Spring Plants & Ants
Happy spring everyone! This is my favorite time of year. Our migratory birds are on their way north, bumble bee queens are rousing from their winter slumber, salamanders are wriggling around vernal pools, and our spring ephemeral wildflowers are beginning to emerge from the forest floor. The last phenomenon is the one I’d like to discuss in this newsletter. And in particular I want to discuss a very specific aspect of our spring wildflowers: seed dispersal.
Seed dispersal is an important aspect of a plant’s life cycle. Dispersing seeds away from itself is one way to ensure the parent plant isn’t competing for resources (e.g., sunlight; nutrients; water) with its progeny. Seeds of plants are dispersed in a variety of ways. Some, like samaras (a.k.a. helicopters) of maples or the cottony masses of cottonwoods and willows, are blown by the wind to areas far from the parent plant. Others, like buckeyes and walnuts, can float downstream until the river deposits them in a flood plain. Many fleshy fruit (e.g., berries; drupes) producing trees (e.g., pawpaw), shrubs (e.g., viburnum), vines (e.g., Virginia creeper), and perennials (e.g., ginseng) attract wildlife, such as songbirds, who consume the fruit and then fly away and “deposit” the seeds far from the parent plant. The list of seed dispersal strategies goes on and on.
In our neck of the woods there is a very interesting and special seed dispersal strategy used by many of our spring ephemeral wildflowers. Approximately 30 to 40 percent of early blooming forest wildflowers—species like large-flowered trillium & other trilliums, violets, spring beauties, wood poppy, and bloodroot—produce a fleshy appendage on their seeds known as an “elaisome”. Elaisomes are rich in lipids, amino acids, and other nutrients. They tend to give off chemical cues similar to those of dead insects, a common food item for forest floor scavengers, like ants. It turns out that over the millennia spring wildflowers have been producing seeds with elaisomes and atttracting ants, primarily those in the genus Aphaenogaster, who have been locating these seeds, taking them to their nests, feeding the elaisomes to their young, and then discarding the seeds. This provides two major benefits for the plants: 1) the seeds are taken away from the parent plant, thereby reducing potential competition, and 2) the discarded seeds are placed in locations conducive for germination—more so than where seeds that aren’t moved by ants are located. Of course, the ants are getting something out of this transaction through the elaisomes providing nutrient rich food for offspring. The movement of these seeds is typically pretty short—only a meter or two—but the impacts over long periods of time are invaluable for the health of these wildflower communities. By gradually moving seeds of various plants away from the respective parent plants, populations of each species expand on the landscape and merge with others creating extremely diverse communities. In fact, over 80 percent of the diversity of plants in temperate forests—like ours here in Ohio—is harbored in the herbaceous layer, which only rises a few feet from the ground. In other words, 4 out of every 5 plant species in our forests are not the large trees we all know in love, rather they are forest wildflowers, sedges, and grasses. The diversity in the herbaceous layer can partially be attributed to this fascinating seed dispersal strategy.
The best opportunity you’ll have to witness an ant carrying seeds of a spring wildflower is to spend time exploring in the spring to find healthy patches of the flower species that are known to participate in this mutualistic relationship. You’ll want an area with lots of blooms because it’s these blooms that will mature into seeds (*these are also great places to see native pollinators at work). Visit a couple weeks after peak bloom to check on the status of the fruits/seeds of the plants. Once you see seeds beginning to fall to the forest floor that’s when you may get lucky enough to witness this incredible phenomenon. Spend some time patiently waiting in an area with lots of seeds and you may get to observe ants carrying them away back to their nest. If you track them back to their nest you can wait there and see how many other individuals end up bringing seeds back.
I’ll leave you with this thought: we often dismiss organisms and things we don’t understand. It’s only when we invest the time to learn about the things we don’t readily comprehend that we find beauty and meaning in them. While a seemingly tiny ant scurrying across our picnic blanket may seem a nuisance or insignificant, remember their lives and ancient cultures are as rich as anything we can dream up. As we’ve learned today, they play a vital role in the maintenance and health of our forests which are so special and significant to each of us. Take a moment to be grateful for the myriad life that surrounds and sustains us—even if we don’t understand how they do so.
