From flypaper to pitfall traps: function and evolution of trapping fluids

Supervisors: Dr Carmen Galan (School of Chemistry, University of Bristol) – Main supervisor Dr Heather Whitney (School of Biological Sciences, University of Bristol) Dr Ulrike Bauer (School of Biological Sciences, University of Bristol) Dr Monica Berry (NSQI, University of Bristol) Host institution: University of Bristol

Project descriptor:

Importance: The traps of carnivorous are examples of drastic structural and functional modifications of organs and provide a unique opportunity to study evolution. Pitcher leaves are thought to have evolved from simpler flypaper leaves on several independent occasions. Spontaneous mutations can cause the formation of epiascidiate (tubular) leaves in various non- carnivorous plants, e.g. in Codiaeum variegatum or Ficus benghalensis. Virtually nothing is known about the detailed function or the evolution of the trapping fluid, a key component of both flypaper and pitcher traps and milestone invention on the evolutionary road to plant carnivory.

Aims: This project investigates the properties and function of the trap fluids in a group of closely related flypaper and pitcher plants, comprising the sundews ( and ), pitcher plants () and a carnivorous (Triphyophyllum). All these employ polysaccharide-based secretions to aid in the trapping, retention and killing of insects, but the composition and rheology of these fluids remains largely unknown. Chemical analyses of the sticky mucilage of Drosera capensis and Drosophyllum lusitanicum (overview in Juniper et. al 1989) indicate small differences in the polysaccharide composition. Gaume et al. (2007) investigated the rheology of Nepenthes rafflesiana pitcher fluid and reported a highly viscoelastic behaviour which plays a key role in trapping. This project links these fragments of information by 1) characterising polysaccharide content and monomeric composition, ionic content, and pH of trapping fluids throughout the group, 2) interpreting these data in the context of available phylogenetic information, 3) determining the viscosity, shear-thinning properties and extensional viscosity of different trapping fluids and relate these properties to the trapping function (flypaper glue, drowning pitcher fluid) and 4) investigate the interaction of the trapping fluids with the living plant and the environment, e.g. the temporal pattern of fluid secretion and the influence of temperature, humidity and (dilution by) rain on the fluid properties and function.

References:

1. Juniper BE, Robins RJ, Joel DM 1989. The carnivorous plants. London: Academic Press 2. Gaume L, Forterre Y 2007. A viscoelastic deadly fluid in carnivorous pitcher plants. PLoS One 2, e1185