Sticky Friend

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 (

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Salamanders in the Trees

Redwoods are tall. Known scientifically as Sequoia sempervirens, this species is home to the tallest tree known to science. Even the branches of most redwoods would put all but the tallest trees to shame. It is no wonder then that the branches and crotches of these trees can sustain a lot of canopy debris. As debris builds up, it soon begins supporting entire floral communities of ferns, forbs, shrubs, and even other trees.

These epiphytic communities are hot spots of diversity among the redwood canopy. The sheer mass of these mats, with some weighing hundreds of kilograms, means they can hold a lot of water. Organisms that otherwise could not exist in such exposed areas find a safe haven free of desiccation. Everything from microbes to aquatic copepods call these places home. It is no wonder then that predators also haunt these microcosms.

It has been discovered that at least one species of salamander, the wandering salamander (Aneides vagrans) lives at least some of its life in redwood canopies. Though it is not solely a denizen of these trees, they have been found living among these mats during both the dry and wet seasons leading some researchers to believe that at least some individuals live out their entire lives up in the canopy. The mats hold so much water that the microclimates around them stay favorable for these amphibians year round. As roots decay within the mat, small interconnected tunnels form, offering even more protection in an otherwise chaotic environment.