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Introduction. Physcomitrium eurystomum is rare in Europe and threatened with extinction. This study investigates its status and ecology in Britain. Methods. A detailed search was made for P. eurystomum at all sites where it has been reported in Britain, plus four other locations nearby. Geographic coordinates of colonies were recorded with GPS units and used to derive counts of occupied Ordnance Survey (OS) grid cells at resolutions of 1, 10 and 100 m. DNA barcoding was used to help identify non-fruiting plants. Habitat and community composition were recorded by relevés. Results. In this study Physcomitrium eurystomum was found at five locations, one in Hertfordshire and four in West Norfolk, and occupied 109 OS 1 m grid cells. A small pond in West Norfolk (Wicken Pond) supported the majority (61%) of the population. DNA barcoding helped confirm its occurrence at Wilstone Reservoir (Hertfordshire), at which it was thought extinct. The moss occured exclusively within the drawdown zone of seasonally fluctuating freshwater bodies, both natural and artificial. Vegetation was dominated by vascular plants, most frequently Agrostis stolonifera, Persicaria lapathifolia, Ranunculus sceleratus, Rorippa palustris and Stellaria aquatica. Soil pH varied from strongly acidic to slightly alkaline. Conclusions. Unsuccessful searches of five sites with historic records raises concern for the species. The significant importance of Wicken Pond has not been recognised previously and suggests statutory protection of the site is warranted. The non-native and invasive Crassula helmsii is a major risk to P. eurystomum at sites in Britain and elsewhere in Europe. 

The relative contribution of bryophytes to plant diversity, primary productivity, and ecosystem functioning increases towards colder climates. Bryophytes respond to environmental changes at the species level, but because bryophyte species are relatively difficult to identify, they are often lumped into one functional group. Consequently, bryophyte function remains poorly resolved. Here, we explore how higher resolution of bryophyte functional diversity can be encouraged and implemented in tundra ecological studies. We briefly review previous bryophyte functional classifications and the roles of bryophytes in tundra ecosystems and their susceptibility to environmental change. Based on shoot morphology and colony organization, we then propose twelve easily distinguishable bryophyte functional groups. To illustrate how bryophyte functional groups can help elucidate variation in bryophyte effects and responses, we compiled existing data on water holding capacity, a key bryophyte trait. Although plant functional groups can mask potentially high interspecific and intraspecific variability, we found better separation of bryophyte functional group means compared with previous grouping systems regarding water holding capacity. This suggests that our bryophyte functional groups truly represent variation in the functional roles of bryophytes in tundra ecosystems. Lastly, we provide recommendations to improve the monitoring of bryophyte community changes in tundra study sites.