With Spring on the way, things are starting to change in the Orchid House. Here are Les Nesbitt’ notes from the August Journal 2019 Vol 43 No 7
Terrestrial Culture – August
The days are getting longer now, noticeably so after the middle of the month. When the clouds clear, the sun is stronger & higher in the sky. Temperatures increase and growth speeds up. Lots of buds are developing so there is plenty to see in the orchid house. The greenhoods are a feature with Pterostylis curta, nutans, pedunculata and their hybrids are all flowering.
Pests become more active. Look out for aphids on flower stems. Depending on the season deflasking can start after the middle of the month if a sunny and dry Spring is forecast, otherwise wait until September.
The NOSSA Spring show is only a month away. Start preparing your specimen pots for the display. Any spare pots can be sold on the trading table. There are never enough terrestrials on the trading table at the show to meet the demand.
Photograph your orchids when the flowers are at peak condition. Then hand pollinate a flower or two to get seed for the NOSSA Propagation Workshop or for sowing around mother plants next autumn. Prepare two pots of each species, one for showing and one for seed.
How to hand pollinate.
Look closely at the flower column to see the positions of the pollen and the stigmatic surface. Flowers can be self-pollinated if there is only one. Fatter pods with more viable seeds result if two plants of the same species are cross pollinated. That is transfer the pollen from one flower to a flower on another plant. Cross pollination mixes the gene pool to prevent inbreeding. Use a toothpick or a she-oak needle to touch the pollen which will stick to the wood. Wipe the pollen across the stigmatic surface of the other flower and the job is done.
If pollination is successful, the flower will collapse in a few days and the ovary will start to swell. For greenhoods the stigmatic surface is halfway up the front of the column. Remove the front of the flower and the lip so you can see what you are doing. Greenhoods have yellow pollen. For Diuris and Thelymitra the white pollen is hidden behind the sticky stigma. Caladenia have yellow pollen under flaps at the top of the column. Stroke upwards to open the flaps as would an insect backing out of the flower. The stigma is a hollow sticky depression just below the pollen. You will have to tip the flower right back to see it.
Certain flowers in large colonies were most popular over several days and both sexes were observed feeding on the boss, which suggests a food-related attraction. Virtually nothing was known about the Corybas pollinators and primary literature to date only offered hypotheses. Based on our findings, the persisting statement in literature that ‘Corybas species attract fungus-gnats as putative brood-sites’ is incorrect for the taxa in Victoria. No evidence of ovipositing in flowers was found. Females feeding looked gravid and were presumed to be unfertilised. All individuals looked fresh with undamaged wings and it was apparent they had recently hatched.
Is this a hypotheses that needs revising? Rudie definitely demonstrates the importance of careful and meticulous observations.
Rudie Kuiter et al have been observing orchid pollinators over many seasons spending hours watching and becoming familiar with pollinator interaction with the orchid, learning when to anticipate pollination activity.
Their observations of various Pterostylis species has been documented in Overview of Pterostylis Pollination (Orchidaceae) in Victoria. In all, they observed 53 Pterostylis species and 40 species of pollinators from several different genera. They noted that some pollinators species were active most of the day but others were only active in the late afternoon whilst others were “only seen on dusk and possibly are nocturnal as well”.
“The person who first records the whole pollination event will be very lucky indeed.” So wrote Bob Bates (South Australia’s Native Orchids, 2011). He was referring to the pollination event for Bearded Greenhoods in the genus Plumatichilos. As with many orchids there has always been a lot of conjecture about the pollination strategy involved so it is good to finally have photographic evidence of a previously unknown pollinator.
For several years now Rudie Kuiter, Mitchell Findlater-Smith and Rober Lindhe have been researching the relationship between orchids and insects, spending much time in the field observing and photographing the insects. Finally they have managed to obtain a photograph of a pollinator but it was not one of their photographs. Instead it was Neil Blair who took the photograph and observed a dagger fly pollinating a Plumatichilos. The male of these fascinating insects catches another insect and offers it for a nuptial gift to a female in order to be accepted as a mate. The photographs are amazing. It’s worth reading the paper Pollination of the Bearded Greenhoods (Orchidaceae) by Dagger Flies (Diptera: Empididae) just to see the pictures.
Continuing last week’s blog, here is the completion of Rudie Kuiter’s Introducion, Orchid Pollinators of Victoria. In this section he discusses some factors of hybridisation and the value of regular observation by local people interested in orchids.
Lissopimpla excelsa is the pollinator of all members of Cryptostylis, but hybrids are not known, even when sympatric, thus a molecular mechanism is in place that prevents cross-fertilisation. Hybrids in other orchid genera do occur and these usually are amongst closely related species. Several congeneric orchids attract the same male pollinator species, thus would be emitting the same kairomones, the scent that is a mimic of the female’s sex-pheromones, but normally these orchids are allopatric or have different habitat preferences. The land clearing, frequent fires, changes of watercourses, gold-diggings are amongst many unnatural human habitat interference of recent times. Historically in undisturbed natural habitats sibling orchid species that attracted the same male insect were not sympatric, not flowering at the same time or were in close vicinity to each other. In disturbed sites the situation has changed, as closely related species may have become sympatric and hybridisation take place. Spider-orchids that attract thyniid wasps with kairomones normally target a certain local species, but many allopatric species are know to share the same pollinator and readily hybridise where they became sympatric. In Pterostylis greenhoods the known hybrids are also caused when different species attract the same pollinators.
We still have much to learn to fully understand how adaptable the orchids are, the role insects play and how to interpret what we see. Orchids are finely tuned to their world and can change and adapt in ways that most people seem to underestimate. I requires observations of the same plants over many seasons to get a good understanding of their variability and adaptability. Unusual forms often show after a drought or fire may look like a new species, but soon change back to typical or normal within a few good seasons or after regeneration. It is usually the local people taking an interest that see the changes in the same plants over time that dispute what the ‘on-the-fly’ taxonomist come up with.
Creatures evolved as part of an endless combination of life-forms, ranging from microscopic to the tallest tree, that together form an ecosystem in which all organisms depend on each other. The climate, weather and other factors changes the environment constantly that influence the members differently, dome doing better than others, but it collectively maintains a balance. Natural events such as a major fire or flood may benefit environments in areas as part of seemingly long cycles, but they are very short in evolutionary terms. Unnatural man-made fires are very destructive as these are conducted much too frequently, wrong time of the year, and in the wrong place. Not obvious, but also very detrimental is the use of insecticides that seems to effect the Diptera members the most. Many of the important pollinators such as the fungus-gnats have gone locally extinct and most of the Pterostylis depend on them. To work with the pollinators it is essential to have a good understand of the life-cycles of the insects involved and watch the flowers in the wild. After witnessing Pollinator behaviours of the fungus-gnat on Pterostylis nutans countless times, the principal pollinator is easily recognised with other species. Unfortunately few good areas to find orchids and learn about their pollinators are left. Many are now rare and measures taken to protect them usually focuses on just a species. To be effective their habitat area and surrounding needs to be cared for, letting the natives grow and have the natural canopy reform. At least, habitats should be protected from further disturbances, especially by badly informed governmental environment departments with their fires.
Note This book is solely based on first-hand observations on the orchid-pollinators in the wild. Descriptions and comments are from many hours of watching each species over multiple seasons.
Apart from Orchid Pollinators of Victoria, Rudie Kuiter has produced several Victorian orchid books. If you are interested in purchasing any please contact us.
This week’s blog, Part One of Two Parts, is quoted directly from the introductory chapter (Pages 2&3) Orchid Pollinators of Victoria 4th Edition, 2016, Rudie Kuiter. Over the years of photographing orchids and their pollinators, Rudie and his team have been discovering much of the hidden world of orchid pollinators. In this first section he highlights the fallacy of the “one orchid-one pollinator” as well as touching briefly on the vast difference between the insects and their role in the ecosystem.
Amongst flowering plants, orchids have evolved in their own special reproductive ways. Their pollen is massed as waxy packages, pollinia, unlike like (sic) other flowers that produce masses of fine pollen grains that mostly go astray. The pollinia are relatively heavy and the usually small creatures need to be strong fliers for cross pollination (see image below). Orchids evolved with amazing strategies to attract specific carriers in order to transfer pollen between flowers of their species only, and in this way eliminating the need to produce great quantities. Various insects, many moths, bees and even birds have been documented as pollinators of orchids around the world (v.d. Cingel, 2001). A number of uniquely different examples of orchids attracting insects for their pollination evolved in Australia, especially in the more temperate southern zones originating from Gondwana times. With very few exceptions the Victorian orchids are terrestrial, ground-dwellers, that rely on small insects such as fungus-gnats, native bees, wasps, ants and many attract only the males by sexual deception. In the case no pollinators visits, many species may self-pollinate as a back up.
When taking an interest in orchids it seems difficult enough to identify some species. Usually one looks and admires the amazing flowers that may resemble an insect and can be difficult to recognise as a flower at first. An insect on a flower may be thought of something that spoils a picture – until taking an interest in the visitor!
I first learned about the orchid pollinators in Orchids of South Australia by Bates & Weber, 1990, an excellent book by today’s standard, but few were seen over the years by just being there at the right time when photographing orchids. During preparation of the book on Caladenia spider-orchids, certain issues developed from questionable statements made in scientific papers about wasp-pollinators. Of particular concern was about the one-to-one relationship – how only one wasp-species would be involved with only one spider-orchid species – and suggesting populations that were thought to represent the same species comprised different taxa if not pollinated by the same wasp-species. A very different story emerged when monitoring the local spider-orchid populations to find the answers and it became clear that there was much more to it. A site in Wonthaggi with a very large colony of Caladenia dilatata proved to be perfect for this study and also to photograph pollinators as it produces flowers for about four months. It was found that a local wasp-pollinator species typically flies for a little over one month, thus this need to be investigated further. Scientific publications on wasp-pollinators were generally based on short-term experiments, and usually employing baiting methods – moving flowers and often taking them to different sites. Responses included unnatural behaviour or attracting sibling wasps at a non-local site. It is certainly true that a particular flower may attract only one species of wasp a t a locality and a certain time in the season, but this reflects a very small part of the picture. It can be different in the long-term, at certain localities or with a season.
The main study site was in coastal dunes, where in a very large population of Caladenia dilatata produced flowers for over four months from September, and under favourable Summer-conditions into January. At least three congeneric (belonging to the same genus) thynniid wasps species were involved in this population. The flying times were up to about 6 weeks for each wasp species, that were separated or slightly overlapping. The flowering times in other populations of C. dilatata in Wonthaggi and Wilsons Promontory were usually about one month in each, and at the corresponding times to the study site the wasps visiting were the same species. A close sibling C. parva in the Wonthaggi heathland habitats and early flowering C. dilatata were pollinated by the same species, but the later flowering C. tentaculata by a thynniid wasp of the different genus.
Whilst a flower may attract only one wasp species, the kairomones (chemical omitted by the orchid to attract a pollinator) of a species may vary between flowers within in a population or when allopatric (growing in different geographical regions), just like colour or morphology. Variations maybe in relation to locality, weather conditions, or ground chemistry and available pollinator. Pollinators may evolve over time, but adaptions usually require many seasons and this would vary with location. The observations made over several seasons suggest that more than one congeneric insect is involved in pollination depending on local or seasonal conditions, especially after a long drought. Chiloglottis gunnii populations in Langwarrin were checked for pollinators since a decade-long drought and no action was seen for many seasons. When wasps finally made an appearance they comprised different taxa of Neozeleboria the first season, but only one became the common and principal pollinator the following seasons. Thynniid wasps are very localised as females lack wings and rely on the males to carry them around during copulation and to provide food. It limits their travelling and their homing range may comprise just a few hundred metres. Thynniid wasp are very vulnerable in small reserves isolated by land-clearing, and certain species have gone locally extinct due to conducting burns. Insects form a crucial and fundamental part of an ecosystem, but their importance is never considered in the planned burning, showing a complete lack of understanding by people in charge. So little is known of ecosystem’s foundations, but controlled burning continues – ruining precious habitats. Orchid species failing to produce seed pods is an indication that pollinators were absent, probably gone locally extinct. Orchid species that have a sexual association with thynniid wasp pollinators are localised and usually have geographically variable flowers. The situation is different with Cryptostylis spp. And their pollinating male wasp Lissopimpla excelsa, as females are a strong flyers. The flowers of Cryptostylis are geographically uniform in each species and the wasp is widespread. Both sexes are very distinctive in colour that show no variation. They are active over Spring and Summer and are great travellers.
Leo Davis is an orchid enthusiast with an eye for detail. Everyone seems to be aware of and gets excited over the flower of the large flying duck orchid but in the article below, Leo takes a look at a more significant event – the rare fruiting of the duck in South Australia.
TAKING A DIFFERENT PERSPECTIVE 1(The Large Flying Duck Orchid)
When approaching an iconic orchid like a flying duck orchid the obvious imperative is to emphasise the flying duck image. But as much fun as that can be, we can find and record some other significant aspects of this species. Do remember to look at all orchid flowers, with or without your camera, from different directions. And don’t forget the leaves.
In the last flowering season at Knott Hill NFR (Oct-Dec 2015) I photographed a double flowered large flying duck (Caleana major) on November 14. At the bottom of the upper left hand side flower you can see a white stigma (♀ part), sitting at the base of the bowl shaped column. The sticky surface of the stigma is ready to trap a pollinium (a sack of pollen grains), if the correct pollinator arrives, with a pollinium attached. Immediately below is a three lobed the triangular yellow pollinium packet (♂ part), as yet not taken by a pollinator. The highly sensitive mobile duck shaped labellum, a modified petal, looms above, waiting to slam a visiting insect down onto the pollinium, so attaching it to the back of the insect.
On December 10 I found the same plant, and one adjacent, in FRUIT. This is not often observed in South Australia and it has been suggested that the specific pollinator may be thin on the ground. I photographed both plants but that of the more advanced plant (shown), with fully withered flowers and plump developing ovaries, interested me more, because it suggested progress towards production of viable seed.
I went back on March 9, this year, and was delighted to find and photograph the fruit that had ripened, dried and split, so releasing the dust like seed. I was prepared for disappointment because the fate of seed pods of many orchid species is to be eaten. For example for the hyacinth orchid (Dipodiun roseum), across both the 2014-15 and 2015-16 flowering seasons, at Knott Hill, all plants that I found had their seed pods consumed. Kangaroos?
Robert Brown established the genus Caleana based upon his description of a specimen of Caleana major (1810). The type specimen was collected in 1803, at Bennilong Point, the site of the Opera House, so the species is extinct at that site now, of course.