Similar to The Burren there are also some continental locations where Dactylorhiza fuchsii tends to develop white or at least bright flowers. In the Belgian province of Liège, near Lanaye, there are dozens of albiflora forms of this species, as Jeroen Gerdes told me – he sent me the photo at the left.

Today I visited a meadow near Biebergemuend in the Hesse part of the mountain range called Spessart. On a space of about 5,000 square meters I counted about 300 Dactylorhiza fuchsii with the following distribution of flower colours (in per cent):

In total 10 of about 300 Dactylorhiza fuchsii are albiflora forms – such a frequency is quite higher than usually observed with this or other orchids species and leads to the assumption that there might be some gradual or saltational evolution under way.

Among the other plants in this area I noted Dactylorhiza majalis (withered), Dactylorhiza fuchsii x majalis, Platanthera bifolia, Neottia ovata, Rhinanthus minor, Cirsium arvense, Campanula persicifolia, Picris hieracioides and Arnica montana. Dactylorhiza majalis grows in the neighbourhood of wet ditches along the meadow – and there are also hybrids of D. majalis and D. fuchsii – still flowering while D. majalis is already withered. The hybrids are rather strong, some of them with a height of up to 50 cm. They can easily be determined by their broad leaves and the rounded labellum of the flowers with a reduced medium lobe. There is also an albiflora form of Dactylorhiza fuchsii x majalis (right).

The evolution of certain orchid species is far from being finished. The Burren, a region in County Clare at the Western coast of Ireland, illustrates this fact by its manifold colour varieties of Dactylorhiza fuchsii. In 1988, R.M. Bateman and I. Denholm, came to the result that the Burren populations of Dactylorhiza fuchsii show more often a lack of the purple pigment anthocyanin than plants in other regions of the British Isles:

(Source: R.M. Bateman/I. Denholm: A reappraisal of the British and Irish dactylorchids, 3. The spotted-orchids. In: Watsonia 17 (1988), p.332)
When exploring the fascinating area around the Lough Gealain and the Mullaghmore mountain these results seem to be quite realistic. In other areas as well there are many plants, which have bright or white flowers but still retain anthocyanins visible in the markings of the labellum. In a limited area of 40 square meters in the region of Rockforest, northeast of Corrofin, I counted 50 flowering Dactylorhiza fuchsii (in addition to 7 with buds) with the following characteristics:

Among the other plants in this area in the middle of a vast limestone pavement there are Orchis mascula, Geranium sanguineum, Rosa pimpinellifolia, Calluna vulgaris, Lotus corniculatus and Pteridium aquilinum.

The following image illustrates the broad variety not only of colours but also of the labellum forms of Dactylorhiza fuchsii in The Burren (some of the examples obviously showing a certain introgression with Dactylorhiza maculata). It becomes clear that most plants have less floral anthocyanins than continental populations of the species – for example the large forest populations in the French region Causses with its deep pink flowers. The pigments are first reduced in the sepals. This reduction continues in the base colour of the labellum. Then the markings of the labellum are reduced, often only a small rest is retained at the mouth of the spur. Even the very white flowers still have coloured pollinia but their colour is less intense. There is also a wide variety of labellum forms. Especially the central lobes largely differ. And there is the extreme case of a white flowering plant whose lateral lobes are reduced to a minimum (lowest row in the middle).

Most Irish and British botanists stress that the Dactylorhiza fuchsii var. okellyi (some authors view this as subspecies or even as species) must not be mixed up with the albiflora forms of fuchsii. Anne and Simon Harrap (Orchids of Britain and Ireland, 2005) are writing: “A lot of controversy surrounds okellyi” and explain: “In The Burren and elsewhere these classic white-flowered okellyi are just part of a population of plants with a variable flower colour”. Brendan Sayers and Susan Sex (Ireland’s Wild Orchids, 2008) stress that Dactylorhiza fuchsii var. okellyi flowers late, beginning in July. The photo in their field guide shows a flower with a labellum, which is deeply divided into three lobes. Charles Nelson (Wild Plants of The Burren and the Aran Islands, 2008) indicates that Dactylorhiza fuchsii f. okellyi flowers from June to August and has pure white flowers “without any pink tints or marks” and a “lip flat with 3 almost equal, deeply-cut lobes”. According to Pierre Delforge (Guide des orchidées d’Europe, 2005), who mentions a flowering period from May to July, the labellum has a maximum width of 8 mm (in contrast to fuchsii with 8-16 mm). Pat O’Reilly and Sue Parker (Wild Orchids in The Burren, 2007) have noted that “groups of pure-white orchids … are more likely to be O’Kelly’s Spotted-orchids than single plants, which might be just very pale examples of the Common Spotted-orchid”. When exploring the limestone pavements between Poulsallagh and Rockforest you’ll find lots of white-flowered Dactylorhiza fuchsii, rather small and with a pyramidal spike in the beginning of flowering, which are very similar to pink-flowered plants of the species – they should be considered as albiflora forms. Two times I found a pair of taller plants, very slender and with a distinct appearance of spike or flowers, which could be addressed as Dactylorhiza fuchsii var. okellyii.

Dactylorhiza maculata also tends to develop very pale flowers in The Burren. But most of them retain at least a faint marking on the labellum. The variety of Dactylorhiza maculata (the plants in Ireland are in general addressed as Dactylorhiza maculata ssp. ericetorum) seems to be not so wide as the variety of Dactylorhiza fuchsii. The relative frequency of Orchis mascula f. albiflora is in the same range as in continental Europe. Among thousands of plants – Orchis mascula being the most frequent orchid of the region – I’ve seen just two white ones. And there wasn’t one single albiflora form of Dactylorhiza incarnata or Dactylorhiza majalis ssp. occidentalis (on the Aran Island of Inisheer).

Compared with the relative stability of the other plants, the broad variability of Dactylorhiza fuchsii in The Burren clearly shows that this species is still in a state of an ongoing evolutionary process. It can only be speculated why Dactylorhiza fuchsii in The Burren prefers brighter or even white flowering – in the midst of an abundance of pink and purple flower colours on the meadows of the region.

Studying a marsh with about 2,000 Broad-Leaved Marsh Orchids (Dactylorhiza majalis) at the Southern edge of the Rhoen region in Germany I saw a group of three albiflora plants together with Menyanthes trifoliata, Caltha palustris and other marsh plants. Even more interesting was another albiflora plant in a distance of about 40 meters with an orchid in its direct neighbourhood showing a kind of partial albiflora: Most of its flowers have the standard purple colour but some flowers are partly purple, partly white – either in the lip or in the petals.
Obviously, the genetic allele containing information for the albiflora form has plaid a certain role for this plant – but it was dominated by the DNA, which contains the information for the standard colour. This observation as well as a similar one in Southern France with Anacamptis morio poses questions about the recessive character of the albiflora allele. There might be some cases where the albiflora allele of one parent plant is not totally restrained by the dominant purple allele of the other parent plant which results in such purple and white spotted flowers. Before I continued the trip to a charming meadow with hundreds of Anacamptis morio (among them two albiflora) and Orchis mascula I made use of the rising morning sun to make some more photos of the Dactylorhiza majalis f. albiflora trio:

In an e-mail exchange following his recent article in the Journal Europaeischer Orchideen (JEO), Richard Bateman, orchid specialist at Kew Gardens, wrote me that albiflora plants “are far more common among diploid Dactylorhiza species than tetraploid species”. A possible reason might be the “buffering of mutations by having four comparable genes in the tetraploid chromosomes”. Diploid species (with 40 chromosomes) are Dactylorhiza fuchsii, D. incarnata and D. sambucina. Tetraploid species (with 80 chromosomes) are D. majalis, D. praetermissa, D. maculata, D. elata, D. sphagnicola and D. traunsteineri.

Albiflora plants of Dactylorhiza fuchsii are quite often observed, and in Ireland there is also the intriguing D. fuchsii ssp. okellyi which is diploid as well. D. incarnata and D. sambucina are known for their colour dimorphism: red and yellow with D. sambucina, purple and yellowish-white with D. incarnata and its var. ochroleuca. In a recent article in the Annals of Botany (2009), Mikael Hedrén and Sofie Nordstroem presented the results of their reasearch about the colour dimorphism with D. incarnata. They observed that there was “no clear pattern of habitat differentiation … among the colour morphs”. With D. incarnata var. ochroleuca “the lack of anthocyanins is probably due to a particular recessive allele in homozygous form” – the diploid chromosome set has both alleles determining the lack of purple in the flowers.

Besides genetics, colour also affects the pollination function of orchid flowers. Bateman wrote me that “in at least a few cases, instantaneous loss of anthocyanins (or even just radical decrease in anthocyanin production) must affect pollinator preference, and lead to lineage divergence”. A potential example of such an evolutionary process could be Gymnadenia frivaldii as a relative of Gymnadenia conopsea.

But in general the question of a certain functionality of colour change is still unanswered. Following his mentioning of white flowers in the above mentioned JEO article, Bateman wrote me it would be “more correct to use the term ‘parallelism’ rather than ‘convergence’, since in most cases no-one has demonstrated a change of function or ‘behaviour’ in the abnormal white flowers”. He further noted “the probability that many different mutations and epimutations generate white flowers”. Recognising that there are quite many open questions, Bateman also asked “whether white is actually a colour at all”, pointing to the “very simple shifts between ‘white’ flowers and ‘green’ flowers in Platanthera”.

The females of this crab spider (Misumenia vatia) can change their colour depending on the colour of the flower where they sit and wait for a prey. On a white flower they have a white body, on yellow flowers it is changed to an intense yellow (right, photo: Olaf Leillinger). Thus, the albiflora form of Dactylorhiza fuchsii (left, photo: Norbert Griebl) is quite a convenient place to hunt insects – the standard purple colour of this orchid would not fit her camouflage strategy. The spider changes its colour by secreting a yellow pigment into the outer cell layer of its body.While sitting on white flowers, this pigment is transported into lower layers. The colour change from white to yellow takes between 10 and 25 days, the reverse about six days.

The magazine of the Arbeitskreise Heimische Orchideen (AHO) has an article of Norbert Griebl in its latest edition giving an overview about the Dactylorhiza species in Austria. His contribution presents two photos of white varieties – a Dactylorhiza traunsteineri, the photo taken at lake Kochel in Bavaria,and a bright flowering Dactylorhiza incarnata, which is defined als Dactylorhiza incarnata f. ochrantha- with a yellowish accent in the lower part of the inflorescence but not as yellow as Dactylorhiza incarnata ssp. ochroleuca – Griebl views this taxon not as a subspecies but as a species of its own, since he argues that there are almost none hybrids between incarnata and ochroleuca.

In an article about maintenance of biotops in Rhineland-Palatinate Juergen Passin mentions a habitat near Vallendar on the Rhine “Orchis militaris, also var. albiflora”.

Sebastian Sczepanski und Peter Rolf schreiben in einem Beitrag für die AHO-Berichte: “Wie bei allen Dactylorhiza-, Orchis- und Gymnadenia-Arten, so treten auch bei D. praetermissa gelegentlich völlig weißblütige Pflanzen auf.” (Das Übersehene Knabenkraut, Dactylorhiza praetermissa (Druce) Soó, in Deutschland – ein Beitrag zur Orchidee des Jahres 2008. In: Berichte aus den Arbeitskreisen Heimische Orchideen, Jahrgang 25, Heft 1, 2008. S.37). Günther Blaich dokumentiert das Foto einer solchen Pflanze in Großbritannien.

Adolf Riechelmann erwähnt in den Berichten aus den Arbeitskreisen Heimische Orchideen (Jahrgang 24, Heft 2/2007) eine Häufung der Albiflora-Form von Dactylorhiza majalis im mittelfränkischen Forchheim: “In der Population des Breitblättrigen Knabenkrauts … finden sich mehr als zehn reinweiß blühende Pflanzen.”

Ein Foto im Forum von terrorchids.org könnte eine Albiflora-Form von Dactylorhiza romana zeigen. In einem Mail-Wechsel berichtet Berthold Gross, dass er die Pflanze von einem Händler in der Türkei bezogen habe und dass neben der Blütenfarbe auch die ziemlich kleinen Laubblätter auffallend seien.