Moehringia macrophylla (Hook.) Fenzl
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Basis for Listing
Populations of Moehringia macrophylla are remote and discontinuous. The species is generally considered threatened throughout its Lake Superior range and in the southern portion of its eastern range. Even in its northwestern range, it is often considered rare or local. In Minnesota, populations are found in rock crevices and small shelves on cliffs in the northeastern counties of Cook and Lake. Only a few of the historic populations have been relocated, despite considerable effort. All evidence indicates that this is a very rare species with limited distribution and restrictive environmental needs. Furthermore, all known populations are small and occur in fragile habitats. Although M. macrophylla often occurs in inaccessible habitats, some populations exist on small cliff features that are easily accessed. It also grows in areas subject to forest management and/or road development. The Minnesota Biological Survey has surveyed much of the potential habitat of M. macrophylla, but new populations may still be discovered in unsurveyed portions of northern Lake and eastern Cook counties. Moehringia macrophylla has been listed as a threatened species in Minnesota since 1984.
Moehringia macrophylla is a small, delicate plant that reproduces largely by rhizomatous growth. Like all members of this genus, it has 5 petals, 5 sepals, 10 stamens, and 3 styles. It bears a close resemblance to the common M. lateriflora (also Arenaria lateriflora, side-flowering sandwort) but can be distinguished by its longer, lance-acuminate, glabrous leaves and by its longer (3-6 mm; 0.12- 0.24 in.) acute sepals.
Most of the documented sites of M. macrophylla in Minnesota occur on sheltered cliffs of slate and diabase in the Rove Formation. In this habitat the plants grow in small rock crevices where organic debris accumulates or where moss mats provide a suitable substrate. Populations are typically associated with cliffs having a northerly aspect, where they are often found near the cliff base on small shelves, cracks, and chutes. They can also occur higher on the cliff face or along the cliff top and associated woodlands. Some populations are known to occur on small cliff inclusions nested within a forest matrix. One site occurs in shallow soils within a conifer woodland near a cliff top. A few populations have apparently colonized areas previously disturbed by logging or road construction. Populations vary in size from more than 200 to only a few plants.
Biology / Life History
Moehringia macrophylla is a perennial rhizomatous herb that propagates both sexually and asexually. White flowers appear from May to August and produce a capsule containing many tiny, black seeds. Vegetative reproduction occurs through the spread of creeping underground stems, which then sprout new plants at the nodes (U.S. Forest Service 1999).
Conservation / Management
Known locations, particularly those on larger cliffs, should be protected from recreational rock climbing. Timber management activities in the vicinity of occupied cliff habitats should be managed to avoid erosion and landslides; small cliffs are particularly vulnerable. Other possible threats include road and trail construction and mining. Populations occurring in forested (non-cliff) habitats are vulnerable because of the fragile nature of the shallow soil and the small size of the populations. Any use of heavy equipment in the vicinity of these populations should be avoided.
Conservation Efforts in Minnesota
The DNR Minnesota Biological Survey has surveyed much of the potential habitat of M. macrophylla. Most populations are either on state or national forest lands, which are most often managed for timber production. One population is on a Nature Conservancy preserve. Portions of a public hiking trail in Cook County were rerouted to protect this and other listed plant species.
References and Additional Information
Butters, F. K., and E. C. Abbe. 1953. A floristic study of Cook County, northeastern Minnesota. Rhodora 55:21-201.
Gerdes, L. B. 2001. A contribution to the flora of the Rove Slate Bedrock Complex Landtype Association, northern Cook County, Minnesota, U.S.A. Thesis, Michigan Technological University, Houghton, Michigan. 79 pp.
Marquis, R. J., and E. G. Voss. 1981. Distributions of some western North American plants disjunct in the Great Lakes region. The Michigan Botanist 20:53-82.
Ownbey, G. B., and T. Morley. 1991. Vascular plants of Minnesota: a checklist and atlas. University of Minnesota Press, Minneapolis, Minnesota. 320 pp.
U.S. Forest Service. 1999. Population viability assessment in forest plan revision. Statement of purpose and reason. Draft species data records: Moehringia macrophylla. United States Forest Service, Region 9.
U.S. Forest Service. 2000. Population viability assessment in forest plan revision. Questions for plant population viability assessment panel: Moehringia macrophylla. United States Forest Service, Region 9, Duluth, Minnesota.
Wisconsin Department of Natural Resources, Bureau of Endangered Resources. 1993. Guide to Wisconsin's Endangered and Threatened Plants. Wisconsin Department of Natural Resources PUBL-ER-067, Madison, Wisconsin. 128 pp.