|The stem of Trichostema laxum (Lamiaceae). The little bubbles on the tips of the glandular trichomes are full of an oily, wonderfully vinegary-smelling fluid, of unknown utility.|
|A Mormon cricket, Anabrus simplex. White Mountain, CA, Sept. 2012. A mind-blowingly large katydid.|
|The glandular trichomes on Aquilegia eximia (serpentine columbine: Ranunculaceae) |
are extremely sticky and entrap enormous quantities of small flies and wasps.
The first approach I took to playing with (e.g. experimenting) external chemicals was testing their efficacy at preventing damage to plants. I did, and continue to do, this in two ways (in the chenopod paper as well as many small unpublished tests). The first way is to remove or reduce the defense, gently, using a paintbrush or a sponge, leaving the leaf surface intact. I then run choice or no choice (palatability) assays on these plants, usually using a the wonderfully generalist spotted cucumber beetle, which rarely fails to eat at least a little bit of a plant (but also will eat a LOT of a plant it likes). The second is to take the external chemical (either from the plant or the known chemical) and place it onto another plant, either in natural concentrations, or varying the concentrations, looking for changes in herbivory.
|Lab-grown, highly glandular Antirrhinum californicum.|
|Deer or jackrabbit eaten A. californicum from the experiment.|
The most satisfying part of these investigations so far (more to be detailed soon) has been combining a variety of approaches to think about a problem. I've made lots of natural history observations (examined lots of plants with secretions), thought about problems in creative ways (can I think of fundamental differences between internal and external chemicals, ecologically?), read the literature (from Darwin and earlier, to the present), planned and ran experiments, interpreted data (with such strange results as in the snapdragons) and am working on integrating it all into a dissertation, which I hope - in a few years - will be a cohesive body of work that other people will add to, build upon and apply to new systems and problems.