Venus flytrap 'teeth' form a 'horrid prison' for medium-sized prey

March 26, 2019

In "Testing Darwin's Hypothesis about the Wonderful Venus Flytrap: Marginal Spikes Form a 'Horrid Prison' for Moderate-Sized Insect Prey," Alexander L. Davis investigates the importance of marginal spikes, the "teeth" lining the outer edge of the plant's snap traps, in successfully capturing prey. He found that Venus flytraps experience a 90 percent decrease in moderate-sized cricket prey capture success when marginal spikes are removed. This effect disappears, however, for larger prey, suggesting that the spikes may provide a foothold for large prey to escape.

The study combined field observations, laboratory experiments and semi-natural experiments, and was the first to test the adaptive benefit of marginal spikes, one of Darwin's original hypotheses about the Venus flytrap. "We provide the first direct test of how prey capture performance is affected by the presence of marginal spikes, trichomes that provide a novel function in Venus flytraps by forming what Darwin described as a 'horrid prison,'" Davis writes.

Botanical carnivory is a novel feeding strategy that has arisen at least nine different times in evolutionary history of plants. Pitfall traps evolved independently at least six times and sticky traps five. The snap traps characteristic of the Venus flytrap, however, have most likely evolved only once in the ancestral lineage. Darwin was the first to document evidence for carnivory in flytraps, and proposed that the cage-like structure enhances prey capture success.

For the laboratory portion, Davis and his coauthors assembled "prey capture arenas," wherein 34 Venus flytraps were set up in planters with "on ramps" for crickets. The number of individual traps open and closed, along with whether or not the closed traps contained prey, were recorded initially, after three days, and again after a week. Davis then removed the marginal spikes from half of the plants. He allowed a week of recovery so the traps could reopen, and conducted a second trial. Cricket mass, the length of the plants' traps, and the prey capture success rate of the traps on each plant were recorded and analyzed using logistic regression models.

Davis and coauthors then moved to a semi-natural experiment in the North Carolina Botanical Garden. Davis placed 22 plants in the North Carolina Botanical Garden, with half of the traps on each plant with intact marginal spikes and the other half with the spikes removed. Plants were kept on the group in a forested, open area of the gardens, and with ramps that allowed terrestrial arthropod access for a period of 4 weeks. For all prey catches, trap length, as well as prey mass and -- digestion permitting -- prey type, were recorded. Results were calculated using a generalized linear mixed effects model, then combined with results from the laboratory experiments using Fisher's method.

Davis found that marginal spikes are adaptive for prey capture of small and medium-sized insects, but not larger insects. In the controlled laboratory prey capture trials, 16.5% of trap closures resulted in successful prey capture, whereas only 5.8% of trap closures were successful when marginal spikes were removed. Similarly, plants in the botanical garden had a prey capture success rate of 13.3% with marginal spikes intact and 9.2% with spikes removed.

The benefits of the marginal spikes were most dramatic for medium-size traps, which experienced the most rapid decline in capture rate for medium-size prey and gained the most from having the marginal spikes intact. Surprisingly, this effect disappeared for larger prey, which Davis speculated could be due to larger insects using the spikes as leverage for prying themselves free.

These findings offer clues for explaining the evolution of one of the most unique plant traits. "Characterizing the role of adaptive traits aids our understanding of selective forces underlying the diversity of trap types and the rarity of snap traps, offering insights into the origins of one of the most wonderful evolutionary innovations among all plants," Davis writes.
-end-


University of Chicago Press Journals

Related Plants Articles from Brightsurf:

When plants attack: parasitic plants use ethylene as a host invasion signal
Researchers from Nara Institute of Science and Technology have found that parasitic plants use the plant hormone ethylene as a signal to invade host plants.

210 scientists highlight state of plants and fungi in Plants, People, Planet special issue
The Special Issue, 'Protecting and sustainably using the world's plants and fungi', brings together the research - from 210 scientists across 42 countries - behind the 2020 State of the World's Plants and Fungi report, also released today by the Royal Botanic Gardens, Kew.

New light for plants
Scientists from ITMO in collaboration with their colleagues from Tomsk Polytechnic University came up with an idea to create light sources from ceramics with the addition of chrome: the light from such lamps offers not just red but also infrared (IR) light, which is expected to have a positive effect on plants' growth.

How do plants forget?
The study now published in Nature Cell Biology reveals more information on the capacity of plants, identified as 'epigenetic memory,' which allows recording important information to, for example, remember prolonged cold in the winter to ensure they flower at the right time during the spring.

The revolt of the plants: The arctic melts when plants stop breathing
A joint research team from POSTECH and the University of Zurich identifies a physiologic mechanism in vegetation as cause for Artic warming.

How plants forget
New work published in Nature Cell Biology from an international team led by Dr.

Ordering in? Plants are way ahead of you
Dissolved carbon in soil can quench plants' ability to communicate with soil microbes, allowing plants to fine-tune their relationships with symbionts.

When good plants go bad
Conventional wisdom suggests that only introduced species can be considered invasive and that indigenous plant life cannot be classified as such because they belong within their native range.

How plants handle stress
Plants get stressed too. Drought or too much salt disrupt their physiology.

Can plants tell us something about longevity?
The oldest living organism on Earth is a plant, Methuselah a bristlecone pine (Pinus longaeva) (pictured below) that is over 5,000 years old.

Read More: Plants News and Plants Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.