Most orchid species don’t like acid boglands – but there are two rare exceptions: One is geographically widely distributed from Belgium to Northwestern Germany and Scandinavia and is mostly addressed as Dactylorhiza sphagnicola. The other grows only in the Danish region of Thy: Just a few hundred meters behind the coastline of the North Sea there is a population of white-flowered orchids which have been described by Henrik Ærenlund Pedersen as Dactylorhiza majalis subsp. calcifugiens (in: Nordic Journal of Botany, 2004). In 2007, Sebastian Sczepanski and Karel Kreutz argued it would be more appropriate to regard these plants as a subspecies to Dactylorhiza sphagnicola – while Pedersen und Mikael Hedrén are viewing sphagnicola only as another subspecies of Dactylorhiza majalis. Apart from colour, the morphological differences of the single flowers of Dactylorhiza majalis subsp. majalis (left), calcifugiens (middle) and sphagnicola (right) are difficult to discern:
src="http://www.albiflora.eu/images/science/majalis_calcifugiens_sphagnicola_sm.png" alt="Dactylorhiza" />The spur of Dactylorhiza sphagnicola is a bit longer than that of D. majalis subsp. calcifugiens. And the leaves of the latter are spreaded in a broader angle than those of D. sphagnicola:
The single flowers don’t show any hue of purple, even the pollinaria lack Anthocyanin. There is rather some yellowish hue in the center of the flower, slightly reminding of Dactylorhiza incarnata subsp. ochroleuca. In contrast to other populations of albiflora forms, e.g. with Dactylorhiza fuchsii, there are no gradual differences in the loss of colour pigments – all the plants are consistent in the white colour of their flowers.
Visiting the region, I found calcifugiens at two places, one near the small fisher village of Lild Strand with only three plants, the other further to the south at a bog called Nissekaer with about 150 plants. Surrounded by dunes this place is a natural depression (danish: “kaer”) with a length of about 1500 and a width of about 250 meters:
In mid-June the orchids are just in the beginning of flowering. Most Dactylorhiza majalis subsp. calcifugiens are growing at the edges of the wet places, not in the midst of them as it is the case with Dactylorhiza sphagnicola in the Venn moors in Belgium. And the calcifugiens plants are quite smaller, reaching just a height of up to 31 cm. Neighbouring plants are Sphagnum palustre, Equisetum fluviatile; Eriophorum angustifolium, Menyanthes trifoliata, Vaccinium oxycoccus, Calluna vulgaris, Trientalis europaea and even Drosera rotundifolia – most of those plants are clear indicators of acid soil. Among the shrubs there is the dominant Myrica gale, which is used by the brewery of the near-by town Thisted.
Some calcifugiens plants show a broader labellum, indicating a possible hybrid influence of Dactylorhiza maculata – similar to the sphagnicola plants of the Venn region.
Among all the white-flowered orchids in the Nissekaer bogland I found two purple-flowered plants which might be a hybrid of Dactylorhiza majalis subsp. calcifugiens and Dactylorhiza maculata (left) and a Dactylorhiza maculata still in buds (right):
As a visiting and possibly pollinating insect of Dactylorhiza majalis subsp. calcifugiens there was a species of the genus Syrphida – as I’ve seen also with Dactylorhiza sphagnicola in the Venn moor (left)
Saturday, July 14th, 2012 | Author: admin
Category: special species