This month’s theme for the photo competition was blue and white. White flowers can occur as a result of lack of colour such as Rosalie Lawrence’s Caladenia latifolia (Pink Fairies) which is normally pink. White orchids can also occur naturally such as the Arachnorchis argocalla (White Beauty Spider Orchid) and Arachnorchis intuta (Ghost Spider Orchid) both photographed by John Fennel, or as a dominant colour such as Lorraine Badger’s Eriochilus collinius (syn Eriochilus sp Hills Woodland).
Of the blue orchids, both Ricky Egel and John Badger entered pictures of Thelymitra x truncata (Blue Spotted Hybrid Sun Orchid) whilst Robert Lawrence entered a Thelymitra grandiflora (Giant Sun Orchid) which was the outstanding winning picture.
Blue in the floral world is unusual colour in the floral world for it is not a naturally occurring colour. In fact, “[t}he key ingredient for making blue flowers are the red anthocyanin pigments. Less than 10 percent of the 280,000 species of flowering plants produce blue flowers.” (Lee, 2010 as cited in Oder 2014).
Whilst blue orchids occur outside of Australia, their “colour cannot rival” … “the intensely blue flowers” … “especially [are] unique in the orchid world” … “of their Australian counterparts. The sun orchids (Thelymitra) in particular are famous for their sky blue flowers.” (Ronse 2008: 103)
Based upon Jones 2006 tome, the following genera have true blue orchid species – Cyanicula (9 species), Pheladenia (1 species), Epiblema (1 species) and the largest group Thelymitra (about 65 out of potentially 118 species) plus one hybrid, XGlossodenia tutelata. Of the epiphytes, blue is almost non-existent except for three which Jones lists that rarely might be bluish and they are Vappodes bigibba, V. lithocola and V. phalaenopsis*.
With such rarity, is it any wonder then that the Chinese attached special significance to it as a plant that could cure lung disease and the Aztecs saw it as a symbol of strength.
*Names used as they appear in Jones 2006 tome
Jones, D. L., A Complete Guide to Native Orchids of Australia Including the Island Territories. Reed New Holland
Lee, David (2010), Nature’s Palette: The Science of Plant Color< Chicago, University of Chicago Press
Oder, T, The Science of Blue Flowers https://www.mnn.com/your-home/organic-farming-gardening/stories/the-science-of-blue-flowers accessed 6 July 2017
Pretty Zesty All About Blue Orchids http://www.prettyzesty.com/2012/11/all-about-blue-orchids.html accessed 6 July 2017
November’s theme was hybrids. Orchids, more than any other plant family, are likely to produce natural hybrids. Even though the overall occurrence of natural hybridisation in orchids is low, it occurs often enough to make some species identification challenging.
Hybrids mainly occur between species of the same genera such as Jenny Pauley’s Arachnorchis brumalis x A. conferta
but, less commonly, it can occur between genera as seen with Pauline Meyer’s Caladenia latifolia x A. brumalis
and her Western Australian photograph of Caladenia x enigma; a hybrid between C. falcata and Drakonorchis barbarossa.
Jones (2006) states that “Natural hybrids are more common in some genera, such as Arachnorchis, Caladenia and Diuris, than in others.” To this list could be added Thelymitra as seen with both of the winning pictures T. x truncata and T. x irregularis. Interestingly with these two hybrids, the parents are not always the same; the parents for T. irregularis could be T. ixiodies or T. juncifolia with either T. carnea or T. rubra.
A similar situation occurs with T. truncata with the parents consisting of T. juncifolia and any member of the T. pauciflora (including T. albiflora, T. arenaria, T. bracteata, T. brevifolia, T. cyanapicata, T. pauciflora) or of the T. nuda complex.
The conditions necessary for hybridisation are that the parents must grow in the same area, have overlapping flowering time and share the pollinator. Brown et al (2103) make the additional observation – Hybrids are more common between wasp and bee-pollinated species than between two wasp-pollinated species or two bee-pollinated species. … However, rare hybrids between species using the same pollination strategies, do occasionally occur …
Obviously hybridisation is more likely to occur when there is an abundance of the parent species. This situation can occur when there is mass flowering following fires or good seasonal rains. Site disturbances either through natural causes or clearing can result in increased incidence of hybridisation.
Hybrids are often infertile and will only last for the life of the individual plant but some have the ability to reproduce vegetatively and, provided the conditions remain favourable, may persist for several years.
One situation that can occur is hybrid swarm. When these occur they can make orchid identification challenging. Hybrids share the characteristic of both parents and by careful observation this can be deduced but swarms introduce an added complexity because the hybrid can backcross with either of the parents or cross fertilise with themselves. The result is a wide range of variation which makes orchid identification difficult.
Finally, some orchids will not hybridise even though the conditions are right. This could be due to specific pollinator or possibly chemical or genetic barriers.
Brown et al (2013) Field Guide to the Orchids of Western Australia, Floreat, WA, Simon Nevill Publications
Jeans, Jeffrey & Backhouse, Gary (2006) Wild Orchids of Victoria, Seaford Vic, Aquatic Photographics
Jones, David (1988) Native Orchids of Australia, Frenchs Forest, NSW, Reed Books
Jones, David (2006) A Complete Guide to Native Orchids of Australia including the Islands and Territories, Frenchs Forest, NSW, Reed New Holland
Introduction to Australian Orchidaceae CD-ROM
https://www.anbg.gov.au/cpbr/cd-keys/orchidkey/html/intro-c_hybrid.html accessed 7th December 2015
Bates, Robert (2011) South Australia’s Native Orchids NOSSA DVD Adelaide
Spotted Pink Sun Orchid – Beautiful, but Only a Hybrid
https://nossa.org.au/2014/09/26/thelymitra-x-irregularis-beautiful-but-only-a-hybrid/ accessed 7th December 2015
100 years ago on 15 July 1915, the state government declared Morialta a National Pleasure Resort. The Friends of Black Hill and Morialta have been holding a series of public events to celebrate the Centenary of Morialta. As part of the celebrations, the Native Orchid Society of South Australia has conducted some orchid walks in the park.
In 2004, an interim Flora Species List was produced by the then Department for Environment and Heritage and 39 orchid species were listed. It is an interim list and considering that the park is 5.33 square kilometres with a range of different habitats, it is possible that there are more species than originally listed.
One native species not included on the list is Caladenia latifolia but its presence is well known to members of the Native Orchid Society. Unfortunately the South African weed orchid Disa bracteata (Monadenia bracteata) has also been found in the park.
In this video most of the shots have not been taken at Morialta but it does showcase some of the orchids that can be found in the park.
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.