(this post should also be regarded as potential project for someone else: I started it in May - there is plenty of time to get up to McLaughlin and do it again this year).
|One of the experimental A. cornutum, showing leaf damage.|
|Stem of A cornutum with an entrapped insect.|
|Flower bud showing short glandular and long nonglandular trichomes.|
During the experiment, plants suffered two main forms of herbivory. The first type, which was most common and most destructive, was that the stems were entirely clipped off. I'm nearly positive this was by jackrabbits (indicated by a single flat cut diagonally across the stem) and it usually killed the plant. The photos below shows what remained.
|A killed experimental A. cornutum plant. See it?!? Its the little stem to the bottom left of the flag. Also notice a nice healthy Lessingia in the background. They, too, are extremely glandular and sticky.|
|A survivor of mammalian herbivory. If the meristem was not completely destroyed, they often came back and branched like this. Like the classic overcompensation "herbivore-plant mutualisms", the resulting plants were often bigger than the others, with more reproductive structures, but unlike this "mutualism", it was too late in the season and they had low fitness, as they could not mature these structures.|
Were they bigger and thus easier to find or just more profitable to eat? They were not significantly different in height, fruit or flower numbers from the other two groups during any check. I don't have data on plant quality (perhaps the less water-limited plants were more nutritious or something?).
The other type of damage was equally-interesting. Heliothis phloxiphaga is a generalist caterpillar on glandular plants. It was the primary herbivore on my columbines, as well as a common herbivore on Trichostema laxum and other sticky plants. Like most heliothiine noctuids, it feeds primarily (but not exclusively) on reproductive structures. I only observed it once on Antirrhinum (eating a fruit), but all the fruit damage I found was consistent with it (and that's one more time than I saw a jackrabbit eat it!).
|The other type of damage: caterpillar fruit predation.|
|A crumby excel graph of proportion fruits damaged.|