Tofieldia pusilla (Michx.) Pers.
Small False Asphodel
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Basis for Listing
Several small populations of Tofieldia pusilla occur on the North Shore of Lake Superior and nearby Isle Royale, but they are isolated from the main range of the species by approximately 650 km (404 mi.). This remarkable pattern of disjunction is seen in several other arctic species and is a result of the local, climate-modifying effect of Lake Superior that simulates growing conditions like those in arctic/alpine regions where these plants may be more common. The small population sizes and sensitive habitat requirements make the viability of the Minnesota populations a matter of immediate concern (U.S. Forest Service 1999).
Tofieldia pusilla is a distinctive but inconspicuous plant. It has several small, whitish or greenish flowers with 3 petals, 3 sepals, 3 styles, and 6 stamens. It has a single, glabrous, leafless pedicel and distinctive, sword-shaped basal leaves that are 2-ranked and linear. The fruit is a capsule (Gleason and Cronquist 1991).
All of the known Minnesota populations of T. pusilla occur in similar habitats on the shore of Lake Superior. This species prefers the massive outcrops of volcanic bedrock, not the unstable gravel beaches or the boulder-strewn shorelines. Suitable habitat is found intermittently from Two Harbors to Grand Portage, a distance of 200 km (124 mi.), but may total only a few hectares in extent. Tofieldia pusilla occurs in vegetation mats of Trichophorum cespitosum (tufted bulrush), Carex spp. (sedges), and other species that persist in crevices in the shore outcrops of Lake Superior. These vegetation mats typically form in low depressions and at the margins of shore pools. Such habitats are small and localized, occurring just beyond the wave-washed zone or in protected areas nearer to lake level. Other rare species that may occur in the same habitat include Pinguicula vulgaris (butterwort), Bistorta vivipara (alpine bistort), and Selaginella selaginoides (northern spikemoss).
Biology / Life History
Tofieldia pusilla is a relatively long-lived perennial. The plants flower in July and are insect-pollinated. The seeds are produced in August. Tofieldia pusilla may reproduce vegetatively from short rhizomes (Gleason and Cronquist 1991; U.S. Forest Service 1999).
Conservation / Management
The most serious threats to the extant populations of T. pusilla include vandalism, over-collecting, recreation (trampling), shoreline development, pollution, the expanding gull population, and any other activities that can change the sensitive microclimate along Lake Superior (U.S. Forest Service 1999). Although the bedrock substrate of these populations is not typically directly threatened by destruction, the fragile vegetation mats that support this species are.
Conservation Efforts in Minnesota
Much of the potential habitat along Lake Superior was inventoried by the DNR Minnesota Biological Survey from 1999-2002. It is possible that a few additional populations occur outside the surveyed areas, such as extreme northeastern Cook County.
Gleason, H. A., and A. Cronquist. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. Second Edition. New York Botanical Garden, Bronx, New York. 910 pp.
U.S. Forest Service. 1999. Population viability assessment in forest plan revision. Statement of purpose and reason. Draft species data records: Tofieldia pusilla. United States Forest Service, Region 9.