Roundleaf sundew is a tiny carnivorous plant, found in low-nutrient acidic bogs and black spruce muskeg in the low elevations of the park. Though it is easily overlooked amidst the mosses, on close inspection is one of the most fascinating members of the flora.
The leaves grow in basal clusters, only a few centimeters long. The leaves grow on long pedicels with a greenish, round leaf blade, margin entire. The upper surface is covered in dark pink hairs, which have glandular droplets at the tips. This sticky substance—the source of the name 'sundew'—serves to catch any insect which lands on the plant. The hairs are also sensitive, and when stimulated by a bug trying to struggle free, the leaf will curl up around the trapped insect. The plant then releases digestive enzymes and breaks down the nutrients contained in its prey.
D. rotundifolia is photosynthetic, and it derives most of its energy from sunlight. The captured insects serve to provide important limiting nutrients (such as phosphorous and nitrogen) and improve growth and fertility. In a study of D. rotundifolia in Germany, plants were found to derive 24-30% of their total nitrogen from captured insects (Schulze and Schulze 1989).
D. rotundifolia is most easily distinguished from the other sundew in the park, D. anglica by its small, round leaf shape, the source of both the common and scientific name.
Plants are perennial, but live only up to five years (Matthews 1994). In late summer, the next years bud (spirally in-rolled leaves covered in bud leaves) is formed. These persist through the winter with the old leaves layered on top of them, opening in spring.
D. rotundifolia has small flowers, which do not produce nectar, and have a low pollen to ovule ratio (Murza and Davis 2003). This is common in species that are self-fertile. The seed coat is inflated, making the seeds buoyant and able to be carried long distances by water. Seed germination is improved with cold stratification, and is best near the surface of soil (Wolf et al. 2006). There is a persistent seed bank, viable for four years (Crowder et al. 1990). Plants can also reproduce vegetatively.
This carnivorous plant may contribute nutrients to bogs (Matthews 1994). Plants are also collected by amateur botanists with an interest in carnivorous plants (seriously endangering some less common species), though this does not appear to be a concern in Alaska.
Drosera rotundifolia is a widespread circumpolar boreal-montane species that occurs in suitable habitat across the lowlands of Alaska south of the Brooks Range. Worldwide, it has a circumboreal distribution, occurring across Canada and on both coasts of the United States, absent from the prairie provinces and states. In Eurasia, roundleaf sundew occurs from Kamchatka and Japan to northern Europe.Drosera rotundifolia is common in the bogs and muskegs in the northeastern corner of Denali and also in wetlands south of the Alaska Range in the park.
D. rotundifolia is most commonly found in low elevations, occurring in nearly 40% of plots under 300 m in the Park. Though the vast majority of individuals are found on flat or low slopes, there is a slight preference for north-facing slopes (which are more likely to be cold and wet, favoring the community types this species is found in).