Press and Media Coverage of INSECTS research
The following article appeared in The New York Times, 15 October 2002, and deals with the work carried out by Duur Aanen at the Department of Population Ecology, Copenhagen University.
Before Adam and Eve, the Farmers Were Termites
By JAMES GORMAN
Sometime, perhaps about 50 million years ago, farming was invented. Not by human beings of course, but by ants, termites and beetles, each of which developed forms of fungi gardening.
Previous studies have tracked the molecular evolution of ants and beetles. The tools used, statistical analyses of genetic variation, are the same ones that have produced the claim, widely but not completely accepted, that human beings are all descended from a single female ancestor in Africa - called Eve, of course - about 150,000 years ago.
Researchers have found Eves and Adams among the ants and beetles as well. Farming appears to have evolved only once among the ants, suggesting one founding pair, although the descendant farmers have domesticated new varieties of fungi several times. In contrast, farming appears to have evolved at least seven different times among the beetles.
Now a European research group has turned its attention to fungus-farming termites, which have been less well studied. What they have found is an out-of-Africa story in which termites and fungi joined together once and have not separated since. It was, apparently, the beginning of a beautiful symbiosis.
Karen Machielsen
Termites have developed a form of fungus farming in which the insects and the fungi seem to be dependent upon each other, scientists say.
At some distant date, probably around the time ants began cultivating their gardens, the researchers say, a termite Adam and Eve produced a colony that successfully began cultivating a genus of fungi.
The termites that descended from these pioneers (the subfamily Macrotermitinae) have not strayed from their fungal partners (the genus Termitomyces), though among 11 termite genera there has been some fungus swapping within Termitomyces.
The fungi have also remained true to the termites in an enduring symbiotic monogamy not seen in either ants or beetles. As Dr. Duur K. Aanen, the lead author of a paper in the current issue of The Proceedings of the National Academy of Sciences, described it, "The fungus growing termites have once domesticated one group of fungi."
Among the ants, Dr. Aanen and colleagues based in Denmark, France and Britain note, farming can be traced to one evolutionary moment. But they have several times taken in a new fungus.
Dr. Aanen, of the Zoological Institute at the University of Copenhagen, said that the termites also differed from farming ants in how new colonies started their fungal gardens. New ant queens bring a bit of starter fungus along to start the new colony's crop. So new colonies inherit specific fungal strains.
Termite behavior is less well known, but in the species so far studied male and female pairs found colonies without bringing along any samples of fungus from the old mound. When the first workers hatch, their job is go forth and forage for fungal spores to start the garden from scratch. There are two notable exceptions, both recent evolutionary innovations. In one species the queen brings a bit of starter fungus along; in the other, it is the king.
The termites feed their fungal gardens with their own droppings. They eat plant detritus and transport it to the colony in their gut, perhaps partly digesting it, before depositing it. Dr. Aanen said that the natural history of the termite behavior, including the extent of digestion involved has not been well studied. As the fungus grows, the termites feed on it. There is still some debate, Dr. Aanen said, about whether the termites also eat some of the plant material a second time, after it has been broken down by the fungus.
There is a symmetry in the relationship between termites and fungi not apparent among the ants. The termites and fungi seem to be completely dependent on each other. Most ants, by contrast, can't live without the fungi, but their crops are very closely related to free-living varieties and may not be completely tied to their farmers. Among certain of the more recently evolved ants, like the leaf-cutters, the dependence is mutual and complete as it is in termites.
In a commentary, Dr. Ulrich G. Mueller of the University of Texas and Nicole Gerardo, a graduate student at the university, review the variety of ant, beetle and termite farming arrangements and the evolutionary origins of the behavior. In all cases, the relationships between insects and fungi clearly benefit both parties, the definition of symbiosis.
In termites, they say, the ancestral insects may have already been feeding on fungi, whereas in beetles the link may have begun with the beetles serving the fungi by dispersing spores. With ants, they write, the insect may have been dispersing spores, or have turned to fungi growing in nests as a nearby food source.
Dr. Aanen and colleagues suggest that the way termites and fungi have evolved raises the question of whether the changes are "fungus driven" as much as they are "insect driven." The question, in other words, is similar to one many human pet owners have asked themselves just before a midnight dog walk or kitty litter duty. Who domesticated whom?
In any case, both parties seem to be thriving. The termite hills in Africa are massive, with millions of individuals. And the fungi are not doing so badly either. One farmed species, said Dr. Aanen, Termitomyces titanicus, has a fruiting body, or mushroom, that can be up to one meter in diameter.
"It is," said Dr. Aanen, "in the Guinness Book of World Records."
U.K. National Science Week (9-16 March 2002)
Francis Ratnieks and Adam Hart from Sheffield gave two school presentations on "The amazing life of social insects: bees, ants, wasps" as part of National Science Week. The first, at Palterton Primary School, near Bolsover, was in the evening to over 30 parents and children aged 9-11. Francis spoke about social insects in general before going on to detail six amazing things that they do: dancing to communicate, making honey and pollinating crops, choosing the sex of their offspring, building prisons, putting out their rubbish, and punishing miscreants. Meanwhile, Adam set up colonies of leafcutting ants, dinosaur ants and honey bees as well as pinned social insects from around the world and a honey tasting display. The honey tasting was particularly popular, with many tasting heather honey, comb honey, and unusual honeys from the USA and Europe for the first time. The children proved to be a knowledgeable and enthusiastic audience with the talk and displays prompting many interesting questions. The second presentation, at Aston Comprehensive School, Rotherham, was to 150 children in Years 8 and 9. Here we were helped by APS student Richard Hanlon, who wants to be a teacher so came along to see what school kids are like. Again, the children heard a talk and afterwards looked at the demonstrations. The leafcutting ants' fungus garden, the size of the dinosaur ants, the behaviour and queen of the honey bees and the wealth of different honeys fascinated the children, causing some to be rather late for their next lesson! Our contact at Aston School was biology teacher Marjorie Skidmore, who took her BSc degree at Sheffield APS a few years ago. They were really psyched up for National Science Week. The entrance had a huge display made by the children, showing what they hoped to learn. Large and colourful bees and ants were very prominent and the teachers were even wearing special Science Week t-shirts.
More details, and pictures, can be seen at: www.shef.ac.uk/aps/temp/science-week.html
The following Letter by Francis Ratnieks was published in The Times on Saturday September 8 2001 in response to two other letters in which people were remarking on seeing some dead wasp nests in sheds, but others still alive elsewhere, and also nests with larvae but no wasps, and speculating on possible diseases:
| Retreat of wasps wholly consistent From Dr. Francis L. W. Ratnieks Sir, There are eight species of social wasps in Britain. Superficially, they all look the same with black and yellow stripes. But they vary considerably in the length of the annual colony life cycle. In all species the nests are founded in the spring by a lone mated queen. Initially, only worker wasps are reared but later only queens and males are reared and the colony gradually dies out due its dwindling workforce. Four species (all in the genus Dolichovespula) have small "rugby ball" nests which end their life cycle in August. Two species (the red wasp Vespula rufa and the hornet Vespa crabro) last another month, and the other two (the common wasp Vespula vulgaris and the German wasp Vespula germanica) have nests that last until November. The observation of dying wasp nests (letters, September 4 and 5) is entirely consistent with this biology and there is no cause for believing that Britain is losing its wasps. Nests built in sheds are almost invariably Dolichovespula and I would expect them all to be dead by now. Common and German wasps usually nest in attics and in the ground and their nests are at peak population in September. At the end of the colony life cycle it is typical that some of the larvae do not get reared due to the lack of workers, which collect all the food. So typical, in fact, that there are several species of flies whose larvae specialise on scavenging the last remaining larvae. My students and I have discovered some remarkable new facets to the life of these familiar insects. For example, in several species the workers "police" each other, eating any eggs laid by other workers and thereby allowing the queen to be chief egg layer. Yours,
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From "The Last Word", New Scientist, 11 August 2001 No. 2303 page 93:
Question: Instead of foraging randomly for nectar, bees tend to stay with the same plant species during a collecting session. The plants benefit from this by being pollinated-but what's in it for the bees.
Answer: Honeybee foragers normally visit only one species of plant when foraging because this helps them gather nectar more efficiently. Flowers typically occur in patches so the same type are close together anyway. But each species of flower has a different shape so that each has to be worked it in a distinct way.
Forager bees have to learn how to work each flower, learning where to put their tongue to extract the nectar. If bees had to shift constantly from one type of flower to another would be slower at handling each individual flower.
In the honey bee, specialization is also a consequence of their waggle dance, which hive-mates use to tell each other where plentiful patches of flowers are located. Yhis means an individual forager doesn't have to spend time prospecting for other flower species while she is foraging. Instead, she can focus entirely on her patch of flowers. When these flowers stop blooming, she either scouts out a new patch herself or, more likely, gets directed to a patch by reading waggle dances back in the hive. Bumble bees, on the other hand, have no communication system. Foragers must constantly sample different species of flowers so they don't miss the most profitable species.
Francis Ratnieks
Laboratory of Apiculture & Social Insects
Sheffield University
From "The Last Word", New Scientist, 28 July 2001 No. 2301 page 137:
Question: Children at my school are always asking me how bees make honey. Can anyone help me explain.
Answer: Honey bees collect both nectar and pollen from flowers, but only the nectar is used to make honey. The pollen is transported back to the hive in baskets on the bees' hind legs, while the nectar is carried in the honey stomach. When full, the honey stomach can weigh more than a third of a forager bee's unladen weight, making its abdomen visibly longer.
Nectar is essentially a solution of sugar in water, usually between 25 and 50 per cent sugar. Back in the hive, the nectar is placed into wax honeycomb cells and the excess water evaporates until the honey is approximately 83 per cent sugar. Each cell is then covered over with a layer of wax. When large amounts of nectar are drying, the bees help the process by using their wings to blow air through the hive. Preventing the nectar from spoiling is crucial, because it may not be eaten for months. The evaporation of the excess water breaks down the sucrose in the nectar into two smaller sugars, glucose and fructose. This creates a solution of sugars too concentrated for yeast and other microorganisms to grow in.
As well as sugar, nectar contains small amounts of other chemicals that give different honeys their distinct colours and flavours. The bees from any one colony will collect nectar from hundreds of different plant species during a summer, but at certain times they collect most of their nectar from just one or a few locally abundant species. The nectar from these collections accounts for most of the honey the bees produce, and beekeepers often harvest honey after such a nectar flow, thereby obtaining honey with a flavour and colour characteristic of a particular plant.
Francis Ratnieks
Laboratory of Apiculture & Social Insects
Sheffield University
An article about the work carried out on waste management in leaf-cutter ants at Sheffield (in collaboration with Copenhagen) appeared in the UK national newspaper The Independent on the 25th April 2001. The web version of the article can be found at: www.independent.co.uk/story.jsp?story=67615 and the text is reproduced below.
Waste managers of the ant world For the leaf-cutting ants, successfully disposing of rubbish is a matter of life or death. And the process is rigidly enforced by a strict social hierarchy By Simon Hadlington. 20 April 2001 One of the defining characteristics of any advanced society is an organised system of waste disposal. Before the Victorians, we were largely content to empty our chamber pots and potato peelings out of the window and on to the street, creating rivers of filth, and epidemics of diseases such as cholera and typhoid. Realising that there was a connection between waste and public health, around 150 years ago the Victorians set about engineering elaborate sewerage and waste disposal systems. So much for man's ingenuity. It turns out that we could learn a lot from the world of social insects, who, it appears, have been practising municipal hygiene for many millions of years. New research by British scientists is revealing that the leaf-cutting ant (Atta cephalotes) has evolved an impressive strategy for ensuring that the colony's potentially harmful waste is kept in secure dumps. Furthermore, the garbage-heap workers that tend this waste are fated to spend their entire lives as untouchables ? if they attempt to join the rest of the workers in the nest, which would risk introducing infection, they are bullied and harried back into their dank nether world. The work on Atta cephalotes has been carried out by researchers in the Laboratory of Apiculture and Social Insects at the University of Sheffield. Dr Francis Ratnieks, the laboratory's director, is interested in the way that complex insect societies are organised. "The social insects include ants, termites and many types of bees and wasp," says Dr Ratnieks. "They live in complex, organised societies. The purpose of the society is to survive and reproduce and good organisation helps do this. We are studying how the nest, work and the workforce are organised, and the role of information passed between individuals in all this." At the Sheffield laboratory, Adam Hart, a graduate student, has been studying one important but hitherto largely neglected aspect of the life of a colony of leaf-cutter ants: how they manage their waste.Leaf-cutter ants live in the Americas and are famous for their remarkable underground farms where they grow their own food in the form of a fungus. The underground nests can be the size of a small house. The nest contains scores of chambers, each as big as a basket ball and almost completely filled with 'gardens' of spongy, off-white fungus which is the colony's food source. Worker ants, who are dedicated to foraging, leave the nest daily along well-worn trails, climb trees and cut sections of leaf to bring back to the nest. The leaf fragments are then successively chewed by other ants into increasingly smaller pieces, ultimately becoming a pulp. The ants spread the nutritious pulp over the garden and seed it with fungus. The garden is tended by specialized, small-bodied, gardener ants who weed it of any unwanted fungi. "The ants are trying to develop a monoculture of the fungus," says Mr Hart. "They do not want it to be contaminated by other fungi, so they remove any pest fungus and also any dead or dying ants." "It is literally farming," says Dr Ratnieks. "Humans may have been farming for 10,000 years, but these ants have been doing it for millions of years." However, as with any community, there is the issue of waste. A large colony of Atta cephalotes might have a population of one million and collect tonnes of leaves per year. Once the fungus has extracted the nutrition from the leaf pulp, the pulp becomes exhausted and useless like spent mushroom compost. What remains, about a seventh of the original mass of the leaf pulp, along with dead ants and other decaying matter is garbage, which must somehow be safely disposed of. "The waste from the garden can be nasty," says Mr Hart. "Often it is contaminated with a very serious weed fungus called Escovopsis, a parasite which lives exclusively on the garden fungus and can completely overrun the garden in severe cases, causing the ants to abandon the nest. The waste itself is also harmful to the ants." | As in any community, therefore, the presence of the waste has serious public health implications. After all, a colony of a million ants is a teeming subterranean metropolis with a population equivalent to that of Sheffield. Simply by leaving the waste lying around ? the entomological equivalent of throwing it onto the street ? presents a significant risk to the well-being of the community. "Because this waste is potentially dangerous, we expect the ants to evolve sophisticated ways of dealing with it to reduce the possibility of infection from the garbage heap back to the fungal gardens," says Dr Ratnieks. "The colony must be able to deal with huge quantities of garbage in a sanitary way." And it does. Using an artificial nest consisting of several Perspex chambers, the researchers have for the first time observed the intricate interactions that take place within the colony to ensure that the garbage does not contaminate the gardens.The ants store the waste in large garbage chambers excavated close to the garden chambers where most of the colony lives. The garbage chambers are bigger than the garden chambers and one garbage chamber can hold the waste from several gardens. While providing a certain degree of isolation, having separate garbage chambers would not eliminate all risk of contamination ? ants tramping to and fro with garbage could pick up infection from the waste dump and return it to the garden. To guard against this, a group of ants is given the job of tending the rubbish. They live in the garbage chamber and cannot leave it. Mr Hart has observed that if a garbage-dweller attempts to go to the main part of the nest she is harassed by the other workers and made to return. "I have also done experiments where I placed normal foragers in a container with garbage and then returned them to the nest," he says. "They get attacked violently, often being ripped to pieces by several ants. Probably some chemical in the garbage causes ants to act aggressively to any contaminated individual." One role of the garbage workers appears to be to carry out good compost management. They turn the waste over and tunnel through it. It is likely that this gives the decaying matter a healthy supply of oxygen, increasing the rate of decomposition. This not only reduces the volume of the waste but also ensures that the disease-causing pathogens, such as Escovopsis, are rapidly destroyed. The separate role of the garbage workers from the rest of the colony is what biologists call 'division of labour'. And while this helps to reduce the risk of contamination, it does not eliminate it. For this, another level of sophistication is required ? something called 'task partitioning'. "'Task partitioning' is a phenomenon where a single task is divided between workers," says Dr Ratnieks. "We have found that it occurs widely in social insects, apparently to increase the specialisation of workers and to make them work more efficiently. For example, honey bee foragers collect nectar but instead of putting it directly into a storage cell, they transfer it to receiver bees: one task becomes two as in a factory production line." In the case of Atta cephalotes ants from the garden bring the waste into the tunnel leading to the garbage heap and place it in a special pile. A garbage worker then emerges from the garbage chamber and collects the new waste. "In our observations in the artificial nest, 97 per cent of all the garbage was handled in this way," says Mr Hart. "This ensures that no worker from the main part of the nest need venture into the contaminated dump." "What we see is a clever system for ensuring that the potentially hazardous part of the nest ? the garbage chamber ? is very effectively isolated," says Dr Ratnieks. "This is achieved by 'division of labour', 'task partitioning' and physical separation ? if necessary reinforced by aggression." This has been the first observation of 'task partitioning' in social insects that does not involve foraging. It is evident from the work carried out in Sheffield that these social insects discovered long before we did that sensible waste management is crucial to the health of any society. "In an ant colony, just like a city, garbage can't just be left lying around or it becomes a public health problem," concludes Dr Ratnieks. "It is directly analogous to what happens in human societies." |
A brief mention of the above research was also made in the In Brief sections of New Scientist, 20th January 2001.
Treated like garbage From New Scientist magazine IT'S not just human societies that deem some of their members to be "untouchable". Colonies of Atta cephalotes ants contain a group of shunned workers that toil in the colony's rubbish dump, researchers at the University of Sheffield have found. The dumps are riddled with disease-causing mites and nematodes, so many of the garbage workers survive only half as long as their clean-living siblings. But any ants trying to leave the dump are hustled back by the workers in the tunnel outside. "The aggressive behaviour is extreme. Workers contaminated with garbage may be ripped to pieces, with legs and heads severed," says graduate student Adam Hart. The study will appear in the journal Behavioral Ecology and Sociobiology. |
The following article, describing more work carried out in Sheffield, appeared in the July 2001 issue of BBC wildlife magazine:
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