An assessment of populations of Dactylorhiza traunsteineri (Sauter) S06 in the British Isles and a comparison with others from Continental Europe. Watsonia 18

The acceptance of Dactylorhiza traunsteineri (Sauter) S06 (Orchidaceae) as a British and Irish species has frequently been questioned. Twelve populations of dactylorchids from widely separate parts of the British Isles which have traditionally or recently been referred to this taxon, have been the subject of a critical morphometric evaluation. An inter-population comparison of the mean values of the key diagnostic characters indicated a degree of uniformity through the twelve populations although some geographical trends were identified. The data obtained were compared to, and found to be closely similar to those for populations of D. traunsteineri from the alpine region of Europe, including the type locality, and from Scandinavia, and this is offered as additional evidence for the inclusion of the species in the British and Irish floras. For D. traunsteineri in the British Isles, a comparison has been made with other dactylorchid taxa and their differences highlighted. The principal diagnostic characters of D. traunsteineri are summarised and a provisional distribution map is given