Flesh-eating plant traps worms with sticky underground leaves

Philcoxia couldn’t look more unassuming. It’s a small herb that lives in Brazil’s Campos Rupestres region, a sparse plateau of rocky outcrops and white sands. All you’d see of it are a handful of twigs sticking out from the grains, topped with small purple flowers and even smaller leaves. You wouldn’t think that it’s the type of plant that can kill animals.

To find Philcoxia’s grisly secret, Caio Pereira had to look underground. The plant biologist from Unicamp, Brazil, found that the plant traps and digests  tiny worms with sticky underground leaves.

Plants have evolved to eat animals at least six times, and over 600 species of them now do so. They catch their prey with slippery water-filled pitchers, fast-snapping traps, sticky leaves and sucking bladders. Their strategies are diverse, but they all tend to grow in areas that are poor in nutrients. For example, familiar species like the Venus’ fly trap and the sundew live in bogs and swamps. In such inhospitable environments, these plants supplement their supplies of nitrogen, phosphorus, and other nutrients by feasting on the flesh of animals.

Philcoxia is no different. When Peter Taylor described the plants in 2000, he noted that they have several features that resemble those of other meat-eating species. Its mountain home is poor in nutrients and frequently starved of rain. Its roots are unusually sparse and lack the fungal partners that help other plants to survive. And it has tiny underground leaves – just a millimetre wide and coated with sticky glands, of the type found in other carnivorous plants.

There was just one problem. There were no signs of captured animals, or bodies nearby. If Philcoxia ate animals, it wasn’t doing so obviously. In 2007, Peter Fritsch found a possible answer. He noticed nematode worms stuck to the underground leaves, and reasoned that the plant was trapping and digesting them. Pereira, working with Fritsch, has now confirmed this hypothesis.

He found that Philcoxia’s underground leaves are littered with the bodies of dead nematodes. To check that the deaths aren’t coincidental, Pereira bred nematodes so that their bodies were full of nitrogen-15 – a rare and heavier-than-usual version of the element. He then “fed” the nematodes to Philcoxia. Two days later, Pereira found that 15 percent of the nitrogen-15 in the worms has been incorporated into the plant’s leaves. It was clear proof that Philcoxia was digesting the nematodes and absorbing the remains into their bodies.
Many meat-eating plants digest their prey with high concentrations of enzymes called phosphatases. Philcoxia does so too. Pereira found loads of the enzymes on Philcoxia’s leaves, which means that the plants are probably digesting the nematodes directly.

Pereira still wants to find out how Philcoxia lures its prey towards its traps. But for the moment, he has shown that its diet of worms greatly raises the level of nitrogen in its leaves, boosting it even above the levels of neighbouring plants that aren’t carnivorous.

That’s interesting, because some scientists have suggested that eating animals is a relatively inefficient way of coping with nutrient-poor environments. This would explain why carnivorous plants are relatively rare. But Philcoxia clearly shows that a fleshy menu can provide more nutrients the strategies of other plants in the same conditions.

Indeed, Philcoxia’s murderous habits suggest that we may have underestimated the true number of meat-eating plants in the world. After all, if this rare species feeds on microscopic prey using hidden traps, perhaps other plants do so too. As Mark Chase wrote a few years back, “we may be surrounded by many more murderous plants than we think”.

Reference: Pereira, Almenara, Winter, Fritsch, Lambers & Oliveira. 2011. Underground leaves of Philcoxia trap and digest nematodes. PNAS http://dx.doi.org/10.1073/pnas.1114199109

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Tree-frog biodiversity warning for Amazon

 

Amazonian tree-frogs are exceedingly well established

Tree-frog hot spots in the Amazon have been established over tens of millions of years, say scientists.

To explain why some areas have greater species richness, experts analysed the distribution of 360 tree-frog species.
They found that the most diverse sites were established over 60 million years ago and more recently colonised areas had fewer unique species.
Researchers suggest this is evidence that damaged rainforest could take millions of years to recover.

TREE-FROG FACTS

• The Amazonian region of Colombia has the highest tree-frog species richness on the planet
• Globally, species can vary dramatically. The gladiator frog pictured has enlarged spiny "thumbs" for fighting
• Tree-frogs can range in size from roughly palm sized to roughly thumbnail sized

"The loss of species richness during our lifetimes may actually take tens of millions of to recover from” Dr John Wiens

Scientists from Stony Brook University, New York, US, aimed to shed light on an ongoing debate with their study published in the journal Ecology Letters.

"The question of why there are more species in the tropics has been a puzzle to biologists for more than 200 years, and a particularly challenging part of the problem is to explain why some sites in the rainforest can have more species than an entire continent," explained principal investigator Dr John Wiens.
In the past, species richness had been attributed to climate and some scientists believed that the biodiversity of tropical rainforest was due to their hot wet conditions.

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BBC Nature News

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