Botrychium oneidense (Gilbert) House
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Basis for Listing
Botrychium oneidense has a very narrow geographic range compared to other Botrychium species. It seems to be restricted to northeastern North America. Throughout its range, B. oneidense occurs along the edges of low areas in shaded, moist, acidic forests and along the edges of swamps (Wagner and Wagner 1993). It was first found in Minnesota in 1991, which sparked an intensive search to determine the full extent of its range within the state. This pursuit will likely be ongoing for many years. Most recorded populations are from moist depressions in hardwood forests in the central part of the state, with a few populations recorded in the extreme southeastern corner. Botrychium oneidense was listed as an endangered species in Minnesota in 1996.
Botrychium oneidense has a single triangular leaf borne parallel to the ground. Mature specimens have a stalked, spore-bearing, reproductive structure. The spore-bearing structure may or may not be produced annually, and can be 3 times as long as the leaf blade. The leaf diverges from the stem about 2.5-5 cm (1-2 in.) above the ground and may be up to 20 cm (8 in.) wide and 20 cm (8 in.) long, usually pinnate 2-3 times. The ultimate leaf segments are mostly obtuse to rounded. Leaves stay bright green throughout the winter with new leaves appearing in the spring (Gleason and Cronquist 1991; Wagner and Wagner 1993).
In Minnesota, B. oneidense occurs in forests of Acer saccharum (sugar maple), Betula alleghaniensis (yellow birch), Fraxinus nigra (black ash), Quercus rubra (northern red oak), and Tilia americana (basswood). It occasionally occurs with Acer rubrum (red maple), Fraxinus pennsylvanica (green ash), Populus spp. (aspen), Pinus spp. (pine), Quercus macrocarpa (bur oak), and Thuja occidentalis (northern white cedar). Within the forest, B. oneidense usually grows in moist loam in low areas, swamp edges, or between the high and low water marks of vernal pools. It most often occurs as a few scattered plants, but as many as 100 plants have been observed at one location. It often occurs with other Botrychium species, most notably B. multifidum (leathery grapefern).
Biology / Life History
As a member of the Ophioglossaceae or evergreen grapefern family, the frond of B. oneidense is not killed by frost in the fall but holds its form through winter. Then, during the summer, typically in late June, a new leaf begins to emerge and unfold. The overwintering leaf tends to disintegrate as the new leaf appears. An immature plant will usually bear a single sterile leaf, not developing a spore-bearing stalk until subsequent years. Therefore, many plants are sterile in any given year. The leaf of older plants is more dissected than the leaf of younger plants. In the past, B. oneidense has been treated as a form or variety of B. dissectum (dissected grapefern) or B. multifidum (leathery grapefern) as well as their hybrid. Botrychium dissectum, B. multifidum, and B. oneidense look very similar when young (U.S. Forest Service 1999). Wagner (1961) determined that B. oneidense is a distinct species, which is supported by Smith's 1967 study of phenolic substances present in this and related species (U.S. Forest Service 1999).
Conservation / Management
So far, B. oneidense has only been found in forested habitats in Minnesota. Most populations are small and localized around small forest wetlands. These limited habitats are vulnerable to certain forest management activities. Forestry practices that create significant gaps in the canopy could alter the species' habitat by allowing more light and heat to reach the ground layer, which could change the composition of the plant community. Any significant damage to the forest floor, such as soil compaction or rutting that might occur during a logging operation, could also threaten existing plants. Selective harvest of trees during winter when the ground is frozen would be a preferred forestry practice. Hydrologic changes and exotic earthworms may also pose a threat to the species and its habitat.
Conservation Efforts in Minnesota
Several B. oneidense populations occur on State Forest and county forest lands. Because these sites are typically managed for timber production, special attention should be given to protecting this rare species and its habitat.
Authorship / Revision
Author: Harriet Mason, May 2001 Revised: Welby Smith, November 2008 Revised: Welby Smith, January 2016
Chadde, S., and G. Kudray. 2001. Conservation assessment for Blunt-lobe Grapefern (Botrychium oneidense). U.S. Forest Service Eastern Region, Milwaukee, Wisconsin. 47 pp.
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.
Ownbey, G. B., and T. Morley. 1991. Vascular plants of Minnesota: a checklist and atlas. University of Minnesota Press, Minneapolis, Minnesota. 307 pp.
U.S. Forest Service. 1999. Population viability assessment in forest plan revision. Statement of purpose and reason. Draft species data records: Botrychium oneidense. 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: Botrychium oneidense. United States Forest Service, Region 9, Duluth, Minnesota.
Wagner, W. H., Jr., and F. S. Wagner. 1993. Botrychium. Pages 86-101 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 2. Oxford University Press, New York.