Corunastylis ciliata – 2019 March Winning Photograph

The winning photograph for March 2019, was Corunasylis ciliata (syn Genoplesium ciliatum). As with so many orchids, it has undergone a few name changes. Originally Prasophyllum, then Genoplesium and currently Corunastylis

Although Genoplesium was split into two with only one species remaining in Genoplesium and the others placed into Corunastylis, this split has not been accepted by the everyone. For example, eflora of SA and PlantNET use Genoplesium whilst VicFlora uses Corunastylis.

Whilst researching C. ciliatum I came across images of Prasophyllum spp. being misidentified as Corunastylis spp. and as it was originally described in Prasophyllum it seems appropriate to examine the similarities and differences between the two genera.

In South Australia (SA), the most obvious difference would appear to be size but across the rest of the country some Prasophyllum species potentially can be similar in size to the much smaller Corunastylis, although Corunastylis species are never as large as many of the Prasophyllum species.

Some of the shared features of the two genera are

  • multi-flowered on a single stem
  • single tubular leaf
  • flowers non-resupinate, that is the labellum is above the column and the dorsal sepal is below (the only other non-resupinate flowered orchids in SA are Gastrodia, Caleana, including Paracaleana, and Cryptostylis subulata)
  • Grow as scattered individuals
Prasophyllum Corunastylis
Size Tends to be a larger plant (up to 150cm), but can sometimes be as small as Corunastylis Always a small plant (maximum no more than 90mm)
Leaf Leaf sheaf opens well below the inflorescence (flower head) Leaf sheaf opens at the base of the inflorescence.
Leaf Often withered at flowering Not withered at flowering
Labellum Immobile Mobile
Usually curved backwards (recurved) resulting in an upright appearance of the flower. Not recurved resulting in a more drooping appearance of the flower
Season Mainly spring flowering Mainly autumn flowering

 

References:

Jones DL A Complete Guide to Native Orchids of Australia including the Island Territories 2006

Prasophyllum and Corunastylis descriptions from VicFlora, accessed 1 May 2029

https://vicflora.rbg.vic.gov.au/flora/taxon/bbf0eb5e-fc8d-426b-9cac-58c384474e17

https://vicflora.rbg.vic.gov.au/flora/taxon/91aa3829-ead8-407f-9db7-db2357ddb7e1

Bates R & Weber J Orchids of South Australia 1990

Jones DL, et al, Australian Orchid Genera CD-ROM 2008 CSIRO

 

Thank you to Greg Steenbeeke for reviewing the article.

 

 

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Orchid Pollination Strategy for Corunastylis littoralis (Part One of Two Parts)

Part One – Attracting Pollinators

Corunastylis littoralis (Photo: Colin Bower)In 2015 a paper was published in the Journal of Plant Systematics Telopea (Vol 18:43-55) titled “Reproductive success and pollination of the Tuncurry MidgeOrchid (Genoplesium littorale)(Orchidaceae) by Chloropid Flies “. Much of the same material had been published earlier in a consultancy report for UrbanGrowth NSW, under the title “Pollination of The Tuncurry Midge Orchid (Corunastylis littoralis) Amended June 2014″ Prepared by Colin C Bower PhD.

Because of their details, research papers can contain some very interesting facts of interest to a wide range of readers. This paper was no different. The aim of the paper was to identify the pollinator(s), how the attractant worked, confirm that C. littoralis was not autogamous (self-fertilizing) or apomictic (reproduction without pollination) and to assess the requirements & long-term viability of the pollinator.

The following summary notes have been drawn from both the research paper and the consultancy report.  Note that Corunastylis littoralis is a synonym of Genoplesium littorale.

One of the interesting issues discussed was the different types of pollination strategies employed by orchids. It is commonly accepted that about one third of orchids use deceptive practices to attract a pollinator whereby they promise but don’t deliver. Some of these strategies are quite unusual. It would appear that there are at least four strategies now known. In order of frequency they are

  1. Food mimicry
  2. Sexual mimicry
  3. Brood-site mimicry
  4. Prey/carrion mimicry

The first two are well known to many orchid lovers. The orchid promises food such as nectar but does not produce any nectar or it has the appearance and even odour of the female insect pollinator so that it fools the male. The lesser known deception is brood-site mimicry where the female insect pollinator is tricked into laying the eggs on the flower but there is no chance for survival of the off-spring. Finally the most uncommon and unusual deception of prey or carrion mimicry, known as kleptomyiophily.

This method was discussed in detail in the report and made for fascinating reading although it was helpful to have a dictionary on hand.

Some insects are kleptoparasitic that is they feed on the haemolymph (roughly similar to blood) but from freshly killed insects. The researchers established that the pollinator for C. littoralis was not Drosophilidae (vinegar fly) but were instead from the families Chloropidae and Milichiidae known kleptoparasitic flies.

It has been observed that the pollinators swarm around the Corunastylis. This is a known behavioural pattern of kleptoparasitic flies that are attracted to the prey of other predators such as spiders, robber flies and other predatory insects.

It was noted that the pollinators were dominated by females. This precludes sexual deception and suggests that the females may require the haemolymph, which is protein rich, for egg maturation. It was also noted that C littoralis is a nectar producing orchid. It was considered that the nectar contained properties that mimic haemolymph.

Based upon these observations it was hypothesized that prey mimicry pollination syndrome was the best fit for the Corunastylis. Though this syndrome has been observed in orchids in the northern hemisphere, this would be the first time that this has been demonstrated as a possibility for Australian orchids.

Photo: Colin Bower
Photo: Colin Bower

Part two will consider the fourth aim of the paper which was to determine the method of reproduction.

Thank you to Colin Bower for checking this post and for allowing the use of his photographs.