Physcomitrium readeri

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Identification notes

This little moss caused quite a stir when molecular analysis of a population collected from a Yorkshire reservoir confirmed it new to Europe (as Ephemerella readeri). Its publication, in 2010, came too late for inclusion in the second edition of Smith’s moss flora or the first edition of the Field Guide and so many bryologists are probably unaware of it.

It’s a species of barish silt on reservoir margins and can sometimes grow in great profusion when conditions are favourable. There is growing anecdotal evidence that it favours lower reservoir margins that are only exposed during exceptionally dry summers. Like other species of Physcomitrium, it is an opportunist with a very short life-cycle. In appearance, it most closely resembles the common P. patens, but it is a smaller plant and, when capsules are mature, they differ in being dark brown to black. They are borne on a short seta, which raises them slightly above the plant. Its leaves are particularly distinctive: they are widest above the middle and so look spathulate or obovate with a short apiculus. Margins have very large and obvious teeth above.

Distribution in Great Britain and Ireland

It remains a very rare plant in Britain, but since its discovery, P. readeri has been found at a few sites as far apart as Yorkshire, Cornwall and Sussex. The extreme summer of 2022 and the exceptionally low water levels of many reservoirs has led to the discovery of a number of new populations.

View distribution from the BBS Atlas 2014

Resources you may find useful

E.J. Hooper, J.G. Duckett, A.C. Cuming, W.E. Kunin and S. Pressel. 2010. Ephemerella readeri Müll.Hal. (Physcomtrella readeri (Müll.Hal) I.G. Stone & G.A.M. Scott, Funariidae, Bryophyta): a genus and species new to Europe. Journal of Bryology 32: 256-264

This paper describes the discovery, new to Europe, of Ephemerella (now Physcomitrium) readeri at a Yorkshire reservoir.



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