By Quinn Rider, BVAC Retail Manager, B.S. Ecology, Behavior, and Evolution
The birds are chirping, the mosquitos are buzzing, and the wildflowers are finally here! Sweet peas line the highway before and around Arnold, but you may notice they stop short of Bear Valley, unable to survive in the harsher, higher elevations. What then is different about our environment and what makes our wildflowers able to survive the unique challenges it poses?
Higher elevations pose a number of problems for plants. Sunlight is more intense here, strong enough to overload photosynthetic systems with photon input, which can lead to a buildup of toxic compounds that may damage the plant and eventually shut down photosynthesis (1). This problem is compounded by our colder temperatures, which slow photosynthesis. Plants solve these problems in a variety of ways. Alpine plants have enzymes that function better in colder environments, a reverse of most enzymes which are more effective in warmer temperatures. They also have leaves that are, on average, 1/10th of the size of their lowland counterparts. This smaller size provides less surface area to uptake light or to be damaged by frost or wind (2). We reside at the top end of the upper montane zone, but this still holds true, if to a somewhat lesser extent.
Some plants also have heavy trichomes (or small hairs, essentially fuzz) on their leaves to shield the leaf from light and to prevent desiccation in our drier climate. The fuzz serves to physically block light, but it also creates a more humid environment along the leave’s surface by trapping moisture in the strands, thereby preventing excess water loss from leaf openings (2). Mule’s Ear is one such species with fuzzy leaves. Waxy leaves are also common among alpine plants, as the waxy coating prevents excess water loss via evaporation (3).
A few other species even take a high-seas approach to sub-alpine life, forgoing photosynthesis in part or entirely to pirate materials from neighbors, typically via the mycorrhizal fungi that the host plant has a mutualistic relationship with (2).
There is yet another problem plants face in the sub-alpine, a lack of pollinators. Our most prolific bee is by far the meat bee (in my opinion), an aggressive species that is in fact a type of wasp, not bee. They are also known as yellowjackets. They do visit flowers for nectar, although you’re more likely to find them trying to take a bite of your lunch – or of you. They are much less effective as pollinators than true bees because they have less hairs to capture pollen when they visit flowers (4).
Plants deal with this either by targeting specific pollinators or by switching to asexual reproduction. Plants that reproduce asexually essentially clone themselves, removing the need for pollination. This method of reproduction also speeds up speciation, the process of one species developing to another, as it ensures that mutations are passed along to all offspring, assuming they are fit enough to reproduce. This may be why the Sierra has 405 endemic species, species that grow nowhere else in the world (5). Some options for pollinators here are hummingbirds, flies, beetles, and butterflies. Red tubular flowers are mainly pollinated by hummingbirds. Colorful, mostly scentless flowers with large leaves are preferred by butterflies. Flies are very important pollinators at high elevations. They are generalists that will pollinate almost any species, but their sensors are keyed to white and yellow. Beetles prefer flowers that are fully open and that produce a lot of pollen, like Miner’s Lettuce (2).
High elevation wildflowers face a number of challenges that they are uniquely suited to handle. They display adaptations ranging from the chemical to the structural, including photosynthetic output and leaf and flower structure. Wildflowers also form many adaptive inter-specific relationships with both flora and fauna. Their often-delicate beauty belies thousands of years of evolution in this demanding and unique environment that allows them to survive where many plants can not.
Works Cited
1. Streb P., Cornic G., Photosynthesis and Antioxidative Protection in Alpine Herbs, In Lütz C. (Ed) Plants in Alpine Regions: Cell Physiology of Adaptation and Survival Strategies, Springer Wien New York, pp 75-97, 2012
2. Wenk, E. (2015). Wildflowers of the High Sierra and John Muir Trail (pp. 1-263). Wilderness Press.
3. Lütz, Cornelius and Gülz, Paul-Gerhardt. "Comparative Analysis of Epicuticular Waxes from Some High Alpine Plant Species" Zeitschrift für Naturforschung C, vol. 40, no. 9-10, 1985, pp. 599-605. https://doi.org/10.1515/znc-1985-9-1002
Figure 1: Mule's Ear is sometimes called Wooly Mules Ear due to the trichomes on its leaves.
Figure 2: Indian Paintbrush has a low amount of chlorophyll because of the orange parts of its leaves. It parasitizes lupine (if there is lupine nearby) for nutrients and water.
Figure 3: Snow Plant is a non-photosynthetic plant that parasitizes the mycorrhizal fungi of conifer trees, especially firs.
Figure 4: Scarlet Gilia is hummingbird pollinated.
Figure 5: Mountain Pride is hummingbird pollinated.
Figure 6: Corn Lily is mostly pollinated by flies.
4. USDA (2018, June 26). Is It or Isn't It a Bee? USDA Agricultural Research Service. Retrieved July 1, 2024, from https://www.ars.usda.gov/pacific-west-area/logan-ut/pollinating-insect-biology-management-systematics-research/docs/is-it-or-isnt-it-a-bee/#:~:text=Finally%2C%20no%20flower%20fly%20can,or%20wasps%20that%20they%20mimic.&text=Yellow%20Jacket%3AYellow%20jacket%20wasps,only%20distantly%20related%20to%20bees.
5. Shevock, J.1996a. Status of rare and endemic plants. In: D.C. Erman, ed. Sierra Nevada Ecosystem Project. Final Report to Congress, Vol. 2 Assessments and Scientific Basis for Management Options, Chapter 24: 691-707. Davis: Univ. of Calif., Centers for Water and Wildland Resources.
