"It's spring...
Australia's native orchids...
insect lures...
photo : [caption : "Fringed Mantis... tricks to get insects to visit."]
http://www.abc.net.au/reslib/200809/r295997_1273705.jpg
Promising food and even tricking insects into thinking they're a sexual
partner...
"They are like humansÂthey seem to have moods, attitudes, they use and
abuse other parts of the natural world; through pollination and their use
of fungi," explains... Kingsley Dixon, director of science at Kings Park
and Botanic Garden in Perth, Western Australia.
...
Australia boasts between 1200 to 1400 [species]... many of which are found
nowhere else on Earth...
...
They grow in a range of habitats across the country, except the arid centre
and a small patch of WA's northwest coast. They are most common in areas
with higher rainfall, and along the coast and coastal tablelands.
Some of the best places to look for orchids are in areas that have been
recently burnt, where they gain an extra nutrient boost from the
organic-rich ground.
They also thrive in swamps, grasslands and woody grassland areas.
...
The Squat Moss Orchid (Bulbophyllum minutissimum), which has red-edged
green flowers just 4mm across and grows along coastal eastern Australia, is
the world's smallest orchid [really ?].
The... Pink Hyacinth Orchid (Dipodium roseum) is found in eucalypt forests
in most states except Western Australia, and grows over one metre tall.
The... endangered Greenhood Orchid (Pterostylis gibbosa), which has a
green, hood-shaped flower during winter, is only found in three locations
in New South Wales in the Shoalhaven and Hunter valleys and Illawarra region.
...
Different species of orchids can be found everywhere in Australia except
the arid centre and coastal WA between Shark Bay and Broome.
...
Most take advantage of moist conditions to flower (southern spring to
summer, wet season in the northern tropics).
...
photo : [caption : Dwarf Hammer-orchid"]
http://www.abc.net.au/reslib/200809/r295993_1273670.jpg
...
Orchids employ... different 'lip conversions' to lure insects.
These can include... pseudo anthers, hinting there's lots of pollen on offer;
sexual lures, where the lip mimics a female insect of its pollinator species;
a glossy appearance, as if the petal is dripping with nectar;
and UV spectrum cues, like spots and lines, which act like runway lights to
guide insects into the flower.
These modifications... lead to a great diversity in orchid species.
A number of Australian orchids have lips that have evolved to mimic female
wasps.
Hammer Orchids (Drakaea species) and
Flying Duck Orchids (Paracaleana species)
both found in southwest Australia, and
Caleana (southeast Australia)
encourage pollination by fooling a pollinator into landing on their
modified lip.
Once the wasp has landed, the flower flicks it into the column where the
wasp becomes dusted with pollen.
Australian Slipper Orchids (Cryptostylis species, found in temperate
Australia) offer their pollinators, ichneumon wasps... a scent chemically
identical [similar ?] to the pheromone signals that female wasps send out
to lure their mates.
"Virgin males that have never seen an orchid before will grasp it and mate
with it within seconds," says Dixon.
Once the orchid has been visited by the wasp up to eight times it
mysteriously becomes less attractive to wasps. They fly off to breed with
their own species, which ensures the orchids' pollinators don't die out.
Scent is... used by orchids such as the Greenhood orchid, which emits a
musty smell that mimics a fungus gnats nest.
photo : [caption : "Gunn's Tree Orchid"]
http://www.abc.net.au/reslib/200809/r295987_1273649.jpg
...
epiphytes... rely on moisture trickling down the trunk to bring nutrients
from organisms such as blue-green algae and lichen.
Around one quarter of Australian orchids are epiphytes...
they grow mainly in the high rainfall forests in Victoria, New South Wales and
particularly north-eastern Queensland, with two species in the Kimberley
region of WA.
Of the epiphytes, the genus Sarcochilus... is rare because of over
collecting and habitat clearing...
photo : [caption : "Rock Lily Orchid"]
http://www.abc.net.au/reslib/200809/r295989_1273651.jpg
The... King Orchid (Dendrobium kingianum), has white to pink flower spikes
and is found from NSW to Cape York in Queensland.
Two epiphyte species are found in Tasmania, Gunn's Tree Orchid (Sarcochilus
australis) and
Dockrillia australatus.
Rock orchids or lithophytes occur on rocky areas where species such as the
Rock Lily Orchid (Dendrobium speciosum) can form spectacular flowering
clumps in springtime.
photo : [caption : "Donkey Orchids"]
http://www.abc.net.au/reslib/200809/r295991_1273662.jpg
Ground or terrestrial orchids are harder to cultivate because of their
dependence on fungi to provide the nutrients they need to germinate...
[some] Orchids have the smallest seeds of all flowers, weighing as little
as 1/100th of a gram.
A seed pod may contain three million seeds.
Dispersing like dust across the environment, seeds require not only a
favourable microclimate to grow but also the particular species of fungus
specific to that orchid species.
As few as one in 10,000 will eventually germinate; fewer still grow to
mature plants.
This reliance on fungus makes conservation of orchids particularly
challenging.
The breadth of terrestrial orchid species is too numerous to do justice to
here but... Mark Clements, of the Centre for Plant Biodiversity Research at
CSIRO Plant Industry, has this advice:
".... look for some of the obvious species; such as the blue and yellow
Donkey Orchids, and go from there.
Most pieces of bush [hard to believe !], unless they're completely
degraded, have some orchids and spring is the best time to look for them."
photo : [caption : "Common Dragon Orchid"]
http://www.abc.net.au/reslib/200809/r295995_1273676.jpg
Most terrestrial orchids dwell in a band from Atherton in far north
Queensland, across south-eastern and southern Australia and up the coast of
Western Australia to Kalbarri, 600 km north of Perth.
The southwest of WA is particularly profuse and has some of the Australia's
most spectacular orchids.
Some common terrestrial species flowering in spring include the bearded Sun
Orchids (Thelymitra),
buttercup yellow or purple Donkey Orchids (Diuris), and
... spider orchids (Caladenia) and
their relatives, including the blue Waxlip Orchid (Glossodia major).
photo : [caption : "Western Underground Orchid"]
http://www.abc.net.au/reslib/200809/r295983_1273614.jpg
...
The genus Rhizanthella has two of Australia's most unique orchid species.
The eastern species, R. slateri, dwells in shallow leaf litter and has
small, purple, tubular flowers that appear from October to November. It's
found from south coast of New South Wales to south-eastern Queensland.
The extremely rare Western Underground Orchid, R. gardneri, looks like an
albino potato.
The plant is epiparasitic - being underground it does not photosynthesise,
instead obtaining carbon and other nutrients from mycorrhizal fungi.
The fungi in turn tap into the roots of the broom honey-myrtle (Melaleuca
uncinata) for their nutrients, so the honey-myrtle feeds not one but two
species.
The orchid is the only plant in the world pollinated by termites.
This sort of specialisation spells certain doom in the drying wheat belt of
WA where the orchid lives.
Without intervention from conservationists the species, which is thought to
have survived for 20 million years, is facing extinction."
URL :
http://www.abc.net.au/science/articles/2008/09/25/2373397.htm?site=science/scribblygum&topic=latest
**************
Regards,
VB
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the OrchidGuide Digest (OGD)
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