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NERC DTP BC219: Biomechanics and ecology of sticky capture fluids in carnivorous plants (Nepenthes)

Supervisor: Dr Walter Federle

Project summary:

Insect-plant interactions play an essential role for most ecosystems, and the mechanisms underlying these relationships are both physical and chemical. Carnivorous plants are model systems for the role of physical factors such as movable structures and slippery or sticky surfaces. These plants have developed complex adaptations to trap arthropods for their nutrition, and some insects have evolved amazing counter-adaptations.

This project will focus on Nepenthes pitcher plants, which have highly modified leaves that act as natural pitfall traps. When insects lose grip on their slippery rim, they fall into the pitcher fluid. This fluid – a solution containing special polysaccharides (PS) - can immobilize prey via its wetting and unusual material properties but many aspects of this interaction are still unclear. The trapping function likely depends on rain, evaporation and PS degradation, affecting both fluid level and PS concentration, but these factors have yet to be studied. Furthermore, while pitcher fluids are specialised to catch and digest arthropods, some inhabit this challenging environment, and how they achieve this remains unclear.

What the student will be doing:

To study the role of sticky capture fluids in Nepenthes pitcher plants, laboratory work in Cambridge and field work at natural sites in Brunei (Borneo) will be conducted on selected species. The approach can be tailored to the student's specific interests:

1) What are the wetting and material properties of pitcher fluid, and how do these influence insect capture?

2) How does the fluid's stickiness depend on the amount of PS, and how do pitchers in the field vary in PS concentration due to environmental factors (dilution, evaporation, new secretion), over time, and between Nepenthes species?

3) How do pitchers maintain constant fluid levels despite rain and evaporation? How are pitchers mechanically designed to prevent flooding? When and to what extent do pitchers absorb 

or secrete fluid? How did sticky fluids evolve within the genus Nepenthes?

4) How are specialised arthropods able to move and live within sticky pitcher trapping fluids?

References:

1. Gaume, L. & Forterre, Y. (2007) A viscoelastic deadly fluid in carnivorous pitcher plants. PLoS ONE, 2, e1185.

2. Bauer, U., Clemente, C.J., Renner, T. & Federle, W. (2012) Form follows function: morphological diversification and alternative trapping strategies in carnivorous Nepenthes pitcher plants. Journal of Evolutionary Biology, 25, 90-102.

3. Collett, C., Ardron, A., Bauer, U., Chapman, G., Chaudan, E., Hallmark, B., Pratt, L., Torres-Perez, M. & Wilson, D.I. (2015) A portable extensional rheometer for measuring the viscoelasticity of pitcher plant and other sticky liquids in the field. Plant Methods, 11, 16.

Specific qualifications desirable for this particular project:

The project will suit a biologist with an interest in field work and physical or mathematical approaches to biology.

Additional information: 

Funding is available for this project via the NERC Cambridge Climate, Life and Earth (C-CLEAR) Doctoral Training Partnership – please refer to their website for more information: https://nercdtp.esc.cam.ac.uk/projects/BC219