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.

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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

Corunastylis littoralis with swollen seedpods

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

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.

 

2015 April Winning Photograph

04 sm HL Calochilus cupreusDespite having five very different but high quality photographs, Helen Lawrence’s photograph of Calochilus cupreus (Aldinga Bearded Orchid) was the clear winner with the vast majority of votes.

In South Australia it is considered endemic and endangered. Researching it was interesting. For instance, there is no mention of it in Jones extensive book (2006) yet it was named by R S Rogers in 1918 with a description appearing in Black’s Flora of South Australia (1922 edition), including a drawing by Rosa Fiveash. Between then and now there was a shift. In the Third edition of Black’s (1978) C. cupreus is absent but C. campestris present. In Bates and Weber 1990 the authors describe C. campetris (C. cupreus). Currently, the eflora of South Australia (the electronic version of 1986 Flora of South Australia) considers it a synonym of C. campestris. This is reflected in the Census.

It would appear that as C. campestris was studied and its variations documented (e.g. article by Jones 1976 Orchadian 5:83) the distinction with C. cupreus was lost. Clements and Jones (2006) state “Calochilus cupreus R.S.Rogers = Calochilus campestris” which means that they are not using C. cupreus. But in Jones’ book an anomaly occurs – he does not include South Australia in the distribution of C. campestris and as result Bates, from 2008, states that it is not recognized as occurring in South Australia.

Though C. cupreus disappeared from the literature the name still continued to be discussed amongst orchid enthusiasts. So when in 1995 NOSSA members found a distinctively different colony at Aldinga they identified it as Rogers’ C. cupreus.

Below is a chart, based upon Dr Rogers’ description, of some of the differences that made him consider C. cupreus a separate species:

C. cupreus C. campestris C. robertsonii
Shorter leafRather rigid or fleshy erect triangular section

Longer leaf

Crescentic section

Longer leaf Crescentic section
Base of labellum oblong glabrous (without hairs) with several raised longitudinal line Base of labellum round thickened, smooth no raised longitudinal lines Whole of labellum hirsute (hairy)
8 – 15 flowers About 8 flowers maximum About 8 flowers maximum

It will be interesting to watch what happens.

References

Bates personal communications

Bates & Weber (1990) Orchids of South Australia

Bates (2011) NOSSA South Australia’s Native Orchids

Bates (2005 to present) Orchids of South Australia CDs various editions

Clements and Jones An Australian Orchid Name Index (27/4/2006)

https://www.anbg.gov.au/cpbr/cd-keys/orchidkey/html/AustralianOrchidNameIndex.pdf

Jones (2006) A Complete Guide to Native Orchids of Australia

NOSSA Journal Vol 25 No 10 November 2001

Rogers R S Transactions of the Royal Society of South Australia V42 (1918) Pages 24, 25

http://www.biodiversitylibrary.org/item/113409#page/40/mode/1up

Greenhood Pollination Strategy

Since orchids, and Australian orchids in particular, first came to the attention of the western world in the 1800s researchers have been fascinated by the so many different aspects of the orchid’s morphology and life cycle. One area of interest has been that of how orchids are pollinated. The mechanism of pollination has not always been clear as the orchids seem to use different and complex methods.  From time to time various papers have been published of observations by researchers.

One such paper was published in the Annals of Botany 113: 629 – 641, 2014 titled ‘Caught in the act: pollination of sexually deceptive trap-flowers by fungus gnats in Pterostylis (Orchidaceae)’ by R D Phillips, D Scaccabarozzi, B A Retter, C Hayes, G Brown, K W Dixon and R Peakall.

The ‘question and answer’ style of the paper helps with ease of reading and is worthwhile perusing, even for the lay person. The accompanying VIDEO is also of interest.

The essence of the paper was to establish whether sexual deception was used to facilitate pollination.  The species researched was Pterostylis sanguinea (syn. Urochilus sanguineus) and the researchers confirmed that this did happen.  Their research showed that the attraction for the insect came only from the labellum which exuded an alluring chemical.  P. sanguinea has a mobile hinged labellum which is a feature of other sexually deceptive orchids such Paracaleana, Caleana, Arachnorchis.

Urochilus sanguineus RWL

Pterostylis sanguinea syn. Urochilus sanguineus with the untriggered labellum

Urochilus sanguineus RWL(1)

Pterostylis sanginea syn. Urochilus sangineus with a side view of the labellum

 

The Role of Orchids

October is Orchid Month with the greatest number of species flowering throughout South Australia; so it is worth considering the role of orchids in the Australian bushland.  Hence this week’s blog is an article written by Belinda Newman, Western Australia.

Orchids: The Canary in the Coal Mine was published in the Friends of Kings Park magazine For Plants and People, Issue 70 p 22-24, 2010.  The article is both a good introduction to, and summary of, her 2009 thesis Orchids as Indicators of Ecosystem Health in Urban Bushland Fragments

Orchids: The Canary in the Coal Mine

Belinda Newman – Research Scientist BGPA

What could orchids and canaries possibly have in common?

Before occupational health and safety and ventilation systems were commonplace in the mining industry, a caged canary would be bought down to the coal seam by the miners.  Canaries are particularly sensitive to methane and carbon dioxide which made them excellent indicators for the build-up of dangerous gases.  A singing canary meant everything was fine, a dead canary spelt trouble and an immediate evacuation.

Although orchids can’t sing, they do possess a number of traits that make them sensitive ecological indicators.  The relationships that orchids have with their surroundings form part of a complex ecological web.  Orchids have specific relationships with mycorrhizal fungi, which they require both for germination of their dust-like seed and ongoing growth of plants in adulthood.  These fungi in turn rely on the appropriate soil moisture content and carbon sources.  Above ground, the majority of terrestrial orchids in the south west of Western Australia rely on pollinators for successful seed set.  For some orchids this plant-pollinator relationship has become so highly evolved that removal of the pollinator would spell the end of the orchid.  The pollinators also have specific requirements for habitat, appropriate food sources and nesting sites.  These above and below ground links to the ecosystem make orchids particularly sensitive to disturbances and changes in their surroundings.

The potential for orchids to be used as indicators of ecosystem health formed the basis of a study between Kings Park and Botanic Gardens and Murdoch University.  The coal seam was eleven urban reserves of varying condition on the Swan Coastal Plain.  The canaries were seven orchids common to Perth’s urban bushlands; the Carousel spider (Caladenia arenicola), Cowslip orchid (Caladenia flava), Pink Fairy orchid (Caladenia laitfolia), Pansy orchid (Diuris magnifica), Dark Banded Greenhood (Pteryostylis sanguinea), Purple Enamel Orchid (Elythranthera brunonis) and the Mignonette orchid (Microtis media).  Before it was possible to see which orchids made the best canaries, it was important to determine the health of each of the bushland sites.  A number of environmental variables were chosen that best reflected the health of the ecosystems.  Extensive surveys and analysis of species composition, plant functional groups against these environmental variables revealed a range of site conditions from close to pristine to highly degraded.  This provided the backdrop against which to determine the effectiveness of orchids as indicators through the measured responses of the orchid species.

Firstly orchid presence and abundance was measured across sites to determine if particular orchid species showed a preference for particular site conditions.  Diuris magnifica and Microtis media showed strong correlations and were most abundant in poor condition sites and Pteryostylis sanguinea showed strong correlations to sites in good condition.  While the abundance and presence of orchids appeared to correlate with site condition, we wanted to know what other aspects of the orchid we could measure as a means of judging the health of an ecosystem.

Successful seed set in plants reflects a healthy ecosystem and the reproductive success of the seven orchid species was investigated to determine the effects of declining site condition on seed set.  Pollination trials were set up to measure natural and artificial pollination events across all sites.  Widespread depression in pollination across all species and sites was found to be occurring, rendering seed set a poor measure of ecosystem health.

Investigations into the below-ground links orchids have with the ecosystem were undertaken by determining the presence and abundance of orchid mycorrhizal for the seven orchid study species across all sites.  Mycorrhizal distribution was found to be patchy within urban reserves and also revealed unoccupied niches capable of supporting orchid germination.  A greater abundance of Microtis media mycorrhizal at sites of poor condition supported earlier correlations of plant abundance at sites of poor condition.  The higher abundance of mycorrhizal symbionts for Caladenia arenicola at sites of very good condition also suggests its potential as an indicator species.

The study also looked at seedling growth in urban reserves.  This was the first time that biomass allocation in orchids has been investigated in light of ecosystem health.  In poor condition sites, Diuris magnifica and Caladenia arenicola increased growth effort to the above ground leaf. In sites of very good condition, these two species increased growth to the tuber to take advantage of being able to store starch as a result of both fungal and photosynthetic activity taking place.  Most importantly this shows a measurable change over a short period time.  Although it is effort intensive, planting orchid seedlings of a standardised size into the field may provide a useful and rapid measure of ecosystem health, much like caged canaries were used in the past.

This research into using orchids as an indicator species is the first of its kind and suggests that orchids can be used as an indicator of ecosystem health.  Future research will need to focus on the thresholds of the species identified as potential indicators in this study.  What aspect of the orchid’s ecology will give clear and repeatable data linked to ecosystem health?  Following the canary analogy, how long can orchids hold their breath? Future studies would need to focus on testing these thresholds.  The results of this study suggest that orchid presence and abundance, orchid growth and orchid symbionts can be used as indicators of ecosystem health, although work needs to be undertaken to refine the understanding of their response to specific disturbances.  This study provides a baseline for investigating the utility of orchids as indicators of ecosystem health in highly fragmented systems.  Perhaps orchids and canaries have more in common than first thought.

 

Help Save South East Austalia’s Unique and Threatened Orchids

Australian orchids are special but Australian orchids have been disappearing from our landscape.  Throughout the country individuals and groups are attempting various conservation methods to help save our orchids.  One such group is Dr Nouska Reiter and her team from Orchid Conservation Program, and arm of the Australian Network for Plant Conservation Inc

Dr Nouska Reiter is seeking to raise money for a conservation laboratory to cultivate threatened orchids for reintroduction into the bushland.  She has a month left; so for details about the project and on how to help, go to Help save South East Australia’s unique and threatened orchids!