Narrow-leaved Marsh Orchid - Dactylorhiza traunsteineroides

The Narrow-leaved Marsh-orchid, D. traunsteineroides, can be identified by its appearance and choice of habitat. Morphologically it looks like an anorexic Marsh Orchid. The stem is thin and looks fragile. The flowers are fewer than other of the genus and quite lax. The lip colour is purple with reddish  loops and spots contrasting, while the leaves are few, narrow as its name suggests, and held nearly erect. The lip also has a noticeable central point. The chosen habitat is calcareous fen, wetter than most others of the genus and usually those favoured by black bog rush Schoenus nigrans. For  this reason its distribution in the British Isles is sporadic. There are populations with the distinctive morphology in southern England, Norfolk, Yorkshire, North Wales, Western Scotland and across Ireland. It is endemic here, though similar species occur in Scandinavia and on continental Europe in Alpine regions. There is a more pigmented variation in Scotland, lapponica, which was formerly thought to be the UK representatives of D. lapponica. Currently the Hebridean Marsh-orchid is also considered to be to be a sub-species, but I will discuss that on its own page.
But hold on! The Narrow-leaved Marsh-orchid looks like upsetting both the "if it looks like a duck" philosophy for orchid identification, and the unsteady ground on which morphometrics sit. Further molecular analyses reveal a more complicated picture. Both plastid haplotype and nuclear micro-satellite data shows that the East Anglian and southern English D. traunsteineroides populations are genetically indistinguishable from D. praetermissa populations, while those  north of a line from the Severn estuary to The Wash are clearly  genetically a distinct entity. This line not only approximates well to the extent of the Devensian ice sheet maximum, but also the southern limit of D. purpurella. At a stroke the Narrow-leaved Marsh Orchid becomes rarer.

This species is an allotetraploid with D. fuchsii and D. incarnata as its  ancestors - earlier versions of those species to be more precise. But how much earlier? There is conflicting opinions as to whether D. traunsteineroides is an older alloploid species that migrated from a southern European refugal area after the ice retreat, perhaps even pre-dating the D. praetermissa migration, or is a more recent species originating in the British Isles.
One of the problems is the D. traunsteineri complex of three morphologically similar species that like the same sort of habitat. These are D. traunsteineri itself which is found in alpine regions, D. lapponica in northern Scandinavia, and D. traunsteineroides growing in Britain and Ireland. Some experts still like to class these as three subspecies of one taxon. However the plastid analysis shows that almost certainly they were the result of three separate polyploid events. A single Austrian D. traunsteineri showed maternal lineage of D. maculata, while D. lapponica had D. fuchsii in this role. However, the British and Irish D. traunsteineroides showed ancestry from the same, as yet unidentified, maternal diploid involved in some D. praetermissa, some D. majalis, D. alpestris, and even a Turkey alloploid D. nieschalkorium Thus multiple lineages of the traunsteineri group is likely.

This information adds to the evidence that D. traunsteineroides is an older polyploid that migrated north from a southern refuge with the retreat of the ice sheets. It's genetic diversity also supports this. However, there remains the fact that in the present day D traunsteineroides is an endemic species, not even represented on the North Sea coast. Could it be that being present on in the more northerly and westerly parts of Britain and Ireland it is adapted well to cooler and wetter climate, and continental Europe is just too clement for its survival.
The survival in a wetter and cooler climate, as well as a tolerance of schoenus fens, has been attributed to methylation of cytosine methylation of certain genes. It is proposed that this can provide a rapid (in evolutionary terms) adaptation for a novel habitat. Recent data has shown that both D. majalis in the Alps and Scandinavia have very comparable patterns of DNA methylation, and those from the Pyrenees are barely separable. British D. traunsteineroides from Yorkshire show a quite different pattern to D. traunsteineroides from Scotland (and to D. ebudensis). This may be laid, not so much on climate, but patterns of soil nutients left by the retreating ice sheet. But for me this does open up a possibility; one that no-one seems to have dared to discuss. Are the D. traunsteineroides regional populations actually different species resulting from independent polyploid events?

This may be a heretical proposition, but for me there is sufficient evidence to warrant consideration.

1. 2. 3. The DNA methylation of two populations of two British D. traunsteineroides populations show as much difference from each other as they do from a Scandinavian population of D. lapponica. Yet D. majalis from the Alps, Scandinavia and the Pyrenees are virtually inseparable. The Yorkshire D. traunsteineroides were once considered sufficiently different in form to be named Var eborensis (derived presumably from the Latin for "Eee-bah-gum"), while at least one Scottish colony was referred to as Var. francis-druceii. The ratio of ITS III to V in the different populations further confirms differences. The Yorkshire population has ITS III from 0.5 to 1.0, with ITS V ranging from 0 to 0.4. The Irish D. traunsteineroides have ITS V and III around 0.35 each. The Scottish and Welsh D. traunsteineroides both have ITS III around 0.1 or less and ITS V 0.7 or higher.

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Of course this does suggest that if there are (at least) three D. traunsteineroides in Britain and Ireland then it is a bit more likely that the polyploid events happened here and in post glacial times. The idea of a single continental species slowly migrating north as the ice retreats does have a few flaws. D. traunsteineroides is a plant of rather specialised habitat - schoenus fens. I have no idea if these formed and subsequently disappeared, following the ice allowing this northward migration. Or was is wind-blown seed chancing on isolated fens in wholly different regions with subsequent isolated genetic modification within each population that has resulted in today's pattern. There are other Dactylorhiza species growing close to D. traunsteineroides colonies, but different combinations of those occur in each region. Low level hybridisation and introgression would lead to different morphological and genetic difference. Anyway, this is just me thinking out loud, but imagine trying to find a common name for each less than 30 letters long.

Over the years there were reports of D. lapponica, the northern Scandinavian species, being found in Scotland. The one paper I have found with results of genetic analysis showed the one specimen firmly in the D. traunsteineroides camp. Bateman has stated that this is a hyper-chromatic variant of D. traunsteineroides that co-exists with and freely hybridises with the parent species. I suspect that means it should be referred to as D. traunsteineroides forma lapponica.

Most recently Dactylorhiza ebudensis has been re-described a subspecies of D. traunsteineroides . Because Prof. Bateman has suggested that further investigations may reverse this, I have retained it as an independent main taxon here, and it has its own page.

You may have noticed that I have avoided using the common name Pugsley's Marsh Orchid. No other British orchid has an invented common name after a person, as this sets a dangerous precedent; not that I expect more species to be found. Naming after a person can be left to the Latin name. Common names should be descriptive in my opinion.

I have to confess that my personal observations have been limited to the Welsh locations on Anglesey, but I hope to rectify this sometime soon in the future.

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