Distinguishing between Epipactis leptochila (Narrow-lipped Helleborine), Epipactis helleborine (Broad-leaved Helleborine) and their putative hybrid, Epipactis x stephensonii at the Warburg reserve, Oxfordshire

Abstract

A drought in May 2020 curtailed snail damage to a population of Epipactis leptochila (Godfrey) Godfrey (Narrow-lipped Helleborine) such that in July there were 33 flowering plants in an area well known for this species at the Warburg nature reserve in Oxfordshire (v.c.23).  Despite growing in a heavily-shaded area under beech, the typical habitat of E. leptochila, some of these plants were actually E. helleborine L. (Crantz) (Broad-leaved Helleborine) based on recognized distinguishing characteristics.  We took morphological measurements (19 floral characters and 10 vegetative characters) for all the flowering plants present and were able to confirm by statistical analysis our initial species identifications. We were able also to discriminate between the species reasonably accurately using leaf characters alone, such as leaf colour, leaf length to width ratios and the angle of turn of the bottom three leaves. Using the outcomes from this analysis we were able to make predictions about the identity of most of the 82 non-flowering plants present. There were 4 plants that defied clear initial allocation to one or the other species and were suspected to be the hybrid E. x stephensonii Godfrey. Statistical analysis confirmed that these plants were indeed distinguishable from either parent, and most characters were intermediate to some degree between the two. The morphology of these putative hybrids is described pending molecular confirmation of their identity.