Hypochrome forms of Neottia nidus-avis

Deutsche Botanische Monatsschrift, 1890

In a contribution for the Journal of European Orchids (Journal Europäischer Orchideen, vol. 50, 2-4, 2018, p. 221-226), Leslie Lewis presents an overview of the hypochrome forms of Neottia nidus-avis and new findings in England. In the introduction, she explains that these orchids have colour pigments – chlorophyll and carotinoids. However, colour variants are also occasionally found, the author writes.

Neottia nidus-avis f. nivea (Photo: Werner Hahn)
Deutsche Botanische Monatsschrift, 1891

It might be questionable ob these colour variants should have a taxonomic relevance. But at least there are scientific descriptions of such forms already in the 19th century, either as varietas (var.), forma (f.) or as lusus (lus.). Leslie Lewis presents those descriptions by Philipp Wilhelm Wirtgen (1806-1870),  Paul Wilhelm Magnus (1844-1914) and others and sorts them like Gustav Hegt (Illustrierte Flora von Mittel-Europa, Bd.2, 1909) in a consistent way on the level of forms:

  • Neottia nidus-avis f. pallida: plants with pale yellow flowers
  • Neottia nidus-avis f. nivea: plants with snow-white flowers
  • Neottia nidus-avis f. sulphurea: plants with sulphur-yellow flowers

Calypso bulbosa forma albiflora

At the edge of the Arctic, Calypso bulbosa is one of the most Northern orchids. After snow smelting, from April to June, the plant is flowering in Northern Sweden or in Canada. It has rose to violet petals, the lip has a white or rose ground, with rose or violet spots. Albiflora forms are extremely rare.

In the Canadian National Park Banff, Jeroen Gerdes has found a white-flowered plant which still has its purplish color pattern in its hypochil. A purely white-flowered plant has been found this year by Marco Klueber in the Swedish province of Dalarna gefunden – here all the Anthocyanine pigments are vanished.  

The small plants grows in moist coniferous forests, on moss grounds. It’s a real dream to find it in this white-flowered form.

Albiflora orchid in Nepal

Photo: Bhakta Bahadur Raskoti

The Nepalese orchid expert Bhakta Bahadur Raskoti found an albiflora form of Neottianthe cucullata together with its regular form. This orchid is distributed in central and western Nepal at altitudes of 3700 to 5000 m. It’s flowering in August. The albiflora form has been described in 1995 by the Chinese botanist P.Y. Fu. The species has its western distribution limit in Poland.

a biased learning experience – how pollinators react to color

Bees and other insects are looking for floral rewards, such as nectar and pollen. And they learn to associate a variety of floral cues, including color with such rewards, as three researchers of the University of Arizona – Avery L. Russell, China Rae Newman and Daniel R. Papaj – explain in an article published this year in Evolutionary Ecology (DOI 10.1007/s10682-016-9848-1). Yet, we don’t know much about the ways how insects are learning.

Andrea spec. with Orchis simia
Andrea spec. with Orchis simia

The Arizona project looks for plants with different colors due to a single loss-of-function mutation blocking the production of floral pigments. Similar to the albiflora orchids presented on this web site, such color polymorphisms may also occur in other plant families. The authors explain that those are quite common, for example with Geranium thunbergii, Antennaria dioica or Aquilegia coerulea – a relative to the European Aquilegia vulgaris.

Aquilegia vulgaris
Aquilegia vulgaris

There study analyzes the behavior of pollinators of hypochromic Solanum tridynamum in an experimental arrangement. It could be shown that initially naïve bees had no preference for purple- or white-flowered plants. The same was the case when the researchers prevented the release of pollen – this was done by sealing the anther pore with glue. But bees with a rewarding experience on plants with purple corollas expressed strong, significant landing preferences for morphs with purple corollas relative to morphs with white corollas. This preference to the rewarding color was much weaker in the case of rewarding flowers with white corollas. The authors came to the conclusion: bees showed a bias in terms of how experience shaped preference: experience with the purple morph had a greater effect on preference than experience with the white morph.

The reason for this bias in learning might be, according to the Arizona researchers, that purple flowers exhibit much greater chromatic contrast, so the hypochromic Solanum tridynamum is likely even less discriminable in real-world foraging conditions. Such biases, the authors conclude, might curtail the success of such morphs and perhaps even contribute to the low frequencies in which they occur. The Arizona case study titled White flowers finish last: pollen-foraging bumble bees show biased learning in a floral color polymorphism is great research – there should be others to follow to see if pigmented flowers have an a priori advantage over hypochromic flowers.