The Carnivorous Dewy Pine

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The dewy pine is definitely not a pine, however, it is quite dewy. Known scientifically as Drosophyllum lusitanicum, this carnivore is odd in more ways than one. It is also growing more and more rare each year.

One of the strangest aspects of dewy pine ecology is its habitat preferences. Whereas most carnivorous plants enjoy growing in saturated soils or even floating in water, the dewy pine's preferred habitats dry up completely for a considerably portion of the year. Its entire distribution consists of scattered populations throughout the western Iberian Peninsula and northwest Morocco.

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Its ability to thrive in such xeric conditions is a bit of a conundrum. Plants stay green throughout the year and produce copious amounts of sticky mucilage as a means of catching prey. During the summer months, both air and soil temperatures can skyrocket to well over 100°F (37 °C). Though they possess a rather robust rooting system, dewy pines don't appear to produce much in the way of fine roots. Because of this, any ground water presence deeper in the soil is out of their reach. How then do these plants manage to function throughout the driest parts of the year?

During the hottest months, the only regular supply of water comes in the form of dew. Throughout the night and into early morning, temperatures cool enough for water to condense out of air. Dew covers anything with enough surface area to promote condensation. Thanks to all of those sticky glands on its leaves, the dewy pine possesses plenty of surface area for dew to collect. It is believed that, coupled with the rather porous cuticle of the surface of its leaves, the dewy pine is able to obtain water and reduce evapotranspiration enough to keep itself going throughout the hottest months. 

Dewy pine leaves unfurl like fern fiddle heads as they grow.

Dewy pine leaves unfurl like fern fiddle heads as they grow.

As you have probably guessed at this point, those dewy leaves do more than photosynthesize and collect water. They also capture prey. Carnivory in this species evolved in response to the extremely poor conditions of their native soils. Nutrients and minerals are extremely low, thus selecting for species that can acquire these necessities via other means. Each dewy pine leaf is covered in two types of glands: stalked glands that produce sticky mucilage, and sessile glands that secrete digestive enzymes and absorb nutrients.

Their ability to capture insects far larger than one would expect is quite remarkable. The more an insect struggles, the more it becomes ensnared. The strength of the dewy pines mucilage likely stems from the fact that the leaves do not move like those of sundews (Drosera spp.). Once an insect is stuck, there is not much hope for its survival. Living in an environment as extreme as this, the dewy pine takes no chances.

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The taxonomic affinity of the dewy pine has been a source of confusion as well. Because of its obvious similarity to the sundews, the dewy pine has long been considered a member of the family Droseraceae. However, although recent genetic work does suggest a distant relationship with Droseraceae and Nepenthaceae, experts now believe that the dewy pine is unique enough to warrant its own family. Thus, it is now the sole species of the family Drosophyllaceae.

Sadly, the dewy pine is losing ground fast. From industrialization and farming to fire suppression, dewy pines are running out of habitat. It is odd to think of a plant capable of living in such extreme conditions as being overly sensitive but that is the conundrum faced by more plants than just the dewy pine. Without regular levels of intermediate disturbance that clear the landscape of vegetation, plants like the dewy pine quickly get outcompeted by more aggressive plant species. Its the fact that dewy pine can live in such hostile environments that, historically, has kept its populations alive and well.

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What's more, it appears that dewy pines have trouble getting their seeds into new habitats. Low seed dispersal ability means populations can be cut off from suitable habitats that are only modest distances away. Without a helping hand, small, localized populations can disappear alarmingly fast. The good news is, conservationists are working hard on identifying what must be done to ensure the dewy pine is around for future generations to enjoy.

Changes in land use practices, prescribed fires, wild land conservation, and incentives for cattle farmers to adopt more traditional rather than industrial grazing practices may turn the table on dewy pine extinction. Additionally, dewy pines have become a sort of horticultural oddity over the last decade or so. As dedicated growers perfect germination and growing techniques, ex situ conservation can help maintain stocks of genetic material around the globe.

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

Further Reading: [1] [2] [3] [4]

 

 

The Carnivorous Waterwheel

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Bladderworts (Utricularia spp.) aren't the only carnivorous plants stalking prey below the water surface. Meet the waterwheel (Aldrovanda vesiculosa). At first glance it looks rather unassuming but closer inspection will reveal that this carnivore is well equipped for capturing unsuspecting prey. 

The waterwheel never bothers with roots. Instead, it lives out its life as a free floating sprig, its stem it covered in whorls of filamentous leaves, each tipped with a tiny trap. The trapping mechanism is a bit different from its bladderwort neighbors. Instead of bladders, the waterwheel produces snap traps that closely resemble those of the Venus fly trap (Dionaea muscipula). These traps function in a similar way. When zooplankton or even a small fish trigger the bristles along the rim, the trap snaps shut and begins the digestion process.

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This similarity to the Venus fly trap is more than superficial. DNA analysis reveals that they are in fact close cousins. Together with the sundews, these plants make up the family Droseraceae. The evolutionary history of this clade is a bit confusing thanks to a limited fossil record. Today, the waterwheel is the only extant member of the genus Aldrovanda but fossilized seeds and pollen reveal that this group was once a bit more diverse during the Eocene. Whenever these genera diverged, it happened a long time ago and little evidence of it remains.

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At one point in time, the waterwheel could be found growing in wetland habitats throughout Africa, Europe, Asia, and even Australia. Today it is considered at risk of extinction. Its numbers have been severely reduced thanks to wetland degradation and destruction. Of the 379 known historical populations, only about 50 remain in tact today and many of these are in rough shape. Agricultural and industrial runoff are exacting a significant toll on its long term survival. To make matters worse, sexual reproduction in the waterwheel is a rare event. Most often this plant reproduces vegetatively, reducing genetic diversity. What's more, natural dispersal into new habitats is extremely limited. 

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Oddly enough, populations of this plant have popped up in a few locations in eastern North America. These introductions were not a mistake either. Carnivorous plant enthusiasts concerned with the plight of this species in its native habitat began introducing it into water ways in New Jersey, New York, and Virginia where it is now established. Oddly enough, these introductions have performed far better than any of the reintroduction attempts made in its native range in Europe. Of course, this is always cause for concern. Endangered or not, the introduction of a species into new habitat is always risky. Still, there is hope yet for this species. Its popularity among plant growers has led to an increase in numbers in cultivation. At least folks have learned how to cultivate it until more comprehensive and effective conservation measures can be put into place. 

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

Further Reading: [1] [2] [3] [4] [5]