Cunninghamia Date of Publication: October 2020 A journal of plant ecology for eastern Australia ISSN 0727- 9620 (print) • ISSN 2200 - 405X (Online) Targeted surveys of a poorly conserved threatened orchid (Pterostylis chaetophora) in Columbey National Park (Hunter Valley, NSW) reveal substantial populations and elucidate occupied habitat Stephen Bell1,3 and Paul Hillier2 1 School of Environmental and Life Sciences, University of Newcastle, University Drive, Callaghan, NSW 2308, AUSTRALIA. 2 Biodiversity Conservation Division, Department of Planning, Industry and Environment, 26 Honeysuckle Drive, Newcastle, NSW 2300, AUSTRALIA. 3 Corresponding author [email protected] Abstract: 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. Cunninghamia (2020) 20: 199–207 doi:10.7751/cunninghamia.2020.20.011 Cunninghamia: a journal of plant ecology for eastern Australia © 2020 Royal Botanic Gardens and Domain Trust www.rbgsyd.nsw.gov.au/science/Scientific_publications/cunninghamia 200 Cunninghamia 20: 2020 Bell & Hillier, Targeted surveys for Pterostylis chaetophora Introduction there are currently 111 accepted taxa and 29 unpublished entities (Janes & Duretto 2010; Backhouse et al. 2019). Two Terrestrial orchids are a diverse group of plants globally subgenera have been constructed around this diverse group (c. 28000 species: Fay 2018) and within Australia (c. 1960 (but see Clements et al. 2011 for a differing view), largely species: Backhouse et al. 2019), and possess high rates of based on the alignment of the lateral sepals (reflexed or both species extinction and speciation (Chase et al. 2015; recurved) and labellum morphology. Pterostylis chaetophora Brundrett 2016). In a review of Australian threatened M.A.Clem. & D.L.Jones (Rusty Greenhood; the subject of orchid taxa, New South Wales (NSW) ranked fifth behind this paper) is the type species for section Oligochaetochilus Queensland, South Australia, Victoria, and Tasmania for the within subgenus Oligochaetochilus, a collection of number of significant (extinct, threatened and rare) species species characterised by multiple flowers comprising the (Backhouse 2007), with 78 (37%) of the then 210 endemic inflorescence, lateral sepals fully recurved, labella with NSW species listed as threatened. Increased listings over distinctive white setae, and column wings with barrier the last thirteen years in line with ongoing threats suggest, trichomes (Janes & Duretto 2010). There are 47 species of however, that State rankings may have changed largely Pterostylis described for section Oligochaetochilus, 19 of through additions of State endemic taxa. Relative to their which occur in New South Wales. Five species are currently earlier work in 2016, Backhouse et al. (2019), for example, listed as threatened in New South Wales (1 critically now show 588 orchid species for NSW and 232 endemic endangered, 2 endangered, 2 vulnerable), while 12 are taxa (including 64 undescribed). Of these, 77 (33%) are listed nationally (3 critically endangered, 5 endangered, currently listed as threatened under the NSW Biodiversity 4 vulnerable). Conservation Act 2016 (NSW BC Act). Apart from South This paper presents the results of systematic targeted surveys Australia (36 taxa), NSW has shown the largest increase undertaken across Columbey National Park over the course (22 taxa) in State endemic taxa over the past three years, of two flowering seasons (2018 and 2019), where only small over Queensland (10 taxa), Western Australia (8 taxa), and populations of Pterostylis chaetophora were previously Tasmania (3 taxa) (Backhouse et al. 2019), and it may be known. It uses Pterostylis chaetophora as a model species expected that increased listings have emanated from this to illustrate the value of systematic searches (rather than pool of endemic species. The Northern Territory has shown ad hoc occasional searches) in potential habitat to improve no change in the number of endemics since 2016, while understanding of distribution and population size. It also Victoria has seen a decrease of 7 taxa, presumably through examines habitat for the species and outlines vegetation the discovery of new populations of formerly Victorian communities currently known to support it, both in Columbey endemics in other States. Clearly, orchid taxonomy, and elsewhere. discovery and listing status remains dynamic, and there is still much to learn about the distribution and ecology of this iconic group of plants. Study Species The discovery of new populations of orchid species can be fortuitous but certain aspects of their morphology lend Pterostylis chaetophora (Figure 1) is a small terrestrial orchid considerable assistance. Many orchid genera produce vivid bearing ornate yet nectar-less flowers, and principally occurs and colourful flowers during a short flowering season which between Taree and Cessnock in central eastern New South aid detection, but the flowers of numerous others are often Wales. Pollination in this genus is thought to be enacted by small, less colourful and relatively insignificant. Knowledge male flies in the families Culicidae and Mycetophilidae, informing the conservation status of all such orchids is heavily attracted to flowers through sexual mimicry and the prospect reliant on the ability of surveyors to detect individuals and of copulation by pseudo-pheromones (Weston et al. 2005). populations within often floristically and structurally diverse The type specimen for the species was grown from material habitats. This is not always an easy task, with variations in collected at Neath, near Cessnock in the mid-Hunter seasonal emergence dramatically influencing measures of Valley in the early 1980s. Apart from a line drawing and population abundance (Gillman & Dodd 1998; Kindlmann & the required Latin diagnosis in Clements (1989), no other Balounova 2001; Kindlmann 2003), coupled with numerous detailed information has been published on this species. environmental stressors operating on plants that limit their Databased populations of Pterostylis chaetophora are effective detection (flowering) period (Kery & Gregg 2003; not representative of the true geographical distribution of McCormick & Jacquemyn 2014; Brundrett 2016). Essentially, this species. Records from the upper Hunter Valley in the measures of abundance in terrestrial orchids are a factor of Wingen (1998) and Denman (2001) localities are in error and detectability during surveys rather than a finite census of a represent different taxa (indeterminate but not Pterostylis population (Kery & Gregg 2003; Bell 2019). Because of the chaetophora for Wingen, Pterostylis aff. praetermissa feeble nature of orchid detection, any population count will be for Denman; L. Copeland, pers. com.), while Queensland an underestimate of the true number of individuals (Sanger & populations now form a separate and distinct un-named Waite 1998; Weston et al. 2005). species with close affinities to Pterostylis chaetophora The genus Pterostylis (‘Greenhoods’) contains at least 262 (Backhouse et al. 2019). Additionally, two early collections species across Australia, Indonesia, Papua New Guinea, New in the Australian Virtual Herbarium (AVH) from Sydney Caledonia and New Zealand, and within New South Wales (PERTH 8885168, R. Brown, 1804, Willoughby area; CBG Cunninghamia 20: 2020 Bell & Hillier, Targeted surveys for Pterostylis chaetophora 201 8704841.1, G. D’Aubert, October 1987, Georges River), drained Yellow Soloths, and shallow moderately-drained and an observation record from Glenhaven (1949), are also Lithosols of the Clarence Town soil landscape. Other less thought to be in error or are now locally extinct. Hosking common soil types include deep well-drained Yellow and and James (1998)