Pterostylis jeanesii N.Reiter, B.Kosky & M.A.Clem., 2021

Reiter, Noushka, Kosky, William & Clements, Mark, 2021, Two new species of Pterostylis (Orchidaceae; Orchidoideae) from the Sunset Country, Victoria, Australia, Phytotaxa 500 (3), pp. 153-165 : 160-162

Pterostylis jeanesii N.Reiter, B.Kosky & M.A.Clem. , spec. nov. ( Fig. 6 )

Type: — AUSTRALIA. Victoria: Murray Sunset National Park, Mopoke , 44 m, 22 Oct 2019, Reiter 407 (holotype: MEL2481870 A) .

Pterostylis jeanesii ( Fig. 5 , revised key to Vicflora Appendix 7) has similarities to P. exelsa but differs from that species by way of lacking a crest of small dense setae on the labellum mound, shorter scape 9–20 cm (versus 80 cm), 2–5 flowers (versus up to 20). Pterostylis jeanesii is similar to P. pedina but differs from this species in the following: wider lateral sepals, longer free points of the sepals, longer labellum, wider labellum, longer prominent setae, taller flower, taller basal mound and wider basal mound. Pterostylis jeansii corresponds to the following illustrations: Backhouse (2019: 358; as P. species ‘Sunset Country’) and Jeanes & Backhouse (2006: 140; as P. sp. aff. excelsa ).

Deciduous terrestrial, solitary, tuberous herbs. Leaves sessile 2–10 in a rosette, imbricate, green, or withered at anthesis; lamina narrowly elliptical, margins entire, acute to acuminate to 2.0  1.1 cm. Scape 9–20 cm tall, 0.4 cm diam. Flowers 2–5, 2.0–4.0 cm tall, 1.0– 2.1 cm thick. Sterile leafy bracts 2–5, ensheathing stem, lanceolate, acuminate, withered at flowering, 0.5–2.5 cm long. Floral bracts ovate-lanceolate, not overlapping at base of scape, clasping stem, apex acute to acuminate, 20–45  3–10 mm. Pedicels slender 2.1–2.9 cm long, enclosed within the floral bract. Ovaries narrowly cylindrical, 4.0–7.0  1.5–3.0 mm. Flowers porrect; galea bulbous, mostly glabrous or with few short bristles along the apical and lateral ridges, gibbous at base, shallowly curved throughout, narrowing to a filiform, decurved apical point,translucent white with predominantly green to brown stripes and markings; petals mostly translucent white with small green or brown suffusions, margins incurved with well-developed basal flanges, usually not touching; lateral sepals usually translucent white with brown or green outline and striping, free points usually brown occasionally green, basal half of lateral margins covered with prominent short, white bristles. Dorsal sepal cucullate, broadest near the base 1.0– 2.1 cm long, tapering to an apical filiform, decurved point 0.2–1.0 cm long. Lateral sepals deflexed, narrow at base and conjoined in basal half, shallowly concave with thickened lateral margins, sparsely ciliate, conjoined part 7–11  5–12 mm; free points curved forward, filiform, 11–19 mm long, slightly spreading. Petals asymmetrical oblong-lancolate, falcate, 1.0–2.1  4.0–5.0 mm, dorsal margin prominently thickened, glaborus, anterior margin curved, glabrous, proximal flange brown prominent, apex acuminate. Labellum insectiform on a visible claw, articulate, highly sensitive to touch, nested between conjoined part of the lateral sepals when exposed and in set position; 4.8–5.7  1.2–2.1 mm, 0.3–0.4 mm deep, usually solid brown or green; laminar obovate to elliptical with basal lobe: 1.4–1.6 mm tall, 0.5–1.6  0.6–2.1 mm; distal margins with a series of spreading, short white setae, largest nearest the base, smaller towards apex, 0.4–2.7 mm long, with twin pairs of prominent long setae, 1.8–4.0 mm long on the labellum below the basal lobe. Column porrect, incurved, extending most of the length of the bulbous part of the galea, partly visible through translucent parts of the galea; column wings rectangular, distal margins covered in a series of fine, dense setae. Anther obtuse, green, c. 1.0 mm long. Pollinia linear, c. 1.0– 1.5 mm long, yellow.

Flowering:— October

Habitat: — Red soils in a low-lying Casuarina pauper woodland with the following commonly occurring species: Casuarina cristata , Sclerolaena diacantha , Chenopodium ulicinum , Enchylaena tomentosa , Maireana brevifolia , Olearia pimeleoides , Atriplex vesicaria , Beyeria viscosa and Eremophila sp. At Borree Plains (NSW) the single herbarium specimen occurred in Casuarina pauper woodland. The Berook site is open Eucalyptus woodland.

Distribution:— Herbarium specimens from four locations ( Figure 1 ) between Murray Sunset National Park and Boree Plains in NSW. However, surveys in 2018 and 2019 only located this species at a single site within the Murray Sunset National Park, Victoria. Road works appear to have destroyed the plants at Berook, and no plants were found near Rocket Lake despite extensive surveys. The plants are likely to still be extant in Boree Plains NSW but were not seen in a survey by Kosky in 2019.

Conservation status: — IUCN criteria CR C2ai ( IUCN, 2012) for critically endangered with observed documented decline, less than 250 individuals known and less than 50 individuals in any known population. The remaining population in Victoria is in a national park.

Etymology: — Named after the Victorian botanist Jeff Jeanes, who discovered the first specimens of this species and has made a significant contribution to the taxonomy of the Orchidaceae and other plant families.

Additional specimens examined: — AUSTRALIA. Victoria: Murray Sunset National Park, Mopoke , 44 m, 24 Oct 2017, Reiter 218 ( MEL2467638 A) ; Murray Sunset National Park, Mopoke , 44 m, 22 Oct 2019, Reiter 406 ( MEL2481869 A) ; Murray Sunset National Park, Mopoke , 44 m, 22 Oct 2019, Reiter 408 ( MEL2481871 A) ; Murray Sunset National Park, Berrook , 52 m, 1 Oct 1991, Jeanes s.n ( MEL2154721 ) ; Murray Sunset National Park, Berrook , 52 m, 20 Oct 1992, Jeanes s.n ( MEL2154720 A) ; Murray Sunset National Park, Rocket Lake , 45 m, 22 Oct 1996, Fletcher 360 ( MEL2034851 A) . New South Wales: Boree Plains Station , 108 m, 27 Oct 2016, Sluiter 16 ( MEL2387265 ) .

Figures

FIGURE 1. Distribution of study sites surveyed: black circles= group 1 (P. biseta); black squares = group 2 (P. jeanesii); white squares = P. jeanesii sites from which there are collected specimens but no plants were found in recent surveys; black triangles = (group 3) P. peakallana.

FIGURE 5. A. Pterostylis jeanesii habitat. B. Inflorescence, side view. C. Inflorescence, front view. Photographer: June Niejalke.

FIGURE 6. A. Pterostylis peakallana habitat. B. Inflorescence, side view. Photographer: Russell Stanley.