Botrychium pallidum W.H. Wagner
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Basis for Listing
This baffling species has been reported as one of the rarest moonworts in North America, occurring only sporadically in Canada, Montana, Colorado, Wyoming, South Dakota, Minnesota, Wisconsin, Michigan, and Maine (Wagner and Wagner 1993). Botrychium pallidum was first discovered in Minnesota in 1992 in Lake County. Since then, it has been observed in a great variety of habitats in northern Minnesota. It is difficult to determine if the known populations are stable because most populations have been located only recently and little is known about their life history. Due to its tiny size, the species is easily overlooked and additional populations may yet be located. When Botrychium pallidum was listed as a state endangered species in 1996, only six populations had been documented in Minnesota. As of August 2009, that number had risen to 65. In light of this, downgrading the species' status to special concern is currently being considered.
This tiny plant is 2.5-7.6 cm (1-3 in.) high and has a pale green leaf with up to 5 pairs of whitish, kidney-shaped pinnae (lobes of the leaf). Each pair of pinnae may be folded towards each other. The bottom, largest pair of pinnae often split into 2 unequal lobes with rounded tips and with veining like the ribs of a fan, with no central midrib. Spore capsules, while typically occurring on the fertile or spore-bearing frond, can also occasionally be found on the lobes of the trophophore or non-spore-bearing frond. Botrychium pallidum commonly produces dense clusters of minute, spherical gemmae at the root bases. Botrychium pallidum can be distinguished from small plants of other Botrychium species by the often-folded pinnae and pale green to whitish color (Wagner and Wagner 1993). Although most populations contain only a few plants, up to 50 individuals have been recorded at a single site.
In Minnesota, B. pallidum has been found in a diversity of habitats ranging from open fields, dry sand and gravel ridges, roadsides, wet depressions, marshy lakeshores, and tailings basins, as well as second-growth forests and shaded, moist, mixed deciduous-hardwood forests. It is often found growing in disturbed, weedy areas and in forest areas without an overstory. Botrychium pallidum also grows in the shade in mixed forests of Acer saccharum (sugar maple), Alnus spp. (alder), Betula spp. (birch), Picea mariana (black spruce), Populus grandidentata (big-toothed aspen), P. balsamifera (balsam poplar), P. tremuloides (quaking aspen), Quercus rubra (northern red oak), Thuja occidentalis (northern white cedar), and Tilia americana (basswood). It is often found growing with other Botrychium species, especially B. matricariifolium (matricary grapefern), B. minganense (Mingan moonwort), B. multifidum (leathery grapefern), B. simplex (least moonwort), and B. virginianum (rattlesnake fern).
Biology / Life History
Gametophytes and young nonemergent sporophytes exist underground for many years (possibly 10 years) before producing the first frond. Mortality can be high during this time (U.S. Forest Service 1999). B. pallidum has been found only in association with other Botrychium species; it has not been found by itself (Wagner and Wagner 1990).
Conservation / Management
This is an unusually tiny plant, and its small size may cause it to be overlooked. Little is known about its habitat requirements, however, it may require early or mid-successional habitats where competition for light is minimal (U.S. Forest Service 1999). The primary threat to B. pallidum is loss of habitat, but it is unclear how suitable habitat should be managed or maintained.
Conservation Efforts in Minnesota
There have been no known conservation efforts directed towards this species in Minnesota.
Chadde, S., and G. Kudray. 2003. Conservation assessment for Pale Moonwort (Botrychium pallidum). United States Forest Service, Eastern Region, Milwaukee, Wisconsin. 40 pp.
NatureServe. 2009. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia.
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 pallidum. 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 pallidum. United States Forest Service, Region 9, Duluth, Minnesota.
Wagner, W. H., Jr., and F. S. Wagner. 1990. Notes on the fan-leaflet group of moonworts in North America with descriptions of two new members. American Fern Journal 80(3):73-81.
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.