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Using vital statistics and core-habitat maps to manage critically endangered orchids in the Western Australian wheatbelt


Abstract and Figures

Vital-statistics data concerning population viability were gathered for four of the rarest orchids in Western Australia using surveys to define population sizes and habitat areas and annual measurements of plant demographics. These orchids were Caladenia melanema, C. graniticola, C. williamsiae and Drakaea isolata from the wheatbelt of Western Australia. This agricultural area has a Mediterranean climate with unreliable rainfall, and is >80% cleared of native vegetation. Surveys with 10–30 volunteers increased population-size estimates by up to 10 times and provided spatial data to define core habitat areas. These areas included most of the individuals of a species, but were only 2–10 ha in size. Within these areas, orchids were often highly aggregated in patches a few metres wide, potentially resulting in a high degree of intraspecific competition. Vital statistics were obtained using 4-m wide and 30–50-m-long transects to measure rates of emergence, flowering, grazing and seed-set for each orchid. Plants emerging at the same position in different years were considered to be the same individual, but most emerged in new positions. Many plants emerged just once in 4 years, and 2–3 years of dormancy was common. Emergence frequencies were used to provide estimates of population sizes that were two or three times larger than suggested by data from a single year. Seed production was typically very low. Grazing by kangaroos and rabbits was most severe for C. melanema, but was greatly reduced by fencing. Severe drought prevented flowering of C. graniticola in the driest year, whereas other species were more resilient. These orchids are likely to persist as long as there are some years where rainfall is sufficient for flowering and seed set followed by a year with adequate rain for seed germination. Populations of all these orchids were stable or increasing, but they are still at high risk of extinction because of the impacts of increasing soil salinity or fire on their habitats. These species are unlikely to spread elsewhere in the highly cleared and fragmented wheatbelt. Intervention by hand-pollination, grazing protection and translocation to new locations is required to mitigate these risks. Results were summarised in vital statistics report cards with thresholds set to inform conservation management for these species. Core habitat maps and vital-statistics report cards should also be valuable new tools for terrestrial-orchid conservation in other biomes.
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Using vital statistics and core-habitat maps to manage critically
endangered orchids in the Western Australian wheatbelt
Mark C. Brundrett
School of Plant Biology, Faculty of Natural and Agricultural Sciences, University of Western Australia, Crawley,
WA 6009, Australia; and Department of Parks and Wildlife, Swan Region, Locked Bag 104, Bentley Delivery
Centre, WA 6983, Australia. Email:,
Abstract. Vital-statistics data concerning population viability were gathered for four of the rarest orchids in Western
Australia using surveys to dene population sizes and habitat areas and annual measurements of plant demographics. These
orchids were Caladenia melanema,C. graniticola,C. williamsiae and Drakaea isolata from the wheatbelt of Western
Australia. This agricultural area has a Mediterranean climate with unreliable rainfall, and is >80% cleared of native
vegetation. Surveys with 1030 volunteers increased population-size estimates by up to 10 times and provided spatial data
to dene core habitat areas. These areas included most of the individuals of a species, but were only 210 ha in size. Within
these areas, orchids were often highly aggregated in patches a few metres wide, potentially resulting in a high degree of
intraspecic competition. Vital statistics were obtained using 4-m wide and 3050-m-long transects to measure rates of
emergence, owering, grazing and seed-set for each orchid. Plants emerging at the same position in different years were
considered to be the same individual, but most emerged in new positions. Many plants emerged just once in 4 years, and
23 years of dormancy was common. Emergence frequencies were used to provide estimates of population sizes that were
two or three times larger than suggested by data from a single year. Seed production was typically very low. Grazing by
kangaroos and rabbits was most severe for C. melanema, but was greatly reduced by fencing. Severe drought prevented
owering of C. graniticola in the driest year, whereas other species were more resilient. These orchids are likely to persist
as long as there are some years where rainfall is sufcient for owering and seed set followed by a year with adequate rain
for seed germination. Populations of all these orchids were stable or increasing, but they are still at high risk of extinction
because of the impacts of increasing soil salinity or re on their habitats. These species are unlikely to spread elsewhere in
the highly cleared and fragmented wheatbelt. Intervention by hand-pollination, grazing protection and translocation to
new locations is required to mitigate these risks. Results were summarised in vital statistics report cards with thresholds set
to inform conservation management for these species. Core habitat maps and vital-statistics report cards should also be
valuable new tools for terrestrial-orchid conservation in other biomes.
Additional keywords: demographics, orchid conservation, pollination, rare ora, seed set.
Received 8 April 2015, accepted 26 November 2015, published online 12 February 2016
The South-west Floristic Region of Western Australia is a
globally recognised centre of plant species richness and
endemism, coupled with a high degree of habitat loss (Myers
et al. 2000; Hopper and Gioia 2004; www.biodiversityhotspots.
org, accessed 2009). This high plant diversity is linked to a long
period since major tectonic or glacial disturbance, highly infertile
soils and periodic minor disturbances such as drought (Hopper
2009). Unfortunately, the exceptionally high biodiversity in
south-western Western Australia (WA) faces many threats that
are primarily of human origin. This is one of the most stressed
regions in Australia, with a high degree of land clearing (>80%)
and fragmentation, as well as declining vegetation health linked
to secondary soil salinity, drought, weeds and other factors
(Commonwealth of Australia 2002).
As the largest plant family globally (>25 000 species), the
orchids are considered to have the highest rate of speciation, the
highest rate of extinctions and the most rare species of any plant
family (Molvray et al.2000; Chase et al. 2015). Most WA orchids
occur in the south-west, which has a Mediterranean-type climate
with cool, wet winters, followed by 58 months of summer
drought when orchids aestivate as dormant tubers. Despite
the long, dry summer, south-western WA is one of the worlds
diversity hotspots for terrestrial orchids with ~400 species, most
of which are endemic; however, their diversity is highest in
coastal areas with more rainfall (Brundrett 2014). In 2013,
there were 40 taxa of WA orchids designated as Rare Flora
and 55 as Priority Species requiring further surveys (orabase., accessed December 2003). The Rare Flora
meet IUCN criteria for population size and habitat area,
Australian Journal of Botany
Journal compilation CSIRO 2016
suggesting that they are threatened with extinction (IUCN 2012;
Table 1). The majority of both rare and common orchids in WA
have highly specic associations with mycorrhizal fungi and
insect pollinators and this may explain why some of them are
restricted to very small habitat areas, despite having wind-
dispersed seeds (Brundrett 2007). Orchids in the present study
are listed as Critically Endangered (the most threatened
category of Declared Rare Flora in WA) because they are
likely to become extinct in the wild without intervention. The
main threats to these orchids result from the scarcity and
fragmentation of suitable new habitats and the impacts of
factors such as weeds, herbivores, infrequent pollination,
salinity, drought and re (Brown et al.1998).
This publication presents some of the results of the Wheatbelt
Orchid Rescue (WOR) Project, which was a Lotterywest-
funded collaboration between the Western Australian Native
Orchid Study and Conservation Group (WANOSCG), the
Friends of Kings Park and the Department of Environment
and Conservation (DEC). The work presented here concerns
four of the rarest orchids in WA, including the granite
spider orchid (Caladenia graniticola), the ballerina orchid
(C. melanema), Williams spider orchid (C. williamsiae) and
the lonely hammer orchid (Drakaea isolata). The present research
aimed to help conserve these Critically Endangered orchids by
obtaining knowledge required for conservation management
and directly contributing to actions listed in existing recovery
plans (Table 1). More specically, the present research aimed to
(1) provide better estimates of population sizes by harnessing
volunteer assistance, (2) measure orchid mortality, seed set and
recruitment, (3) measure orchid habitat areas and (4) identify
the most important threats to species. The second phase of the
present project, which concerned recovery actions such as the
propagation and translocation of orchids, will be described in a
subsequent paper.
Materials and methods
Characteristics of species and their habitat types, rainfall and
the approximate locations of the orchid populations studied are
summarised in Table 1and Fig. 1. The orchids studied were all
long-lived perennial geophytes that are readily identiable and
have been monitored by periodical surveys for several decades
(Fig. 2). Soils of these sites were sandy loams with very low
fertility levels (Brundrett 2011).
Extensive habitat-area surveys
All surveys were run by the author and attended by DEC
conservation staff whenever possible. These survey trips were
attended by up to 30 volunteers (WANOSCG members) who
had up to ve decades of experience in recognising and locating
uncommon orchids. There was a substantial commitment from
volunteers because trips lasted 36 days and involved travel
distances well over 1000 km (Brundrett 2012). At each location,
volunteers and staff were divided into several groups, each of
which recorded numbers of leaves, plants, owers and seed
associated with a GPS coordinate. The impacts of threats such
as grazing or weeds were also recorded. The number of plants
counted was compared with data published in Interim Recovery
Plans for each species (Table 1) to assess population-size trends
and investigate the impact of survey effort and rainfall on
numbers of orchids detected at the same locations. The overall
condition of vegetation was assessed using Landmonitor
vegetation-change imagery based on satellite images from
1988 and 2013 (, accessed 2011). Recorded
GPS coordinates were used to map areas of criticaland core
habitats for each species, as dened below.
Critical habitat is identied in the Australian Environment
Protection and Biodiversity Conservation Act 1999 as being
habitat essential for the survival of a listed threatened species
or community. Habitat means the biophysical medium or media
(1) occupied (continuously, periodically or occasionally) by
an organism or group of organisms, or (2) once occupied
(continuously, periodically or occasionally) by an organism or
group of organisms, and into which organisms of that kind have
the potential to be reintroduced.
Core habitat,asdened here, is the most essential area(s) for
survival of the taxa with highest densities of and/or the majority
of currently known individuals. This area is also the most
susceptible to threats such as, for example, disturbance, re,
weeds and animal grazing. Multiple separate areas, if dened,
are ranked in order of importance.
Intensive demographics studies
Permanent transects were used to measure owering, seed set
and survival rates in a xed area for 4 years in a row for three
orchid species (C. melanema,C. graniticola,C. williamsiae).
For each orchid, a 3050-m long 4-m wide transect was
established in the largest (or only known) population. The
length of transects was dictated by the size of habitats and was
Table 1. Status of four selected Critically Endangered Western Australian wheatbelt orchids at the start of this project, using data from the cited
Interim Recovery Plans
Name Common name Number of
Estimated number
of plants
Interim recovery plan
Caladenia graniticola (Hopper & A.P.Br.)
Hopper & A.P.Br.
Granite spider orchid 5 250 Kershaw et al.2003
Caladenia melanema Hopper & A.P.Br. Ballerina orchid 1 (now 4) 300 Department of Environment and
Conservation (2007a)
Caladenia williamsiae Hopper & A.P.Br. Williamsspider orchid 1 150 Department of Environment and
Conservation (2007b)
Drakaea isolata
Hopper & A.P.Br.
Lonely hammer orchid 1 250 Phillimore et al.2000
BAustralian Journal of Botany M. C. Brundrett
oriented to include as many individuals as possible in the densest
area of occupation for each species. Transects established in
2007 were marked with steel posts at both ends and monitored
several times each year until 2010. Plants on transects were
counted during spring (August or September) to assess plant
emergence, owering and preliminary seed set, and again in
late spring to determine nal seed set (October or November).
Grazing was assessed in each visit because it often increased
during the year. The relationship between total annual or winter
rainfall and the number of emerging and owering plants was
also investigated using data from nearby weather stations
published by the Australian Bureau of Meteorology (www., accessed 2011).
For each orchid plant, the distance along the transect axis and
perpendicular distance from it was recorded. These coordinates
were used to identify plants that were assumed to be the same
individual if they emerged at the same location on different years
(within 2 cm). The accuracy in measurements was increased by
inserting permanent steel pegs as xed reference points every 5 m
along transects. The identication of individual plants was used
to determine how often each plant emerged or owered over the
4-year period of observation.
For Drakaea isolata, photo monitoring of tagged plants was
used instead of establishing a transect because of the widely
scattered nature of clumps of individuals and the existence of
a series of older photos showing the relative position of the
prostrate leaves within groups of plants next to a xed point (a
steel peg with label). Photographs of the same location taken on
different years were compared by tracing outlines of leaves from
these photos. The resulting circles were rotated and transformed
in a vector-drawing program (Adobe Illustrator, Adobe, San Jose,
CA, USA), so that the relative positions of the xed post and
leaves were as close together as possible. These transformations
were necessary because each photo was taken from a different
direction and angle downward.
Population surveys
The population survey for C. graniticola occurred in 2008, on
a year when substantial numbers of orchids emerged as a result
of above-average rainfall in winter (Fig. 3). A team of 30
experienced volunteers searched in suitable habitats for 3 days
within Dragon Rocks Nature Reserve, where three populations
of this orchid were known to occur. This survey resulted in
the discovery of over 300 plants, being an order of magnitude
increase in the size of populations from earlier surveys (Fig. 4).
The majority of plants were owering; however, it was also
possible to reliably identify non-owering individuals by
distinguishing their leaves from those of other orchids. These
orchids were primarily associated with sheoak woodlands
(Allocasuarina huegliana and A. campestris) over granite
rock, although some were in other habitat types nearby. All of
the areas occupied by C. graniticola were very small patches,
totalling 18 ha in a very large nature reserve (332 km
). For
this species, the number of plants emerging and owering is
strongly inuenced by rainfall (Fig. 5a). The most important
core habitat area contained 217 plants and was only 150 150 m
in size. These plants are densely aggregated into two smaller
areas less than 50 m wide. In total, there were ~300 plants in
all three local populations, so the granite spider orchid is a
highly threatened species (small populations occur in 2 other
Surveys for the ballerina orchid (Caladenia melanema), with
the assistance of several volunteers, occurred over several years
in Melaleuca lateriora shrublands on the margins of salt lakes.
These surveys found four new subpopulations of this orchid and
two new populations that were ~10 km from the main population.
These, presumably, arose recently by seed dispersal, because
the number of plants within all subpopulations has increased
substantially since monitoring began (Fig. 5d). Even though a
greater number of plants and several new populations were
found, 90% of known plants of this species were conned to
small patches of fringing shrubland within chain of salt lakes
with a total area 3 1 km in size (Fig. 6a). Satellite imagery
provides evidence that the canopy of shrubs under which
C. melanema grows has substantially declined in cover over
the past 20 years (Fig. S1, available as supplementary material
for this paper). Because most C. melanema plants occur under
the canopy of M. lateriora, the long-term sustainability of
these shrubs is likely to be critical for orchid populations.
Recruitment of M. lateriora seedlings has not been observed
at the site and needs to be encouraged by grazing protection or
planting seedlings raised in a nursery.
A full survey of suitable habitats in the nature reserve where
Caladenia williamsiae occurs was undertaken by three people
in 2010 to count individuals and to accurately map habitat areas
for this extremely rare orchid. Despite the low rainfall in 2010
(Fig. 3), considerably more plants were counted than expected
on the basis of earlier surveys of the same area (450), but these
were concentrated in a very narrow strip of core habitat ~2 ha in
200 km
Fig. 1. Approximate locations of rare orchid populations included in
the present study within the wheatbelt of Western Australia a large area
(155 000 km
) where most native vegetation is cleared for agriculture. Map
data: Google, DigitalGlobe.
Vital statistics and core habitats of rare orchids Australian Journal of Botany C
size (Fig. 6b) and plants were grouped together in small patches
within this area. All populations of this orchid occur within
a critical habitat area of ~1 km
in a single nature reserve. This
orchid was discovered in 1999 and surveys of the same area
between 2000 and 2006 detected from 6 to 143 plants
(Department of Environment and Conservation 2007b). The
apparent increase in population size following the 2010 survey
is probably due to increased survey effort, which was required
to overcome detectability problems, as C. williamsiae is a small
orchid that often grows under shrubs.
Survey data for Drakaea isolata in 2007 with 29 volunteers
revealed almost 300 individuals, of which 50 were owering.
The number of plants found was determined, to a large extent,
by the number of people searching for them, because earlier
surveys found as few as 77 plants in the same area, whereas a
major survey with volunteer assistance found 250 plants in
1989 (Phillimore et al.2000). Thus, the population size and
habitat area for this orchid have not changed much since 1989.
Leaves of this species were aggregated into 56 groups, which
may represent the number of individuals of this species,
because up to 50 leaves were found in each group and
probably arise from clonal division. Almost all known plants
of D. isolata occur in a small square area of ~10 ha. This area is
at a very high risk from rising saline groundwater, because it
is next to a salt lake where severely salt-affected areas are
expanding (Fig. S1).
(e) (f)(g)
Fig. 2. (a)Caladenia graniticola.(b). Drakaea isolata.(c). C. williamsiae.(d). Habitat of C. melanema, showing fence enclosure near salt lake.
(e). C. melanema plant. (f). Grazed leaves and ower spikes of C. melanema. (g) Seed pods on C. melanema. (h). Flies stuck to the stigma of a
C. melanema ower prevent pollination by other insects.
DAustralian Journal of Botany M. C. Brundrett
Detailed demographic studies
Caladenia graniticola
Severe winter drought had a substantial impact on owering of
of C. graniticola, especially in 2010 when rainfall was less than
half of average (Fig. 3) and all plants aborted before owering.
Emergence and owering of C. graniticola were correlated with
rainfall (Fig. 5a).
The emergence of plants at different positions on the transect
(Fig. 7a) allowed individual plant emergence to be observed
over 3 years (data from Year 4 were not available because of
severe drought). For this orchid, only ~1/2 of emergent plants
produced a single ower and very few set seed or produced
two owers, even on years with a relatively wet winter
(Figs 8a,9a). As shown by Fig. 10a,b, on average, 37% of
plants emerged each year and 17% owered. It seems that ~1/2
of the orchids that exist as dormant tubers emerged in 2008,
which was a wet year, whereas only 1/3 or 1/4 of these plants
emerged in years with winter drought. There were limited
impacts of grazing at this site. This orchid has a relatively low
frequency of annual emergence from dormant tubers and the
proportion of plants that emerge, but fail to ower, is also
greater than for other species and none owered more than
twice over 4 years (Fig. 10a,b). The average length of
dormancy was close to 2 years, but was measured only for
3 years because of drought in Year 4 (Fig. 11a).
Data on orchid emergence rates were used in combination
with survey data, to provide a revised estimate for orchid
population size. Because ~1/2 of the detected plants on the
transect emerged in 2008 when 300 plants were counted
during surveys, it would suggest that there are ~600 plants in
total in all three populations in the single nature reserve where
most plants of this species occur (Table 2). This conrms that
C. graniticola is at high risk of extinction (populations occur in
2 other reserves, but contain less than 150 additional plants).
Caladenia melanema
There was no strong correlation between rainfall and plant
numbers for C. melanema, but annual trends tended to be
overwhelmed by the steady population-growth trend over time
(Fig. 5b,d). As shown in Fig. 8b, plants were very densely
aggregated at several points along the 50-m transect where
clumps of plants are almost touching, with 5062% of all
plants on the transect growing in a single patch ~1 m wide.
This made identifying individual plants within the most
crowded area impossible, so only plants in the rst 15 m of the
transect were identied by location (Fig. 7b). Dense clumps
of orchids result from clonal division by daughter-tuber
production next to the parent tuber, and these locations were
also hotspots for reproduction from seed, resulting in new
clumps of orchids within close proximity to each other. Each
clump had 130 leaves and 114 owers, with an average of
4.6 leaves and 2.5 owers per clump in 2009. All owers were
Orchid plants detected
Fig. 4. Numbers of Caladenia graniticola plants counted in surveys of the
same populations, including data from the 2008 survey reported here (dark
bar) and earlier surveys reported in Kershaw et al.(2003) as light bars.
1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
Total rainfall (mm)
Lake grace
Survey period
Fig. 3. Rainfall recorded at the weather stations closest to locations where the four orchids in the present study occur (, accessed
20092011 ). The present research occurred during the last 4 years on the graph and 2010 was exceptionally dry.
Vital statistics and core habitats of rare orchids Australian Journal of Botany E
single (Fig. 9b). There was good pollination of C. melanema
owers, but many were grazed before seeds matured (Fig. 8b).
A thynnid wasp (Rhytidothynnus sp.) was observed to be a
potential pollinator, whereas ies were abundant on years with
warm winter weather and became stuck in owers. Flies block
the stigma because they are not strong enough to escape, and so
prevent pollination by other insects (Fig. 2h).
Data on relative plant positions (Fig. 7b) showed that, on
average, 40% emerged each year and 16% owered, whereas
seed set was only 2% of all plants (dormant plus emergent).
Over 60% of plants emerged and owered only once in 4 years
(Fig. 10c,d), and 3 years of consecutive dormancy or two
episodes of dormancy within 4 years were most common
(Fig. 11b). These data suggest that there were ~1350 plants on
the transect (including dormant plants), so there was an estimated
total of 40005500 plants within the 3-km
critical habitat area
of this species (Table 2).
In response to severe grazing of plants observed throughout
the critical habitat area in 2007, a 10 10 m enclosure of 1-m-
high rabbit-proof fencing was erected on the transect that
(b) Caladenia melanema Plants
y = 6.591x2 – 26360x + 3E+07
R2 = 0.758
2000 2002 2004 2006 2008 2010
(d) Caladenia melanema
0 100 200 300 400 500 600
Rainfall (mm)
(c) Caladenia williamsiae
70 (a) Caladenia graniticola
Fig. 5. (ac) The relationship between annual rainfall and numbers of
emergent and owering plants for three orchids. (d) Numbers of plants
recorded for one entire Caladenia melanema population over one decade
show a strongly increasing trend.
(b) Caladenia williamsiae
(a) Caladenia melanema
100 m
200 m
Fig. 6. (a)Caladenia melanema plants are highly aggregated into six
subpopulations separated by small salt lakes (imagery not shown) within a
narrow critical habitat area 3 km long. (b) In total, 95% of known plants of
C. williamsiae which occur within a narrow 400 50 m zone of vegetation.
The 50-m transect where detailed demographics studies occurred is also
shown (line).
FAustralian Journal of Botany M. C. Brundrett
summer when plants were dormant. Subsequently, 75100% of
uneaten seedpods on the transect were located in the enclosure.
The type of grazing differed within the enclosure, where owers
were sometimes eaten, but there was almost no grazing of
leaves. Four new enclosures were erected in 2009 to protect
other subpopulations and these also greatly reduced grazing,
but did not eliminate it. It is not clear what caused grazing
within fenced enclosures.
Caladenia williamsiae
Monitoring plants on a 50 4 m transect for 4 years showed
that grazing and infrequent seed production were the most
signicant threats to C. williamsiae (Figs 7c,8c). Grazing
impacts, especially of owers, varied from 6% of plants in
2008 and 2010, to 26% in 2009 (Fig. 8c). The numbers of
plants emerging or owering varied considerably from year
to year, but remained low each year and were not strongly
linked to rainfall (Fig. 5d). Relatively few plants set seed,
except in 2007, where 28% had capsules (Fig. 8c), so
pollination (presumably by a thynnid wasp) is unreliable.
Overall, rates of seed set are probably adequate, whereas the
volume of seed in capsules is low compared with that in most
other Caladenia species. As shown in Fig. 9c, from 60% to 90%
of plants owered, and most of these produced a single ower.
The fact that most plants remain dormant each year limits their
reproductive potential and may be due to the exposed habitat
of this orchid, which grows on upland ridges within very well
drained lateritic gravel. It was also observed that grazed plants
are often growing in the open, whereas those protected under
the canopy of shrubs were less likely to be grazed. There is clear
evidence of high kangaroo population levels at the site (tracks,
scats and sleeping areas).
Comparison of the same plants showed that most appeared
only once in 4 years and owering was even less frequent
(Fig. 10e,f). Only 32% of plants emerged more than once at
the same position, only 29% of plants owered more than once
and 16% did not ower at all in 4 years. The majority of plants
were dormant for 2 or 3 years in total, with one or two dormancy
20 20
60 (a) Caladenia graniticola
51 13
47 47
47 4
(b) Caladenia melanema 2007
17 16
Leaves Flowers Grazed Seeds
(c) Caladenia williamsiae
Fig. 8. (ac) Seasonal variation in emergent plants, owering, grazing and
seed set for three orchids over 4 years, using data from transects.
Distance from transect (m)
(b) Caladenia melanema
2008 2009 2010
0 5 10 15 20 25 30 35 40
Position along transect (m)
(c) Caladenia williamsiae
2008 2009 2010 2007
0 5 10 15 20
(a) Caladenia graniticola
2008 2007 2009
Fig. 7. (a) Individual plants of Caladenia graniticola emerging on one or
more years over 3 years identied by their relative positions along a transect.
Plants aborted before owering because of drought in Year 4. (b) The
relative position and density of leaves and owers of C. melanema
emerging over 4 years. (c). The relative position and density of leaves and
owers of C. williamsiae emerging over 4 years. Note that the vertical scale
is much ner than the x-axis scale in all graphs.
Vital statistics and core habitats of rare orchids Australian Journal of Botany G
episodes in 4 years (Fig. 11c). The number of individuals on
the transect was estimated to be 108, of which 34% emerged
and 22% owered, on average, each year (Table 2). The transect
emergence data in combination with survey data provided a
revised estimate for an orchid population size of ~1400 plants
for all populations of the Williams spider orchid (Table 2).
Drakaea isolata
Photographs taken by DEC staff of a tagged group of leaves
in 2003 and 2004 were compared with those taken by the author
in 2007 at the same coordinates to compare leaf and ower
numbers (Fig. S2, available as Supplementary material for this
paper). Comparisons of photos required image transformation
to overcome varying camera positions. Many leaves occupy
similar positions in all photos, whereas others present in 2007
appear to have recruited since 2004. There are also two leaves
present in the rst photos that may have died since 2003, or
were dormant. In 2004, there were eight inorescences at this
location, but all were grazed. Comparison of ve groups of
tagged plants showed that most of the plants observed in 2003
were also found in 2007; however, Groups 4 and 5 may no longer
exist (Brundrett 2011). It seems that the larger groups of
D. isolata are stable over time. Unlike the Caladenia species,
there was little evidence that substantial numbers of D. isolata
plants were dormant, because most leaves appear in all three
photographs of each group. Leaves of this orchid are relatively
xeromorphic (Brundrett 2014). Each leaf is connected to a
separate tuber, whereas all those in a group are likely to be the
same clonal individual.
The Wheatbelt Orchid Rescue Project established that surveys
that included substantial numbers of highly experienced
volunteers were very effective at both counting numbers of
individuals and mapping their core habitat areas within large
nature reserves. Both the time spent at locations and areas
covered increased considerably in surveys with volunteers.
Comparisons with earlier surveys established that surveys
with one or two people substantially underestimated numbers
of plants in many cases. Unfortunately, the large number of
rare species in WA has resulted in very limited resources to
survey many of these species (Coates and Atkins 2001; West
Australian Auditor General 2009). For example, there are 125
plants designated as Rare Flora in the wheatbelt region of
WA (, accessed April 2015), but
only two Flora Conservation Ofcers to manage them. The
comparative merits and risks of including volunteers in
surveys need to be considered (if locations are not already
fairly well known), and it also needs to be recognised that
effective monitoring is not possible without volunteer support
if areas to be surveyed are very large. In WA, locations of rare
orchids are generally fairly well known by enthusiasts, who often
have key roles in discovering and monitoring these locations.
A key outcome of surveys was the identication and
mapping of core habitat and critical habitat areas for each
species, which is required to manage orchid populations within
nature reserves, especially from disturbance and re. These
areas were dened, listed in order of importance and provided
to the land manager as reports and GIS datasets (Brundrett
2011). Core habitat areas are the highest priority for re
protection, grazing control or weed management. These areas
were very small for rare wheatbelt orchids, varying from 2 to
10 ha. Core habitats are smaller than the area of occupancy of a
rare species, as dened by the IUCN (2012), and arise because
these rare orchids had aggregated distributions where most
individuals occur in a few small patches within their area of
occupancy. For example, ~50% of all known individuals of
C. graniticola occur within a 1-ha area that contains the
largest of its ve populations, whereas the area of occupancy
is much larger (5 km
). Unfortunately, many of the core habitat
areas are highly vulnerable to re or salinity (Table 2).
The distributions of orchids were aggregated at three or
more nested spatial scales, including (1) critical habitat areas
of a few square kilometres enclosing each population and
other habitat with similar vegetation and landforms, (2) core
habitat areas of 210 ha where most individuals occur and
135 129
(b) Caladenia melanema
20 21
No flowers 1 flower 2 flowers
(c) Caladenia williamsiae
(a) Caladenia graniticola
Fig. 9. (ac) The owering effort (owers per plant) for three orchid
HAustralian Journal of Botany M. C. Brundrett
(3) dense patches of orchids a few metres wide within the
core habitat where many individuals grow. The aggregated
distributions of the orchids studied here suggest that intense
competition for resources, such as nutrients provided by
mycorrhizal fungi or pollinator visitations, is likely to occur in
the densest patches. The resources required by mycorrhizal
fungi would primarily consist of coarse soil organic matter and
litter where the inoculum of orchid fungi is most concentrated
(Brundrett et al.2003). Individual insect pollinators quickly
learn to avoid areas where sexually deceptive owers occur
(Alcock 2000; Menz et al.2013), so pollination is more
frequent if plants are widely dispersed. Density-dependent
impacts on orchid tness may be less severe in non-productive
years when more plants remain dormant. In the case of
C. melanema, overcrowding is most severe in one densely
occupied area, with over 500 plants within 1 m
. In the case of
clonal orchids such as the C. melanema, it is recommended
that some tubers be moved to less crowded areas to determine
whether this is benecial to future owering and division. It
should be possible to do this when plants are dormant in
the summer without harming them, as dormant tubers can be
handled without harm when they are re-potted in ex situ
collections. For C. melanema, individuals in the same clump
are likely to be genetically identical because of clonal division.
Estimating mortality and recruitment for these orchids would
require longer survey times. However, there is already sufcient
evidence that these populations were steady (2 species) or
growing (2 species), on the basis of long-term monitoring of
specic subpopulations (see Table 2). Clonal recruitment-rate
estimates were also provided for C. melanema and D. isolata.
There has been a steady increase in numbers of individuals
and populations for C. melanema, from a few individuals
1 year
2 years
3 years
4 years
(e) Caladenia
1 year
2 years
3 years
4 years
1% None
(f) Caladenia
1 year
2 years
3 years
4 years
(c) Caladenia
1 year
2 years
3 years
4 years
(d) Caladeni
1 year
2 years
3 years
(a) Caladenia
1 year
2 years
(b) Caladeni
Fig. 10. (a,c,e) Average values for the total number of years in which plants emerged from dormancy over 4 years. (b,d,f) Averages for the total number
of years in which owers were produced by these orchids over 4 years. Noneindicates that orchids emerged at least once but did not ower in any year.
Vital statistics and core habitats of rare orchids Australian Journal of Botany I
discovered in 1985 to over 5000 in 2010. This trend and the
absence of records before 1985 suggest that this species is of
recent hybrid origin. It is part of a large species complex that
includes many similar species requiring further taxonomic
investigation (Brundrett 2014).
Annual assessments that identify orchids by their locations
within a xed area each year for 4 years were used to accurately
measure vital statistics such as emergence, owering, pollination
and grazing rates. These studies revealed annual variations in
numbers of plants that emerge from dormant tubers, produce
owers, set seeds or are grazed, so it was much easier to
determine the impacts of these factors with 4 years of data.
However, longer surveys are required to measure rates of
recruitment and estimate the lifespan of individuals (see
below). Vital-statistics data gathered from xed areas were
used in combination with overall population-size data from
surveys, to provide an overall estimate of orchid population
size, based on an estimated emergence rate for the year of the
survey. This approach overcame problems with previous
population data for these species that were not based on a
consistent area or survey effort and occurred irregularly.
Because only a fraction of dormant orchids emerged each
year, long-term monitoring of the same areas was required to
allow population-size estimates to be obtained and to investigate
the impact of climatic factors such as rainfall on orchid
emergence and owering. For the three Caladenia species,
emergence frequencies were lower than expected, with many
plants emerging only once in the 4-year period. These data
revealed that orchids in dry habitats are time travellers that
tend to skip multiple years, even in years with relatively wet
winters. This makes accurate counting of these rare terrestrial
orchids much more difcult. Other studies of terrestrial
orchids have found that they can remain dormant for 12 years
(Shefferson et al. 2005), or 14 years (Kéry et al.2005); however,
occasionally they have been observed to re-emerge after as long as
718 years (Light and MacConaill 2005). In these studies, it was
observed that orchids that remain dormant for more than 4 years
were likely to be dead.
There is a trade-off in terms of duration of demographic
studies relative to the accuracy of estimates of population size,
because increases or decreases in populations over longer time-
frames would become more important than annual uctuations
in emergent orchids. In the present study, it was not possible to
conrm that plants owering at the same location (within 2 cm)
were the same individual, because it is possible that several
orchids emerged on different years, which is a potential source
of underestimation for population size. However, there were
also potential sources of overestimation errors in identifying
individual orchids by their position, such as position-measuring
errors and the fact that growth from tubers is not always
vertical (they usually grow upward through the remains of the
previous years plant base). Excavation of these rare species
to conrm that assumptions are correct was not permitted.
Grazing can also have an impact on numbers of orchids
counted, because it may not be possible to separate dormant
orchids from those that are eaten (in most cases, leaf bases could
still be counted). Another assumption was that newly observed
plants were not seedlings; however, this can be ruled out as
most were of owering size. None of these issues is likely to
substantially affect numbers of plants counted.
Several different approaches have been used to estimate
the size and dynamics of orchid populations where dormancy
is common. Kéry et al.(2005) recommend multistate capture
recapture models after comparing methods to estimate survival
rate. Pfeifer et al.(2006) used matrix models to estimate long-
term survival probabilities on the basis of rates of transition
between life states. Tremblay et al. (2009a) used a Bayesian
capturerecapture multistate analysis for nine Australian
Caladenia species to estimate dormancy and survival
probabilities. Only C. graniticola is included in both Tremblay
et al.(2009a) and the present study, allowing comparisons to
be made. For this species, most of the parameters estimated
by modelling approaches are similar to those measured in the
present study, except one, which is different (dormancy for
C. graniticola was several years longer in the present study).
It is worth noting that the population of C. graniticola where
data for the Tremblay et al. (2009b) were collected seemed to be
relatively viable in the past (their quasi extinction rate for 50% of
None 1 year 1+1 years 2 years 1+2 years 3 years
(c) Caladenia williamsiae
25 (a) Caladenia graniticola
and duration
Number of plants
(b) Caladenia melanema
Fig. 11. (ac) The length and frequency of dormancy for three orchids
measured over 3 years (Caladenia graniticola) or 4 years (C. melanema and
C. williamsiae).
JAustralian Journal of Botany M. C. Brundrett
Table 2. Vital-statistics report card for four rare Western Australian terrestrial orchids
Statistic Caladenia
Threshold for action
A. Population size and habitat area
1a. Overall number counted (maximum) 304 2270 450 297 See 4a
1b. Populations where data was collected
(total populations)
3 (of 5) 1 (of 4) 1 (of 1) 1 (of 1)
2a. Variability in counted data (high/low
10345See 2c
2b. Annual variability with same methods
and area 4a
2c. Survey issues (effort, detection, area) Effort, area Effort, grazing Effort, detection Effort Any issue
3. Population trends Increasing Increasing Steady Steady Decreasing
4a. Population-size estimate for measured
populations (including dormant plants)
600 5000 1350 300 Decrease greater than
normal variability (2b)
4b. Population-size estimate for entire
750 5500 1350 300 Major decrease
5. Estimated area of critical habitat (km
) 5 3 1 0.5 Current area
6a. Area of main core habitat (ha) 2 2 2 10 Current area
6b. Proportion of all plants in main core
70% 50% 95% 95% 50%
7. Spatial dispersal of populations
High Moderate n.a. n.a. High
8. Spatial aggregation of plants within
critical habitat
High Very high Moderate High High
9. Presence of weeds, disturbance, or other
adverse factors in or near plots
Salinity Salinity Any factor
10. Vegetation health
Declining Seriously declining Healthy Seriously declining Declining
B. Vital statistics from annual xed-area data
11. Number of orchids in plot (range over 4
2053 264757 1759 2033 Current number
(lower end of range)
12. Proportion of emerging plants that
46% 41% 67% 18% Current number
13. Number of owers per owering plant 1.1 1 1.05 1
14. Proportion of owers setting seed 6.0% 8.3% 15.2% 85%
15. Recruitment from seed Not seen Low Not seen Not seen Low
16. Recruitment from clonal division (over
4 years)
0 400 of 800
0 9 of 33
Current number
17. Grazing of leaves, owers, or seeds 11% 22% 13% 29% 20%
18. Dormancy frequency (no. of events/no.
of years)
0.32 0.43 0.36 Low Current number
19. Dormancy in years, range (average) 13 (1.4) 13 (1.6) 13 (2) n.a. Current number
20. Average annual emergence
(proportion of estimated total plants)
37% 40% 34% most Current %
21. Overcrowding in some parts of core
Moderate Very high Low High High
22. Impact of rainfall on emergence and
High Low Low Low High
C. Seed germination and pollination
23. Seed viability (bioassay or sterile
High High High n.a. Low
24. Fungal inoculum levels in soils
(germination in soil bioassays
proportion of samples)
15% 30% Trace n.a. Requires study
25. Pollinator identity (abundance) Not seen (likely
to be a thynnid
Thynnid wasp
(not conrmed)
Not seen (likely
to be a thynnid
Not seen
(may self-
Requires study
Vegetation-change data from satellite imagery.
Data from Phillips et al.(2014).
Estimated from Fig. 5c.
Estimated from counting plants in colonies.
Most plants within 10% of core area.
From Fig. 5.
Vital statistics and core habitats of rare orchids Australian Journal of Botany K
populations was 24 years); however, no plants have been seen
in the plot where these data were obtained for a decade (they are
still growing nearby). This highlights a problem with estimates
of long-term population viability produced by models, because
they must assume that habitat conditions are relatively constant
or change gradually and predictably. However, this is often not
the case for many of the WA rare orchids because impacts such
as re, rising saline groundwater, the severity and frequency of
drought, grazing pressure, or weed invasion have the capacity to
rapidly change habitat conditions and often become more severe
over time.
Numbers of owering, vegetative, seedling and dormant
plants need to be accurately measured to determine orchid
lifespans and dormancy; however, some of these cannot be
directly measured (germination and dormancy are subterranean).
In the case of the rare WA orchids studied here, it was easy to
measure numbers of emergent, owering and seeding plants,
but seedlings were rarely observed. It will not be possible to use
these data to model the probability of long-term persistence of
these populations without more data on seedling establishment.
The low rates of seed production noted here would be expected
to cause low recruitment. However, very good seed germination
was observed for two of these species when seed and organic
matter were combined in a controlled environment off site,
showing that both seed and mycorrhizal fungi within natural
habitats were viable (Brundrett 2011).
Seed germination in these habitats seems to either be very
rare or, else, is more dependent on soil moisture than are
emergence and owering. It may be necessary to have two
consecutive years with sufcient rainfall, the rst to support
owering and seed set, coinciding with conditions suitable for
pollinator activity, and the second to support fungal activity and
seed germination. Thus, we should expect that the productivity
of some orchids may be lower in the future because of expected
climatic trends, because rainfall is expected to decline and
become less consistent in the WA wheatbelt (http://www.,
accessed 2015). Fortunately, these orchids are time travelers
that often remain dormant for multiple years, so should persist
as long as there are some years when rainfall is sufcient. If
seed germination is less than plant mortality, it is reasonable to
assume that populations will eventually become extinct. This
contrasts with observations summarised in Table 2that show
that the populations studied here seem to be stable or increasing
over several decades of observations. In the case of C. melanema,
this primarily results from the multiplication of tubers and
D. isolata also spreads clonally. The other species probably
had occasional years when reproduction was sufcient to
maintain or expand populations of these long-lived individuals.
The present 4-year study was sufcient to estimate population
sizes; however, longer-term studies are required to measure
recruitment form seedsor mortality, becausethese were infrequent.
The capacity of rare orchids in WA to spread to new habitats
is expected to be very low owing to infrequent pollination,
grazing impacts on seeds and the highly cleared and extremely
fragmented landscapes where they grow (Brundrett 2014).
Consequently, they require intervention in the form of
supplemental pollination, watering to promote seed germination,
protection from grazing and translocation of plants or seeds
to new locations to reduce the risk of extinction. This risk is
especially high for C. melanema and D. isolata because of rising
saline groundwater, whereas the habitats where C. graniticola
and C. williamsiae grow may be highly vulnerable to re.
Thus, evidence that populations were stable in the past does
not guarantee future survival if habitat conditions deteriorate
or change suddenly. In the case of C. graniticola tree-canopy
decline, possible linked to drought or an extended time since
the last re, has resulted in increased light levels in the
Table 3. How vital-statistics data can be used to sustainably manage rare orchid populations
Factor Data (Table 2) Potential management actions if impact exceeds threshold set
Population size 1, 2, 3, 4 Continue monitoring of populations and set threshold for actions
Overcome survey problems, owing to detection or effort
Monitor outcomes of management actions
Habitat area 5, 6 Locate additional unoccupied apparently suitable habitat(s) within or outside local
protected area for translocation
Genetics 4, 7 Undertake taxonomic or genetic studies, if deemed necessary
Spatial factors 7, 8, 20 Translocate propagated seedlings or move plants to reduce localised overcrowding
Address habitat fragmentation, if possible
Habitat viability 9, 10 Manage habitats to control weeds, exclude grazers, reduce human disturbance
Manage major impacts to landscapes such as re and other disturbances, if possible
Address declining vegetation health by restoration, if possible
Threats to orchids 9, 17 Continue monitoring and set thresholds for actions
Reduce grazing by fencing, or cages
Manage localised human impacts such as trampling and harvesting
Flowering and seed production 12, 13, 14, 24 Protect owers from grazing
Undertake supplemental cross-pollination
Seed viability and germination 22, 23 Test seed viability and fungal inoculum potential in soils
Articial propagation of seedlings
Recruitment 11, 15, 16 Articial seed dispersal
Translocation of plants
Climate 18, 19, 22 Investigate impacts of rainfall or other climatic factors on emergence, owering,
reproduction and mortality
LAustralian Journal of Botany M. C. Brundrett
understorey and a substantial increase in the numbers of plants
observed recently (Brundrett 2011). In the longer term, declining
canopy vigour could also be detrimental to orchids because of
increased competition from other native plants and weeds in
the understorey. Research on impacts of climate change and
the duration of intervals between res on rare orchids in WA
is required.
For C. williamsiae, low seed set and small population size,
coupled with a small area of occupation (2 ha), were major
threats to the long-term survival of this unique orchid that
has no close relatives. The long-term viability of all the rare
orchids studied here is threated by altered rainfall patterns in
the wheatbelt of WA linked to climate change, because this
area is already on the margin of the orchid diversity hotspot
in the South-west Floristic Region of WA (Brundrett 2014).
Changes in rainfall patterns may also affect orchids indirectly,
if canopy decline opens up the habitat and results in increased
competition with other species. The available evidence suggests
that C. graniticola is more susceptible to drought than are the
other species examined and this species occurs in a lower-
rainfall area. These impacts should be evaluated by long-term
monitoring of transects established in the present study.
Additional research is required to develop an understanding
of habitat specicity and why the majority of apparently
suitable habitat is unoccupied for most orchids. The role of
mycorrhizal fungi in determining habitat preferences should
also be investigated further. This requires seed-baiting
experiments, where seed germination is used to detect suitable
fungi in soil, and compatibility testing of mycorrhizal fungi to
determine whether they also associate with co-occurring orchids
that are more common (Brundrett et al.2003; Bonnardeaux
et al. 2007). For the orchids studied here, seed-baiting trials
conrmed that: (1) seed of these orchids was highly viable;
(2) compatible fungi were more widespread than their orchids
in most suitable habitats; and (3) sites likely to be suitable for
translocation of these orchids could be identied (Brundrett
Conclusions and recommendations
Table 2provides an example of a report card for gathering
and interpreting vital statistics using orchids from the present
study. This report card identied the main threats to these rare-
orchid populations as grazing, low seed set and inconsistent
recruitment. These statistics were also used to set thresholds
for management actions for each species (Table 2). In most
cases, thresholds were set at levels close to those measured
during the present study, because these species are already
designated as Critically Endangered owing to low populations
sizes and small areas of occupation following IUCN Criteria
(IUCN 2012). Management actions that are available to
reverse a gradual population decline include supplemental
pollination, grazing control, weed management and habitat
restoration. However, vital-statistics measurements may not
detect impacts of catastrophic events such as re or rising
saline groundwater in time to prevent the loss of populations
or subpopulations. Many of the vital statistics are rainfall
dependant, so can also be used to monitor impacts of
climate on orchid populations (i.e. Factors 1122 in Table 2).
Making conservation plans for rare orchids is complicated
by the fact that some of the key data from Table 2are often
missing. Further research is required to determine whether we
can use surrogate data from other closely related species growing
in similar habitats. Table 3demonstrates how vital-statistics
data can be combined to identify key threats to the viability of
orchid species and provides examples of management actions
that could address these threats. For example, the identication
of grazing as a threat during the present study resulted in fences
being erected to protect core habitat areas for C. melanema and
substantially increasing seed set in subsequent years. Further
information about conservation actions for these species are
provided in reports (Brundrett 2011) and summarised in the
Australian Species Prole and Threats Database (www., accessed 2015). Propagation and
translocation trials for these orchids will be described in a
subsequent publication.
I determined that vital statistics data were relatively easy to
obtain from xed area transects within the time constraints
caused by travel to remote locations (24 h per site) and
should be feasible despite the limited resources available for
monitoring rare ora in WA. Population-size estimates required
3 or 4 years of data to compensate for annual variations in
emergence and 13-year dormancy periods. Long-term
measurements of xed plots are the best approach to obtain
population-size and -viability data for orchids. Pfeifer et al.
(2006) found that 4 years of data are usually adequate for
modelling population size for terrestrial orchids, whereas
longer periods of observation are better for studying population
dynamics. Unfortunately, there are no annually repeated
measurements of xed plots for most of the rare orchids in
WA and the existing population-size census data for these
species is of limited use for assessing plant population size
because of infrequent surveys, variations in sampling intensity
and detectability problems (West Australian Auditor General
2009; Brundrett 2011). It is recommended that monitoring
protocols that allow population size and viability to be better
estimated be adopted in the future. Volunteers from community
groups are increasingly becoming major contributors to rare
ora surveys in WA (Brundrett 2011; Adopt and Orchid
Project, available at, accessed 2015)
and would have the capacity and skills (with some additional
training) to undertake annual xed-area surveys for rare orchids.
Planning for new monitoring programs of this type is currently
Vital-statistics data are essential decision-making tools
for orchid conservation in WA, because they allow changes to
population size and viability to be detected before populations
are lost and can be used to allocate conservation resources to
the most threatened orchids. These data can be gathered from
a relatively small xed area, so are an efcient means of
determining the most important threats to orchid populations
without having an impact on them. It is recommended that these
data are summarised in a report-card format, with thresholds
set for management actions for key criteria such as population
size and reproduction. Mapping of core habitat areas was also
found to be a vital tool for conservation planning for rare species
and management of the areas where they occur. Vital-statistics
report cards with thresholds set for conservation actions should
Vital statistics and core habitats of rare orchids Australian Journal of Botany M
also be valuable tools for the management of rare terrestrial
orchids in other biomes.
The Wheatbelt Orchid Rescue Project was funded primarily by Lotterywest.
Andrew Brown of DEC Species and Communities Branch and Conservation
Ofcers Beth Laudon, Erica Shedley, Marie Edgley and Kris Brooks made
major contributions to project planning and survey work. I especially
acknowledge Ann and Barry Rick of Newdegate who provided invaluable
assistance, accommodation and advice and Judy Williams of Brookton for
eld trip assistance and knowledge of habitats. I also thank the Western
Australian Native Orchid Study and Conservation Group volunteers who
assisted in surveys and helped acquire data along the transects, especially
Mayne Merritt, Margaret Petridis, Pam Goodman and Ray Grant as well as
Jocelyn Ward and Lucy Skipsey from wheatbelt community groups. Graham
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NAustralian Journal of Botany M. C. Brundrett

Supplementary resources (2)

... Terrestrial orchids are a diverse group of plants globally (c. 28000 species : Fay 2018) and within Australia (c. 1960species: Backhouse et al. 2019, and possess high rates of both species extinction and speciation (Chase et al. 2015;Brundrett 2016). In a review of Australian threatened orchid taxa, New South Wales (NSW) ranked fifth behind Queensland, South Australia, Victoria, and Tasmania for the number of significant (extinct, threatened and rare) species (Backhouse 2007), with 78 (37%) of the then 210 endemic NSW species listed as threatened. ...
... Knowledge informing the conservation status of all such orchids is heavily reliant on the ability of surveyors to detect individuals and populations within often floristically and structurally diverse habitats. This is not always an easy task, with variations in seasonal emergence dramatically influencing measures of population abundance (Gillman & Dodd 1998;Kindlmann & Balounova 2001;Kindlmann 2003), coupled with numerous environmental stressors operating on plants that limit their effective detection (flowering) period (Kery & Gregg 2003;McCormick & Jacquemyn 2014;Brundrett 2016). Essentially, measures of abundance in terrestrial orchids are a factor of detectability during surveys rather than a finite census of a population (Kery & Gregg 2003;Bell 2019). ...
... Terrestrial orchids, like other deciduous geophytes, comprise a difficult group in this regard because detection of individuals is reliant on suitable conditions for emergence and flowering (Pfeifer et al. 2006;McCormick & Jacquemyn 2014), and on the adequacy of survey within potential habitat across their known geographical extent. Individual orchids may remain dormant in the ground for several years awaiting appropriate conditions for emergence (Weston et al. 2005;Brundrett 2016), but when they do emerge knowledge on the most suitable time to conduct surveys ('peak flowering') can be critical for correctly timed surveys (Yare et al. 2020). Added to this are the sizeable number of naturally occurring processes that impact on detection in any one season, including grazing and/or trampling by vertebrates (e.g. ...
Systematic targeted surveys for the vulnerable and poorly conserved Pterostylis chaetophora (family Orchidaceae) were undertaken during peak flowering over ten days in 2018 and 2019 across 720 ha of Columbey National Park (Columbey). The assumed population size of this species in Columbey prior to this study (c. 20 individuals) was found to be unrepresentative of the number of sub-populations (175) and individuals (544) subsequently located along 141 km of search transects. Extrapolation of this result across the full Columbey study area suggests an upper population size of nearly 3000 plants, increasing the total documented New South Wales population 15-fold. The most commonly occupied communities for Pterostylis chaetophora were found to be Floodplain Redgum-Box Forest (57% of individuals and 54% of sub-populations), Lower Hunter Spotted Gum-Ironbark Forest (28% of individuals, 25% of sub-populations), and Seaham Spotted Gum-Ironbark Forest (14% of individuals, 18% of sub-populations). The largest sub-populations (>10 individuals) were in Floodplain Redgum-Box Forest where Eucalyptus moluccana dominated the canopy, followed by Lower Hunter Spotted Gum-Ironbark Forest and Seaham Spotted Gum-Ironbark Forest. All three occupied communities are relatively widespread in the lower Hunter Valley and lower North Coast regions, suggesting that such habitat elsewhere may harbour undetected populations of Pterostylis chaetophora. These results suggest that systematic targeted surveys for other threatened orchids are necessary to fully understand both the magnitude of a species' population and its occupied habitat. Such surveys may ultimately lead to re-assessment of the conservation status of some of these species where, like Pterostylis chaetophora, considerably more populations and individuals are uncovered within secure land tenure.
... Terrestrial orchids are perhaps overrepresented in the literature documenting translocations, but rank fourth behind shrubs, trees, and herbs in Australia (Commander et al. 2018). In part, this is a reflection on the aesthetic value and importance placed on this group by orchid enthusiasts, but also due to its high rates of species extinction and speciation (Chase et al. 2015;Brundrett 2016). In addition, the impressive diversity in this family, and the habit in which they often "turn up" unexpectedly, proffers them an inflated conservation value. ...
... Pre-flowering (approximately winter) rainfall has been previously shown to influence emergence and flowering in-ground orchids (e.g. Pfeifer et al. 2006;Brundrett 2016). To test this, analysis of rainfall annually and during various pre-flowering periods (autumn, Mar-May; winter, Jun-Aug; individual winter months) was undertaken to identify which best explained variation in detection, using on-site weather stations maintained by Glencore ("influence of rainfall"). ...
... Variability in winter rainfall (particularly July-August) had the greatest overall impact on orchid detection, and supports studies completed elsewhere (e.g. Pfeifer et al. 2006;Brundrett 2016). Over the study period both wet (aboveaverage) and dry (below average) months occurred, with orchid detectability varying accordingly and consistently across non-mined and post-mined land. ...
Re‐introduction of threatened plants is an emerging tool in biodiversity conservation, however the efficacy and success of translocations varies. This study documents translocation of two threatened terrestrial orchid species (Diuris tricolor , Prasophyllum petilum ) over eight years within coal mining areas in the Hunter Valley of NSW, Australia. In the largest scale orchid translocation known (and the only one translocating into mine rehabilitation), six events have progressively re‐located 3,030 mature orchids (1,206 D.tricolor , 1824 P.petilum ) into biodiversity offsets (non‐mined: 1099 D.tricolor , 1,493 P.petilum ) and mine rehabilitation (post‐mined: 127 D.tricolor , 311 P.petilum ), and 300 salvaged tubers into non‐mined (20 D.tricolor , 180 P.petilum ) and post‐mined (10 D.tricolor , 90 P.petilum ) lands. Monitoring of orchids for 3–8 years revealed significant relationships between winter rainfall (July for P.petilum , August for D.tricolor ) and orchid detection. Both species survived significantly better in non‐mined and post‐mined land when translocated in soil cores than as salvaged tubers. Diuris tricolor was more detectable overall, with rates 3–8 years post‐translocation as high as 53–67% in good years and 16–47% during drought. Prasophyllum petilum was less detectable, returning 4–12% in drought but rising to 52–63% during wetter seasons. Diligent searching prior to flowering doubled detection for D.tricolor and increased it by one third for P.petilum . Two monitoring inspections per season increased detection by up to 12%. After 3–8 years post‐translocation, orchids have persisted and are well established. Staged translocation over eight years with adaptive management to operational procedures and monitoring has increased orchid detectability, and can be applied to future orchid translocations. This article is protected by copyright. All rights reserved.
... Orchid conservation research and actions are urgently required, as the largest plant family with half its members listed on the IUCN Global Red List of threatened species . Major threats to orchids in Australia include loss of habitat, altered fire regimes, tourism and recreation, collecting, drought, weeds and grazing (Brundrett 2007, 2016, Wraith & Pickering 2019. Most of the orchids in WA are geophytes with summer dormancy and occur in areas of mediterranean climate with relatively high rainfall (Brundrett 2014). ...
... So far, I have only been able to set up detailed demographic monitoring plots for 9 of the rarest orchids in WA (e.g. Brundrett 2016). ...
... In addition to population surveys, detailed orchid demographics data are required to measure sustainability of orchid populations and to guide conservation actions (Whigham & Willems 2003, Brundrett 2016. This essential data includes actual population sizes (including dormant plants), plant lifespans, pollination rates and recruitment rates (Fig. 1A, Table 1). ...
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This paper presents a comprehensive and adaptive framework for orchid conservation programs illustrated with data from published and unpublished case studies. There is a specific focus on West Australian terrestrial orchids, but many of the approaches have universal relevance. Aspects of the framework include (1) setting appropriate objectives, (2) establishing effective collaborations between scientists, volunteers and regulators to fill knowledge and funding gaps, (3) use of survey and demographics data to determine extinction risks and management requirements for species, (4) effective habitat management to overcome threats such as grazing, (5) finding potential new habitats by modelling climate and site data, (6) investigating the effectiveness of pollinators and (7) using seed baiting to detect mycorrhizal fungi. The relative cost and effectiveness of different methods used to propagate orchids for translocation are compared. Methods known to be successful, in order of complexity, include placement of seed in situ, vegetative propagation, symbiotic germination in non-sterile organic matter, symbiotic germination in sterile culture, asymbiotic sterile germination and clonal division in tissue culture. These form a continuum of complexity, cost, time required, faculties needed, as well as the capacity to maintain genetic diversity and produce seedlings preadapted to survive in situ. They all start with seed collection and lead to seed storage, living collections used as tuber banks and seed orchards, as well as translocation for conservation. They could also lead to commercial availability and sustainable ecotourism, both of which are needed to reduce pressure on wild plants. Overall, there has been a strong preference to use relatively complex, expensive and time-consuming methods for orchid conservation, despite evidence that simpler approaches have also been successful. These simpler methods, which include in situ seed placement and non-sterile germination on inorganic substrates, should be trialled in combination with more complex orchid propagation methods as part of an adaptive management framework. It is essential that orchid conservation projects harness the unique biological features of orchids, such as abundant seed production and mycorrhizal fungi which are far more widespread than their hosts. This is necessary to increase the efficiency and coverage of recovery actions for the largest and most threatened plant family.
... Most missing orchids do not re-appear in later years, so were not dormant. This differs from more arid habitats in WA where dormancy lasting one or more years is common [56]. Sudden decline of local populations can occur in habitats which are in good condition. ...
... Sudden decline of local populations can occur in habitats which are in good condition. Grazing animals such as kangaroos observed in other studies [56,57] were rare at the study site. However, suspected symptoms of virus infection were sometimes observed before plants disappeared. ...
... Comparing these metrics can help to separate the effects of flower production, pollinator abundance and plant density on reproductive outputs. Many rare orchids do occur in dense aggregations [56], so their critical pollination rates should be reconsidered using SGA and LGA values. Annual variability in pollination rates was substantial in some cases, but was found to be less important than plant density. ...
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The pollination of 20 common terrestrial orchids was studied in a 60-ha urban banksia and eucalypt dominated woodland in Western Australia. Five years of data (24,000 flowers, 6800 plants) measured fruit set relative to floral areas, capsule volumes, climate, phenology, pollination mechanisms, disturbance tolerance and demography. Pollination varied from 0–95% of flowers, floral displays from 90–3300 mm2 and capsules from 15–1300 mm3 per spike. Pollination traits strongly influenced outcomes, with self-pollination highest (59—95%), followed by sexually deceptive autumn or winter-flowering (18–39%), visual deception (0–48%) and sexually deceptive spring-flowering (13–16%). Pollination was limited by drought in autumn or spring and cool winter temperatures. Some orchids were resilient to drought and one formed seed after the leaves withered. Plant density had the greatest impact on fruit set for orchids forming large groups, especially for sexually deceptive pollination. Consequently, small group average (SGA) pollination was up to 4× greater than overall averages and peak seed production occurred in the best locations for genetic exchange and dispersal. SGA rates and seedpod volumes were strongly linked to clonality, but not to demographic trends. Resource competition limited flowering at higher plant densities and competition within spikes resulted in smaller, later-forming seedpods. Pollination data from co-occurring common orchids identified five evolutionary trade-offs linked to pollination, provided baseline data for rare species and revealed impacts of changing climate.
... Below average rainfall in the three months leading up to flowering place individual orchids under stress, meaning that flowering may be postponed for that season for all but the most robust individuals. Because of this trait, terrestrial orchids have been described as 'timetravellers' (Brundrett 2016), encapsulating the uncertainty in determining their presence in any given area. ...
... Total rainfall (Jun to Aug WSN) Total rainfall (Jun to Aug WSS) Mean rainfall (Jun-Aug;2010-2018 Trans # 2 (n=376) Trans # 3a (n=400) Trans # 3b (n=400) Trans # 3c (n=420) Trans # 4 (n=121) Trans # 5 (n=218) Trans # 6a (n=254) Trans # 6b (n=203) Trans # 7 (n=200) ...
Two threatened terrestrial orchids (Diuris tricolor, Prasophyllum petilum) have been the subject of a major translocation program in the upper Hunter Valley of New South Wales. After up to eight years of monitoring and adaptive management, a number of lessons have been learnt that can be transferred to other orchid translocation projects. A key observation for any monitoring program is that the measurement of translocation success is all about the ability to detect translocated individuals: an absence of detection is not necessarily an indication of an absence of life.
... Mycorrhizal fungi are generally widespread in the landscape, and occur independently of orchid distribution: orchids need fungi, but the reverse is not also true (McCormick & Jacquemyn 2014). High taxonomic diversity in this family is consequently attributed to specialization of either pollinator or mycorrhizal fungi, inherently increasing the risk of extinction in highly specialized species (Tremblay et al. 2005;Brundrett 2016;Fay 2018). ...
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Phenological studies are important to gain insights into the ecology of plant species, particularly those that are threatened and require specific management actions such as regular population monitoring. For many species of terrestrial orchids, limited fundamental knowledge on peak flowering, pollination and seed production restricts effective monitoring outcomes. In this single-season study, phenology data from one population of the vulnerable Diuris praecox were collected, with the aim of informing future management relating to monitoring surveys and to assist in conservation of this species. To this end, six sub-populations (three each in forest habitat and along maintained powerline easements) were visited weekly from the onset of flowering until seed release, with observations made on 134 tagged individuals within 10 x 10 m plots. During the 2019 flowering season, 37% of all plants developed capsules, and 35% released seed. However, success varied between locations, with greater floral displays along powerline easements resulting in stronger pollination rates, while sparse sub-populations in forested locations showed lower pollination. Significantly more flowers per inflorescence (range 1-7) were evident in forest than easement sites, but there was no significant difference in inflorescence height across these habitats. For most sub-populations at least one orchid set seed, even when occurring in low densities (<10 plants). Overall, substantial floral displays did not necessarily result in abundant fruiting, and impacts from desiccation, predation and grazing likely prevented more successful capsule production in any given sub-population. The synchronously flowering shrubs Daviesia ulicifolia and Pultenaea villosa co-occurred across all sub-populations, suggesting that the nectar-less Diuris praecox may mimic these species to attract pollinators. Peak flowering was determined to be approximately 20 days from the onset of flowering, with 83% of all plants in flower at that time. For ongoing monitoring, the timing of surveys to occur approximately three weeks after the first observed flowering, will likely maximize return-for-effort, particularly when survey resources are limited, although it is acknowledged that different seasons and populations may vary from this timeframe.
... Management of threatened flora impacted by grazing is primarily through fencing of sites to exclude herbivores (e.g. Brundrett, 2016;Rathbone and Barrett, 2017). ...
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The Southwest Australian Floristic Region (SWAFR) is a global biodiversity hotspot with high plant diversity and endemism and a broad range of threatening processes. An outcome of this is a high proportion of rare and threatened plant species. Ongoing discovery and taxonomic description of new species, many of which are rare, increases the challenges for recovery of threatened species and prioritisation of conservation actions. Current conservation of this diverse flora is based on integrated and scientific evidence-based management. Here we present an overview of current approaches to the conservation of threatened flora in the SWAFR with a focus on active management through recovery and restoration that is integrated with targeted research. Key threats include disease, fragmentation, invasive weeds, altered fire regimes, grazing, altered hydro-ecology and climate change. We highlight the integrated approach to management of threats and recovery of species with four case studies of threatened flora recovery projects that illustrate the breadth of interventions ranging from in-situ management to conservation reintroductions and restoration of threatened species habitats. Our review and case studies emphasise that despite the scale of the challenge, a scientific understanding of threats and their impacts enables effective conservation actions to arrest decline and enhance recovery of threatened species and habitats.
Many orchids are characterized by small, patchily distributed populations. Resolving how they persist is important for understanding the ecology of this hyper-diverse family, many members of which are of conservation concern. Ten populations of the common terrestrial orchid Drakaea glyptodon from south-western Australia were genotyped with ten nuclear and five plastid simple sequence repeat (SSR) markers. Levels and partitioning of genetic variation and effective population sizes (Ne) were estimated. Spatial genetic structure of nuclear diversity, together with plastid data, were used to infer the effective number of seed parents per population. We found high genetic diversity, Ne values that generally exceed predictions based on the number of flowering individuals and moderate levels of gene flow. Two populations were founded by less than five colonists suggesting some populations are colonized by few seeds, with growth largely resulting from in situ recruitment. A value of 3.65 for mp /ms indicates that pollinators play a greater role than seed in introducing genetic diversity to populations via gene flow. Our results highlight that D. glyptodon is highly effective at persisting in patchily distributed populations. However, it is important to examine how insights from this common, widespread species transfer to species that are rare and/or occur in fragmented landscapes.
Terrestrial orchid life-cycles are complex and dependent on pollinators and mycorrhizal associates. Worldwide, orchid populations are declining because of urbanization, atmospheric nitrogen deposition and climate change. To advance understanding of the factors determining orchid population viability, we review knowledge about orchid demography, life histories and population dynamics. Orchids can produce thousands of seeds, although few survive to reach maturity, with mortality rates declining from juvenile to adult life states. Flowering and fruiting rates vary widely between years, and many populations, especially of deceptive species, are pollen- and seed-limited. Many species have long lifespans and periods of vegetative dormancy and exhibit costs associated with reproduction, sprouting, vegetative dormancy, growth and size. Population growth rates range from 0.50–2.92 (mean: 0.983 ± 0.026). Although vital rates can fluctuate widely between years and be strongly correlated, these correlations have little impact on population dynamics. Variation in spatial density of fungi and microsite quality, limited dispersal and competition generate density dependence in vital rates. Future research should elucidate the roles of biotic and abiotic factors on population dynamics to underpin effective management for conservation. Understanding the impact of idiosyncratic individual plant behaviour on population dynamics will also improve demographic parameter estimation, including population growth rate and net reproductive rate.
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This book is divided into two sections, each of which has a different purpose. The introductory chapters provide an overview of the orchid family and unique features of their biology and ecology. Key topics include the global importance of Western Australia as an orchid diversity hotspot, the amazing interactions between orchids and pollinating insects, an overview of orchid conservation issues and advice for orchid tourists. The second larger section of the book focuses on orchid identification with keys and pictorial guides to species as well as information on the pollination, ecology, cultivation and taxonomy of each genus. For each species, a brief description focuses on defining features with the majority of space used for photos that clearly show identifying features. There are over 1500 detailed photographs of orchids. This book is designed to be user friendly by limiting the use of terminology in keys, but also aims to make identification as accurate as possible.
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The Wheatbelt Orchid Rescue Project was a Lotterywest funded collaboration between the Western Australian Native Orchid Study and Conservation Group, the School of Plant Biology at the University of Western Australia, the Friends of Kings Park and the Department of Environment and Conservation. This project aimed to help conserve Critically Endangered orchids in the Western Australian wheatbelt by obtaining knowledge required for sustainable management and directly contributing to recovery actions. These rare orchids were the granite spider orchid (Caladenia graniticola), ballerina orchid (C. melanema), William’s spider orchid (C. williamsiae, lonely hammer orchid (Drakaea isolata) and underground orchid (Rhizanthella gardneri). Vital statistics data were gathered by establishing permanent transects to monitor plant abundance and reproduction for three of these orchids. The main threats identified were animal grazing, low seed set and very small habitat areas. New methods for orchid propagation were developed and seedlings translocated into very dry habitats.
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This review summarises scientific knowledge concerning the mycorrhizal associations, pollination, demographics, genetics and evolution of Australian terrestrial orchids relevant to conservation. The orchid family is highly diverse in Western Australia (WA), with over 400 recognised taxa of which 76 are Declared Rare or Priority Flora. Major threats to rare orchids in WA include habitat loss, salinity, feral animals and drought. These threats require science-based recovery actions resulting from collaborations between universities, government agencies and community groups. Fungal identification by DNA-based methods in combination with compatibility testing by germination assays has revealed a complex picture of orchid-fungus diversity and specificity. The majority of rare and common WA orchids studied have highly specific mycorrhizal associations with fungi in the Rhizoctonia alliance, but some associate with a wider diversity of fungi. These fungi may be a key factor influencing the distribution of orchids and their presence can be tested by orchid seed bait bioassays. These bioassays show that mycorrhizal fungi are concentrated in coarse organic matter that may be depleted in some habitats (e.g. by frequent fire). Mycorrhizal fungi also allow efficient propagation of terrestrial orchids for reintroduction into natural habitats and for bioassays to test habitat quality. Four categories of WA orchids are defined by the following pollination strategies: (i) nectar-producing flowers with diverse pollinators, (ii) non-rewarding flowers that mimic other plants, (iii) winter-flowering orchids that attract fungus-feeding insects and (iv) sexually deceptive orchids with relatively specific pollinators. An exceptionally high proportion of WA orchids have specific insect pollinators. Bioassays testing orchid-pollinator specificity can define habitats and separate closely related species. Other research has revealed the chemical basis for insect attraction to orchids and the ecological consequences of deceptive pollination. Genetic studies have revealed that the structure of orchid populations is influenced by pollination, seed dispersal, reproductive isolation and hybridisation. Long-term demographic studies determine the viability of orchid populations, estimate rates of transition between seedling, flowering, non-flowering and dormant states and reveal factors, such as grazing and competition, that result in declining populations. It is difficult to define potential new habitats for rare orchids because of their specific relationships with fungi and insects. An understanding of all three dimensions of orchid habitat requirements can be provided by bioassays with seed baits for fungi, flowers for insects and transplanted seedlings for orchid demography. The majority of both rare and common WA orchids have highly specific associations with pollinating insects and mycorrhizal fungi, suggesting that evolution has favoured increasing specificity in these relationships in the ancient landscapes of WA.
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Dormancy is a condition in which an herbaceous perennial does not sprout for one or more growing seasons. To test whether dormancy is an adaptive response to environmental stress, we defoliated and shaded individuals of two rare geophytic orchids, Cypripedium calceolusand Cephalanthera longifolia, in five Estonian populations early in the growing season in 2002 and 2003. We also censused plants at the same time, and conducted one more census in 2004. Mark-recapture models were used to estimate the probabilities of dormancy (d, the complement to resighting, p), and apparent survival (f). Apparent survival varied little by treatment, with Cypripediumand Cephalantherasurviving at 0.986 6 0.014 and 0.974 6 0.021 (mean 6 SE), respectively. In contrast, treatment impacted dormancy dramatically. For both Cephalanthera and Cypripedium, defoliated (def.) plants were most dormant (0.320 6 0.055 and 0.095 6 0.036, respectively). However, while both control (cont.) and shaded (sh.) plants were roughly equally least dormant in Cypripedium (dcont. 5 0.048 6 0.020 vs. dsh. 5 0.045 6 0.021), the least dormant Cephal- anthera had been shaded (0.182 6 0.040 vs. dcont. 5 0.206 6 0.050). We conclude that dormancy may allow the plant to buffer stress in the short term without increasing mortality risk.
Since the last classification of Orchidaceae in 2003, there has been major progress in the determination of relationships, and we present here a revised classification including a list of all 736 currently recognized genera. A number of generic changes have occurred in Orchideae (Orchidoideae), but the majority of changes have occurred in Epidendroideae. In the latter, almost all of the problematic placements recognized in the previous classification 11 years ago have now been resolved. In Epidendroideae, we have recognized three new tribes (relative to the last classification): Thaieae (monogeneric) for Thaia, which was previously considered to be the only taxon incertae sedis; Xerorchideae (monogeneric) for Xerorchis; and Wullschlaegelieae for achlorophyllous Wullschlaegelia, which had tentatively been placed in Calypsoeae. Another genus, Devogelia, takes the place of Thaia as incertae sedis in Epidendroideae. Gastrodieae are clearly placed among the tribes in the neottioid grade, with Neottieae sister to the remainder of Epidendroideae. Arethuseae are sister to the rest of the higher Epidendroideae, which is unsurprising given their mostly soft pollinia. Tribal relationships within Epidendroideae have been much clarified by analyses of multiple plastid DNA regions and the low-copy nuclear gene Xdh. Four major clades within the remainder of Epidendroideae are recognized: Vandeae/Podochileae/Collabieae, Cymbidieae, Malaxideae and Epidendreae, the last now including Calypsoinae (previously recognized as a tribe on its own) and Agrostophyllinae s.s. Agrostophyllinae and Collabiinae were unplaced subtribes in the 2003 classification. The former are now split between two subtribes, Agrostophyllinae s.s. and Adrorhizinae, the first now included in Epidendreae and the second in Vandeae. Collabiinae, also probably related to Vandeae, are now elevated to a tribe along with Podochileae. Malaxis and relatives are placed in Malaxidinae and included with Dendrobiinae in Malaxideae. The increased resolution and content of larger clades, recognized here as tribes, do not support the ‘phylads’ in Epidendroideae proposed 22 years ago by Dressler. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177, 151–174.
Our understanding of orchid population behavior can be critical to the selection of appropriate conservation measures, yet less than 50% of North American and 5% of world orchid species respectively are currently subject to long-term study. Such studies often must be accomplished with limited resources. Whatever the situation, however, the selected approach should be both comprehensive and well thought out, if there is to be a conservation pay-off.
Males of the thynnine wasp Thynnoturneria sp. attempt to mate with female decoys in the flowers of the elbow orchid Spiculaea ciliata. Experimentally shifted orchids usually attract male wasps quickly, often within 2 minutes of presentation of the 'bait' orchids in appropriate habitat. Although the orchid effectively exploits the scramble competition mating system of the wasp, the insect is not totally at the mercy of the deceptive orchid. Fewer than half of all arriving males contact the column of the orchid flower, as required for orchid pollination. Moreover, the number of deceived visitors falls sharply over a short period and the number of wasp visitors does not rebound with the replacement of one bait orchid by another at that location. These observations suggest that patrolling wasp pollinators can discriminate to some extent between orchid decoys and female wasps, especially by learning to avoid particular locations that are associated with unrewarding flower decoys.