Rare Species Guide

  Synonyms

Botrychium simplex var. compositum, Botrychium simplex var. tenebrosum, Botrychium simplex var. simplex

  Basis for Listing

There are three varieties of Botrychium simplex in Minnesota. Botrychium simplex var. simplex is probably the most common and widespread of the three. It appears to be adapted to a wide variety of habitats and occurs at scattered locations across the northern half of the state. Botrychium simplex var. tenebrosum is probably the least common and the one most likely to warrant recognition as a distinct species (Farrar 2006). It also appears to be the most habitat-specific of the three, and the one that is most likely in need of conservation consideration. It appears to occur over a much smaller range in the north central part of the state. The third entity is B. simplex var. compositum, which is poorly known in Minnesota. It apparently occurs in the northwestern prairie counties, though too little is currently known about it to evaluate its status. Botrychium simplex (at the full species level) was listed as a special concern species in Minnesota in 1996.

  Description

Like all the moonworts (Botrychium subgenus Botrychium), B. simplex is a small, inconspicuous fern that can be easily overlooked. All that is seen above ground is a single leaf divided into a sterile portion and a fertile spore-bearing portion. The shape of the sterile portion is diagnostic for Botrychiums. The sterile portion of Botrychium simplex is quite variable, which has led to the naming of several taxonomic varieties and forms. It can be simple (undivided) or 2 - 3 pinnate, linear to ovate-oblong to oblong to fully triangular in shape, and up to 7 cm (2.8 in.) long and 0.2 cm (0.08 in.) wide; the texture is fleshy to thin, papery or herbaceous. There can be up to 7 pairs of well-developed lobes. The basal pair of lobes are commonly much larger and more complex than the adjacent pair, and they are cuneate to fan-shaped. The margins are usually entire and the apex is usually rounded, undivided or divided. Positive identification will likely require the aid of a specialist who has experience with this species. In every case, a leaf specimen will need to be collected, carefully pressed, and dried. Photographs are not adequate.

  Habitat

Botrychium simplex var. simplex occurs primarily in open sites, including prairies, wetlands, and abandoned mine sites. Botrychium simplex var. tenebrosum prefers forest interiors, especially low and moist spots in mesic hardwood forests. Botrychium simplex var. compositum appears to be a prairie species, at least in Minnesota, though it is the least well understood of the three varieties.

  Biology / Life History

Botrychium simplex is a small, perennial fern that produces a single leaf each year. Reproduction is accomplished by the production and dispersal of spores. The spores are dust-like in size and designed to be carried on wind currents. Although it is entirely possible that the spores can be carried great distances, most travel no more than a few feet. Most plant species are now believed to have a symbiotic relationship with soil fungi, however species of the genus Botrychium are thought to rely on this relationship more than most. That being the case, the health and condition of the soil fungal community may have a greater role in maintaining populations of Botrychium species than factors occurring above ground. It is possible that fungi may supply water, minerals, and even fixed carbon to individual Botrychium plants in times of drought or other environmental stress.

Mature sporangia are not needed to confirm the identification of B. simplex, so searches can be conducted anytime in July and August.

  Conservation / Management

At this time, it appears that B. simplex var. tenebrosum may be the only one of the three varieties in Minnesota that may need special management consideration. It is not certain, but it seems to occur primarily in stable, late successional forests that have an intact tree canopy and a diverse, healthy community of herbaceous species.

  Conservation Efforts in Minnesota

No known conservation efforts have been directed towards this species in Minnesota.

  References and Additional Information

Chadde, S., and G. Kudray. 2003. Conservation assessment for Least Moonwort (Botrychium simplex). U.S. Forest Service, Eastern Region, Milwaukee, Wisconsin. Accessed 16 September 2009.

Farrar, D. R. 2006. Moonwort (Botrychium) Systematics. . Accessed 13 Apr 2009.

Farrar, D. R. 2006. Systematics of moonworts Botrychium subgenus Botrychium. . Accessed 09 Mar 2009.

Smith, W. R. 2023. Ferns and lycophytes of Minnesota: the complete guide to species identification. University of Minnesota Press, Minneapolis. 368 pp.

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, New York.