Buxbaumia aphylla Hedw.
Basis for Listing
Buxbaumia aphylla (bug-on-a-stick moss) has a nearly continuous world distribution of temperate affinity. It has been recorded regionally from Ontario, Iowa, Wisconsin, and the Upper Peninsula of Michigan. In Minnesota, only two populations have been found, one in The Blufflands of Winona County and the other from the Border Lakes Subsection of St. Louis County. The species occurs as a pioneering colonist on disturbed soils or old logs in hardwood forests at the edge of creeks. Because only two populations have been documented in Minnesota, there is too little information available to detect a statewide population trend at this time (Janssens 2005). Further survey work is needed to better define the species’ distribution and specific habitat needs in Minnesota. Based on its apparent rarity, Buxbaumia aphylla was designated special concern in 2013.
Buxbaumia aphylla is truly distinct in appearance, with its disproportionately large inclined capsules appearing like lentils on a stalk earning it the name “bug-on-a-stick.” It looks more like a fungus than a true moss (McKnight et al. 2013), having essentially no green leafy parts or with only a few reduced leaves at the base of the capsule stalk. Instead, the gametophyte (the sexual phase in the life cycle of mosses that is typically the green leafy plant) is almost entirely protonema, a mat of brown and green algal-like threads that are produced from germinating spores. These brown thread-like protonema blend in with the soil, making them difficult to see at first glance. The capsules are somewhat egg-shaped, 3.0-6.0 mm (0.1-0.2 in.) long, and are bright green when young, turning a shiny copper when mature. The capsule also has a pointed beak that is often ringed by dark red. The seta (stalk of capsule), which is 4.0-11.0 mm (0.2-0.4 in.) tall, is also purplish to red. There are no other species that have similar capsules; and since the leaves are so minute, they are not likely to be noticed on their own (McKnight et al. 2013).
This species is a pioneer on disturbed sandy or clayey soil and has been reported to occur on sites that have experienced fire in the recent past (Crum and Anderson 1981). However, it is a poor competitor, which may explain why plants are sometimes not relocated in subsequent searches. Across its range, B. aphylla has been found on decaying wood, humus, shallow acid soil, and soil depressions on rock outcrops in partially shaded to open sites (Schofield 2007). In Minnesota, it has been found in two very different habitats, one being on a wooded bluff in Winona County and the other on the forest floor in a mesic hardwood forest in St. Louis County.
Biology / Life History
The name of the species refers to the essentially leafless state of the gametophyte (Crum and Anderson 1981). The flat-topped capsules are inclined at a 45–90 degree angle, facing the direction of maximum sunlight. Raindrops striking the capsules help expel spores, which are largely shed from May through July (McKnight et al. 2013). Photosynthesis is primarily restricted to the persistent protonema and immature green capsules, which may be associated with cyanobacteria and mycorrhizal fungi (Christy 2006).
One factor that may be contributing to the impression of scarcity of this plant is the short season of the visibility of the genus. In California, Buxbaumia capsules are quickly reduced to the naked seta due to what is presumed to be mouse predation (Jepson Flora Project 2016). Plants are also ephemeral, documented as appearing up to 15 years after fire or disturbance, then disappearing after a few seasons as competition from invading plants increases.
Conservation / Management
Despite its pioneer status on soil and decayed wood, populations are usually small, discontinuous, and subject to disappearance (Christy 2006). Threats may include fire, or essentially any type of disturbance that may open the canopy during the early stages of forest succession or growth, since the species does not compete well with other vascular plants.
Best Time to Search
The best time to search for Buxbaumia aphylla is from May through September, or essentially anytime the ground is not covered by snow. That said, new bright green capsules begin to appear during winter, allowing for an early start to searching once the snow begins to melt.
Erika R. Rowe (MNDNR), 2018
(Note: all content ©MNDNR)
References and Additional Information
Christy, J. A. 2006. Species fact sheet for bug-on-a-stick moss (Buxbaumia aphylla). U.S. Forest Service, Pacific Northwest Region (Reg. 6), Portland, Oregon.
Crum, H. A., and L. E. Anderson. 1981. Mosses of eastern North America. In two volumes. Columbia University Press, New York, Yew York. 1330 pp.
Flora of North America Editorial Committee, editors. 2007. Flora of North America north of Mexico. Volume 27, Bryophytes: Mosses, Part 1. Oxford University Press, New York, New York. 734 pp.
Hancock, J. A., and G. R. Brassard. 1974. Phenology, sporophyte production, and life history of Buxbaumia aphylla in Newfoudland, Canada. The Bryologist 77(4):501-513.
Janssens, J. A. 2005. Proposed candidates of endangered, threatened, and special concern species of bryophytes for Minnesota: update June 2005. Report to the Minnesota Department of Natural Resoucres, County Biological Survey, St. Paul. 18 pp.
Janssens, J. A. 2009. MS Access database on Minnesota bryophytes. Lambda-Max Ecological Research, Minneapolis, Minnesota.
Jepson Flora Project (eds.). 2016. Jepson eFlora [web application]. Jepson Herbarium, University of California, Berkeley. <http://ucjeps.berkeley.edu/IJM.html>. Accessed 29 September 2016.
McKnight, K. B., J. R. Rohrer, K. McKnight-Ward, and W. J. Perdrizet. 2013. Common mosses of the Northeast and Appalachians. Princeton University Press, Princeton, New Jersey. 392 pp.
Minnesota Department of Natural Resources. 2003. Field guide to the native plant communities of Minnesota: the Laurentian mixed forest province. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 352 pp.
Minnesota Department of Natural Resources. 2005. Field guide to the native plant communities of Minnesota: the eastern broadleaf forest province. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 394 pp.
NatureServe. 2009. NatureServe Explorer: an online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. <http.//www.natureserve.org/explorer>. Accessed 10 June 2009.
Schofield, W. B. 2007. Buxbaumiaceae. Pages 118-120 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 27, Bryophytes: Mosses, Part 1. Oxford University Press, New York, New York.