Isoetes ×jermyi hyb nov. (Isoetaceae), a new quillwort (lycophyte) hybrid from western Europe

ABSTRACT

Isoetes ×jermyi, hyb nov. (Isoetaceae), is the sterile hexaploid (6x) hybrid quillwort of diploid (2x) I. echinospora x decaploid (10x) I. lacustris. It has been identified from cytologically confirmed plants at several sites in the western United Kingdom and by the morphological determination of herbarium specimens from sites in north-eastern France and Småland, Sweden. Clarification is provided for the distinctions of 6x I. ×jermyi from the similar, apparently heptaploid (7x) Pyrenean endemic I. ×brochonii and the misapplied 6x North American endemic I. ×hickeyi. The possibility that enigmatic Irish quillwort I. morei could represent this taxon is discussed and rejected. The frequency of its occurrence in the United Kingdom suggests that I. ×jermyi can be expected to occur regularly within mixed I. echinospora and I. lacustris populations across the wide area of north-western Europe where the two species are sympatric.

KEYWORDS:

• Isoetes ×jermyi
• Isoetes echinospora
• Isoetes lacustris
• Isoetes ×hickeyi
• I. morei
• Europe

Acknowledgments

This paper would not have been possible without the contributions of the late Clive Jermy (Natural History Museum, London, UK) and Donald Britton (University of Guelph, Guelph, CA). It is a privilege to complete this project ’with’ them, and to tangibly honour Clive’s major global contributions to the study of Isoetes in this way. DFB is grateful yet again from permission to examine and employ elements within the extensive SEM image library developed by Donald Britton. In that regard, his thanks also go to Paul Sokoloff of the Canadian Museum of Nature, Ottawa, CA and Germinal Rouhan, Curator of Ferns and Lycophytes in the Muséum national d’Histoire naturelle de Paris, FR, for their collaboration in the recent procurement of I. morei and I. echinospora SEM images. The authors would like to thank Alison Paul for her assistance with herbarium and other material at BM and Dr. Peter Stroh (BSBI) for help with the creation and provision of the distribution map. The efforts of the curators and collection management staff of the many herbarium consulted over the years have been invaluable.

Disclosure statement

No potential conflict of interest was reported by the authors.

Author Contributions

Conceptualization: D.F.B.; Data gathering and curation: D.F.B., F.J.R.; Methodology: D.F.B.; Documentation review: D.F.B., F.J.R.; Data Analysis: D.F.B., F.J.R.; Microscopic Imagery: D.F.B.; Writing - original Draft: D.F.B.; Writing – revision and editing: D.F.B., F.J.R.