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Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities

Lead Supervisor: Walter Federle, Zoology

Brief summary: 
This project will study how carnivorous pitcher plants use sticky capture fluids to trap insects, how this affects their ecology and evolution, and how specialised insects can overcome the plant's traps
Importance of the area of research concerned: 
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.
Project summary : 
The aim of this project is to study the role of sticky capture fluids in Nepenthes pitcher plants, focusing on their biomechanics, physiology, ecological implications, and insect counter-adaptations. 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?
What will the student do?: 
Laboratory work in Cambridge and field work at natural sites in Brunei (Borneo) will be conducted on selected Nepenthes species. The approach can be tailored to the student's specific interests. Laboratory work: The pitcher fluid's (de)wetting behaviour will be studied using goniometry, interference microscopy and SEM, and its rheological properties using portable setups. Synthetic model fluids and force measurements on insects will test the contributions of surface tension and rheology to insect capture. Biomechanical adaptations of specialist arthropods to move in sticky pitcher trapping fluids will be studied using high-speed video and model fluids. Field work: The PS concentration of pitcher fluids will be measured, along with weather conditions from dataloggers. Experiments will test how PS concentration is affected by fluid dilution/evaporation and prey capture. Simulated rain on pitchers will be studied using video analysis, and experiments will be conducted to study how pitchers control their fluid level. The presence and concentration of PS will be mapped onto existing phylogenies of Nepenthes to test for correlation with other pitcher traits.
References - references should provide further reading about the project: 
Gaume, L. & Forterre, Y. (2007) A viscoelastic deadly fluid in carnivorous pitcher plants. PLoS ONE, 2, e1185. DOI: 10.1371/journal.pone.0001185.
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. DOI: 10.1111/j.1420-9101.2011.02406.x.
Kang, V., Isermann, H., Sharma, S. Wilson, D.I. & Federle, W. 2021. How a sticky fluid facilitates prey retention in a carnivorous pitcher plant (Nepenthes rafflesiana). Acta Biomaterialia 128: 357-369. DOI: 10.1016/j.actbio.2021.04.002.
You can find out about applying for this project on the Department of Zoology page.
Dr Walter Federle
Department of Zoology Graduate Administrator