Selaginella selaginoides (L.) Link
Basis for Listing
This small moss-like plant has widespread distribution in arctic and boreal regions, as well as montane and sub-alpine regions of the western U.S. It also has an isolated southern range around the upper Great Lakes. In Minnesota, Selaginella selaginoides (northern spikemoss) has been found only in association with the shore of Lake Superior (North Shore Highlands), specifically on the prominent outcrops of bedrock that are scattered along the shore and near-shore islands rather than on the gravelly or boulder-strewn beaches. It was discovered in Minnesota near Grand Marais in Cook County by the L. S. Cheney expedition in 1891. It was subsequently found in the Susie Islands, an archipelago of small near-shore islands in Cook County. In 2019, a small population (three plants) was found in a similar habitat in Lake County. The small size of S. selaginoides and its superficial resemblance to the mosses with which it grows makes it very difficult to find. In fact, several of the specimens previously collected were found by bryologists while searching for mosses. The rocky habitat of this species is not threatened with destruction, though the delicate vegetation on the rocks is vulnerable to damage in areas of heavy recreational use, such as Grand Marais. It is the natural rarity of the species and the specificity of its habitat requirements that form the basis of concern. Selaginella selaginoides was listed as an endangered species in Minnesota in 1996.
Distinguishing this species from the nonvascular mosses with which it commonly grows is a difficult task for anyone not thoroughly familiar with the morphology of spikemosses (Selaginellaceae). Selaginella selaginoides plants are very small, rarely more than 4-5 cm (13-16 in.) high, barely, if at all high enough to reach above the mosses. Their sterile branches are weak, thin, creeping on the substrate (though not rooting), and often forming small delicate mats. Leaves are uniform, lance-shaped, with a few hairs along the margins, and they gradually taper to a tip. There is no bristle at the tip of the leaf. The fertile branches are erect and have similar leaves, but the upper ones are somewhat larger and bear the sporangia (spore containing cases). Spore cones are cylindrical rather than square. The presence of spore-bearing cones is the most obvious means of separating this species from mosses (Cobb 1984; Lellinger 1985; Kershaw et al. 1998).
This species occurs in moist crevices on the exposed shore rocks of Lake Superior. These crevices are typically vegetated with Trichophorum cespitosum (tufted bulrush), Carex spp. (sedges), and various mosses. The roots of these species create a mat that holds moisture and supports S. selaginoides. These vegetation mats typically develop at the margins of shore pools or in rock crevices just above the line of normal wave action.
Biology / Life History
Spikemosses are considered lycophytes, distant relatives of the ferns. Like the ferns, S. selaginoides produces spores in spore cones and have two distinct generations – sporophyte and gametophyte. The spores, which are either male or female, germinate on a moist substrate and develop into gametophytes. These are small short-lived scale-like plants that are seldom seen. When the female gametophyte is fertilized it forms a new sporophytic plant, which is the plant we see. This sporophytic plant produces spores, which completes the cycle. The spores are dispersed by wind currents, though dispersal is probably limited to a few meters in most cases. It is unlikely that the spores or the gametophytes can remain dormant in the environment for extended periods of time, so a sampling of the more easily seen sporophytes may give a reasonable estimation of the status of the population.
Conservation / Management
Established populations of S. selaginoides along the north shore of Lake Superior in Minnesota exist under very severe environmental conditions. They are exposed to direct impacts of heavy rains and high winds in the summer and cold temperatures and potential ice-scouring in the winter. They appear supremely adapted to survive under such conditions, though exactly how they do this is uncertain. However, impacts to S. selaginoides and shoreline vegetation that are caused by heavy recreational use and housing/commercial development are a different matter. Such impacts can irreversibly alter the essential biological character of the habitat. Hence, shoreline protection is vital.
Best Time to Search
Searches for Selaginella selaginoides can be conducted from about midsummer through autumn when the spore-producing cones are present.
Conservation Efforts in Minnesota
Three populations of S. selaginoides are located on three islands in the Susie Island archipelago in Lake Superior. These islands have been returned to the Grand Portage Band of Lake Superior Chippewa. The Band has zoned the islands for ‘preservation’, a designation that exists to sustain areas with historical, cultural, religious, geographic or environmental significance to the ‘The People’ of Grand Portage. Human impact on the islands will be kept to a minimum (MPR 2017).
Welby R. Smith (MNDNR), 2021
(Note: all content ©MNDNR)
References and Additional Information
Kershaw, L. J., A. MacKinnon, and J. Pojar. 2017. Plants of the Rocky Mountains. Second edition. Partners Publishing, Howell, New Jersey. 384 pp.
Lellinger, D. B. 1985. A field manual of the ferns and fern-allies of the United States & Canada. Smithsonian Institution Press, Washington, D.C. 389 pp.
MPR News Staff. 2017. Lake Superior island returned to Grand Portage tribe. MPR News. 21 September 2017; Morning Edition. <https://www.mprnews.org/story/2017/09/21/susie-island-change-hands>.
Smith, W. R. 2023. Ferns and lycophytes of Minnesota: the complete guide to species identification. University of Minnesota Press, Minneapolis. 368 pp.
Valdespino, I. A. 1993. Selaginellaceae. Pages 38-63 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 2. Oxford University Press, New York, New York.