Botrychium lunaria (L.) Sw.
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Basis for Listing
Botrychium lunaria is the most widespread of the moonworts, occurring across boreal North America as well as in northern Europe, Asia, South America, Australia, and the Pacific Islands of New Zealand. In spite of its wide distribution, B. lunaria often appears to be rare or local. Only a handful of occurrences have ever been recorded in Minnesota and only in the northern tier of counties. Despite extensive searches in suitable habitats in this state, only a very few of the recorded observations have been seen in recent years. Botrychium lunaria was originally listed as a special concern species in Minnesota in 1984, but given its extreme rarity, it was reclassified as threatened in 1996.
Botrychium lunaria may be 2.5-17.8 cm (1-7 in.) tall, with a single leaf bearing 1 sterile segment and 1 fertile segment per season. The sterile segment has up to 9 pairs of fan-shaped pinnae that often overlap except when growing in deep shade. The fertile segment bears several round spore cases that turn yellow when ripe. After shedding spores, both sterile and fertile segments wither. Botrychium lunaria may occur with other species of Botrychium, such as B. minganense (Mingan moonwort), with which it is often confused. Botrychium minganense can be distinguished by the elongate sterile segment of the leaf that has narrower, nonoverlapping pinnae. Large specimens of B. minganense may have pinnae with 1 or more shallow incisions.
In Minnesota, B. lunaria appears to prefer open habitats such as gravelly banks, rocky ledges, and talus. It has also been found in open, sparsely vegetated habitats with grasses and scattered shrubs. Along the shore of Lake Superior, B. lunaria has been found in fire-dependent forests among mosses and lichens. Botrychium lunaria grows singly, but may occur in groups of up to 20 or more plants. Some areas apparently have a history of logging and fire.
Biology / Life History
The classification of B. lunaria has been revised many times. Wagner and Wagner (1993) contend that this species has a notably uniform morphology but does occasionally hybridize with other Botrychium species. Typically, one leaf emerges per year in spring, dying in the latter half of summer after releasing spores. However, an individual plant may not appear aboveground for one or more years, possibly due to stress such as drought. It is not unusual for B. lunaria populations to fluctuate without determinable cause (U.S. Forest Service 1999).
Conservation / Management
Botrychium lunaria is small, difficult to find, and it may be easily overlooked. In addition, it is often challenging to determine what factor or combination of factors is impacting Botrychium populations. Potential threats to populations include drought, fire, timber harvesting, herbicides, herbivory, non-native earthworms, and vegetation succession. Many of these activities have been shown to be detrimental to the aboveground portion of the plant, but the effects are unknown on the belowground structures and the population as a whole (U.S. Forest Service 1999).
Conservation Efforts in Minnesota
No conservation actions on behalf of B. lunaria have been taken to date.
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 lunaria. 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 lunaria. 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.