Evol Ecol Res 2: 231-249 (2000)     Full PDF if your library subscribes.

Variable chemical defences in plants and their effects on herbivore behaviour

Angela L. Shelton

Department of Environmental Studies, University of California, Santa Cruz, CA 95064, USA


e-mail: angies@cats.ucsc.edu

ABSTRACT

Most plants exhibit very high chemical variability from scales of within individuals to between populations and between species. This extraordinary variation has not yet been adequately explained. One potential explanation is that variability may benefit the plants by making them a more unpredictable environment for herbivores. I explored this possibility with a dynamic state variable model. I assumed a concave benefits curve and modelled the behaviour of a herbivore on two types of plants. Each plant type had the same mean level of toxins, but one had a variable distribution of toxins while the other was completely predictable. In each time step, the herbivore either foraged or reproduced. If it foraged, it could either accept or reject the plant encountered. The model predicted that, when herbivores had intermediate energy levels, they would reject variable-toxin plants, as long as there were constant-toxin plants in the environment and the benefits curve was sufficiently concave. This emphasized the importance of herbivore choice in plant defence and demonstrated that variability can be an additional level of defence for some plants.

Keywords: chemical variation, dynamic state variable model, herbivore choice, herbivory, plant defence theory, secondary metabolites.

DOWNLOAD A FREE, FULL PDF COPY
IF you are connected using the IP of a subscribing institution (library, laboratory, etc.)
or through its VPN.

 

        © 2000 Angela L. Shelton. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

       Subscribing institutions/libraries may grant individuals the privilege of making a single copy of an EER article for non-commercial educational or non-commercial research purposes. Subscribing institutions/libraries may also use articles for non-commercial educational purposes by making any number of copies for course packs or course reserve collections. Subscribing institutions/libraries may also loan single copies of articles to non-commercial libraries for educational purposes.

       All copies of abstracts and articles must preserve their copyright notice without modification.