WSBEorchids

Cymbidium dayanum (Himalayan form) – 365 days of orchids – day 998 – evolution in action?

This gorgeous Cymbidium species has been causing a real stir amongst the school students this week as it opens alongside Cymbidium angustifolium – day 992 (which is synonymous with Cymbidium dayanum or sometimes known as Cymbidium dayanum ‘red’.

Are we able to see evolution in action in this species from the Himalayas and South east Asia?

Todays variety of Cymbidium dayanum is the one found in the Himalayas, through Southern China and Japan, with striking red and white flowers on pendulous spikes. It is a native of lowland forests where it is reported growing on trunks and lower branches of large trees in shade. We know this habitat well from our trips to Sikkim, Assam and Arunachal Pradesh where lowland forests are semi-evergreen, hot and wet in the summer but much dryer and significantly cooler in the winter. We recreate these conditions, growing plants in constant shade in our Warm Asia section. We keep plants watered throughout the year but much wetter in the summer. As you can see from the photographs taken yesterday evening, plants flower profusely and the flowers are long lasting and fragrant.

Our excitement is to see this flowering next to the much smaller and rather different variant of the species from Sabah in Borneo (below)

Although the different versions of the species show clear similarities the differences seem significant to my team of growers in Warm Americas:

  1. Vegetatively the red plant is less than half the size of the striped plant which has leaves more than twice the length and twice the width.
  2. The flowers on the red plant are again around half the size of their striped relation, and most significantly the opening of the lip (lip to column height) is much smaller. This implies that the red form of Cymbidium has a different and smaller pollinator.
  3. The deep red colour of the Sabah form may also indicate a change in pollination strategy from the more common striped form. There is good evidence that many Malaysian red orchids are fly pollinated (see this interesting article) while in Japan the striped variety is reported as being pollinated exclusively by the Japanese honeybee Apis cerana japonica. Could it be that the normal bee pollinators of Cymbidium dayanum are absent from the habitat in Sabah, forcing the species to evolve into a rather different plant through natural selection. (The standard large red and white flowers are not pollinated but some smaller redder flowered plants are pollinated by flies leading to redder and redder flowers over the generations) – perhaps the net stage will be for the red flowered plants to develop an unpleasant small attractive to flies?

While sitting every lunch time and pondering the possibilities of the two varieties of Cymbidium dayanum being or becoming two separate species with different pollination strategies, we would love the opportunity to observe the species in the field and test the hypothesis we have developed.

For those who are wondering, Cymbidium dayanum does not give any reward (such as nectar) to pollinators and is reliant on deceit pollination.

 

 

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