Photo by David A. Hofmann licensed under CC BY-NC-ND 2.0

We have all had encounters with sticky plants. Outside of being an interesting sensory experience, the sticky nature of these floral entities would appear to have some evolutionary significance. Considering the cost of producing the glandular trichomes responsible for their stickiness, function is a reasonable question to ask about. For anyone who has taken the time to observe such plants, you will have undoubtedly noticed that insects tend to get stuck to them.

For carnivorous plants, the utility of these glands is readily obvious - trapped insects become food. Even non-carnivores like Roridula gain a nutrient benefit in the form of nutrient-rich feces deposited around the plant by specialized carnivorous bugs that consume trapped insects. However, there are many species of plants out there that fall under the category of "sticky" and a new paper explores this in a more general way.

The serpentine columbine (Aquilegia eximia) is endemic to the Coastal Range of California and it is indeed quite sticky. Its surfaces are covered in glandular hairs. Any given plant can be covered in insects unfortunate enough to come into contact with it. However, it is not a carnivore. As such, researchers wanted to see what benefits, if any, the columbine gained from producing these glands.

By manipulating the amount of insects that were stuck to each plant, researchers found that plants without "victims" actually received more insect damage. The key to this mystery were predators. Plants with lots of trapped victims had more predatory bugs hanging around. These predators, when present, reduced herbivory by deterring other insects that were too large to get stuck. What's more, most of the benefits were observed in the flower buds, which means predators increased the overall reproductive fitness of the serpentine columbine. If the columbine did not trap small insects, these predators would have no reason to hang around.

These predatory bugs were by no means specific to the columbine. In fact, observation of the surrounding plant community found that these predatory insects were present on other sticky genera such as Arctostaphylos, Hemizoni, Holocarpha, Calycidenia, Cordelanthus, Castilleja, Mimulus, Trichostema, and Grindelia. This suggests that the relationship between sticky plants and these generalist predators is more widespread than previously thought. It may also offer a unique window into one possible driver behind the evolution of carnivory in plants.

Photo Credit: David A. Hofmann (http://bit.ly/1l9OtwC)

Further Reading:
http://www.esajournals.org/doi/abs/10.1890/15-0342.1

Roadways have been surprising me quite a bit as of late. Where I live, they are havens for aggressive invaders such as crown vetch (Securigera varia), sweet pea (Lathyrus odoratus), and a seemingly endless variety of turf grasses. However, this does not seem to be a pattern that repeats itself everywhere. More and more I have come to notice that roadsides in other locations harbor a wide variety of native plant life, some of which are downright surprising.

My most recent foray into Canada revealed some surprising roadside botany. While cruising down a highway, my friends and I began noticing bright red dots spread about the shoulders of the road. The red was so bright it was impossible to ignore. We had to find out the source. Within a few steps we soon realized where the color was coming from. It was none other than the scarlet paintbrush (Castilleja coccinea).

Needless to say, I was beyond excited. I have tried for years to grow this plant, which is endangered in the state of New York. All of my attempts have been met with failure so finally getting a chance to see this species was a momentous occasion. Like all others in this genus, C. coccinea is a hemiparasite. Using specialized roots it taps into the roots of neighboring plants and steals nutrients. Research has shown that C. coccinea doesn't seem to be too picky as to which plants it parasitizes, though it is likely that some plants are better hosts than others.

The plight of this species extends far beyond my home state. Native to much of eastern North America, this lovely species has been all but eradicated from the New England states. The most common reason for this is habitat destruction. We simply love to develop and farm the kinds of places that C. coccinea grows.

Another serious but less obvious threat to C. coccinea is succession. As is typical of our species, we tend to manage the land in a feast or famine sort of way. Its either total destruction or an adherence to an often false ideal centered around the word "pristine." A lack of disturbance is great for some species but spells disaster for others. Thus, as woody species, especially invasives such as multiflora rose (Rosa multiflora), encroach into open habitat, plants that cannot handle shading such as C. coccinea quickly disappear from the landscape. This is a species that requires some disturbance to survive. Land managers and stake holders would do good by paying attention to the habitat requirements of such species.

Further Reading:
http://www.newfs.org/docs/pdf/Castillejacoccinea.pdf
http://www.jstor.org/stable/2483296…
http://plants.usda.gov/core/profile?symbol=caco17