of the paper, which appears in the January 25 issue of Science.

"The traits the female is choosing somehow predict how successful the pair will be in nesting," Chaine said. "One possibility is that certain traits are associated with the male being a good forager, and other traits predict how well he could defend the nest from predators. So, if there are lots of ground squirrels, which are a major nest predator, she wants a good defender, but in a year when grasshopper populations are low, she needs a good provider. These are ideas we still need to test."

With a mostly black body and bright white wing patches, the male lark bunting is a distinctive bird of the Great Plains. Females choose a new mate every year, and parenting duties are shared by both members of the pair. The males are territorial during the breeding season, flying up over their territory and singing as they descend to attract a mate. Once they acquire a mate, however, they no longer defend the territory. The researchers found no correlation between the quality of a male's territory and his success in attracting a mate.

The white wing patches and other male plumage traits serve as signals in aggressive interactions between territorial males, Chaine said, meaning that female mate choice is not the only factor influencing those traits. But the researchers found that the role of those signals in competitive interactions between males was consistent from year to year. The level of aggression didn't vary between years either.

"Male competition can't explain the overall pattern, but it may be an important factor in the evolution of male plumage traits," Chaine said.

The variability of the male plumage was one of the first things Lyon noticed when he began studying lark buntings on the Pawnee National Grasslands in Colorado. (The lark bunting is the state bird of Colorado.) Chaine joined Lyon the following year and began an exhaustive long-term study, gathering data from 1999 to 2003.

"We had to conduct studies every year over several years before we could see what was going on," Lyon said. "We saw two patterns of variation in the correlations between male traits and female mate choice. In some cases, it was either on or off--a trait was important to females one year and not important in other years. We also saw reversals--for example, one year the females preferred males with bigger wing patches, and the next year they preferred smaller wing patches."

Lyon cautioned that additional experiments are needed to provide definitive evidence of female preferences. The study was based on statistical correlations, which provide clear evidence that the traits of mated males differ from those of males without mates. "We suspect it's because females are choosing males with particular traits," Lyon said. "Ideally, we would like to test that with field experiments."

The dynamic sexual selection seen in lark buntings is probably occurring in other species as well, he added. That has implications for theoretical models of how sexual selection influences the evolution of male traits.

"The assumption that sexual selection is static is something we've all taken for granted," Chaine said. "This study might cause some people to rethink their systems and take another look at their data."

This research was supported by grants from the National Geographic Society, National Science Foundation, American Museum of Natural History, Sigma Xi, and the American Ornithologist's Union.

SOURCE : University of California - Santa Cruz

Test To Protect Food Chain From Human Form Of Mad Cow Disease

Scientists are reporting development of the first test for instantly detecting beef that has been contaminated with tissue from a cow's brain or spinal cord during slaughter — an advance in protecting against possible spread of the human form of Mad Cow Disease.

Jürgen A. Richt and colleagues point out that removal of brain, spinal and other central nervous tissue after slaughter is "one of the highest priority tasks to avoid contamination of the human food chain with bovine spongiform encephalopathy," better known as Mad Cow Disease. "No currently available method enables the real-time detection of possible central nervous system (CNS) tissue contamination on carcasses during slaughter," the report states.

They describe a test based on detection of the fluorescent pigment lipofuscin, a substance that appears in high concentrations in the nervous tissue of cattle. The researchers found that it was a dependable indicator for the presence of brain and spinal tissue in bovine carcasses and meat cuts.

"Small quantities of bovine spinal cord were reliably detected in the presence of raw bovine skeletal muscle, fat and vertebrae. The research lays the foundation for development of a prototype device allowing real-time monitoring of CNS tissue contamination on bovine carcasses and meat cuts," the report says.

It was done with colleagues from the National Animal Disease Center of the USDA-Agricultural Research Service and Iowa State University.

SOURCE : American Chemical Society

Evolution Of Male-female Differences Within A Shared Genome

One of the major components of the world's biological diversity are the differences between males and females in traits related to mating, including weapons used when competing for mates and display traits used to seduce them. Such gender differences are thought to arise because selection acts differently on each sex. The conflicting interests of males and females in reproduction are thought to be a key source of sex-specific selection on such traits.

The evolution of sexual dimorphism is hampered, however, because the sexes share the majority of their genomes; an adaptive response to selection in one sex may therefore cause nonadaptive changes in the other as a correlated response.

In a recent study, Steve Chenoweth and colleagues Howard Rundle and Mark Blows from the University of Queensland, Australia, tackle the combined issues of genetic control and sex-specific selection in a comprehensive investigation of the evolution of male-female differences in a set of sexual display traits in the Australian fruit fly, Drosophila serrata.

Both male and female Drosophila serrata use a set of pheromonal displays during mating, but differ in the relative concentrations of the individual compounds. Using a series of natural populations collected across a wide latitudinal gradient along the east coast of Australia, the authors show that the amount of sexual dimorphism varies and that these differences among populations are genetic. Using classic quantitative genetic methods, they demonstrate that the relaxation of genetic constraints appears to have occurred largely via genes on the X chromosome.

"There are a number of mechanisms by which genetic constraints can be overcome," says Dr. Steve Chenoweth, "Our results suggest that sex-linkage may be key." By manipulating both natural and sexual selection and observing the evolutionary response in the laboratory, the authors also show that, as expected, sexual selection appears to generate sex-specific optima for these pheromones. Contrary to expectation, however, females and not males responded to sexual selection.

"This suggests that the classic scenario of males as the sole target of sexual selection may be overly simplistic," states Dr. Howard Rundle. "If you want to know why males and females differ, you need to consider all forms of selection on both sexes."

This research was published in the January issue of the American Naturalist.

SOURCE : University of Chicago Press Journals

Aphids Are Sentinels Of Climate Change

Aphids are emerging as sentinels of climate change, researchers at BBSRC-supported Rothamsted Research have shown. One of the UK's most damaging aphids – the peach-potato aphid (Myzus persicae) – has been found to be flying two weeks earlier for every 1°C rise in mean temperature for January and February combined.

This year, the first aphid was caught on 25 April, which is almost four weeks ahead of the 42-year average.

Dr Richard Harrington of the Rothamsted Insect Survey said: "One of the most noticeable consequences of climate change in the UK is the frequency of mild winters. As a direct result of this, aphids seeking new sources of food are appearing significantly earlier in the year and in significantly higher numbers. We have been studying the seasonal biology of aphids for a long time now and we know that populations can continue to grow over the winter and spring provided that conditions are warm enough. After a warm winter, there are much larger numbers flying and they are hence detected much earlier. This means that there are more aphids flying in spring and early summer, when crops are particularly vulnerable to damage."

Scientists at Rothamsted Research have been monitoring the flying form of all aphid species for 42 years. They use a network of 16 suction traps (12 in England and 4 in Scotland), placed at various sites, to collect a representative sample of all flying insects. The long term data on aphids can be used to understand the wider implications of climate change, and also to prepare for the season ahead by determining the need for and timing of aphid control measures (based on preceding winter temperatures).

As well as being important indicators of a changing climate, aphids can cause devastating damage to crops. They extract large amounts of sap, weakening the plant, and also spread plant viruses. In addition, because the sap is very high in sugars the aphids excrete very sticky honeydew, which can encourage the growth of sooty moulds that build up and prevent sunlight from reaching the leaves, causing further weakening.

Professor Nigel Brown, Director of Science and Technology, BBSRC said: "Environmental change is one of the big challenges facing the world today. These long-term data on the seasonal appearance of flying aphids not only show that there are already noticeable changes in the UK climate, but they also provide the knowledge which will help to mitigate the consequences."

This work is reported in BBSRC Business, the quarterly research highlights magazine of BBSRC (the Biotechnology and Biological Sciences Research Council).

SOURCE : Biotechnology and Biological Sciences Research Council

Are Pronghorns Smarter Than Classical European Royalty?

Over the past two decades, John Byers has proven that female pronghorns are smarter than many humans when it comes to mate selection. Rather than going for the male with the biggest body or most impressive horns, female pronghorns expend a ton of energy searching for the most vigor and best stamina; traits that will give their offspring the greatest chance of success.

 An American pronghorn male chases an intruder away from his territory. 

Pronghorns are commonly accepted as the second fastest land animal 

in the world--behind only the cheetah--reaching speeds in excess of 45 miles per hour. 

(Credit: John Byers, Department of Biological Sciences, University of Idaho)

But are they smarter than classical European royalty? When pronghorns select a mate, can they factor in what many historians believe doomed the famous Hapsburg dynasty – inbreeding?

Thanks in part to a four-year, $600,000 grant from the National Science Foundation, Byers will be able to answer that exact question.

“We’ve shown the pronghorns know the benefit of selecting the best males,” said Byers, a professor of biological sciences at the University of Idaho. “Now we’re trying to show whether females can balance the cost benefits of selecting a strong male versus a closely related one. Will they accept mating with a relative if the projected cost of inbreeding is not too high? Or reject the male because the cost is way off the chart? Or will they breed without any regard to genealogy?”

Because Byers has worked with the same pronghorn herds in eastern Montana since the early 1990s, and can identify each pronghorn by sight, he is in a unique position to carry out this study. During that time, he has proven female pronghorns expend 50 percent more energy while searching for the strongest males, and that offspring sired by the chosen few are stronger, have a much higher chance of survival and strike out from their mothers much sooner. Because of this mate testing, nearly all offspring are sired by a small subset of males.

As a result of his research, Byers has a complete pedigree of the entire population. When a fawn is born, genetic testing removes any doubt which male is the father.

When a drought in 2003 killed off most of the males and about 30 percent of the females, Byers knew he was in a unique place to study mate selection based on inbreeding.

“I realized we were going to be in an incredibly interesting position,” he said. “We now know females select males for their vigor with a real benefit in survival for their offspring. But today, about three years after the weather caused a bottleneck in the population, they’re faced with a different set of choices.”

Byers’ research will be two-fold. First, the research team will test the paternity of new fawns, measure their living conditions and monitor their survival rate to see what, if any, negative effects occur in pronghorns from inbreeding. Once that is determined, scientists will study female behavior to see if females avoid closely related males – even the best choices for mates – if the benefits of strong genes are outweighed by the average negative effects of inbreeding.

“I think they’ll be able to discern the best choice,” said Byers. “But only time will tell.”

The results of Byers’ study should help conservationists keep the population of pronghorns – and perhaps many other types of hoofed animals – healthy in the future.

SOURCE : University of Idaho  

Red Flour Beetle's 'Selfish' Gene Sequenced

Tracking the red flour beetle in grain storage facilities could become easier, thanks to research to identify a key gene in this grain-feeding pest.

Determining the genetic code of a key gene could make the red flour beetle (Tribolium castaneum), a major problem.in grain storage facilities, easier to track and may offer new ways to control this pest. (Credit: Photo by Peggy Greb)

Researchers with the Agricultural Research Service (ARS), Purdue University, the Human Genome Sequencing Center at Baylor College of Medicine, Kansas State University, and Exelixis, Inc. in South San Francisco, Calif., have determined the genetic code of the so-called "selfish" gene in the red flour beetle (Tribolium castaneum).

This genetic information may offer a potential tracking tool for facilities where grain is stored. Operators could use the information to determine whether beetles are local or from a distant location--and even to develop a plan to control infestations.

ARS entomologist Richard Beeman and molecular biologist Marcé D. Lorenzen at the agency's Grain Marketing and Production Research Center in Manhattan, Kan., deciphered the genetic code of the "selfish" gene. The research was reported in the Proceedings of the National Academy of Sciences.

The selfish gene is important because red flour beetles that don't inherit it from their mother don't survive. It is called the selfish gene because, whether beneficial or deleterious, it ensures its own perpetuation through the population. These genes are widespread in natural populations of red flour beetles, but are otherwise unknown in the invertebrate world.

According to Beeman, the discovery in red flour beetle may provide a useful vehicle for driving desirable genes into populations, since the gene spreads almost like a disease, and since hitchhiker genes can be attached to it. Malaria researchers think other, similar genes introduced into mosquito populations could reduce the spread of mosquito-borne malaria infections. It may be possible to "attach" another gene to the malaria gene that could negate or minimize its function, thus impeding mosquitoes from spreading the disease.

SOURCE : USDA - Agricultural Research Service

Global Warming's Effects Extend To World's Smallest Butterfly

The latest issue of Conservation Biology examines the viability of the Sinai baton blue and the results of human population pressures. The study predicts that in the absence of global warming, grazing, and plant collection (three activities directly linked to humans) the world's smallest butterfly would persist for at least 200 years.

The population could withstand small increases in grazing intensity that would decrease their climate, but not increases in temperature. As the level of global warming raises its impact, extinction rapidly accelerates. This implies "... that there may be an annual average temperature, specific to each endangered species, above which extinction becomes much more likely," authors Martin Hoyle and Mike James state. There is no such threshold of grazing pressure.

The authors mapped the entire global range of this butterfly and obtained data on the intensity of livestock grazing. The Sinai baton blue is one of only two endemic animals in St. Katherine's Protectorate, one of Egypt's most recently designated protected areas. Based on the authors' model, the effect of global warming on the chance of extinction does not depend on the future level of habitat destruction due to this grazing; the growing number of families that live on the protectorate keep a small herd of goats and sheep that graze on the plants the butterflies thrive on. Global warming is the deadly culprit.

"If the areas of habitat patches individually fall below certain prescribed levels, the butterfly is likely to go extinct,"the authors conclude.

###

This study is published in the August issue of Conservation Biology. Media wishing to receive a PDF of this article please contact journalnews@bos.blackwellpublishing.net

Conservation Biology is a top-ranked journal in the fields of Ecology and Environmental Science and has been called, "required reading for ecologists throughout the world." It is published on behalf of the Society for Conservation Biology.

Martin Hoyle is at the School of Biological and Chemical Sciences at the University of Exeter, Hatherly Laboratories. He has performed research on metapopulation dynamics and has been published in numerous journals.

SOURCE : Blackwell Publishing Ltd.

Amber Specimen Captures Ancient Chemical Battle

It appears that chemical warfare has been around a lot longer than poison arrows, mustard gas or nerve weapons -- about 100 million years, give or take a little.

A new study by researchers at Oregon State University has identified a soldier beetle, preserved almost perfectly in amber, which was in the process of using chemical repellents to fight off an attacker when an oozing flow of sap preserved the struggle for eternity.

An ancient example of “chemical warfare” about 100 million years old is captured in this sample of amber, in which a soldier beetle is exuding a certain toxin to protect itself from an attacker.
(Credit: Image courtesy of Oregon State University)

The discovery is the earliest fossil record of a chemical defense response, scientists say, and indicates that this type of protective mechanism -- now common in the insect world and among other animal species -- has been around for more than 100 million years. It's a sophisticated form of defense that clearly was in good working order while dinosaurs still roamed the Earth.

"The chance of these circumstances all coming together at the exact right second was pretty slim," said George Poinar, Jr., a courtesy professor of zoology at OSU and one of the world's leading experts on distant life forms preserved in amber. "You have a prehistoric insect being attacked, using its defenses to ward off the predator and the whole event becoming captured in action as sap flowed down a tree. It's quite remarkable."

The beetle was a small insect, about one-quarter inch long, which may have been in the process of becoming lunch for a giant roach or some other larger insect that apparently was 2-3 inches long, judging by the length of an antenna from the other insect also found in the specimen. The other insect either escaped the sap or was preserved in a different piece of amber, in these samples of Burmese amber that came from the Hukawng Valley in Myanmar.

"This particular insect is now extinct, but the broader family of soldier beetles still exists, and they still use this same type of chemical defense mechanism," Poinar said. "That this type of defense has been preserved through 100 million years of evolution is evidence that it works pretty well."

At the time of this event in the Early Cretaceous Period, huge animals such as dinosaurs still dominated the Earth, but scurrying beneath them were early mammals and large numbers of terrestrial invertebrates, such as these insects. Soldier beetles, then as now, were omnivores that lived on things like aphids, other tiny insects or plant pollen. Among other things, this finding pushes back the known existence of this type of beetle by about 60 million years. And at that distant time, they had already evolved ways to defend themselves.

"This beetle was able to exude a sticky chemical substance that was irritating to potential predators, and caused them to go away or leave it alone," Poinar said. "It could even conserve its excretions and control the direction of the defense; in other words, produce the substance only on its left rear side if that was where the attack was coming from."

Building on these types of early defense mechanisms, Poinar said, modern insects now have a wide range of defensive chemical arsenals -- things that are distasteful, nauseating or caustic, from chemicals such as phenols, aldehydes and ketones. Some contemporary soldier beetles can produce types of carboxylic acid, as well as triglycerides and glyceride esters.

In insects, these types of defensive mechanisms are often a key to their survival.

Amber provides a unique mechanism to preserve specimens such as this. Beginning as viscous sap from certain kinds of trees, it can trap small animals or other materials, acts as a natural embalming agent, and eventually can turn into a semi-precious stone that displays these ancient life forms in nearly perfect, three-dimensional form. The phenomena has been invaluable in scientific and other ecological research, allowing experts to help re-create more accurate pictures of ancient ecosystems based on the insect life that lived then.

"Insects give us a fascinating window to the world, and they are survivors," Poinar said. "This particular species lived right on through the K-T Boundary at 65 million years ago, when the dinosaurs and many other species disappeared."

"These insects were here a long time before humans, and we can learn a great deal from their remains," he said. "And they'll probably still be here a long time after our species is gone."

The findings were just published in the Journal of Chemical Ecology.

SOURCE : Oregon State University

Amber Fossils Reveal Ancient France Was A Jungle

Research on a treasure trove of amber has yielded evidence that France once was covered by a dense tropical rainforest with trees similar to those found in the modern-day Amazon. The 55-million-year-old pieces of amber was discovered in the Oise River area in northern France.

In the new study, Akino Jossang and colleagues used
laboratory instruments to analyze the fossilized tree sap in an effort to link specific samples of amber to specific kinds of trees. The amber remained intact over the ages, while the trees from which it oozed disappeared. Efforts to make such connections have been difficult because amber from different sites tended to have very similar chemical compositions.

The report describes discovery of a new organic compound in amber called "quesnoin," whose precursor exists only in sap produced by a tree currently growing only in Brazil's Amazon rainforest.

Researchers say that amber probably seeped out of a similar tree growing in a tropical forest that covered France millions of years ago before Earth's continents drifted into their current positions.

"The region corresponding to modern France could have been found in a geographically critical marshy zone belonging to Africa and a tropical zone 55 million years ago extending through North Africa to the Amazon," the report states.

The study "Quesnoin, a Novel Pentacyclic ent-Diterpene from 55 Million Year Old Oise Amber" is scheduled for the Jan. 4 issue of ACS' Journal of Organic Chemistry.

SOURCE : American Chemical Society