Intro to Plant Life
10 December 2012
The Evolution of Carnivorous Plants
In addition to being a subject in the occasional Hollywood horror movie, carnivorous plants are possibly the most fantastic members of the plant world. Over time, they have developed unique morphological characteristics in order to survive, paying homage to Darwin’s theory of natural selection. How carnivorous plants evolved is still somewhat unknown to botanists, this, in addition to their morphology, adds to the mystery surrounding them. In examining the evolution of carnivorous plants, it’s important to take into consideration the various hypotheses used to explain evolution, their unique morphology, functionality and efficiency, and habitat. These grisly flora are the mysterious strangers of the plant world, disregarding the traditional order in the food chain and carrying with them a fascinating history.
Carnivorous plants are plants that trap and consume animals, usually insects, in order to obtain some of their nutrients. There are five basic trapping mechanisms: pitfall traps, flypaper traps, snap traps, lobster pot traps, and bladder traps. These traps are all unique morphological adaptations that allow these plants to make up for soil lacking nutrients in the form of nitrogen and calcium. They often reside in areas like bogs, living in waterlogged soil that has a low, acidic pH. Other necessary elements, such as consistent sunshine exposure and moisture, are present in these habitats as well as a relatively low level of competition. In addition to allowing growth and reproduction, carnivory allows these plants to make up for what they can’t get in the soil they reside in, that being nitrogen and phosphorous (Thoren, Karlsson). Carnivorous plants have evolved to thrive against adverse environmental conditions. The question that remains to be fully explained is how exactly these plants have evolved.
The difficulty in explaining the evolution of carnivorous plants stems from the scarcity of fossils. The vast majority of the few fossils that have been found are usually seeds or pollen. Even if the plants were fossilized, the traps probably wouldn’t be preserved. It is known that carnivorous plants have evolved independently at least six times in five angiosperm orders (Ellison, Gotelli). Despite this, they maintain a high level of morphological convergence. This means that they have independent origins yet similar development. For example, it was long thought that pitcher plants in North America and Asia were cousins due to their methods of trapping insects. Both have leaves forming a pitcher shape rimmed with nectar glands that attract insects, only for them to fall into the pitchers and be broken down by digestive juices in the tubes. Although the American and Asian appear to be closely related, it’s recently been discovered that they’re very distant relatives, having descended from completely different blood lines (Angier). New data shows that in comparison to those with simple sticky traps, carnivorous plant genera with morphologically complex traps have higher relative rates of gene substitutions (Ellison, Gotelli). With this knowledge, botanists have developed two hypotheses regarding the evolution of these plants. The energetics hypothesis states that rapid morphological evolution from a few changes in regulatory genes is responsible for meeting high energy demands of traps. The predictable prey capture hypothesis states that carnivorous plants developed complex traps because they yield more predictable and frequent captures (Ellison, Gotelli). Botanists believe that traps developed from modifications of the same basic structure, the hairy leaf (Slack, Gate 18). The hairy leaf catches water, which causes insects to land on it, become trapped by the water’s surface tension, and suffocate. The water promotes bacteria growth on the leaf, so bacteria breaks down the organism and the leaf absorbs its nutrients....
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Brittnacher, John. "Carnivorous Plant Trapping Mechanisms." International Carnivorous Plant Society. International Carnivorous Plant Society, n.d. Web. 10 Dec. 2012.
Ellison, Aaron M., and Jim Karagatzides. "Carnivorous Plants ' Evolution Explained : Discovery News." Carnivorous Plants ' Evolution Explained : Discovery News. Discovery, n.d. Web. 10 Dec. 2012.
Ellison, Aaron M., and Nicholas J. Gotelli. "Energetics and the Evolution of Carnivorous Plants—Darwin’s ‘most Wonderful Plants in the World’." Journal of Experimental Botany 60.1 (2009): 19-42. Web.
Pavlovic, Andrej, Lucia Singerova, Victor Demko, and Jan Hudak. "Feeding Enhances Photosynthetic Efficiency in the Carnivorous Pitcher Plant Nepenthes Talangensis." Annals of Botany 104.2 (2009): 307-14. Print.
Slack, Adrian, and Jane Gate. Carnivorous Plants. London: Alpha, 1988. Print.
Thoren, Magnus L., and Staffan P. Karlsson. "Effects of Supplementary Feeding on Growth and Reproduction of Three Carnivorous Plant Species in a Subarctic Environment." Journal of Ecology 506.3 (1998): 501-10. Print.
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