Two spring beauties and a beeSpring beauties, Claytonia virginica, are among the earliest blooming of our so-called “spring ephemerals,” the woodland wildflowers that bloom in succession between March and May. Spring beauties survive the winter as a mini-potato-like tuberous root that provides the plant with another name, the “fairy spud.” As soils warm in the spring, the tuber sprouts a pair of leaves with buds that open into attractive saucer-shaped flowers with five petals and bright pink anthers at the tip of each stamen.

Spring beauty flowers bloom for just a few days; the stamens stand upright and release pollen for just the first of those. Fruits of pollinated flowers mature in about ten days and then eject their seeds, each of which bears a fatty, tasty attachment (an eliasome) that attracts ants. The ants carry off the seeds to their nest, where they consume the eliasome and leave the seed, effectively planting the next generation.

Insects are instrumental in achieving pollination, too. At the early date when spring beauties start to bloom, the diversity of insect pollinators is somewhat limited. Still, a number of insects emerge with the warming soils. For spring beauties, the most important among those is a smallish bee from the miner bee family, Andrenidae.

Miner bees are a diverse group of solitary nesting bees; each female digs her own burrow where she lays her eggs. In sites with favorable soil—often sandy spots that are good for digging—many miner bees may nest in close proximity, giving the appearance of a hive. These nesting congregations may well occur in lawns and gardens, where they should be valued; the bees are totally harmless to humans and are important pollinators.

The particular miner bee that pollinates spring beauties is Andrena erigeneae, the spring beauty miner, one of about 100 Andrenid bee species in Ohio. (Miner bees have fuzzy bands between their eyes, but identifying them to species can be challenging.) Not surprisingly from their name, spring beauty miners are specialist pollinators of spring beauties. The bees feed from nectar in the flower center, directed there by pink veins in the petals and by UV-reflecting stamen filaments. In the process, pollen collects on their hairy bodies, providing a fashionable pink tint. This pollen collection is so effective that it can deplete the flowers of pollen. As long as the bees subsequently visit and pollinate other spring beauties, though, they have done their job.

The female miner bee takes adherent pollen back to her underground nest, where she crafts it into a little ball on which she lays a single egg. That egg hatches into a larva during summer, feeds on the pollen, then metamorphoses into a pupa. In late autumn, adults emerge from the pupae, but they remain underground until the following spring. Presumably, their emergence depends on temperature cues that align with those triggering spring beauties to bloom.

Spring beauties are abundant in local woods, and a quick scan reveals that not all spring beauties look the same. On some plants, the petals are nearly pure white, contrasting with the bright pink stamen tips. For others, the petals and stamens form a matched set, glowing pink against the brown leaf litter. Why that variation?

What appears to be the case is that pink flowers are more effectively pollinated than white, especially by spring beauty miners. Distinctively pink flowers may help the bees avoid mistakenly visiting other white spring ephemerals that are blooming nearby, thereby facilitating efficient pollination. However, pinker flowers also suffer some detriment. In particular, the leaves of plants with pinker flowers suffer more damage from herbivorous slugs. White petals, it turns out, are richer in chemicals called flavonols; those chemicals are present in leaves, too, and they deter slug herbivory. As a further complication, that damage from herbivores apparently induces the plants to gear up against other damage, and as a result, the white-flowered plants (with less slug damage, and so less elevated defenses) are more susceptible to fungal attack. The relative intensities of these various factors—pollinator preference and the threats from herbivores (slugs) and pathogens (fungi)–probably vary from year to year. And so, the flower color that more successfully sets seeds also varies from year to year. Like many aspects of ecology and physiology, the color of spring beauty flowers represents a trade-off, and the population ends up including a mix of flowers ranging from white to pink.

Spring beauties vary in another way, too, one that is not so visible. Plant cells, like those of animals, normally have two copies of each chromosome, the so-called “diploid” condition. However, many plants undergo processes during cell division, gamete (ovule and pollen) formation, and fertilization that end up producing cells with extra sets of chromosomes, so-called “polyploidy.” Plants seem to tolerate polyploidy better than animals. Although there can be negative consequences of polyploidy, including reduced fertility, there may be benefits, too. For example, the additional copies of each gene mean that the original copy can continue to perform its original function, while the extra copies can diverge to provide new capabilities. As a result, polyploid plants may be better able to tolerate more variable or harsher conditions than “regular” diploid relatives. Spring beauties seem to be even more susceptible to, or tolerant of, polyploidy than most plants, and a population of spring beauties may include plants with 2, 4, 8, even 12 copies of each chromosome. This presents a variety of interesting possibilities for ecological adaptation and the evolution of traits and species—though those sorts of outcomes have not yet been well defined for Claytonia virginica.

Spring beauties and spring beauty miner bees help to ring in springtime and, in the process, they exemplify a variety of issues in ecology and evolution. Each species has its own interests and secrets, but at the same time each is dependent on the other. Spring beauties and the bees; it’s a tale as old as time.

Article and photo contributed by Dr. David L. Goldstein, Emeritus Professor, Department of Biological Sciences, Wright State University.