What is the British distribution oiEpipactis leptochila (Narrow-lipped Helleborine)?

摘要

Epipactis leptochila (Narrow-lipped Helle-borine) and its close relative E. dunensis (Dune Helleborine) have a complex taxonomic history. Once treated as clearly distinct entities, with Narrow-lipped Helleborine confined to southern beechwoods and Dune Helleborine found exclusively on coastal dunes in northern England and on Angles, the situation became complicated with the discovery of inland populations of a similarly self-pollinating Epipactis in northern England and southern Scotland. Some of these northern plants were placed with E. dunensis and others with E. leptochila, with the distinction resting essentially on the shape of the outer part of the lip (the epichile). The discovery of these inland populations was followed, however, by reportsthat some sites held plants intermediate between the two taxa, and this led inexorably to the conclusion that leptochila and dunensis were conspecific. Further, dunensis was reduced not to a subspecies, but to the rank of a mere variety of the widespreadEuropean species E. leptochila. This significant taxonomic change (it involved the 'loss' of a species, indeed a species endemic to Britain) does not appear to have been fully documented and, indeed, I have not be able to trace any details of the intergradation of leptochila and dunensis in northern England, apart from two brief reports (Richards 1986, 1989) and a short discussion by A.J. Richards in Stewart et al. (1994). Whatever the reason, all the records were mapped as 'Epipactis leptochila Narrow-lipped Helleborine' by Preston et al. (2002), with not a mention of E. dunensis. Even more drastically, E. leptochila was itself lumped with E. muelleri of Continental Europe by, for example, Stace (2004).