Scientists prune list of world's plants

A project helping conservation work has deleted more than 600,000 species of flowering plants that were duplicated or not 'new'

A dahlia in full bloom. 

Scientists estimate the total number of flowering plant species around the world to be around 400,000. Photograph: Harish Tyagi/EPA More than 600,000 plant species have been deleted from the dictionary of life after the most comprehensive assessment carried out by scientists.
For centuries, botanists from different parts of the world have been collecting and naming "new" plants without realising that many were in fact the same. The humble tomato boasts 790 different names, for example, while there are 600 different monikers for the oak tree and its varieties.
The result was a list of more than 1 million flowering plant species. Although experts have long known that it included many duplicates, no one was sure how many. Later this year, the study team, led by UK and US scientists, will announce that the real number of flowering plant species around the world is closer to 400,000.
The project - which has taken nearly three years - was the number one request made by the 193 government members of the Convention on Biological Diversity at their meeting in 2002. There were concerns that without this work, it would be impossible to work out how many plants were under threat and how successful conservationists were in saving them.

The information will also be vital for any organisation or researcher looking at "economically important" plants, such as those for food and nutrition or medicine, said Alan Paton, assistant keeper of the herbarium at the Royal Botanic Gardens at Kew, west London, one of the four leading partners in the project.

"On average, one plant might have between two and three names, which doesn't sound a great deal, but if you're trying to find information on a plant, you might not find all [of it] because you're only looking at one name," Paton said. "That's even more critical for economically useful plants: because they are more used, they tend to have more names."
In one example, researchers calculated that for the six most-used species of Plectranthus, a relative of the basil plant, a researcher would miss 80% of information available if they looked under only the most commonly used name. On another database, they found only 150 of 500 nutritionally important plant species using the names cited in current literature.
"By going for one name, we missed the majority of information mankind knows about that plant, which isn't too clever," said Paton. "What's really a breakthrough is we have a place which allows people to search through all the names used."
Kew Gardens joined up nearly three years ago with Missouri Botanical Garden in the US, and experts on two of the biggest and most valuable plant families: legumes, or peas and beans, and Compositae, which include asters, daisies and sunflowers.
They have since attempted to search existing plant lists and work out an "accepted" name for each species, and then list all known variations. One of the databases was originally set up using £250 left in the will of Charles Darwin. The full results will not be published until the end of the year, but so far the researchers have found 301,000 accepted species, 480,000 alternative names, and have 240,000 left to assess.
Although work will continue to assess smaller plant groups in more detail and check for missed duplications, Paton said they now believe that the true number of plant species will turn out to be "400,000 or just over".
"You can't give an absolute number of names, but we have narrowed the possibility," he said. Previous estimates, without the help of a full assessment, put the figure at between 250,000-400,000.
Most of the work of the study group was sifting and sorting different names allocated to one species, often because scientists were simply not aware of the work of rivals and colleagues who had previously "described" the plant in a scientific journal, or because of confusion caused by superficial differences such as different sized leaves in different climates. In some cases, plants thought to be the same have also been judged to be different species because of differences which have been revealed by later scientific discoveries, such as DNA.
As well as the likely 400,000-odd flowering plants, there are thought to be 15,000 species of ferns and their allies, 1,000 gymnosperms such as conifers, and 23,000 mosses and allies making up the plant kingdom. For comparison there are more than 1 million species of insects listed by science, 28,000 living species of fish, 10,000 birds and 5,400 mammals.
A meeting of the Convention on Biological Diversity in October in Japan is likely to declare that targets to halt biodiversity loss by this year failed and set tougher new aims to halt the problem.
This article was amended on 20 September 2010. The original said that poplars are gymnosperms. This has been corrected.

 Story

Breezy Love, or the Sacking of the Bees

By OLIVIA JUDSON

Olivia Judson on the influence of science and biology on modern life.

Birds do it. Bees do it. Beetles, bats and light summer breezes do it.

I refer, of course, to that raunchiest of sex acts: the pollination of flowers.

Ruby Washington/The New York Times SEDUCTION Bee and flower meet.

When it comes to sex, plants have more headaches than the rest of us. One problem is that they can’t travel about to find a mate — they are, after all, rooted to the spot — so they have to depend on intermediaries to bring egg and sperm cells together.

For mosses and ferns, the intermediary is water. For conifers like pine trees and cypresses, the intermediary is wind. But for most flowering plants, the intermediaries are animals.

Flowering plants are the largest, most successful group of plants on the planet today. There are thought to be more than quarter of a million different species — nearly 10 times more than all the other types of plants added together. (To put things in perspective, the number of living species of fish, amphibians, reptiles, birds and mammals combined is less than 58,000.) The flowering plants include roses and waterlilies, grasses and oak trees, tulips and orchids. They include, in short, most of the plants that come to mind when one thinks of vegetation.

It was not always thus. Before the mid-Cretaceous, 100 million years ago or so, flowering plants were scarce: conifers and their relations ruled the landscape. But then, for reasons that are not well understood, flowering plants upstaged all others, and the Earth came into bloom.

Flowering plants were not the first to seduce animals into spreading their pollen for them. Fossils suggest that some earlier groups of plants, now extinct, had evolved a dependency on insects like scorpionflies. Nonetheless, the earliest flowers appear to have been pollinated by insects, and the full-scale blossoming of flowering plants coincides with the rise of animals as go-betweens. Bees, for example, buzzed onto the scene with flowering plants; the evolutionary history, and success, of both groups is intimately linked.

Librado Romero/The New York Times

The appearance of flowering plants brought a new flamboyance to the planet. Flowers pollinated by animals tend to be big and colorful; they often smell. (To a human, flowers pollinated by bees typically smell pleasant; flowers pollinated by flies tend to smell foul, like rotting meat.) Often, flowers offer something for the animal to eat — a sip of nectar, perhaps. Sometimes, they provide heat.

(One plant that heats its flower is Philodendron solimoesense, an Arum from the South American tropics. In doing so, it turns itself into an assignation hotel for scarab beetles. The beetles arrive in the evening, spend the night feeding and mating, spend the morning recuperating and head off to a new flower later on — complete with pollen from their host. Sure enough, the heat saves the beetles energy. Beetles in a heated flower don’t have to use as many calories to keep warm as they would if they spent the night outdoors.)

Yet, from time to time, flowering plants abandon their animals, evolving instead to throw pollen to the wind. Wind-pollination — if you’re a vocabulary fiend, the technical term is “anemophily,” meaning lover of wind — has evolved at least 65 times in flowering plants, and around 10 percent of the species do it. Indeed, as I mentioned last week, many grasses are pollinated by the wind.

It’s not clear what causes this transition, though there are several ideas. One is that it happens in plants that, although generally pollinated by insects, already have a small capacity for wind pollination — small, light pollen grains, and flowers that can, in principle, catch pollen if it floats past on a breeze. Then, the balance between insects and wind can easily shift. In a tropical forest, for example, the advantages of insects are great: they provide highly targeted pollen-delivery in a complex milieu. But in big open spaces, the wind may do a better job — especially if the climate is inhospitable, and insects are few. Such circumstances may cause a shift away from traits that lure insects, and enhance those that seduce the wind.

A plant that has sacked bees or other insects can make its flowers smaller, less colorful and more aerodynamic. Liberated from the expense of making nectar, it can make more pollen instead. A bee, after all, can only carry so much pollen at once. The wind is not so limited.

And wind-pollinated plants tend to produce huge quantities of pollen. Whereas animal-pollinated plants produce a median of 3,450 pollen grains for every ovule, wind-pollinated plants produce almost 10 times as much. No wonder wind-pollinated plants are the chief causes of eye-itching, nose-tickling human misery. (It’s not just the anemophilous flowering plants that are to blame, though. Wind-blown cypress pollen is a major cause of allergies in some parts of the world.)

This massive production of pollen is usually put down to the inability of wind to make reliable deliveries.

Librado Romero/The New York Times

Charles Darwin himself suspected the wind of being a fickle and inefficient messenger, and that view has largely held until this day. But there is little actual evidence that wind-pollinated plants have more difficulty getting themselves fertilized than other plants do. (Indeed, plants seem adept at plucking pollen of the right species out of the breeze. How they do this isn’t known.) Moreover, in animals, large numbers of sperm tend to evolve when competition between different males to fertilize a female’s eggs is fierce. In many wind-pollinated species, plants flower all together, and for a brief time. Perhaps wind-pollinated plants face greater competition from their rivals.

But whatever the causes, I’m glad that most plants have not sacked their bees. In a world pollinated only by gusts and breezes, spring would be less beautiful. And, for many of us, it would also be more tortured.

Story and additional Notes

Nature’s masquerade

New York Times News Service

Naturalist Bates observed flies that looked like bees, beetles that looked like wasps, even caterpillars that looked like pit vipers. The creatures use what are now recognised as four strategies to avoid being eaten, mimicry; concealment ; the display of warning colours; and masquerading as inedible objects, writes Sean B Carroll

In the summer of 1859, an Englishman named Henry Walter Bates returned home after 11 years of roaming the vast Amazon jungle with specimens of more than 14,000 species he had collected. Just as Bates set about organising and describing his vast collection, Darwin’s ‘On the Origin of Species’ was published, which gave Bates an entirely new way of thinking about all that he had seen in the jungle. He was able to provide some fresh and very timely evidence in support of natural selection because it explained a phenomenon he had closely observed, one that intrigued him and continues to hold the attention of naturalists today: the close resemblance of some animals to living or inanimate objects. It is a pity that the work of Bates is so little known, not only because of its value but also because it was accomplished at considerable personal cost. He had travelled to South America with Alfred Russel Wallace, who was to forever live in Darwin’s shadow as the other person who came up with the theory of evolution by natural selection. Bates and Wallace arrived together in Brazil in May 1848, but split up after a year or so exploring the Amazon, ostensibly to “cover more territory.” After a year on his own, Bates nearly gave up. He had received no money from his agent in England (who was to sell specimens Bates shipped back from the Amazon). His clothes were worn to rags. He was shoeless, “a great inconvenience in tropical forests,” he noted. And he had been robbed of nearly all of his money. Just as he was planning to leave Brazil, Bates caught yellow fever and became too sick to travel. While recovering, he received money from his agent and news that his collections were a success in England. He turned around and plunged back into the jungle for eight more years. On his return to England and his encounter with Darwin’s great opus, Bates soon realised that he had noticed some things that Darwin had not mentioned but that could support his controversial new theory. Bates wrote to the famous naturalist, “I think I have got a glimpse into the laboratory where Nature manufactures her new species.” Darwin was taking a beating from critics over ‘On the Origin of Species.’ He was eager to hear whatever fresh evidence this hardy explorer could provide. In ‘On the Origin of Species,’ Darwin relied heavily on the analogy between artificial selection by humans for desirable traits of livestock and natural selection for traits in the wild. Now Bates had a whole new body of evidence for natural selection in the wild. Analogous resemblance Bates explained to Darwin that he had found many instances in which a completely harmless and potentially edible animal resembled a distasteful, inedible, noxious or poisonous species. He observed flies that looked like bees, beetles that looked like wasps, even caterpillars that looked like pit vipers. He referred to these as “analogous resemblances” or “mimetic analogies.” Bates deduced that defenseless mimics gained an advantage by resembling well-defended species. Also, that the many cases he had observed were not mere coincidences, as the mimicking forms only occurred in the same geographical area as the species they imitated. He offered the phenomenon, still referred to today as Batesian mimicry, as “a most beautiful proof of the theory of natural selection.” Some less scientific, more sentimental naturalists of the day were inclined to view these resemblances among species as merely nature’s proclivity for beauty and ornamentation. Bates countered by pointing to other kinds of imitations, like moths and caterpillars that resembled bird droppings. Where was the beauty in that, he asked? There is good experimental evidence for Batesian mimicry and the advantages gained by innocuous animals that resemble well-defended animals. But, until recently, there were few tests of how the imitation of bird waste, thorns, twigs or stones actually works. The challenge is to distinguish whether the ruse is a matter of concealment, with the predator failing to detect the animal, or a case of “masquerade,” with the predator actually detecting the imitator, misidentifying it as something inedible, and then ignoring it. Recently, biologists John Skelhorn and Graeme D Ruxton at the University of Glasgow and their collaborators Hannah M Rowland and Michael P Speed at the University of Liverpool devised such a test using the twig-imitating caterpillars of the brimstone moth and early thorn moth as prey. The hawthorn experiment For masquerade to work, a predator must have had some experience with the objects being imitated. So the scientists divided young chickens into several groups, one group was exposed to a hawthorn branch, which is a common home for the caterpillars, another group was exposed to a hawthorn branch that was wound in coloured thread in order to alter its appearance, and a third group was exposed only to an empty testing cage. The groups were then, split into three, one getting a single brimstone caterpillar, one getting a single early thorn caterpillar, and the third getting a plain hawthorn twig in otherwise empty cages. The researchers then measured how long it took the chicks with different previous experiences to attack the caterpillars, or to peck at the twig. Even when the caterpillars were the only objects in sight, birds that had been exposed to natural hawthorn branches took much longer to attack the caterpillars or the twig, several minutes on average compared with just seconds for birds that had not encountered the hawthorn branch or been exposed to the branch wrapped in coloured thread. The experiment demonstrated that the birds that had encountered the hawthorn branch subsequently misidentified the masquerading caterpillars as twigs, even at close range and in plain view. Skelhorn and his colleagues noted that at least 50 species of British moths and butterflies alone resemble inanimate objects at some point in their life cycle. The jungle creatures that enthralled Bates use what are now recognised as four distinct strategies to avoid being eaten, mimicry; concealment, known as crypsis; the display of warning colours; and masquerading as inedible objects. When Bates’ scientific paper describing various imitations was published, Darwin told him it was “one of the most remarkable and admirable papers I ever read in my life” and “it will have lasting value.” Story