ABSTRACT
Introduction.
Initial morphometric investigations into the differences between Leucobryum glaucum (Hedw.) Ångstr. and L. juniperoideum (Brid.) Müll.Hal. in Britain showed that some populations could not be clearly assigned to either species. An intensive morphological and molecular study was therefore undertaken to understand the diagnostic characters of the European species of the genus, including L. albidum (Brid. ex P.Beauv.) Lindb., whose reported presence in Europe was surrounded by uncertainty. There has been little agreement among previous authors on the relative taxonomic importance of the different morphological characters, or on their metrics.
Methods.
Molecular sequencing using nuclear and chloroplast markers, in conjunction with previously accessioned data, allowed judgement of the taxonomic importance of various methods for morphological discrimination. These methods included both existing published techniques and newly discovered diagnostic characters. This integrated process was cyclical, the morphological analysis being directed and confirmed by the sequencing of selected specimens.
Results and discussion.
Data are presented demonstrating the correlation between molecular identification and certain morphological characters in the three European species of Leucobryum. Leucobryum albidum is confirmed as a locally frequent member of the British flora and it is also shown to be present in Ireland and western part of continental Europe. Leucocyst pore morphology is described and its value as a diagnostic character is discussed. An identification key is provided for the three species. Plants from two sites are shown to have a discordance between nuclear and plastid molecular markers and we consider the possibility that horizontal gene transfer could explain the observed patterns.
Acknowledgements
Many BBS members are thanked for supplying specimens or in other ways: Astrid Biddle, Sam Bosanquet, Des Callaghan, Jeff Duckett, Anne Haden, Claire Halpin, Jan Hendey, Jacqui Hutson, Roy Jeffery, Stephen Lemon, Howard Matcham, Sean O’Leary, John Norton, Sharon Pilkington, Ron Porley, Sue Rubinstein, Brad Scott, Barry Stewart, Matt Sutton and Malcolm Watling. Tim Blackstock lent numerous specimens that he had used in his 1987 work on male plants. Claire Halpin and Sue Rubinstein are also thanked for testing morphological methods. Robert Vogt, curator at B (Berlin) herbarium, and colleagues are thanked for their assistance with the loan of type specimens of Leucobryum juniperoideum and L. albidum; Gareth Griffith, the curator of the ABS herbarium in Aberystwyth University kindly requested the loans and made available laboratory facilities for their study. Katherine Slade is thanked for organising the loan of numerous specimens of Leucobryum from BBSUK and NMW, both sited at the National Museum Wales, Cardiff. Neil Bell, David Long and staff at RBGE are thanked for the loan of specimens from E. Len Ellis helped with a specimen of L. glaucum from Greece held in BM. Neil Bell is also thanked for helpful discussions concerning incongruence. Peter Erzberger prompted us to investigate what we term here transverse pores as a means of separating L. glaucum from L. juniperoideum. Brad Scott’s expert help is acknowledged in deciphering the label on the Tenerife type specimen of L. juniperoideum and tracking down the associated historical detail. Rosalina Gabriel helped with information regarding the status of L. albidum in the Azores and sent specimens of it from the island of Terceira. Manuela Sim-Sim and Ron Porley are thanked for sending specimens of L. juniperoideum from Madeira. From America, specimens were sent by Blanka Aguero (NC), Barbara Andreas (OH) and John Brinda (GA, PA, MO, NC, OH). Alžběta Manukjanová undertook much of the laboratory work in the plant molecular laboratory of the Faculty of Science, University of South Bohemia. T.W.O. was fortunate enough to be able to discuss several aspects of the work with Arthur Chater over coffee in Aberystwyth.
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No potential conflicts of interest were reported by the authors.
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Notes on contributors
Tom Ottley
Tom Ottley is the Cardiganshire recorder of Bryophytes for the BBS with wider interests in taxonomy. Before moving to Wales, he discovered Pterygoneurum papillosum in Sussex, new to Britain, and has written on the taxonomy of Racomitrium obtusum. More recently he made the surprising discovery of the mainly tropical and subtropical Bryoerythrophyllum campylocarpum in Wales.
Jan Kučera
Jan Kučera is an associate professor at the Department of Botany of the Faculty of Science, University of South Bohemia in the Czech Republic. His main research activities are taxonomy and molecular phylogeny of mosses, particularly of the haplolepidous family Pottiaceae but recently he has also started several projects in pleurocarpous mosses. He is further actively pursuing the biology of rare bryophytes and local bryofloristic research.
Tom Blockeel
Tom Blockeel read Classical History and Literature at Oxford University where he graduated in 1972. He is an independent researcher with a lifelong interest in bryophytes, especially concerning taxonomy and floristics. In addition to his studies on the British and Irish flora, he has explored many parts of Greece and published widely on the bryophytes of that country.
Jacky Langton
Jacky Langton read Botany at Durham University, graduating in 1965. She obtained an M.Sc. in Biological Recording at Manchester Metropolitan University in 2016; her dissertation compared the morphology of Leucobryum glaucum and L. juniperoideum.