Population status and ecology of Philonotis marchica (Hedw.) Brid. in Britain

ABSTRACT Introduction The moss Philonotis marchica (Hedw.) Brid. is rare in Europe and threatened with extinction. In this study, its status and ecology in Britain were investigated. Methods Surveys were carried out at all sites from which Philonotis marchica has been reported in Britain since 1859, together with further locations nearby. Geographical coordinates of colonies were recorded with a GPS unit and used to derive counts of occupied Ordnance Survey grid cells at resolutions of 1, 10 and 100 m. The habitat and community composition of relevés were recorded. Key results Philonotis marchica was found at two closely located sites on the Isle of Wight, occupying a total of 32 1 m grid cells. It was not refound at the only other previously known location in Britain, which is in Yorkshire. The species was found exclusively within perennial seepages (pH 7.4–7.6) over steep sandstone rock, where vascular plants are sparse and the most frequent bryophyte associates include Didymodon tophaceus (Brid.) Lisa, Pellia endiviifolia (Dicks.) Dumort. and Pohlia melanodon (Brid.) A.J.Shaw. Sporophytes of P. marchica in Britain have never been reported and populations seem to comprise only females. Axillary bulbils, produced abundantly, are probably of key importance for local dispersal and population maintenance. Conclusions Philonotis marchica appears to have become extinct in Yorkshire and has undergone a historical decline at Shanklin Chine, Isle of Wight. The population at Lake Cliffs, Isle of Wight, appears to be secure and deserves statutory protection given its key importance for the future survival of P. marchica in Britain.