March 2016 Winning Photograph

1603 sm JS Arachnorchis sp

We frequently receive entries from Western Australia but this month our entries were from both the west and the east. Allen Jennings entered a Calanthe triplicata (Christmas Orchid) from New South Wales. Pauline Meyer’s was from the west, (Western) Flying Duck Orchid, Paracaleana nigrita. The other entries were South Australian, Jenny Pauley’s recently photographed Leporella fimbriata (Fringed Hare Orchid), Greg Sara’s Thelymitra rubra (Common Pink Sun Orchid) and Judy Sara’s Plumatochilos sp. (Bearded Orchid) and Arachnorchis sp. (Spider Orchid).

The winning photograph was Judy’s Spider Orchid. Obviously it was one of the Green Comb Spider Orchids – A. dilatata complex. Of this group there are about a dozen possibilities. Knowing the location, Mt Boothby, helped to narrow the options with the most likely candidate being Arachnorchis stricta but it wasn’t convincing. It would appear that the tips of the sepals may have been chewed off when in bud.

A distinguishing feature of this species is that there are no clubs or osmophores on the sepals. Other species of this complex have clubs. Another feature is that the dorsal sepal is bent over the column unlike many other green combs which have an erect dorsal sepal. The features that caused doubt were lateral sepals looking droopy instead of being characteristically stiffly held out but dry conditions could cause this. The other was that the labellum did not strictly fit the description of A. stricta but then again it is a variable species.

The conclusion was a possible hybrid but there is no information on the likely parents or that is an atypical A. stricta that may have been damaged in bud.

This is an example of the difficulties that can occur when attempting to identify a plant from one photograph.

Reference:

Personal communications Thelma Bridle (NOSSA Conservation Officer)

Personal communications Bob Bates

Bates, R. J., ed. (2011). South Australian Native Orchids. Electronic version, 2011. NOSSA

Rules of entry:

The subject matter must have something to do with Australian orchids.  Any format is acceptable including Photo shopped images, artwork, etc

How to enter:

Email nossa.enquiries@gmail.com – jpg as large as you are able to send it, preferably A4 ratio for printing

Post: PO Box 565, Unley, 5061

Bring in to the meeting

WHAT ORCHID IS THIS? HOW PHOTOS CAN HELP! – Part One of Two Parts

The following article is from the April 2016 Journal of the Native Orchid Society of South Australia.  The article is complete in itself but Part Two of this post will illustrate how images can help with images of Crytostylis robusta and C. reniformis.

Orchids are beautiful plants and many of us like to capture that beauty on photographs. And there are many beautiful pictures around.

Many times NOSSA, the Herbarium and other specialist groups receive images requesting identification but the vital information is missing.

When photographing for identification, it is necessary to take more than one image, particularly if you are unable to easily return to the site for more images. When in doubt, take several shots from many different angles highlighting different features of the plant and its habitat.

Another very important point to remember is, when there are several of the same plant, to photograph the orchid that is most representative of the group, not the atypical or unusual plant.

General Guide

As a general guide, it is helpful to take a picture of each of the following

  • whole plant
  • individual flower – both from the front and the side, occasionally the back.
  • flower head
  • leaf or leaves
  • habitat

Other helpful things to consider photographing are:

  • capsules of the finished flower – sometimes it can yield useful information.
  • for some genera, the stem can also be a helpful feature as between some species there can be a difference in the hairiness of the stem.
  • It is also worth including in a photograph an indication of whether the plants are growing in colonies with others or as scattered individual plants.

Importance of Size

It is also good to give an idea of size, this can be as simple as using a thumb or hand, a coin (show the reverse not the head) or any item that had an easily recognized size. It is important to have the object next to the feature being photographed. For example, a coin on the ground next to a leaf or a hand immediately behind the flower gives a clear indication of size. Remember to take another photo without the hand or coin.

Some Specific Identifying Features

Some species are distinctive and easily recognised, eg the Flying Duck Orchid, but others are not and it is helpful to know what part of the plant to photograph as different genera will have different identifying features.

  • Spider orchids – the tips of the segments (petals and sepals) and details of the labellum are important
  • Sun orchids – the column in the middle, the ovary at the base of the flower, and the number of bracts (leaf-like growth) on the stems
  • Pink fingers – the length of the leaf in comparison with the length of the flower stalk; also the back of the flower is helpful
  • Gnat orchid – the leaf is the best identifying feature, but also the bud can be helpful
  • Hyacinth orchid (of the Adelaide Hills) – labellum
  • Mosquito, Mayfly and Helmet orchids when not in flower – both sides of the leaf
  • Gastrodia – the flower spike
  • Rufoushoods – side view of the flower and close up of the labellum as the hairs on or surrounding the labellum are important features.
  • Leek Orchids – the labellum is very important, as well as part if not all of the flower spike as the distance between the individual flowers aids identification
  • Greenhoods – if present, the non-flowering rosette of leaves

The Australian Virtual Herbarium has some good tips for photographing flower. Click here to visit the site

 

Spider Orchid
Spider Orchid Photo: Robert Lawrence

This image lacks the ends of the segments to determine the identification.  The presence or absence of  clubs on the ends of the segments (petals and sepals) can often be the distinguishing feature with many of the Arachnorchis (Spider Orchids).

Atypical Cyrtostylis leaves

These leaves are an unusual shape and by themselves are not suitable for identification

THE DUCKS – TAKING A DIFFERENT PERSPECTIVE PART TWO of TWO

In Part One, Leo Davis’ first article centred on the Large Flying Duck, this second part is about the lesser known Little Duck.

TAKING A DIFFERENT PERSPECTIVE 2 (The Small Flying Duck Orchid)

There are at least three speceis of flying duck orchids in SA, one in genus Caleana and two others having been moved from there to genus Paracaleana.

My favourite, of the two duck orchids that most of us see, is the small duck orchid (Paracaleana minor).  It is actually rarer than the more popular species, can bear six or more flowers on a spike, and has a more delicate and quirky charm, to my eye. 

As with the large flying duck the usual angle of photographing the smaller species is to emphasise the ‘flying’ nature.  But again there is other detail to see and to be illustrated from other view-points.

The accompanying image of the little duck flower, viewed from the front, shows variations on the same structures shown previously in the large duck orchid.  Down at the bottom of the flower is the sticky stigma (♀ part), not white this time, and immediately below is the triangular yellow pollinium packet (♂ part).  Again both structures sit in the bowl shaped column.

Paracalean minor arrows copy
Paracalean minor (Little Flying Duck Orchid)

Note the three part symmetry of the pollinium, with a distinctive Mercedes Benz logo (or Mitsubishi if your budget only stretches that far) to tease us.

The location of the female (♀) and male (♂) organs, adjacent to each other, fused to form a column, is one of the main distinguishing characteristic features of the orchid family.

As an afterword let me remind you that the little duck (like the larger, collected in Sydney in 1803) started out as Caleana minor but was moved to a new genus, leaving the large duck as the only member of its genus.  Rules of nomenclature mean that the small duck had to keep its specific name (minor), hence we now have Paracaleana minor but there is no, and never will be, Paracaleana major.  But Caleana minor still appears in publications and some folks may still use that name.

Some of you choose to use different scientific names to some that others use. Recently some of us bought a propagation pack that Les Nesbitt produced, to grow the maroon banded greenhood (Pterostylis sanguinea.) In the unlikely event that my pack produces seedlings I will label them Urochilus sanguineus.  And we can both justify our choice.  And then, of course, some taxonomist could move the little duck back to its original genus one day. 

Then, of course, there is the added complication that David Jones (Native Orchids of Australia Including the Island Territories. 2006, p148) calls the species Sullivania minor!

Leo Davis

The Ducks – Taking A Different Perspective Part One of Two

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)
Leo Davis

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.

OLYMPUS DIGITAL CAMERA
Caleana major (Flying Duck Orchid) – note the location of the stigma and pollinium

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.

Caleana major fruiting body
Success – Caleana major Fruiting Bodies

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?

OLYMPUS DIGITAL CAMERA
Dehiscent (splitting of the seed pod to allow dispersal of the seed) Caleana major

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.

 

February 2016 Winning Photograph

1602 sm PM Caleana major

For our first competition of the year we had five photographs – three of flowers and two of participants on a field trip.  The species represented were David Mangelsdorf’s Calochilus robertsonii (Southern Bearded Orchid); Robert Lawrence’s Pheladenia deformis (Blue Bearded Orchid) and Pauline Meyer’s Caleana major (Flying Duck Orchid) which was the winning photograph.

There is no doubt that the Duck Orchids are very photogenic and that people want to see and photograph them.  When seen the for the first time their small size surprises most.  The flower is no bigger than a thumbnail, perched atop a spindly stalk that may only reach 50cms (20 inches).

Although the rusty red colour of the flower is quite exquisite, this means that it blends in with the surrounding leaf litter and scrub and is not easily spotted.

As species of Heathy Woodlands, in South Australia, it is often found growing in sparse colonies near the base of trees.  Other plants associated with them are banksias, eg Banksia ornata, Eucalyptus baxteri and bracken.  The soil is sandy, often from leached acidic dunes, or gravelly.

Reference:

2008 Department for Environment and Heritage Electronic Flora of South Australia species Fact Sheet: Caleana major R.Br. Available from pa-fact-pafactcaleanamajor.pdf

Bates, R. J., ed. (2011). South Australian Native Orchids. Electronic version, 2011. NOSSA

What Pots Should I Use For My Terrestrial Orchids?

The best size pots to use for terrestrial orchids should be between a minimum of 125mm (5 inches) to a maximum of 175 mm (7 inches).  Black plastic pots are better than terracotta as they last longer and are easy to sterilize.

If the pots are too small, they dry out too quickly in Autumn and Spring.

If they are too large, it gets too wet for the tubers.  If using a larger pot, then the drainage needs adjusting by adding coarser sand to the mix.  Specimen pots for show purposes utilize pot sizes up to 300mm holding 30-50 plants.  Clay pans are sometimes used for show work.

The pots should not be shallow. 125mm depth is the minimum recommended for reliable results.  For instance, the Arachnorchis like deeper pots as the tubers tend to go down deep.  Droppers have been known to come out of the bottom drainage holes.  When this happens to stop the tubers shrivelling up in summer, it will be necessary to stand the pot on the sandy soil of another pot.

Used pots can be cleaned by blasting off loose grime with a high pressure jet of water and then soaking in a bucket of water & White King (bleach).

Pot of Caladenia latifolia cultivated by Les Nesbitt
Caladenia latifolia – show specimen in larger size pot

CLUES TO ORCHID IDENTIFICATION – Prasophyllum & Microtis Leaves

Orchids are attractive and abound in variety. It is the variety that often provides the challenge of identification. As a novice it can be a bit overwhelming. In the eye of the beginner, the experienced orchid hunters appear to have no difficulty with identification. Over the years they have accumulated various clues that guide them toward accurate identification.

This series aims to document the clues that orchid hunters use.

Prasophyllum and Microtis Leaves

The first in the series relates to distinguishing between Microtis and Prasophyllum leaves. When in flower it is easy to see which is which but not so when only in leaf; and as they do not always produce flowers it is helpful to be able to separate them out at leaf stage.

Both leaves are green. Both are cylindrical. Both are hollow. Both resemble onion leaves.

M & P Leaves
Both types of leaves are long, thin and green.  The damaged Microtis leaf (below) shows the hollow.

The differences can be found in one or two areas. Microtis leaves are always green at the base whereas Prasophyllum leaves usually but not always will have a red or purplish coloured base. To help in identification, it is necessary to examine the base by moving the leaf litter aside to see where the plant emerges from the soil.

M & P Leaf Bases
The bases reveal the difference between the two genera.

Prasophyllum species that could have a green base are P. laxum, P. occulatans, P. sp Jip Jip, P. elatum, P. sp Sandplain, P. pallidum (although this is short and usually in bud when noticed), P. spicatum, P validum.  So further observations are necessary.

Another other area of difference is that the broken leaf of a Microtis yields a mucilaginous (thick sticky) sap; the Prasophyllum leaf does not.

Within the segregate genera used by many NOSSA members, there are two other genera with similar leaves. They are Microtidium and Hydrorchis. Again they are green, cylindrical, hollow but only hollow in the lower half. The top half is solid.

It should also be noted that Microtis can form dense colonies but Prasophyllum will never form more than loose colonies.

Finally, if upon gently feeling the base of these leaves it feels solid, that will indicate that there is a bud and it will most likely flower this season.

M & P Flowers
Once in flower, the differences between the two genera is obvious.

It’s Not Extinct at Ferris-McDonald After All

Leo Davis is an enthusiast about the natural world and shares his knowledge through different journals.  He is a keen observer and meticulous in his record keeping.  He is also very knowledgeable about orchids.  The following is one such article of Leo’s.

GOOD NEWS FROM FERRIES-McDONALD CONSERVATION PARK
Leo Davis

I was aware of the Star Spider Orchid from Bates who lists the species as ‘3E, critically endangered in South Australia, nationally rare’ (pp. 242–243). I knew that in the past it had been found at Monarto and Hartley and discussions with members of the Native Orchid Society of SA (NOSSA) suggested that it had been seen at Ferries-McDonald Conservation Park, but was now possibly extinct there. My searches over five years had all failed.
On August 2, 2014, I ran into, then strangers, Len Stephens and his grandson Rickey Egel, in Monarto C.P. They had just come from Ferries-McDonald C.P., about 8 km further south. Rickey, who has a very good eye for spotting orchids, showed me an image, in his camera, of ‘the common spider orchid’. From my hurried glimpse I knew immediately it was far from ‘common’ and told him so. I headed straight for Ferries-McDonald C.P. for the first of many fruitless searches.  On August 14, 2015 Rickey and Len showed me a few Star Spider Orchids in flower at Ferries-McDonald C.P. Because I was to lead the Botany Group of the FNSSA on an outing to Ferries-McDonald C.P. on September 5, I had been visiting the park almost weekly and so was able to spend many hours looking for the orchid. It is difficult to spot, being quite small. This year’s plants, perhaps not typical given the very dry June, are between 8 and 20 cm high with flowers only about 35 x 30 mm.
Plants were only found in Broombush (Melaleuca uncinata) associations. As soon as Eucalyptus species were present the orchid was no longer found.
Any survey, especially by a single person, will produce a lower count than the actual population. Leaves of non-flowering or beheaded (the fate of so many spider orchid flowers) plants will not be recognised, some flowers will not be spotted and some plants will flower before or after surveys, with some areas surveyed on different days. Between August 14 and September 5, 2015 just 18 flowering plants (Fig. 1) were positively identified (about the same number of likely leaves and buds, adjacent to these, were noted) over a narrow area of approximately 3,000 m2. The area searched was very much greater than this. Small as this tally is, it establishes a significant population other than the only other South Australian one that I know.  That is on the private property of farmer […], at Hartley. With his kind permission I have counted over 100 flowering plants there during five visits from July 28 (buds only) to August 30 (Fig. 2). The actual population will be larger because I did not cover all of that location. My observations suggest the populations I know to be around 150 to 200 plants with other occurrences probably existing around Monarto and Hartley.
Why have I avoided the scientific name? Many of you will follow the Electronic Flora of South Australia which lists the Star Spider Orchid as Caladenia stellata, as does Backhouse (pp. 456–457). I prefer to follow Jones (p. 76) (who does not recognise the species occurring in SA) and Bates (p. 242) (who says it does occur in SA), both of whom call it Arachnorchis stellata. Backhouse points out that the nearest other occurrence, the major one, is in central southern New South Wales, south of Rankin Springs, several hundred kilometres away, and that the plants there differ from our populations in having smaller flowers. He suggests that we are looking at a separate undescribed species, Caladenia sp. ‘Murray mallee’ (p. 484), but that it might indeed be co-specific with the Rock Star Orchid (sic), Caladenia saxatilis, which is similar and occurs further north, in the northern Mt Lofty and the southern Flinders Ranges. Bates told me in conversation, that he disagrees with Backhouse and believes the local plants are the same as those in NSW and distinct from A. saxatilis, which grows in soils of different pH (acidity).

 

Good News from Ferries-McDonald-1 38LD
Fig 1: Arachnorchis stellata, Ferries-McDonald CP,  August 22, 2015.  Photo: Leo Davis

Good News from Ferries-McDonald-2 38LD
Fig 2: Arachnorchis stellata Hartly, South Australia, August 5, 2015.  Photo: Leo Davis

BIBLIOGRAPHY:

Backhouse, G. (2011). Spider-orchids – the genus Caladenia and its relatives in Australia. DVD/pdf, Backhouse, Melbourne.
Bates, R.J. (2011). South Australia’s Native Orchids, DVD, NOSSA, Adelaide.
eFlora SA. Electronic Flora of South Australia; last updated August 22, 2015.
Jones, D.L. (2006). A complete guide to native orchids of Australia including the island territories. Reed New Holland, Sydney.

 

 

Used by permission, extract from The South Australian Naturalist Vol. 89 No 2 July-December 2015.

Are there any orchids growing in the desert?

Think of deserts and the image is that of a bleak barren landscape with little to see but this is not so.  The conditions are harsh but there is a myriad, though not an abundance, of hardy fauna and flora if one but looks closely.

But concerning orchids – No orchids have been found in true deserts…..  They also appear to be absent from the arid mountains of the far north-west, or at least no-one has ever found orchids there.

Orchids need moisture and so they do not grow on unstable soils such as dry sand-hills, gibber plains or the many saline areas of the far north but on the desert fringes there are micro-climates where the moisture, humidity and soil structure is  just right (to quote Goldilocks) for orchids.  This micro-climate is created by [s]hrubland  [which] is … [an] … important dryland orchid habitat. Besides providing shade and shelter for the orchids, shrubs like the many species of wattles, Acacia and hop-bush Dodonea drop fine leaves which help to hold the soil together and slowly break down into humus rich with nutrient and water storing capability. These shrublands usually form in soils too dry or shallow for trees. Orchids of course have no need for deep soils as they are shallow rooted. 

Robert Bates Semi-arid Shrubland.jpg
Semi-arid Shrublands, Flinders Ranges

Of the five desert botanical regions, the Eastern region contains the most number of species with over a dozen species.

Botanical Regions Map
Colour added to indicate the desert regions (in red)

Orchids of the Eastern Region – this region is from the east of the Flinders Ranges to the New South Wales border and includes the Olary Spur and Lake Frome.

Arachnorchis toxochila – Dry Land Spider Orchid or Bow Lip Spider Orchid.
Corunastylis tepperi – Mallee Midge Orchid
Diplodium robustum – Common green shell-orchid.
Hymenochilus pagophilus – Mountain Shell-orchid
Microtis eremaea – Desert onion orchid
Microtis frutetorum – Common woodland onion orchid.
Oligochaetochilus bisetus species complex, Rusty rufous-hoods

Oligochaetochilus sp. Blue-bush Plain – Blue Bush rufous-hood (O. bisetus complex)

Oligochaetochilus sp. Outback – Outback rufous-hood (O. bisetus complex)

Oligochaetochilus cobarensis – Little desert rufous-hood
Oligochaetochilus sp. Crossed Sepals Bibliando rufous-hood. (O. hamatus complex)
Oligochaetochilus sp. Bimbowrie Bimbowrie Rufoushood (O boormanii complex)
Oligochaetochilus linguus – Swept-back Rufoushood

Oligochaetochilus sp. Old Boolcoomatta Large-lip rufous-hood (O. linguus complex)

Oligochaetochilus sp. Quartz – Quartz hill rufous-hood (O. linguus complex)

Oligochaetochilus sp. Slender desert – Slender Desert rufous-hood (O excelusus complex)
Undescribed not within any other Oligochaetochilus complex

Oligochaetochilus sp. Canegrass – Desert Sand-hill Orchid.

Oligochaetochilus sp. Oratan Rock – Diminutive rufous-hood

Oligochaetochilus sp. ‘Mt Victoria Uranium Mine’ – Uranium rufous-hood

Prasophyllum odoratum – Scented Leek-orchid

Prasophyllum sp. Desert Desert Leek-orchid (P. odoratum complex)

The Gairdner-Torrens region includes, besides the salt lakes it is named after, the Gawler Ranges and the southern part of the Great Victoria Desert.  Though not as many species as the Eastern region, it contains some different species including a Sun Orchid.

Thelymitra megcalyptra
Thelymitra megcalyptra
Arachnorchis interanea – Inland Green-comb Spider Orchid
Arachnorchis toxochila – Dry Land Spider Orchid or Bow Lip Spider Orchid.
Hymenochilus pagophilus – Mountain Shell-orchid
Hymenochilus pisinnus – Tiny Shell-orchid
Jonesiopsis capillata – Pale Wispy Spider Orchid
Linguella sp. Hills nana – White haired little-greenhood.
Microtis eremaea – Desert onion orchid
Oligochaetochilus ovatus – Ovate Lip Rufoushood
Oligochaetochilus xerophilus – Desert rufous-hood
Prasophyllum sp. Desert Desert Leek-orchid (P. odoratum complex)
Thelymitra megcalyptra – Scented or Dryland Sun Orchid

Third of this group is the Nullabor region.  Consisting of flat treeless limestone plains, this area, surprisingly, has two species both of which have been found close to the coast.

Urochilus sanguineus – Maroon banded greenhood
Corunastylis sp. Intermediate – Halbury Midge Orchid (C. rufa complex)
Urochilus sanguineus
Urochilus sanguineus

The final two regions Lake Eyre and North-Western contain the vast expanses of desert of the far north of South Australia.  Definitely not a place to find orchids yet one specimen has been collected from each of these two regions.

Oligochaetochilus sp. Everard Range (L. Scott 173), Mimili Orchid (possibly O. woollsii complex) from North-Western Region.

Oligochaetochilus sp. Gammon Range (O excelusus complex) from the Lake Eyre region.

It is unusual to find orchids in the desert because they only grow when there have been good winter rains which isn’t very often.  But nevertheless, here in South Australia we have over 20 possible species – an astonishingly high number for such a harsh area!

Reference:

Bates R J ed, South Australia’s Native Orchids, 2011 Native Orchid Society of South Australia

Map adapted from Flora of South Australia, Fourth Edition, 1986

 

 

Orchids, Insects and Fire

Recently, 10th February 2016, Anita Marquart, PhD student, Adelaide University spoke at the Field Naturalists Society of South Australia. She is a recipient of the Society’s Lirabenda Endowment Fund Research Grant.   At the meeting she gave a summary of her research – Orchids, Insects and Fire: Investigating the impacts of prescribe burning on orchid pollinators in Southern Australia. Though she has not finished collating the data she has kindly supplied a summary of her talk with her preliminary findings.

It is always encouraging to see research on our native orchids. They are the Barometer of the Bush, so the more we can discover about them, hopefully the more we will better understand how to manage our native bushland.

 

Orchids, Insects and Fire: Investigating the impacts of prescribed burning on orchid pollinators in Southern Australia

Anita Marquart, Renate Faast, José M. Facelli, Andrew Austin

School of Earth and Environmental Sciences,

The University of Adelaide, Adelaide 5005 Australia

PhD Project

Summary

Fire is an important ecological factor in Australian ecosystems. Orchids that depend on specific pollinators may be more susceptible to disturbance than more generalist species. Therefore, declines or changes in pollinator communities due to prescribed burns and wild fires could lead to reduced pollination success and consequently declines in orchid populations. The project combines traditional plant and insect ecology with advanced molecular techniques to identify orchid pollinators and assess their response to prescribed burns and wild fires. Insect relevant habitat characteristics (such as floral abundance, vegetation height, presence of logs, litter and standing litter) were assessed and trapping surveys of potential orchid pollinators were conducted in spring, before and after prescribed burns. The effect of both spring burns and autumn burns is being investigated.

Study sites are located in the Adelaide hills with always one burn and one adjacent control site respectively in Kersbrook Native Forest, Millbrook Reservoir, Para Wirra Recreation Park and South Para Reservoir. Some parts of the study sites in Kersbrook and Millbrook were affected by the Sampson Flat Bushfire. Affected sites are used to compare the effects on orchid pollinators after prescribed burns in contrast to wild fires.

Potential orchid pollinators are being identified using DNA barcoding with the mitochondrial cytochrome oxidase I (COI) gene. Sequencing results will be compared with existing databanks and confirmed using morphological identification. As the data accumulates it will build up a reference library of COI barcodes for the species found in the surveys.

The outcome of this research project might help to advise the optimal management of orchid species under fire-managed regimes in the Mount Lofty region of South Australia, as well as more generally in south eastern Australia.

160219 Anita Marquart Melangyna collatus on Caladenia rigida
A hoverfly, Melangyna collatus on Arachnorchis rigida syn Caldenia rigida (Rigid White Spider Orchid)

 

Orchids and their pollinators

Native bees, thyninne wasps and Syrphid flies are known orchid pollinators of South Australian orchid species. Orchids of main interest for this study were Caladenia rigida, Caladenia behrii, Caladenia tentaculata and Glossodia major. Caladenia tentaculata and C. behrii are sexually deceptive orchids and are known to be pollinated by thynnine wasps (Bates 2011). In contrast, C. rigida is food advertising and uses a broad range of bee and fly species, such as native bees and hoverflies (Faast et al. 2009). Glossodia major is a generalist in its pollination strategy and is using small native bees of several genera (Bates 2011, personal observations).

Preliminary findings

Syrphid flies were successfully separated into different species using DNA barcoding methods. Results show that we have two dominating species on our field sites in the Adelaide hills. Both species, Melangyna collatus and Symosyrphus grandicornis are common native Australian species. Both species were caught with orchid pollinia attached and were observed on Caladenia rigida flowers.

First findings suggest that hoverflies don’t seem to be much affected by prescribed burns or bushfires. Syrphid fly numbers vary greatly between the years of sampling, but we did not find a significant impact of prescribed burning or the Samson Flat bushfire.

Statistical analyses for the data on syrphids, native bees and thynnine wasps are currently underway.

Preliminary findings suggest that a range of pollinators are still present on field sites after prescribed burns and even after bushfires. Nevertheless, some specific species might be more sensitive to fires and might have disappeared from the study sites. For example, orchids relying on one species of wasp could be more affected by changes in the abundance of their pollinator after fire, than orchids that are pollinated by a number of different insects.

We will have to analyse our results in more detail to look into the specific species composition for the insect families, especially for native bees and thynnines, rather than looking at overall abundance.

160219 Anita Marquart Melangyna collatus with pollinia
Hoverfly, Melangyna collatus with orchid pollinia attached

References:

Faast R, Farrington L, Facelli JM, Austin AD (2009). Bees and white spiders: unravelling the pollination syndrome of Caladenia rigida (Orchidaceae). Australian Journal of Botany 57, 315–325.

Bates, R. J. (2011). South Australia’s Native Orchids. Native Orchid Society of South Australia.