Irish Marsh Orchid - Dactylorhiza occidentalis

If there is one species of Dactylorhiza that has confounded the experts, this is it. Variously going under the common name of Broad-leaved, Irish or Western Marsh Orchid, it has also encompassed D. kerryensis, occidentalis or cambrensis, with subspecies or varieties scotica and ebudensis. It seems as if it was a bucket species for specimens that did not fit in elsewhere, yet failed the criteria for species. Features present in a population raised them to subspecies or variety level, yet it took molecular analysis to provide answers. D. cambriensis has been `moved' to D. purpurella, D. ebudensis became a species before further demotion, and I have no idea of the fate of D. scotia.

The Irish Marsh Orchid, Dactylorhiza occidentalis, is an allopolyploid of D. maculata and D. incarnata - a unique combination in Britain and Ireland, matched only by the Scandinavian species D. sphagnicola. These two are like a matching pair of opposites, one prefering alkaline flushes and the other sphagnum bogs. Bateman in 1983 proposed that this species should be called the Western Marsh Orchid because it was not exclusively Irish, but as actually is confined to Ireland then Irish Marsh Orchid is most appropriate.
The genetic data indicates that the polyploid event creating this species occurred in Ireland and within the last 8,000 years.

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