Schistostega pennata (Hedw.) Web. & Mohr
Gymnostomum pennatum, Schistostega osmundacea, Schistostega pennata, Schistostegia pennata
Basis for Listing
Schistostega pennata has a widespread, circumboreal distribution, but is rare and scattered throughout its range (Schofield 1992). In North America it appears to be amphi-continental; near Minnesota it is recorded from Ontario, Wisconsin, and Michigan (Harpel 2007; Janssens 2010). To date, there are only two collections of S. pennata from Minnesota. In 1975, Frank D. Bowers collected specimens from a few small populations in the Kadunce River State Wayside about 19 km (12 mi.) north of Grand Marais in Cook County. In 1994, Cal C. Harth collected specimens from a significant population on the south shore of Lake Four in northern Lake County. Notwithstanding extensive searching for this very characteristic moss at many suitable sites since 1981 and during several years with supposedly optimal climate conditions, no other populations except the 1994 discovery have been found. Given its extreme local rarity, S. pennata was listed as an endangered species in Minnesota in 1984.
When growing in dimly lit habitats, S. pennata is distinguished by its peculiar, luminous protonemata (juvenile, filamentous stage of the gametophyte developed immediately after spore germination). This characteristic is the origin of it common names "luminous moss" and "goblin gold" (Crum and Anderson 1981; Glime 1993; Crum 2004). The protonemata are persistent in S. pennata and brood bodies are produced along the edge of conidia-like clusters of the vesiculose cells (Crum and Anderson 1981; Crum 2004; Harpel 2007). Mature plants, which are 4-7 mm (0.16-0.28 in.) high, often with naked stems below, have a peculiar leaf insertion, appearing feathery or fern-like (distichous-complanate). The ecostate and indistinctly bordered leaves, which are 0.7-1.2 mm (0.03-0.05 in.) with a 1/2 phyllotaxy, are reoriented and inserted vertically on stems. The bases of adjacent leaves are confluent. The 2-5 mm (0.08-0.20 in.) long sporophytes produced on somewhat diminutive female plants (note that both Minnesota specimens appear to be sterile) have a small, 0.4-0.5 mm (0.016-0.020 in.) high, subglobose or ovoid capsule without annulus or peristome.
Protonemata and mature plants are found in humid habitats such as caves, among boulders, between tree roots, and in cavities created by uprooted trees. One of the two Minnesota populations was found on a cliff face, probably rhyolite or icelandite, near the Lake Superior shore in the North Shore Highlands ecological subsection. The other was found inland in the Border Lakes ecological subsection. This large population, about 1 m² (11 ft.²), was located at the base of a cave-like split in an outcrop of anorthositic gabbro, on moist duff. It is not clear if S. pennata is a calciphobe (see Kanda (1972) and compare Crum and Anderson (1981) and Crum (2004) with Glime (1993)).
Biology / Life History
Schistostega pennata has a short life cycle and likely disappears during drought years. The persistent protonemata, as mentioned above, consist of beads of lens-shaped cells in thread-like filaments. The parabolic inner surface of each cell focuses the dim light that falls into the cave onto the chloroplasts in the back of the cell. The light is then reflected unidirectionally back from this area, resulting in a greenish glow emitted by the cell masses. For interested readers, excellent microphotography appears in some Japanese papers, such as in Johnson (1926); Kobayabi and Watari (1935); and in Kanda (1972). All collections mention dimly lit habitats. Schistostega pennata appears to be well-loved in Japan (Glime 1993) with an opera as well as a monument dedicated to it!
Conservation / Management
Schistostega pennata is rarely found in Minnesota, where it is most likely at the edge of its eastern range in North America. Despite recent searches, the original Cook County population has not been successfully relocated. Recent evidence suggests that once a population is established, it may easily expand locally if a suitable moist climatic situation persists for some years. However, the species is then so obvious and unique that it is vulnerable to extirpation by avid collectors (J. Janssens, pers. comm). Climate change may also threaten the species' viability in Minnesota since the loss of moist, shaded habitat conditions would likely decimate the species.
Conservation Efforts in Minnesota
Besides its listing as an endangered species, no known conservation efforts have been taken to protect S. pennata in Minnesota.