As a teacher of ecology, I’m always on the lookout for examples of species interactions. Students often seem to find plants invisible, or at least think of vegetation as merely a backdrop for the “interesting” biology. So I am especially keen to find examples of plants and the various animals, fungi, microbes, or other plants with whom they interact. My walk around the Stephens Tract wetland outside Hepburn in Page County, provided evidence for several plants hosting other organisms; clearly in most instances this is no more nor less than an assault on the plant. Let’s have a look.
Willows (Salix) are a common wetland plant, and I saw both tree and shrub species here. Two different insect attackers had elicited characteristic growth responses: the Willow Pinecone gall is a response to attack by a midge (Rabdophaga strobiloides), and the plant grows a conelike structure (you can read about at this page). The gall ends up whitish and fuzzy, very fun to examine. And it sort of does resemble a little cone.
Next up, the Willows attacked by a related midge, (Rabdophaga rosaria) forming a related gall, but instead of a cone, we see a “rose” which houses the insect larva. A web page prepared by specialists in Finland has great photos, summer and winter, and a peek inside the gall. The page also mentions that Willows are subject to many different insect attacks, and I certainly have seen many types of galls, in great numbers, looking at Willows in my travels. Anyway, whether cone or rose gall, either way you are looking at a response by the Willow to an invader (insect grub) manipulating its growth, forming an abnormally-shortened stem, with plant tissues providing a shelter for the young insect.
Over the years of its life, a tree will likely be attacked by an array of organisms. Trees at this site exhibited bracket/shelf fungi, and holes excavated by birds (presumably digging for insects in the wood of the trunk). As a tree, you’re not going anywhere, so you’ve just got to “grow with it,” as it were. And so they have. Can plants actively resist attack? Or, even manipulate animal’s behavior? Take my Ecology class to learn about it 🙂
Anyway, trees have friends, too. I noted big Cottonwoods (Populus) along the edge of the wetland with branches drooping down, with shaggy structures the size of tennis balls attached to the slender branches and hanging down. They are Baltimore Oriole (Icterus galbula) nests! One in particular I really liked—a colorful structure, intricately woven—those enterprising scavengers will employ some unconventional “grass” fibers in their design, such as from a nearby tarp. Fun!
Those Orioles are good news for the trees. The nest is designed to hang safely from the twig (obviously, without breaking it). The adult birds feed on insects, presumably helping with pest control. So, I’d guess these birds are welcome visitors indeed, from the tree’s point of view. And for the record: they are boldly-colored and have a lovely song—so I like them, too!
Overall, much like a Paul Simon album, our wetland is filled with “Negotiations and Love Songs.” I hope you enjoyed our visit and these ecological interactions. Let’s continue the conversation! According to Charly at the County Conservation Board, the Jim Stephens family donated this 4 acre tract of ground upon the passing of Mr. Stephens in 1987. A survey found 60 plant species in this one spot! If you’ve been to the site, or know about its namesake (Mr. Jim Stephens), leave a note in the comments, please. Tell us the story!