NORTHWEST COAST NATURE Carnivorous Plants of Eastern Vancouver Island

Butterwort © Gert-Jan van Vliet

NORTHWEST COAST NATURE Carnivorous Plants of the Eastern Vancouver Island

LUNA LOISEAU-TREMBLAY

WHILE MANY OF US emerged from the dark, wet months of winter into what was supposed to finally be a sunny spring, this year has turned out to be one of the wettest in a long time. Without a greenhouse, planting basil, tomatoes and squash in these cool temperatures is proving to be a faraway dream. However, the natural environment around us is benefiting heavily from the big rains of spring, such as the various types of wetland ecosystems throughout Eastern Vancouver Island and the surrounding Islands.

My personal favorite wetland type has always been a peatland, full of plants that are adapted to nutrient poor conditions. As described in the book Wetland Plants by Julie K. Cronk and M. Siobhan Fennessy (2001), peatlands are classified into two main types, depending on the source of water: Fens, which are fed by groundwater, have a high calcium concentration and the pH is usually high; and Bogs, which rely mostly on rainwater, in which nutrient and pH values are low. The chemistry of a wetland is intricate and detailed. Basically, a low pH value means the bog is acidic and it is dominated by Sphagnum spp. while in a fen, the presence of calcium carbonate buffers the acidity and it is dominated by sedges. In each of these bog and fen categories, there are different parameters, such as plant species present, water chemistry, elevation, availability of nutrients etc. that further separates the categories. While the dynamics and interaction of plant species present in and around these low nutrient bogs are intricate, fascinating, and unique, one group, the carnivorous plants, never ceases to amaze.

On Eastern Vancouver Island, we have at least five species of carnivorous plants which can be found in various wetland ecosystems, one of which was only discovered a short time ago as getting some of its nutrients from insects. There are six plant families which

are carnivorous, and two of them, Droseraceae and Lentibulariaceae, hold the genera with the greatest number of species, Drosera (sundew) and Utricularia (bladderwort).

Carnivorous plants can be found in every corner of the world, from the huge and fantastical rodent trapping pitcher plant, Nepenthes attenboroughii of the Philippines, to the northern pitcher plants of the Sphagnum bogs of Eastern Canada and the US in the genus Sarracenia, the Venus Flytraps in the savannah’s and peatlands of southeast North Carolina and the little Butterworts of the subarctic regions of Canada and Alaska. While this diverse group of plants does photosynthesis, much of their nutrients comes from digesting prey nutrients.

Carnivorous plants display six types of traps to catch their prey, of which the types are used to differentiate between genera. The types of traps are pitfall traps (pitcher plants), lobster pot, passive adhesive, active adhesive, bladder and snap-trap (ie. venus flytraps).

On Eastern Vancouver Island, the carnivorous plant species that we have use three types of these traps. One of the most common carnivorous plant types that we have present in bogs, lakesides, or maybe floating on a dead log in a lake in this area is Drosera rotundifolia,

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Wetland Bog © Luna Loiseau-Tremblay

Great Sundew © Luna Loiseau-Tremblay

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Great Sundew © Luna Loiseau-Tremblay

Round-leaved Sundew and Great Sundew, Drosera angelica, which use active adhesive traps to catch their insect prey. Sundews have gland covered tentacles covered in a sticky substance, with one type of gland responsible for trapping the insect as it gets glued to it and another type of gland used to digest and absorb nutrients. Once stuck, the movement of the insect triggers the stalked glands to move around it, curling slowly around the prey. Sessile glands secrete another substance which works to break down, digest and absorb the nutrients from the insect. Sundews move the glands in response to an insect prey struggling in the sticky substance, and by moving the glands, positions the prey into a better position, touching more glands for better digestion of nutrients.

Pinguicula vulgaris, the common butterwort, is a species of carnivorous plant we have in acidic bogs in our area, and it also uses active adhesive traps. The leaves of Pinguicula have glands which behave in the same manner as the tentacles of a Sundew. When the prey is stuck on the leaves, the struggling triggers the margins of the leaf to roll inward to aid in digestion.

Another carnivorous species that we have in this area is the Greater Bladderwort, Utricularia vulgaris. Bladderworts, which are rootless, use bladder traps which are positioned along the stems submerged in water. The bulbous traps have external hairs that are sensitive to movement in the water, and respond by opening and sucking in zooplankton. After the trap has shut, the plant pumps out water and the nutrients get dispersed within the wider system of the plants. (Cronk and Fennessy, 2001) Within the last two years a common wetland plant, Western False Asphodel, Triantha occidentalis, was just discovered to be able to obtain some of its nutrients from insect prey, by way of passive adhesive traps. False Asphodel has a very sticky stem, and in the field it was always obvious that fruit flies, mosquitos and other small insects become glued onto the stem and die there. As this was thought previously to be an adaptation against herbivory, it was not clear that the plant was obtaining nutrients from the trapped insects.

As with many other vascular plants, carnivorous plants have flowers that need to be pollinated and rely on many different species of pollinators to do the job. The majority of carnivorous plants have flowers that grow at the top of a long stem, far away from the traps used to catch prey. This is thought to be an adaptation in order to make sure that potential pollinators are not mistaken as prey. In False Asphodel, the trap that is the sticky stem is much closer to the flower than many other kinds of carnivorous plants, however, it is now thought that the sticky substance that is the digestive enzyme traps only small insects not needed for pollination.

Carnivorous plants are fascinating and are appreciated by many different kinds of people. In consideration of this, it is of utmost importance that plants in the wild stay in the wild. All species of carnivorous plants are prone to a high degree of poaching by major collectors, and many people are unable to replicate the requirements needed to survive. If you are purchasing a carnivorous plant from a store, consider if it is ethically sourced and if so, purchasing one from a store is much better than removing it from the wild.

False Asphodel © Luna Loiseau-Tremblay

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