Predators, Parasites, Plants?
The day is clear, the sun shines bright, and you are a fly in a wetland. Life as a fly in a wetland is simple but dangerous - you spend your days in search of food and water while also avoiding the hungry mouths of predators. You are buzzing about on this bright, clear day when the glint of sunlight off dew catches your attention. You turn to find the dew and spot a plant coated in it, the delicate scent of nectar wafting towards you on the breeze. You zip down to the plant, watching for predators as you fly, and land without trouble in the middle of the plant. You attempt to drink some dew from the leaves but find yourself stuck, unable to move. As you struggle harder and harder to free yourself the leaves of the plant curl up around you, trapping you inside. Within 15 minutes you’ll be dead.
Drosera, commonly known as sundews, are one of the largest genera of carnivorous plants with over 190 known species. You can find at least one sundew species native to every continent except Antarctica! These carnivorous plants utilize the flypaper method of trapping; they secrete a sticky mucus-like substance that traps unsuspecting insects, who are then digested by enzymes in the mucus. For some carnivorous species, just trapping the insect on the leaf is enough but Drosera species are special. They have unique stalk glands that wrap around their prey, making escape even more difficult. Around these parts, the species you’d be most likely to find is round-leaved sundew (Drosera rotundifolia), but it’s not the only carnivorous plant native to the Sierra Nevadas.
Unlike the genus Drosera, which contains numerous species, there is only one species in the genus Darlingtonia. Found in Northern California and Oregon, the California pitcherplant (Darlingtonia californica) is elusive. As its name suggests, the California pitcherplant uses a pitfall trap to catch prey but it’s got a few adaptations that make it truly unique compared to other pitcher plants. Where most pitcher plants rely on rainfall to fill their pitchers, the California pitcherplant uses water absorbed through its roots. This mechanism provides the pitcherplant more control over how full its pitcher is, helping to prevent the problem of overflowing. Another adaptation (and the most notable) of the pitcherplant are its leaves and coloration, which give rise to the other common name of this plant - the cobra lily. The leaves form a hood over the pitcher and fork towards the end, giving the appearance of a striking cobra. The speckled coloration of the plant looks like snake skin but it actually helps trap prey inside the pitcher; sunlight can filter into parts of the pitcher and create false exits, confusing insects that climb inside.
The differences between round-leaved sundew and the California pitcherplant are vast but what links them (and all other carnivorous plants) together is their preference for nutrient poor soils. Carnivory in plants evolved as a method of survival - if the soil lacks nutrients, find those nutrients somewhere else! While the sundew has a larger growing range than the California pitcherplant, it’s not uncommon to find them growing in the same areas of the Sierra Nevada. The Butterfly Valley Botanical Area in Plumas National Forest supports a healthy population of both species, along with over 500 other species of plants. Butterfly Valley is a type of wetland known as a fen - groundwater provides plenty of water and minerals but also makes the soil acidic, which makes accessing soil nutrients difficult for plants. Some fens might have a pH as low as 4.5! Carnivory is one adaptation that helps plants survive in difficult situations but it’s not the only adaptation in the world.
Over 500 plant species call Butterfly Valley home and among them is Cephalanthera austiniae, the phantom orchid. The phantom orchid is aptly named - it’s white and pale yellow, no green in sight! If you can remember the plant unit in biology class, plants are green because of the pigment chlorophyll. Chlorophyll is a major component in photosynthesis, the process where plants turn sunlight into energy. If a plant lacks green (meaning it has no chlorophyll), how can it photosynthesize and make energy to live? The answer: parasitism! Plant parasites are similar to animal parasites; the parasite species targets one or more host species to steal nutrients from, often harming the host in the process. Phantom orchids parasitize a type of fungi called mycorrhizae, which form vast networks in the soil. Mycorrhizae specialize in transporting water and nutrients through soil making them an optimal host for a parasite, however (fortunately for the fungi) most plant parasites tend to parasitize other plants.
Plant parasites are often found attached to the roots or stems of other plants. If you’ve ever enjoyed a walk through a forest with madrone trees and manzanita shrubs, you probably spotted some California groundcone (Kopsiopsis strobilacea) and ignored it. This parasitic plant is often mistaken for the cone of a Douglas fir but they tend to grow in groups and stand straight up, which looks odd. Another parasite that’s more easily recognized is mistletoe. There are a variety of dwarf mistletoe species native to North America and many of them can be spotted parasitizing evergreens like pine, juniper, and fir trees. Mistletoe is considered a pest species; it spreads plant diseases and it usually kills its host. Despite the negative impacts mistletoe has, many animals rely on it for food and shelter; a whopping 43% of spotted owl nests are found in mistletoe!
The day is clear, the sun shines bright, and you are a sundew in a wetland. Your leaves shine bright with sticky mucus as you wait for your next victim, some poor fly to land for a quick drink. Your trap, which catches and kills many insects in the wetland, evolved over millions of years to become what it is today - highly efficient and very necessary to your life. The death of these insects provides you with the nutrients to survive in the poor soil of this area and you know that this pattern will continue for years to come.