Typification and diagnosis of Weissia × mittenii (Bruch & Schimp.) Mitt. emend. A.J.E.Sm. (Weissia multicapsularis × W. rostellata) (Pottiaceae, Bryophyta)

ABSTRACT

Introduction. Weissia × mittenii (Bruch & Schimp.) Mitt. emend. A.J.E.Sm. (Weissia multicapsularis × W. rostellata) has only been reported from five localities globally, all in south-east England, and was last found in 1920. The purpose of this paper is to typify the name W. × mittenii, provide a description of this hybrid taxon and clarify its diagnostic features.

Methods. The main British herbaria were consulted, as well as the herbarium of William Mitten (NY). Variation in morphological traits across specimens was reviewed and compared with related species.

Results. A lectotype and syntypes are designated, and a description and diagnosis provided.

Conclusions. The key feature that characterises Weissia × mittenii is large variation in spore size in a single capsule, a range of 5–28 μm vs. 3–5 μm in similar species. Other characters of the gametophyte and sporophyte can also help identification. Further work is needed to confidently determine parentage.

KEYWORDS:

• hybrid
• moss
• spore size

Acknowledgements

Many thanks indeed to Len Ellis (BM), who very kindly provided much invaluable help. Thanks also to Tom Blockeel, Bill Buck (NY), Jeff Duckett, Janice Glime, Serena Marner (OXF), Oliver Pescott, Sally Rae (E) and Kath Slade (NMW) for various kind assistance.

Notes on contributor

Des Callaghan is a consultant bryologist operating under Bryophyte Surveys Ltd, working throughout Britain and further afield. His research is focused on threatened species, taxonomy and conservation ecology.

ORCID

Des A. Callaghan http://orcid.org/0000-0002-0415-1493

Additional information

Funding

Funding for part of this work was provided by The Botanical Research Fund.