Abstract Detail

Ecology

Barnes, Christopher [1].

Spatial-temporal variation in the defence compounds of Thapsia garganica, and their inhibition to fungi.

Understanding the composition and concentrations of plant chemical defences have been a source of great interest for ecologists and evolutionary biologists alike, with many models developed to understand the inter- and intra-specific variation in them. One such model, the optimum defence model states that vegetative tissue is easier to replace than reproductive tissue, and therefore is better protected. It also states that under increasing risk of attack (i.e. herbivory), there will be an increase chemical defences, and that chemical defences are greatest in the mid-season. Thapsia garganica is a slow growing plant restricted to the Mediterranean from Portugal and Morocco to Turkey and Greece, which contains potent anti-herbivory compounds, thapsigargins. These compounds have long been used as medicinal compounds, but their regulation is almost entirely unknown. In this study we sampled populations of T. garganica from 6 sites across the island of Ibiza, which spanned a herbivory gradient (ranging from an active farm to sites that have not been grazed for over 10 years). Sampling was performed three times over a 12-week period, where thapsigargins in the root and root bark were quantified, and where present, the leaves, bracts, flowers and fruits. The evolutionary processes regulating thapsigargins were subsequently investigated by analyzing differences in thapsigargin concentrations between different tissue types, under the herbivory gradient and temporally, and results compared to the optimum defence model. We additionally investigated the role of the abiotic (soil and climate) and biotic (soil fungi) factors in regulating thapsigargins. Results here suggest that the optimum defence model fits well for T. garganica. There were significant differences between tissue types, with fruits and flowers better protected than the leaves, whilst there were limited effects of herbivory and no significant temporal variation. We therefore suggest that tissue type is the best predictor of chemical defences in T. garganica, followed by herbivory and then temporal variation. Finally, we found that increasing soil nitrogen increased belowground thapsigargin concentrations, and that the roots of T. garganica had very low rates of fungal colonisation, with thapsigargins shown to powerfully inhibit soil fungal growth in the laboratory. Thapsigargins may therefore have previously uncharacterised functions in the belowground defence of T. garganica.

1 - University of Copenhagen, Natural History Musuem of Denmark, Oester Voldgade 5-7, København K, Copenhagen, 1350, Denmark

Keywords:
plant defense
plant-fungus interaction
Optimum defense model
Thapsia garganica.

Presentation Type: Oral Paper
Session: 2, Ecology Section - Functional Traits and Responses
Location: 104/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 11:00 AM
Number: 2012
Abstract ID:702
Candidate for Awards:None