Pitcher plants are famous for feeding on insects. But last year, Smith found a young yellow spotted salamander trapped in one of the pitchers of the purple pitcher plant Sarracenia purpurea purpurea while doing field work with undergraduates at Algonquin Provincial Park in Ontario. He mentioned it to Patrick Moldowan of the University of Toronto and other researchers.
They started looking out for trapped salamanders and soon made further discoveries. In August and September, Moldowan did a survey, checking the contents of more than plants on several occasions. In late August and mid-September — the time when thousands of newly metamorphosed salamanders emerge en masse from a nearby lake — he found a fifth of plants had caught at least one salamander.
There are currently around species of carnivorous plant known to science. Although most meat-eating plants consume insects, larger plants are capable of digesting reptiles and small mammals. Smaller carnivorous plants specialise in single-celled organisms such as bacteria and protozoa and aquatic examples also eat crustaceans, mosquito larvae and small fish. Carnivory is such an efficient adaptation that it has evolved independently several times and occurs in unrelated plant families.
But while it's great for a nutrient top-up, carnivory doesn't replace the need for photosynthesis and root systems. Being carnivorous simply helps the plants make the most of all available resources. The habitats of carnivorous plants are varied but usually involve wet, low-nutrient sites including bogs, swamps, waterbodies, watercourses, forests and sandy or rocky sites. Carnivorous plants can be found on every continent except Antarctica and there are many species native to the UK including sundews, butterworts and bladderworts.
Common butterwort Pinguicula vulgaris grows throughout the UK on bogs, fens, wet heaths and moors. This plant employs sticky mucilage on the leaf surface to secure its prey. Purple blossoms appear atop a long stalk to help keep pollinators from their carnivorous leaves. Found only near the summit of Mount Victoria on the island of Palawan in the Philippines, Attenborough's pitcher plant Nepenthes attenboroughii is critically endangered.
One of the largest of all carnivorous plants, it grows 1. Carnivorous plants use a variety of strategies to lure prey into their traps. Some produce strong-smelling nectar and have intense colouration that mimic flowers.
Others camouflage themselves seamlessly into their surroundings so that victims blunder into them. The intense colouration of trapping organs can give the impression that they are flowers when they are, in fact, ingeniously adapted leaves.
Carnivorous plants keep prey separate from useful pollinating insects by growing their real flowers at the end of long stalks, which blossom as far as possible from tempting and deadly digestive organs. The trumpet pitchers of a Sarracenia plant are carnivorous leaves but are as bold and colourful as flowers. Most carnivorous plants produce digestive enzymes that dissolve their prey into a nutritious bug stew. Some provide an enticing home for symbiotic bacteria that they depend upon to break down their catch for them.
Though there are hundreds of species, each with unique adaptations, carnivorous plants can be classified into five groups based on their trapping methods: pitfall, adhesive, snap, snare and suction. Pitfall-type traps are formed by a single leaf or rosettes forming tubular or pitcher-shaped traps. Prey is drawn to nectar at the pitcher rim. A slippery substance at the rim causes prey to lose its footing and slip into the base which is filled with digestive fluid.
Image via Wikimedia Commons. Endemic to Borneo, the giant montane pitcher plant Nepenthes rajah is the largest carnivorous plant in the world. Its urn-shaped traps grow up to 41 centimetres tall with a pitcher capable of holding 3. Scientists have observed vertebrates and small mammals in their digestive fluid. Native to swamps in mountainous regions of the USA, the cobra plant Darlingtonia californica has hooded, tubular leaves that resemble a striking cobra. It is the only species of its genus and does not produce its own digestive enzymes, relying on bacteria to break downs its prey.
Low's pitcher plant Nepenthes Iowii gathers nutrients in a way unlike most carnivorous plants. Its wide, toilet bowl-shaped pitchers are very sturdy and just the right size for a tree shrew to stand astride while feeding on the nectar at the lid. While feeding, shrews excrete directly into the pitcher, delivering useful, already-digested nutrients.
Low's pitcher plants grow on only a few mountainsides in Borneo. The bat pitcher plant Nepenthes hemsleyana has a fascinating alliance with woolly bats. Carnivorous plants occur across the flowering-plant family tree. The Australian pitcher plant Cephalotus follicularis —native to a sliver of coastline in Southwest Australia—is closer kin to the starfruit Averrhoa carambola than to other species of pitcher plants found in the Americas and southeast Asia. This suggests that carnivory has evolved repeatedly in plants, probably to cope with the nutrient-scarce soils in which they grow, Albert says.
These included genes involved in making starches and sugars that may help to produce the nectar that lures insects to their deaths, as well as genes encoding waxy substances that may make it hard to escape from the pitcher.
To determine how pitchers eat their prey, the researchers sampled the digestive cocktail from Cephalotus and several other unrelated carnivorous plants and identified a total of 35 proteins, using mass spectrometry. Many of the proteins are related to those that other flowering plants use to fend off pathogens.
For instance, plants typically produce enzymes that break down a polymer called chitin as a defence against fungi, which make their cell walls out of the chemical. But Albert suspects that Australian pitchers and other carnivorous plants have repurposed the enzyme to digest insect exoskeletons, which are also made of chitin.
In the new analysis, Albert and his colleagues also found that in distantly related carnivorous plants, including species of pitcher plants, the genes deployed to make the digestive-fluid proteins have a common evolutionary origin. The researchers don't have proof yet, but they think that the mutations might help to stabilize the enzymes when they are present together in digestive fluid.
While researchers already appreciated the importance of convergent evolution for carnivorous plants, says Aaron Ellison, an ecologist at Harvard Forest in Petersham, Massachusetts, the new study is important because it demonstrates how this convergence can occur down to the molecular level, he says.
0コメント