midge orchids

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.

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

Part Two – Different Ways of Orchid Reproduction

Part One – Attracting Pollinators looked at pollination strategy, but the fourth aim of the paper was to establish that Corunastylis littoralis reproduced by xenogamy or geitonogamy and that the species was not autogamous or apomictic, that is, pollinated, self pollinating or non pollinating plants.

Xenogamy or geitonogamy that is vector mediated pollination or out-crossing is when fertilization occurs by the transfer of pollen from one flower to another flower usually by the means of insect.

Autogamy or self-pollinating is when the flower is pollinated by its own pollen.

Apoximis is when reproduction occurs without pollination, that is, vegetative reproduction.

As explained in the paper, there are visual clues for determining which process is used by the plant.

Xenogmay	Autogamy	Apoximis
Pollinia removal and pollen deposition	Pollinia not removed	Lacks pollen or it is tightly bound
	Pollinia weakly attached to the viscidium	If pollinia present, then unable to be removed
Not all the ovaries are fertilized	All the ovaries are fertilized and have viable seeds
		Swelling of the ovaries can occur whilst in bud
Perfumed	Likely to have no perfume
Attracts insects
	Flowers short lived

More detailed information was gained by dissecting the flower.

To read the full paper, click here.

To read the report, click here.

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

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

Part One – Attracting Pollinators

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

Food mimicry
Sexual mimicry
Brood-site mimicry
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.

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.

Murray Mallee Midges Autumn 2011

R.J. Bates May 2011

The title of this article refers of course to mallee midge orchids of the genus Corunastylis which have been poorly understood.

Summer and autumn 2011 saw good rains across the Murray Mallee from Pinnaroo to Renmark and thus NOSSA members took the opportunity to study mallee midge orchids in flower in March and April. The results are summarised here.

Murray Mallee Midges_2007E_6Jun11 — *Corunastylis* sp. Box Flat
Ngarkat Conservation Park
Photo: June Niejalke

Aims:

To match species to habitat.
To assess the distribution and population of each species.
To take images of all species.

Midges were found all the way up to Chowilla sand hills, which are just north of the River Murray. Almost every patch of mallee eucalypts seemed to have some Corunastylis species but an understanding of their ecology was needed to find the flowers. Degraded or weedy mallee did not have any midge orchids, nor was hard clay, loose white sand, bare trampled soil or dense ground cover worth searching as midges are very small plants and easily crushed, covered up or sand blasted.

Flowering plants were found mostly in the leaf litter under mature mallee, often with associated patches of native pine or circles of Triodia sp. (porcupine grass). Areas with extra water run off and disturbed soil along road corridors seemed to have produced localised population explosions. A 4WD vehicle proved handy for reaching remote corners of larger parks like Billiat Conservation Park near Alawoona.

The most common species was the red and green flowered mallee midge Corunastylis tepperi while the similar but purplish Corunastylis sp. Intermediate came in second. Next came the black midge orchid C. nigricans which seemed to have finished in early March and were found mostly in capsule.

Species of the Corunastylis rufa complex were mostly found in the southern fringes of the mallee. Their classification is ambiguous seeing Australian orchid expert D.L. Jones says Corunastylis rufa is confined to NSW. The un-named species of the complex seen included Corunastylis sp. Dark midge and Corunastylis sp. Narrow segments.

In any case, no fringed labellum species of any kind were observed, so all mallee midges belong to the C. nigricans and C. rufa complexes.

Tiny fruit flies of several species were seen working the flowers but we could not tell if each midge orchid attracted a different fly as the flies are too small to compare! I suspected that specificity of pollinators is low as apparent hybrid midge orchids were noted.
Recognising the different mallee midge orchids:

If the flowers are bright green and the labellum is rounded, deep purple or maroon then it will be C. tepperi, also known as C. fuscoviride. The latter is a better name as it means bright dark and green. C. tepperi has a narrow spike of many tiny flowers. The finished flowers and capsules will take on a yellowish look.
If the labellum is rounded and the flowers are mottled brown to wholly purple-brown, except for white or white striped petals, the species is C. sp. Intermediate.

DNA studies may be required to check the species limits of the many taxa found.
It is doubtful that such a good display will be found next autumn!

Many thanks to NOSSA members who sent me images of mallee midges recently, especially June Niejalke.