Pultenaea praecipua M.A.M.Renner & P . H .Weston subsp. praecipua

Renner, Matthew A. M., Barrett, Russell L., Clarke, Steve, Clugston, James A. R. & Wilson, Peter H. Weston Trevor C., 2022, Morphological and molecular evidence refute a broad circumscription for Pultenaea glabra (Fabaceae: Mirbelieae), with implications for taxonomy, biogeography, and conservation, Australian Systematic Botany 35 (3), pp. 225-277 : 266

6a. Pultenaea praecipua M.A.M.Renner & P. H.Weston subsp. praecipua

Pultenaea sp. Genowlan Point ( NSW 417813) NSW Herbarium, PlantNet [https://plantnet.rbgsyd.nsw.gov.au/ accessed 22 Feb. 2022] .

Diagnosis

Pultenaea praecipua subsp. praecipua is distinguished from P. praecipua subsp. temperata by having wider oblanceolate leaves 0.6–2.1 (average 1.2) mm wide whose adaxial surface is mostly exposed, such that the glaucous colour imparted by the dense covering of columnar papillae presents as a striking feature of the plants in the field.

Densely branched, clump-forming shrub up to ~ 1 m tall, branches horizontally spreading from multi-stemmed base; strikingly coloured with two-tone leaves whose upper surface is wholly glaucous, stems yellow–green, bearing short antrorse appressed hairs. Branching irregular. Stipules black–red, aging black; furcate, narrowest at sinus apex, from there disc is flared below and lobes curve laterally above; lobes eccentrically keeled, apex acuminate but not attenuate, disc margins irregularly dentate, teeth close set. Leaves oblanceolate, 9.2–21.6 (average 13.9) mm long by 0.6–2.1 (average 1.2) mm wide, broadening towards the apex from a narrow base; incurved but not enclosing the adaxial surface, which remains visible; nearly glabrous, hairs present on the leaf base and the petiole only, the hairs antrorse, straight, appressed; abaxial leaf surface mamillose, mamillae formed by single epidermal cells, triangular to dome-shaped; adaxial leaf surface with dense tall columnar papillae that imparts a white–glaucous colour to the adaxial leaf surface; apex pungent, orange–brown; leaf anatomy with five vascular traces, outermost faint, with two enlarged cells on the abaxial side of the medial vascular trace, without orange-pigmented cells, the abaxial epidermis hyaline. Inflorescence with little or no internode contraction, flowers in axils of normal vegetative leaves, stem continuing vegetative growth flowering; stipules associated with flowers similar to, or shorter than, those of sterile leaves. Flowers pedicellate, pedicel glabrous. Calyx lobes broad, apex apiculate; ventral lobes auriculate at junction with dorsal lobes; calyx tube and lobes sparsely hairy, with short antrorse hairs; margins of ventral lobes hyaline. Bracteoles short, triangular, not exceeding adjacent calyx sinus, with sparse short hairs. Corolla keel blood-red, other segments yellow. Anthers pale apricot, filaments cream, with yellow hue. Pollen cream, with slight yellow hue. Ovary glabrous. Pods not seen ( Fig. 26 , 27 ).

Distribution and ecology

Pultenaea praecipua subsp. praecipua is known from a single population of ~12 plants at Genowlan Point, the northernmost extension of the plateau within Mugii Murum-ban, where they grow on a flat sandstone pavement with skeletal soil on the edge of a precipice, fully exposed to the north, with scattered Eucalyptus sparsifolia to immediate south-east. The pavement community comprises discontinuous sparse low shrubs including Hibbertia , Isopogon , Leptospermum , Calytrix , Leucopogon , Boronia , Acacia and scattered sedges. The Pultenaea plants occur as scattered, usually isolated, individuals in fully exposed situations.

Recognition

Pultenaea praecipua subsp. praecipua can be recognised by the combination of oblanceolate leaves 0.6–2.1 mm wide with a distinct apiculus, crowded, tall, pillbox papillae on the adaxial surface, and triangular mamillae on the abaxial surface. No other Pultenaea species in the Greater Blue Mountains has this combination of characters. Other distinctive features include the low dense shrub growth habit and the inflorescences on leafy shoots that continue vegetative growth. Pultenaea praecipua subsp. praecipua has a unique field aspect imparted by the broad oblanceolate leaves the upper surface of which bears crowded, tall, pillbox papillae. These papillae cause the adaxial leaf surface to appear glaucous, to the extent that they are nearly white. As such the leaves appear striped, with the glaucous–white adaxial surface between the mid-green abaxial surfaces, and from above the shrubs appear almost wholly glaucous. Flowering plants, with their combination of vibrant two-toned orange and red flowers overlaying the strikingly contrasting white and green leaves arranged in radiating series presents a remarkable plant. The leaves of P. praecipua subsp. praecipua are generally broader than those of P. praecipua subsp. temperata , up to 2.1 mm wide, whereas in P. praecipua subsp. temperata the leaves are up to 1.2 mm wide.

Conservation status

Pultenaea praecipua subsp. praecipua qualifies for listing as Critically Endangered under the IUCN criteria, as it is known from one population comprising fewer than 50 individuals. The taxon has an exceptionally small area of occupancy and extent of occurrence (both ~0.15 ha), a small population size, and is threatened by exotic herbivores including goats and deer, and by stochastic processes to which small populations are susceptible, particularly those that increase mortality rates and reduce recruitment, including severe drought, and intensified fire-regimes. Proximity to the cliff edge may mean that this taxon is also at risk from cliff-fall, through weathering or seismic events and ex situ conservation of all genotypes should be a priority for conservation of this rare taxon.

Specimens examined

New South Wales: Central Tablelands: Mujii Murum-ban National Park: the very tip of Genowlan Point, Capertee valley , 29 Nov. 1997, J. M. Allen & H. G . Washington, ( NSW 417813 ); Oct. 1997, H. G. Washington, ( NSW 417816 ); 24 May 1998, H. G. Washington, ( NSW 423425 ); 17 Oct. 2018, M. A. M. Renner 9056, ( NSW 1052717 ); 17 Oct. 2018, M. A. M. Renner 9057, ( NSW 1052718 ); 17 Oct. 2018, M. A. M. Renner 9058, ( NSW 1052719 ); 7 Oct. 2018, M. A. M. Renner 9060, 1 ( NSW 1052721 ); 17 Oct. 2018, M. A. M. Renner 9061, ( NSW 1052722 ) .

Figures

Fig. 26. Pultenaea praecipua subsp. praecipua (= P. sp. Genowlan Point (NSW 417813)) line drawing. (a) Flowering branch detail; (b) habit; (c) stipule; (d) flower, lateral view; (e) flower, perianth removed, lateral view; (f) standard petal, ventral view; (g) wing, lateral view; (h) keel, lateral view; (l) leaf abaxial surface; (j) leaf, adaxial surface; (k) leaf cross-section and adaxial surface; (l) leaf cross-section and abaxial surface. Scale bar: 10 mm (a); 26.7 mm (b); 2.7 mm (c); 8 mm (d–h); 5 mm (i, j), 1.6 mm (k, l). All from NSW 1052720, b from dried material, a, c–l from spirit.

Fig. 27. Pultenaea praecipua subsp. praecipua (= P. sp. Genowlan Point (NSW 417813)) photos. (a) Habit, showing the striking two-toned leaves, contrasting with the orange and orange–red flowers. (b) Close-up of flower buds. (c) Flower from the front, showing the splayed wings, orange–red keel and red nectar guides. (d–f) Shoot apices bearing flowers, showing flowers produced in association with normal or nearly normal leaves. (g) Close-up of shoot showing the glaucous adaxial leaf surfaces. All from the type plant at Genowlan Point.