Listing Statement for Pterostylis atriola (snug greenhood) Pterostylis atriola snug greenhood T A S M A N I A N T H R E A T E N E D S P E C I E S L I S T I N G S T A T E M E N T Image by Mark Wapstra Scientific name: Pterostylis atriola D.L.Jones, Austral. Orchid Res. 3: 140 (1998) Common name: snug greenhood (Wapstra et al. 2005) Group: vascular plant, monocotyledon, family Orchidaceae Name history: Speculantha atriola Status: Threatened Species Protection Act 1995: rare Environment Protection and Biodiversity Conservation Act 1999: not listed Distribution: Endemic status: Endemic to Tasmania Tasmanian NRM Region: Cradle Coast, North, South Figure 1. Distribution of Pterostylis atriola Plate 1. Pterostylis atriola (image by David Tng) 1 Threatened Species Section – Department of Primary Industries, Parks, Water and Environment Listing Statement for Pterostylis atriola (snug greenhood) IDENTIFICATION AND ECOLOGY subpopulations to persist. For example, Pterostylis atriola is a multi-flowered tall herb in a individuals in the subpopulation at Snug Plains group of orchids known as greenhoods. The occur on poorly-maintained 4WD tracks but name greenhood arises because the dorsal sepal also extend into adjacent burnt and unburnt and petals are united to form a predominantly shrubby forest. Individuals in the green, hood-like structure that dominates the subpopulation in the Wielangta area occur on flower. When triggered by touch, the labellum both the edge of old fire trails and throughout flips inwards towards the column, trapping any Eucalyptus obliqua dry sclerophyll forest that was insect inside the flower, thereby aiding burnt about 3 years previously. Individuals in pollination as the insect struggles to escape. the subpopulation near Railton are most Greenhoods are deciduous terrestrials that have strongly associated with old trails through the fleshy tubers, which are replaced annually. At selectively harvested forest. some stage in their life cycle all greenhoods produce a rosette of leaves. Survey techniques Pterostylis atriola is an autumn-flowering Pterostylis atriola is part of a complex of four greenhood with a short flowering period closely related species with similar features. between January and March, with a peak in Species in this complex are easily identifiable by February (Wapstra et al. 2008). It can only be their multi-flowered scapes with small inward- positively identified from fresh or fertilised facing flowers (which are apparently semen- flowers, perhaps as late as May at some sites. scented) and are unlikely to be confused with any other taxa. The species are easily recognised Description during the flowering phase because of their Pterostylis atriola has 1 or 2 leaf rosettes on lateral height and distinctive flower arrangement that growths arising from the base of the scape makes them easily distinguishable from other (flower stem) or on sterile plants. The 3 to 6 herbs on the forest floor. leaves are dark green and have an ovate lamina Pterostylis atriola reproduces entirely from seed in 3 to 14 mm long and 4 to 9 mm wide with association with mycorrhizal fungi. The friable entire margins, a subacute apex and 3 to 7 mm nature of the pollen and basal siting of the long petioles. The scape is slender, wiry and 20 stigma suggest autogamy (self-pollination), to 35 cm tall. Plants have 1 to 10 inward-facing although this requires confirmation (Jones striped dark green and white flowers that are 8 1998). Clonal colonies are apparently absent in to 9.5 mm long and 2.5 mm wide with a brown this group of greenhoods i.e. the “Speculantha” apex and scabrous distal parts of the dorsal species-complex (Jones 1998). sepal and petals. The apex of the galea (hood- like structure) is curved and the dorsal sepal Pterostylis atriola plants may not flower every and petals are of similar length. The dorsal year, though when they do, they flower for a sepal is boldly striped, ovate-lanceolate and 12 short period each year (in the order of weeks) to 15 mm long and 6.7 mm wide. The erect before being fertilised and old flowers often lateral sepals closely embrace the galea. They persist on the stalk for many weeks. Natural are conjoined with tapered and curved forward mortality in all phases of its above-ground free points about 3 mm long, the tips just existence is likely to be low and caused by higher than the galea, the sinus (gap) step-like at grazing (by native marsupials, or stock, if the top, flat or gently sloping and very shallowly present), drought-stress (in periods of extreme notched, with an opening about 1 mm wide. drought only) and fire (wildfire). It is noted, The petals are linear-oblong, 8.5 to 10 mm long however, that the species is likely to survive and 2 mm wide, strongly curved and subacute. into subsequent years because of the presence The labellum is linear-elliptical, 3 to 3.5 mm of an underground tuber (Jones et al. 1999). long and 1.5 mm wide, blunt and not visible through the sinus in any position. Pterostylis atriola appears to respond favourably [description based on Jones 1998, Jones et al. to disturbance but does not rely on it for 1999, Jones 2006] 2 Threatened Species Section – Department of Primary Industries, Parks, Water and Environment Listing Statement for Pterostylis atriola (snug greenhood) Confusing species upper slopes, frost hollows, gorges, rock Pterostylis atriola is part of a complex of four plates). It occurs in dry sclerophyll forest, closely related species (within Tasmania) with typically with an open understorey (e.g. shrubby similar features, included by some authors Eucalyptus obliqua forest, shrubby/heathy within the genus Speculantha (Jones & Clements Eucalyptus amygdalina forest) (Jones 1998, Jones 2002). Within this complex, Pterostylis atriola is et al. 1999, Jones 2006). distinguishable by its relatively taller scape, small narrow green and white flowers with POPULATION ESTIMATE brown petals, a flat sinus when viewed from the It is likely that Pterostylis atriola has a wider side, a very narrow frontal opening to the distribution than shown in Figure 1. Several flower, scabrid bumps on the dorsal sepal, subpopulations have been detected since the attenuate free points that extent just above the description of the species in 1998 and further galea, and a linear-elliptical reddish labellum survey effort by people familiar with the species (Jones et al. 1999). at the appropriate time of year is likely to detect further subpopulations. However, focused Pterostylis atriola differs from Pterostylis aphylla in surveys are considered impractical given that having taller, wiry, as opposed to fleshy, the species appears to occur in a wide range of flowering stems and a narrower opening to the vegetation types, at different altitudes and on flower. It differs from Pterostylis parviflora in that different substrates. the tip of the hood is rough to touch and consistently brown, and the flowering stem is The area of occupancy and the number of generally taller. In Pterostylis parviflora, the mature individuals indicated in Table 1 are opening to the flower is wider and the tip of likely to be underestimates as extensive the labellum can be seen through the opening. searching has not been undertaken at most Pterostylis atriola differs from Pterostylis uliginosa in locations. Some subpopulations have proven to having taller and wiry, as opposed to fleshy, be more extensive than originally reported. For flowering stems, and flowers that are rough to example, when found in 1997, the total size of touch at the tip and with a narrower opening to the Snug Tiers subpopulation was estimated at the flower. The flowers of Pterostylis uliginosa are 80 to 100 mature individuals though over 1,000 smaller and shiny green without brown tips. plants were estimated following more extensive searching in the vicinity in 2009, making this DISTRIBUTION AND HABITAT the largest subpopulation known to date. While Pterostylis atriola is endemic to Tasmania. It is 82 individuals were counted in the known from widely separated localities ranging subpopulation at Railton in 2008, the size of from near-coastal lowland and hinterlands in the subpopulation was estimated to be in excess the north and east to 600 m above sea level in of 250, and possibly much higher based on the the southeast (Figure 1, Table 1). The linear 9 to 10 ha extent of potential habitat (ECOtas range of the species is about 300 km and the 2008). Current estimates suggest that the total extent of occurrence about 31,500 km2. The population size of Pterostylis atriola is in the low area of occupancy is more difficult to calculate 1,000s, up from 120 to 130 mature individuals as most subpopulations occur over much less when the species was listed in 2001. than 1 ha but several are represented by The number of plants in any one subpopulation numerous sites spread over several kilometres in any year is likely to fluctuate according to of track and adjacent forest (e.g. Snug Tiers) or seasonal conditions (e.g. amount of 10s of hectares of suitable habitat (e.g. Back winter/spring rain), disturbance history (e.g. Run Hills, Wielangta Hill). fire) and other factors (e.g. natural vegetation Pterostylis atriola occurs on generally stony soil succession). However, the number of plants at on a wide range of substrates including Jurassic discrete sites is generally and consistently small dolerite and Devonian granodiorite and on suggesting that extreme fluctuations in numbers varying aspects/topographies (exposed ridges, are unlikely from season to season. 3 Threatened Species Section – Department of Primary Industries, Parks, Water and Environment Listing Statement for Pterostylis atriola (snug greenhood) Table 1.