Meesia uliginosa Hedw.
Basis for Listing
Meesia uliginosa (swan moss) has a nearly continuous distribution in the northern hemisphere, with subarctic and boreal affinity. It has been recorded regionally from Ontario, Manitoba, Wisconsin, and the Upper Peninsula of Michigan. In Minnesota, two populations have been found, one in Roseau County and the other from Koochiching County, both from large patterned peatland communities (Northern Minnesota & Ontario Peatland Section). Meesia uliginosa is an excellent but rare indicator of calcareous fens and swamps. Because only two populations have been documented in Minnesota, there is too little information available to detect a statewide population trend at this time. Further survey work is needed to clarify the species’ distribution in Minnesota as well as potential threats to its survival. Based on its apparent rarity, Meesia uliginosa was designated a species of special concern in 2013.
Meesia uliginosa is an erect plant,1.0-3.0 cm (0.4-1.2 in.) tall, often forming dense green to yellowish green tufts. Stems can be branched or unbranched. The leaves of this species are erect when moist and often contorted when dry, 2.0-4.0 mm (0.08-0.16 in.) long, and have a distinctly narrow linear-ligulate shape, with an apex that is obtuse to rounded (Crum and Anderson 1981; Vitt 2007; Favreau and Brassard 2011). Margins of leaves are entire and strongly revolute, at least in the lower half. The costa (midrib) is wide, ending just before the apex. Setae (stalk) are usually quite long, ranging from 1.5 to 5.0 cm (0.6-2.0 in.), supporting a yellowish-brown capsule that is 1.8-2.5 mm (0.07-0.10 in.) long (Vitt 2007; Favreau and Brassard 2011). Meesia uliginosa is similar to M. triquetra (meesia moss), which also occurs in Minnesota; however, M. triquetra has leaves that are arranged in 3 longitudinal ranks along the stems, are ovate-lanceolate with acute apices, spreading to squarrose when wet, with margins plane or recurved only near the middle and serrate or serrulate nearly to the base, and the costa only extends to about 1/4 of the leaf base (Crum and Anderson 1981; Christy 2007).
Across its range, M. uliginosa occurs on wet soil or peaty humus, rarely on logs, in calcareous habitats, rich fens, and cedar swamps; it also occasionally occurs on sandy margins of beach pools or in the wet crevices of limestone cliffs (Crum and Anderson 1981; Vitt 2007). This species is much more common in the Arctic, from Greenland to Alaska. In Minnesota, it has been found in northern rich spruce swamp adjacent to spring fen channels dominated by calcareous groundwater as well as in a rich black spruce-cedar swamp.
Biology / Life History
Meesia uliginosa is usually dioicous (male and female reproductive organs are on separate plants) and sometimes autoicous (male and female reproductive organs in separate inflorescences on the same plant). The name "uliginosa" refers to a swampy or marshy habitat (Crum and Anderson 1981).
Conservation / Management
Meesia uliginosa has a short life cycle; therefore, any existing populations will be vulnerable to local extinction (Janssens 2005). Changes to the hydrology of these wetlands and bogs could result in the loss of suitable habitat for M. uliginosa. Wetland habitats are often impacted by water diversion, water impoundment, drainage projects, road construction, and commercial harvest of peat and sphagnum moss (Christy 2007). Changes in water regime, nutrient inputs, and succession can lead to the disappearance of fen communities and species such as M. uliginosa.
Best Time to Search
The best time to search for M. uliginosa is from May through September, essentially anytime the ground is not covered by snow or the wetlands in which it might occur are not saturated by high spring water tables.
Erika R. Rowe (MNDNR), 2018
(Note: all content ©MNDNR)