ABSTRACT 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.

中文翻译：

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发作性苔藓 Physcomitrium eurystomum Sendtn 的种群状况和生态学。在英国

摘要介绍。Physcomitrium eurystomum 在欧洲很罕见，并面临灭绝的威胁。这项研究调查了它在英国的现状和生态。方法。在英国报告的所有地点以及附近的其他四个地点对 P. eurystomum 进行了详细搜索。殖民地的地理坐标用 GPS 单位记录，并用于以 1、10 和 100 m 的分辨率导出被占用的军械测量 (OS) 网格单元的计数。DNA 条形码用于帮助识别非结果植物。栖息地和社区组成由相关记录。结果。在这项研究中，Physcomitrium eurystomum 在五个地点被发现，一个在赫特福德郡，四个在西诺福克，占据了 109 个 OS 1 m 网格单元。西诺福克 (Wicken Pond) 的一个小池塘养活了大多数 (61%) 的人口。DNA 条形码有助于确认它在威尔斯通水库（赫特福德郡）的发生，在那里它被认为已经灭绝。苔藓仅出现在季节性波动的天然和人工淡水水体的下降带内。植被以维管植物为主，最常见的是 Agrostis stolonifera、Persicaria lapathifolia、Ranunculus sceleratus、Rorippa palustris 和 Stellaria Aquatica。土壤pH值从强酸性到弱碱性不等。结论。对五个具有历史记录的地点的搜索失败引起了对该物种的关注。Wicken Pond 的重要性以前没有得到认可，这表明该场地的法定保护是有必要的。在英国和欧洲其他地方，非本地和侵入性的 Crassula helmsii 是 P. eurystomum 的主要风险。