About Splachnum rubrum Hedw.
Splachnum rubrum Hedw. forms tufts of varying density that grow on herbivore dung. Its gametophyte is green to yellow-green, with leaves clustered at the apex of a stem that typically measures 1.5 to 3.0 cm long. Individual leaves are 5–7.5 mm long, shaped obovate or acuminated, and have a costa that disappears in the apical lamina. Leaf margins are coarsely toothed. The sporophyte is the plant's most conspicuous part, and it is often mistaken for an angiosperm flower due to its shape and coloration. Its capsule is orange-brown, with a bright magenta, umbrella-shaped hypophysis, and it sits on a long, straight, orange-red seta that measures 5–13 cm long. Splachnum rubrum develops its characteristic form in summer, when its sporangium matures. In spring, its immature sporophytes may be confused with mature sporophytes of Splachnum sphaericum or immature sporophytes of Splachnum ampullaceum. When mature, this species can be easily distinguished from Splachnum luteum by its coloration. This species occurs mostly in swamps and muskeg, and it is very rare. It is the least common Splachnum species in North America, where it is found in boreal regions of Canada stretching from Newfoundland and Labrador to northern British Columbia and Alaska. A small number of specimens have also been observed in the Midwestern United States. In Eurasia, it occurs in Northern Europe, Estonia, and Siberia. It is classified as imperiled (S2) in Ontario and Alberta, and critically imperiled (S1) in Minnesota and Nova Scotia. Splachnum rubrum grows only on the dung of large herbivores; in North America it grows mainly on moose dung, while in Europe it also grows on cattle dung. In North America, S. rubrum is likely absent outside of the native moose range, so the decline of moose populations may further imperil this species. S. rubrum is an entomophilous species, meaning it disperses its spores with the help of insects. Dipterans are attracted to the dung this moss grows on, as they use it as a site to find mates and lay eggs. When a fly lands on the dung, it contacts mature capsules, and spores attach to the fly's body. The fly then carries these spores to another patch of dung, facilitating spore dispersal. The main spore dispersers are flies from the genera Scathophagaidae, Delia, Myospila and Pyrellia, which reproduce in early summer when S. rubrum's sporophytes mature.
