The Parrot Pitcher Plant

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Southeastern North America is the true home of the carnivorous plants belonging to the genus Sarracenia. Seven of the approximately eight species in this genus reside in North America's coastal plain forests and nowhere else. These evolutionary marvels are famous the world over for their carnivorous pitfall traps but not all members conform to this style of prey capture. The most aberrant of these carnivores is the so-called parrot pitcher plant (Sarracenia psittacina).

The parrot pitcher plant would be easy to pick out of a lineup, even with an untrained eye. Instead of tall, lanky, upright pitchers, it produces a rosette of smaller, entirely prostrate pitchers. Additionally, the leaf-like hood that covers the pitchers of its relatives appears to have grown into a dome-like structure speckled with translucent patches. Finally, the belly of each pitcher sports a leafy fin called an "ala" that runs the whole length of the tube. Indeed, with the exception of perhaps the purple pitcher plant (S. purpurea), the parrot is truly an oddball.

Its unique appearance is likely an adaptation to seasonal flooding and has changed the way in which this particular species captures prey. The pitchers of the parrot pitcher plant do not function as pitfall traps like those of its relatives. Instead, this species utilizes the "lobster trap" method of prey capture. Lured to its pitchers by their bright colors, insects gradually explore the traps. The fin-like ala directs these unsuspecting victims to the mouth of the pitcher. The translucent patches on the domed hood lure the insect into a false sense of security.

Once inside, the insects become disoriented and cannot easily find the proper escape rout. As they crawl farther into the pitcher, backward pointing hairs ensure that escape is impossible. Death is followed by digestion as the pitcher obtains yet another nutrient-rich meal. However, insects aren't the only game in town for the parrot pitcher plant.

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Because of its prostrate habit, the parrot pitcher plant regularly finds itself underwater whenever its already wet habitat floods. This would be bad news for most other pitchers as their upright position would allow whatever was inside to float out and away. Such is not the case for the parrot pitcher. Underwater, the pitchers become even more like a lobster trap. Everything from aquatic insects to tadpoles and fish can and do fall victim to this plant. As such, not even seasonal flooding can put a damper on this unique pitcher plants meal ticket. It is a wonderful example species adaptation.

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Like all members of the southeastern coastal plain community, the parrot pitcher plant is losing its habitat at an alarming rate. Habitat loss is an ever present threat, both in the form of outright destruction from logging and development as well as from sequestration of fire. Coastal plain communities are fire-adapted ecosystems and without it, the myriad species that call this region home are overgrown and choked out. Research has shown that the parrot pitcher plant, as well as other pitcher plants, greatly benefit from regular fires. Fire clears away competing vegetation and the plants respond with vigor.

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Luckily, parrot pitcher plant numbers are stable at this point in time. Its low growth habit saves it from threats like mowing, which means that it can do well in places like roadside ditches that are less favorable for its taller relatives. I have said it before and I will say it again, if you value species like the parrot pitcher plant, please do everything you can to support land conservation efforts. Please check out what organizations such as The Longleaf Alliance, Partnership For Southern Forestland Conservation, The Nature Conservancy, and The National Wildlife Federation are doing to protect this amazing region. Simply click the name of the organization to find out more.

Photo Credits: [1] [2] [3] [4] [5]

Further Reading: [1] [2] [3]

 

Bacteria Help the Cobra Lily Subdue Prey

The aptly named cobra lily (Darlingtonia californica) is one of North America's most stunning pitcher plants. Native to a small region between northern California and southwestern Oregon, this bizarrely beautiful carnivore lives out its life in nutrient poor, cold water bogs and seeps. Although it resides in the same family as our other North American pitcher plants, Sarraceniaceae, the cobra lily has a unique taxonomic position as the only member of its genus.

It doesn't take much familiarity with this plant to guess that it is carnivorous. Its highly modified leaves function has superb insect traps. Lured in by the brightly colored, tongue-like protrusions near the front tip of the hood, insects find a sweet surprise. These tongue-like structures secrete nectar. As insects gradually make their way up the tongue, they inevitably find themselves within the downward pointing mouth of the pitcher. This is where those translucent spots on the top of the hood come in.

These translucent spots trick the insects into flying upwards into the light. Instead of a clean getaway, insects crash into the inside of the hood and fall down within the trap. The slippery walls of the pitchers interior make escape nearly impossible but that isn't the only thing keeping insects inside. Research has shown that the cobra lily gets a helping hand from bacteria living within the pitcher fluid.

Unlike other pitcher plants, the cobra lily does not fill its traps with rain water. The downward pointing mouth prevents that from happening. Instead, the pitchers secrete their own fluid by pumping water up from the roots. Although there is evidence that the cobra lily does produce at least some of its own digestive enzymes, it is largely believed that this species relies heavily on a robust microbial community living within its pitchers to do most of the digesting for it. This mutualistic community of microbes save the plant a lot of energy while also providing it with essential nutrients like nitrogen in return for a safe place to live.

That isn't all the bacteria are doing for this pitcher plant either. As it turns out, the pitchers' microbial community may also be helping the plant capture and subdue its prey. A recent study based out of UC Berkeley demonstrated that the presence of these microbes helps lower the surface tension of the water, effectively drowning any insect almost immediately.

The microbes release certain compounds called biosurfactants. Through an interesting chemical/physical process that I won't go into here, this keeps insects from using the surface tension of the water's surface to keep them afloat, not unlike a water strider on a pond. Instead, as soon as insects hit the bacteria infested waters, they break the surface tension and sink down to the bottom of the pitcher where they quickly drown. There is little chance of escape for a hapless insect unlucky enough to fall into a cobra lily trap.

Although plant-microbe interactions are nothing new to science, this example is the first of its kind. Although this prey capture role is very likely a secondary benefit of the microbial community within the pitchers, it very likely makes a big difference for these carnivores living in such nutrient poor conditions.

Photo Credit: Wikimedia Commons

Further Reading: [1]