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Sunday, October 18th, 2009 | 

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”.

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Tuesday, March 17th, 2009 | 

The females of this crab spider (Misumena 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.

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Thursday, February 05th, 2009 | 

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”.

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Friday, November 14th, 2008 | 

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.

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Thursday, March 13th, 2008 | 

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.”

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Friday, February 08th, 2008 | 

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.

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