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Gardens’ Bulletin Singapore 73(2): 457–460. 2021
doi: 10.26492/gbs73(2).2021-14
A new species of Petrocosmea (Gesneriaceae)
from Myanmar
D.J. Middleton1, Thant Shin2 & Y. Baba3
1Singapore Botanic Gardens, National Parks Board,
1 Cluny Road, 259569 Singapore
david_middleton@nparks.gov.sg
2Forest Research Institute, 15013 Yezin,
Zayarthiri Township, Naypyidaw, Myanmar
3Auckland War Memorial Museum Tāmaki Paenga Hira,
Private Bag 92018, Auckland 1142, New Zealand
ABSTRACT. The new species Petrocosmea villosa D.J.Middleton from Shan State, Myanmar
is described. It is most similar to Petrocosmea kerrii Craib, P. crinita (W.T.Wang) Z.J.Qiu
and P. heterophylla B.L.Burtt in Petrocosmea sect. Deinanthera but differs particularly in
inorescence structure, inorescence indumentum and in the long calyx lobes.
Keywords. Petrocosmea crinita, Petrocosmea heterophylla, Petrocosmea kerrii, Petrocosmea
sect. Deinanthera, Shan State
Introduction
The genus Petrocosmea Oliv. consists of between 47 species (Wen, 2019) and 55
species (GRC 2021, continuously updated) in southwestern China, northeastern India,
Myanmar, Thailand and Vietnam. Craib (1919) recognised two sections within the
genus based on the relative sizes of the upper and lower lips of the corolla. Wang
(1985) added a third section, Petrocosmea sect. Deinanthera W.T.Wang, to include
the species with the anthers constricted at the apex to form a short thick beak. Qiu
et al. (2015) suggested, however, that the existing sectional treatment of the genus
insufciently reects its morphological diversity and phylogeny.
A specimen, Baba et al. 103535, collected from Myanmar, Shan State, Lomkok
Mountain at 1106 m elevation, has the anther shape characteristic of Petrocosmea sect.
Deinanthera, which has about nine species altogether and which is most diverse in
nearby northern Thailand (Wang, 1985; Middleton & Triboun, 2010). It is not one of
the known species of this section so is here described as new.
Only two other species of Petrocosmea are currently recorded from Myanmar,
P. kerrii Craib and P. kingii (C.B.Clarke) Chatterjee (Kress et al., 2003), although it
would be surprising if P. bicolor D.J.Middleton & Triboun, P. formosa B.L.Burtt, P.
heterophylla B.L.Burtt, P. pubescens D.J.Middleton & Triboun and possibly even P.
umbelliformis B.L.Burtt were not also eventually to be found in the country given their
collection localities in Thailand close to the Myanmar border.
Gard. Bull. Singapore 73(2) 2021
458
New species
Petrocosmea villosa D.J.Middleton, sp. nov.
Similar to Petrocosmea kerrii and P. crinita (W.T.Wang) Z.J.Qiu in the shape and
colour of the corolla but differs from both in having both sessile and petiolate leaves
(petiolate only in P. kerrii and P. crinita), longer calyx lobes (11–12 mm long in P.
villosa, 1.5–4 mm long in P. kerrii and P. crinita) and more owers in the inorescence
than P. kerrii (8–12 in P. villosa, 1–4 in P. kerrii). Also similar to Petrocosmea
heterophylla in having two types of leaves and in the shape and colour of the corolla
but differs in the sessile leaves being smaller (to 2 cm long in P. villosa, to 5.5 cm long
in P. heterophylla), the villous hairs in P. villosa (pubescent rather than villous in P.
heterophylla), inorescence more congested in P. villosa (lax in P. heterophylla), and
longer calyx lobes (11–12 mm long in P. villosa, 4.5–8 mm long in P. heterophylla).
– TYPE: Myanmar, Shan State, Taunggyi Township, Lomkok mountain and pagoda,
1106 m, 20°49′2.4″N 97°13′26.6″E, 20 September 2015, Y. Baba, K. Kertsawang, C.
Kilgour, S. Ruchisansakun, P. Srisanga, P.P. Hnin & Yo El 103535 (holotype MBK;
isotype RAF n.v.). (Fig. 1)
Rosulate herb with two types of leaves: a cluster of sessile leaves and long-petiolate
leaves. Sessile leaves few, c. 2 cm long, densely villous. Petiolate leaves: petioles 2.5–
8 cm long, densely pubescent; blades ovate, 1.9–13.2 × 1.1–6.6 cm, 1.4–2.1 times as
long as wide, base rounded to weakly cordate, apex acuminate, margin denticulate, 4–7
pairs of ascending secondary veins, pubescent above and beneath, more densely so on
venation. Inorescences few per plant, with 8–12 owers, 8–10 cm long, umbelliform
with owers crowded at apex, densely white villous throughout; peduncle 5.5–8 cm
long; pedicels 3–7.5 mm long. Calyx pale green, weakly 2-lipped, the lower 2 lobes
free, the upper 3 lobes fused at base for 2 mm, all lobes narrowly triangular, apices
caudate, margins crenulate towards apex, densely villous outside, glabrous inside;
lower lobes 12 × 2.1 mm, upper lobes 11–12 × 2.4–2.9 mm, lateral ones slightly
falcate. Corolla c. 1 cm long, tube short and limb spreading resulting in a at-faced
ower, white tinged yellow at base of upper lip, with orange-yellow markings at base
of lower lip, outside pubescent on lobes and with sessile glands, inside with short hairs
at throat and with sessile glands at base of upper lip; tube c. 3 mm long; limb 2-lipped;
upper lip 2-lobed, c. 7 mm long, lobes c. 7 × 7 mm, sinus between them c. 3.5 mm
deep; lower lip 3-lobed, c. 8.5 mm long, lateral lobes c. 5.5 × 6 mm, middle lobe c.
4 × 5 mm. Stamens inserted at base of corolla tube, anthers pressed face to face but
not coherent in rehydrated owers; laments c. 1 mm long, c. 1.1 mm wide; anthers
2, c. 4.7 × 2.5 mm, apical beak c. 1 mm long; staminodes 3, c. 0.7 mm long. Pistil c.
9.5 mm long, eglandular pubescent throughout; ovary c. 4 mm long; style and stigma
c. 5.5 mm long. Fruit a plagiocarpic capsule on elongated pedicels, 5.5–6 mm long.
Distribution. Only known from the type locality.
Ecology. Edge of evergreen forest on limestone karst.
459
Petrocosmea villosa, a new species from Myanmar
Fig. 1. Petrocosmea villosa D.J.Middleton. A. Flower front view. B. Flower side view. (Photo:
S. Ruchisansakun)
Gard. Bull. Singapore 73(2) 2021
460
Etymology. The specic epithet refers to the dense hair covering on the inorescence.
Provisional IUCN conservation assessment. Data Decient (DD) according to the
IUCN Red List Categories and Criteria (IUCN Standards and Petitions Committee,
2019). As it is currently only known from the type collection and its distribution and
population size are insufciently known, it is assessed here as DD. The collection
locality is not within a protected area but there is a pagoda near the collection locality,
affording protection from large scale destruction (such as mining).
ACKNOWLEDGEMENTS. We thank the collectors of the type and the collectors in turn
are grateful to Dr Nyi Nyi Kyaw, Director General, Forest Department, Ministry of Natural
Resources and Environmental Conservation for his continuous support for oristic research
in Myanmar. The eld work was conducted under an MoU between the Myanmar Forest
Department and Kochi Prefecture Makino Botanical Garden (MBK). The curatorial staff of the
herbarium at MBK are thanked for the loan of material to Singapore Botanic Gardens (SBG).
We thank Dr Saroj Ruchisansakun for the photographs used in Fig. 1.
References
Craib, W.G. (1919). Revision of Petrocosmea. Notes Roy. Bot. Gard. Edinburgh 111: 269–275.
GRC 2021 (continuously updated). Gesneriaceae Resource Centre. http://padme.rbge.org.uk/
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IUCN Standards and Petitions Committee (2019). Guidelines for Using the IUCN Red List
Categories and Criteria. Version 14. Prepared by the Standards and Petitions Committee.
Available from: http://iucnredlist.org/documents/RedListGuidelines.pdf.
Kress, W.J., De Filipps, R.A., Farr, E. & Kyi, D.Y.Y. (2003). A checklist of the trees, shrubs,
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Middleton, D.J. & Triboun, P. (2010). Two new species of Petrocosmea (Gesneriaceae). Thai
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