Caroli Linnæi ... Flora zeylanica: sistens plantas indicas Zeylonæ insulæ ...1747

With beginning of the new year, the international botanical community has dismissed two requirements in describing new species or other taxa. It is now no longer necessary to include a Latin description of the plant, and the article describing a new species must not be printed, but can also be published online. “Beginning 1 January 2012 names of new plants, algae, and fungi may now be published with a validating diagnosis or description that is written in either Latin or English”, says an article which explains the decisions of an international botanical congress in July in Melbourne. The rules of introducing valid taxa are stated in International Code of Nomenclature for algae, fungi, and plants (ICN).

Still looking for any hints to shed some light on the albiflora phenomenon, I visited Richard Bateman in London. The white-flowered morphs “are of greatest interest to me because of their relative frequencies in the diploid and the tetraploid groups of Dactylorhiza”, he told me. “If your mind works its ways through the different diploids – incarnata, fuchsii, sambucina – they all show colour polymorphism. And they all have a certain number of very pale or white individuals.” Quite different are the observations with tetraploid Dactylorhiza species like praetermissa, majalis or alpestris. Bateman noted: “I’ve only found one albino praetermissa and one albino traunsteinerioides in 30 years of going in the field.” Quite younger is the albiflora.eu project – but up to now only some scattered findings of white-flowered Dactylorhiza majalis have been reported – and none of praetermissa or traunsteineri. As a possible explanation Bateman noted: “Presumably, in the tetraploids there has to be a minimum of four copies of a gene that is malfunctioning to cause the albinism. So I think the tetraploids are buffered against albinism by having additional copies of the genes that generate the anthocyanin pigments.”

Arguing with him about the negative connotations of the term malfunction, Bateman answered: “Most organisms are ‘designed’ to remain the way they are and not to change [substantially]. So, from a genetic viewpoint, any change that is expressed is a malfunction. I agree the malfunction could be beneficial rather than negative but most times it’s negative.”

Bateman’s main interests in research are the questions of speciation or at least the question of what might lead to evolutionary divergence between populations: “The genus level – for me at least – is solved. The species level interests me the most now. That’s were the most challenging topics still have to be addressed – how orchids speciate.” Despite a huge literature on the topic, Bateman noted, those questions are still not adequately solved. “Each time I address a particular set of orchids, the answer [to this question] is different.” So up to now, no generalization is possible. But, Bateman said, “I strongly believe that the importance of pollinator [specificity] is being exaggerated by a lot of workers.”

At least one general observation can be stated according to Bateman: “New [evolutionary] strategies are tried out constantly – more than most people believe – but I think they succeed less often than most people believe.”

In addition to such reflections on stability and change in the genetics of orchids, we wondered why hypochrome forms of Ophrys are rather green than white – obviously the Ophrys flowers still contain chlorophyll even if they lack the anthocyanins – and with good reason: “The rosette leaves of Ophrys (and Himantoglossum as well) tend to be dead before the flowers properly open”, Bateman said. “So I don’t think there is much supply of nutrient coming from [root to flower]. The flower has become autonomous … whereas in Orchis or Anacamptis the flowers are far less independent.” So, Ophrys flowers are quite special. “One of the most striking things when you start working on the flowers, cutting them up looking at them under microscope, you realize how much energy is invested in an Ophrys flower. There is a lot of tissue.”

After the visit, the Royal Botanical Gardens in Kew have been the very right place to further contemplate on the miracles of nature. (With thanks to Richard Bateman for reviewing his quotes, additional notes are marked with brackets)

Oops, that’s a quite special Anacamptis morio which Norbert Griebl has found near Sittendorf, southwest of Vienna. In addition to the absence of anthocyanins (which happens quite often with this species) the lip has the same form as the sepals, with green veins. Here, not only the colour of the flower has changed, but also its morphological pattern.

In July, the dark red heads of Nigritella rhellicani (syn: Nigritella nigra ssp. rhellicani) are covering many alpine meadows. In some rare places, the flowers show remarkable colour variatation. After studying the Nigritella hues of the Dolomite Alps, this year I visited the Swiss canton Valais: Near Chandolin there is a place in an altitude of about 2400 m with pink and yellow flowering Nigritella rhellicani. The tableau above shows the colour varieties in both the Dolomites and Switzerland. The yellow flowering forms grow near Chandolin – they obviously miss the anthocyanins, but have other pigments as probably carotenoids. The reasons for this special forms are unknown up to now.

Exploring the Crimean Pensinsula for orchids, species like Comperia comperiana, Steveniella satyrioides or Orchis punctulata are especially noteworthy. Albiflora forms, though, are quite rare in this Ukrainian region. Vladimir Isikov of the Nikita Botanical Garden told me that he has seen only three species with white-flowered forms: Orchis simia, Neotinea tridentata and Anacamptis morio ssp. caucasica (which he referred to as Orchis picta). Obviously there are no orchid species on the Crimean Peninsula heading to a direction which favours white flowering.

But near тылобое (Tylovoye) we found an edge of a forest with a group of 26 Orchis simia under a pine and 5 albiflora plants among them. In this small population there was obviously some kind of reproduction of the white-flowered plants.

Neotinea tridentata has a marked variability, as it is also noted by H. Kretzschar, W. Eccarius and H. Dietrich in their book „Die Orchideengattungen Anacamptis, Orchis, Neotinea“ (Buergel 2007, p. 206/207). On the Crimean Peninsula the dominant colour of flowers is light purple. I’ve found 3 white flowered plants, which led me to a rough estimate of 2 albiflora plants per 1000 Neotinea tridentata.

Among the Anacamptis morio, Orchis mascula, Orchis purpurea or Anacamptis pyramidalis seen on our 10-day-trip there have been no white-flowered plants. But in a forest near гончарное (Goncharnoye) there was an albino form of Epipactis helleborine.

Beyond the orchid flora I noticed white flowers of Polygala major, the endemic Onosma taurica and Papaver spec. Interesting was also a Polygonatum odoratum with half white leaves.

Form and function of the flower organs are the main focus of the new fascinating book The Flower of the European Orchid by Jean Claessens and Jacques Kleynen. Illustrated by great macro as well as microscopic photos this important opus presents a comprehensive description of the structure of orchid flowers with the different European genera. In a foreword, Richard Bateman writes: „No other family of plants can match the orchids for their sheer charisma“. But the excitement goes along with a certain scientific pain – Bateman stresses that there still remain major scientific uncertainties which „further torment us“ – among them questions of evolutionary adaptation.

The orchids’ strategies of fertilization are manifold and the book explains how the specific construction of the column (gynostemium) supports allogamy by pollinators or autogamy (self-fertilization). Especially intriguing are the strategies of Dactylorhiza, Orchis and other genera without any nectar in the spur. Claessens and Kleynen explain that the pollinators of Orchis mascula are „recently emerged, naïve bees or exploratory insects that have not yet learned that the flowers offer no reward” (p. 220). The authors also cite the study of L. Dormont, R. Delle-Vedove, J.-M. Bessière, M. Hossaert-Mc Key und B. Schatz about the presence of white-flowered Orchis mascula which underlines „the importance of visual cues for attracting pollinators“ (p. 220).

In the Dactylorhiza chapter the authors write: „Colour can also influence pollinator behaviour“ (p. 240). With regard to the red and the yellow forms of Dactylorhiza sambucina they refer to experiments showing that experienced bumblebees „preferred by far the morph that most resembled the rewarding plant on which they have fed previously“. Vice versa it may be presumed that there may be a form of evolutionary adaptation directed to develop visual cues which are different from non rewarding plants being abundant in a certain region – as it could be the case in Western Ireland with the many white-flowered forms of Dactylorhiza fuchsii on meadows with earlier flowering Orchis mascula.

In the latest issue of “Berichte aus den Arbeitskreisen Heimische Orchideen” (27/2, 2010), Klaus Boie presents a rare hypochrome form of Ophrys speculum in his article about orchid-findings in western Andalusia (p.117-122). He found this forma flavescens in the Spain region of Andalusia, in the midst of a large group of Ophrys speculum, as he writes.

The marking of the labellum is just white, the other parts of the flower are yellowish-green. As with other hypochrome forms of Ophrys, the photo shows a total lack of anthocyanins. But the flower has still chlorophyll embedded – in contrast to albiflora forms of other orchid genera with their their pure white flowers. Probably the Ophrys species need the flower’s contribution to photosynthesis, because the leaves of the rosette are withering at an early stage.

White-flowered orchid varieties are not just a “freak of nature” – they have quite obviously some biological function. A group of scientists in Montpellier in Southern France has found that the existence of albiflora plants in a population of Orchis mascula is connected with a much higher fruit set of the purple-flowered plants than in populations where there are no white-flowered Orchis mascula:

“Surprisingly, our study showed that the presence of co-occurring white-flowered individuals led to significantly higher reproductive success of nearby purple-flowered individuals (mean fruit set 27%), while white-flowered plants themselves had the same low fruit set (6%)”, the authors of the study – L. Dormont, R. Delle-Vedove, J.-M. Bessière, M. Hossaert-Mc Key and B. Schatz – wrote in their article in New Phytologist (2010) 185: 300–310. The flowers studied – overall 11 709 at 805 plants – showed almost the same increased fruit set when the researchers planted some ping-pong balls which mimic the white Orchis mascula inflorescences: “The effect was virtually identical in magnitude (fruit set increased from 6 to 27%), whether the nearby white-coloured object was an O. mascula inflorescence or a ping-pong ball.” The nearer a purple-flowered plant to the white colour, the higher was the fruit set developed due to a successful pollination.

The authors explain their surprising results with pollinator behaviour after visiting Orchis mascula who belongs to the food-deceptive orchids: “It seems plausible to suppose that after unrewarding visits to purple flowers, naïve pollinators probably avoid homogeneous populations of purple flowers, and may then preferentially orient to a different colour or to a colour contrast such as a mix of white and purple flowers.” Pollinators of Orchis mascula are bumblebees (Bombus, Psithyrus), solitary bees (Eucera, Nomada, Andrena, Apis) and the beetle Cetonia aurata.

The albiflora varieties are quite rare in the populations studied in Southern France: The authors counted 0.9 to 1.4 percent in different populations. But this is much higher than the percentage which could be assumed in the case of spontaneous mutations affecting floral pigmentation genes with an average of just 0.1 percent. Regarding the higher percentage of albiflora varieties with Orchis mascula the authors state that “it is unlikely that such high frequencies could be the result of repeated spontaneous mutations alone” – and this should also apply to the case of other orchid species with a higher percentage of white-flowered plants like Anacamptis morio or Dactylorhiza fuchsii in Western Ireland.

The white-flowered Orchis mascula themselves have only a low fruit set, but they “help” the purple-flowered plants of their species to be pollinated. “In O. mascula, the presence of whiteflowered variants might be regarded as an adaptation that benefits the purple-flowered relatives of white-flowered morphs, rather than providing a direct benefit to whiteflowered individuals”, the authors wrote and assumed that there is some “mechanism of kin selection” responsible to grant a higher percentage of albiflora plants.

The scientists in Montpellier are pursuing their research with other species as well. Laurent Dormont wrote me that they have also studied white-flowered plants of Calanthe sylvatica on the Caribbean island of La Réunion (the results to be published in Plant Systematics and Evolution and also the floral volatiles of white-flowered orchis species.

This year I had the chance to visit the white flowering form of Cephalanthera rubra in the Hesse part of the Rhoen some days earlier than last year. But first I followed a hint and looked up a place further in the South, near Ahlersbach. Quite near a path through the forest a white Cephalanthera rubra with a slight hue of pink! The pink colour is well visible in the buds, where the remaining pigments are more concentrated than in the opened flower.

At the second place near Huenfeld, characterized by an old beech mentioned by Marco Klueber in his great book about “Orchids in the Rhoen” the albiflora plants of Cephalanthera rubra are splendidly flowering. The Swedish botanist L. Anders Nilsson showed (in an article in Nature, 1984) that Cephalanthera rubra mimics the floral coloration of Campanula in the visual system of bees in order to be pollinated by them, especially by male bees of the genus Chelostoma. Since Cephalanthera rubra is flowering before Campanula, they are quite attractive for the bees. It would be interesting to see how bees are reacting to the albiflora forms of Cephalanthera rubra.

With regard to pollinators my visit on June 24th had a special highlight when I saw a wasp (Argogorytes mystaceus) pollinating Ophrys insectifera. The insect pseudocopulated two flowers in a timeframe of more than seven minutes.

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).