Pilea guizhouensis A.K. Monro, C.J. Chen & Y.G. Wei, 2012

Monro, Alex K., Wei, Y. G. & Chen, C. J., 2012, Three new species of Pilea (Urticaceae) from limestone karst in China, PhytoKeys 19, pp. 51-66 : 57-58

Pilea guizhouensis A.K. Monro, C.J. Chen & Y.G. Wei sp. nov. Figs 3 D, E , 6 A-C , 7 A-C

Diagnosis.

Most similar to Pilea boniana from which it can be distinguished by the shorter inflorescence length, staminate flowers composed of four rather than five and valvate rather than imbricate tepals, and smaller achene size.

Type. China.

Guizhou: Xingyi County, Xingyi City, Malinghe Gorge, 950 m, 025°08'32.9"N, 104°57'11.7"E (DMS), 12 May 2010, A. K. Monro & Y.G. Wei 6715 (holotype: IBK; isotypes: BM001001220, MO, PE).

Description.

Herb or subshrub to 50 cm, epipetric or terrestrial. Stems erect, drying brown to dark brown, green and maroon at the nodes when fresh, glabrous, brown peltate glandular on young stems and flowering nodes, cystoliths elliptic or absent, the internodes 18-200 × 1.5-2.0 mm, irregularly circular and grooved in cross-section, striate. Stipules 2.0-2.5 mm, deltate, drying red-brown. Leaves petiolate, distichous; petioles at each node unequal by ratio 1:1.8-8.5, 1.5-37 mm, glabrous; laminae at each node subequal or unequal by ratio 1: 1.9-5.4, laminae 12-130 × 5-26 mm, ovate, lanceolate, asymmetrically elliptic, oblanceolate or obovate, chartaceous; 3-nerved, the lateral nerves visible for>7/8 or more of the lamina length, secondary nerves 8-14 pairs, borne 60-75° to the midrib, weakly curved; upper surface drying dark brown, dark green when fresh, glabrous, cystoliths 0.250-0.375 mm, ‘V’ shaped, midrib raised; lower surface drying brown to dark brown, pale green when fresh, glabrous, eglandular; base symmetrical or asymmetrical, cuneate or obtuse; margin discretely serrulate or serrate, the basal 1/8-1/4 entire; apex symmetrical, attenuate to acuminate. Inflorescences ca 3 per stem, unisexual, staminate and pistillate inflorescences synchronous, born on separate stems; bracts 0.75-1.0 mm; bracteoles 0.50-0.675 mm. Staminate inflorescences 15-20 mm, bearing ca 60 flowers in a loose cyme; peduncle ≤1/4 inflorescence length, 0.5 mm in diameter, glabrous; pedicels 1.0-1.5 mm, glabrous. Staminate flowers 1.5 × 1.5 mm immediately prior to anthesis, pale green; tepals 4, 1.75 mm, valvate, broad elliptic or obovate, fused for their basal 1/2, glabrous, the subapical appendage ≤0.25 mm, ridge-like, glabrous; stamens 4. Pistillate inflorescences solitary, 2.0-3.5 mm, bearing 19-42 flowers in a compact cyme; peduncle 1/4 to 1/3 inflorescence length, 0.375 mm in diameter, glabrous, cystoliths absent; pedicels 0.375-0.50 mm, glabrous. Pistillate flowers 0.50-0.75 mm, tepals 3, unequal, adaxial tepal 0.5 mm, oblong to keel-shaped, the tepal appendage 0.375-0.50 mm, appearing inflated; the lateral tepals 0.375 mm, asymmetrically ovate; staminodes not visible. Infructescences 4.0-4.5 mm; achenes 0.675 × 0.375 mm, compressed, asymmetrically ovoid, the margin narrowly thickened.

Paratypes.

CHINA: Guizhou: Libo County, Yaolu Town, Huangcaoping, 650 m, 025°28'25"N, 108°04'15"E (DMS, both altitude and coordinates taken from Google Earth based on label data), April 24 2005, S. Qing & D. Londong 34 (BM001001221, PE).

Distribution.

Guizhou Province, Xingi County and Libo County, 650-950 m, in limestone Karst. The two localities are separated by ca 310km and represent semi-natural or naturally disturbed sites within an agricultural landscape.

Etymology.

The species name refers to Province from which both collections of this species are known.

Discussion.

Comparison of the holotype and paratype material with type specimens from the herbaria listed in the methods section recovered Pilea boniana Gagnep. and Pilea rubriflora C. Wright as most similar to Pilea guizhouensis . Pilea guizhouensis can be distinguished from Pilea boniana based on stipule, staminate, pistillate inflores and achene length and staminate tepal number as summarised in Table 4 . Pilea guizhouensis can be distinguished from Pilea rubriflora based on internode, stipule and, staminate and pistillate flower morphology as summarised in Table 5 .

Pilea guizhouensis falls within Weddell’s (1869) Heterophyllae-Gerontogeae subdivision and Chen’s (1982) Urticella Section of the genus.

Conservation status.

Using IUCN criteria ( IUCN 2001) Pilea guizhouensis is considered Vulnerable (VU). Pilea guizhouensis is known from two localities (IUCN criteria D2, number of locations <5). These two localities are ca 320 km apart and assuming that this species occurs within the 650-950 elevation range then the Extent of Occurrence between these localities is calculated to be 12,800 km2 (IUCN criteria B1, <20,000km2). Using the IUCN methodology our Global Conservation Assessment for Pilea guizhouensis is Vulnerable (VU) based on criteria B1 with a plausible future threat that could drive this taxon to Near Threatened in a very short time. Plausible threats include the presence of a tourist trail running through the Malinghe Gorge which may be expanded, re-routed or rebuilt resulting in damage to the populations. In addition the second locality is located close to an agricultural area and is therefore vulnerable to conversion from forest to farmland.

Figures

Figure 3. Habitats ofspecies described in this manuscript. A, B Pilea cavernicola, Yangzi cave, Fengshan County. Locality for Monro & Wei 6669 A Interior of cave B Exterior view of the cave C Habitat of Pilea shizongensis, Feng Huang Gu gorge, Shizong County. Locality for Monro & Wei 6727 D, E Habitat of Pilea guizhouensis, petaloid travertine wall of Malinghe Gorge E close-up of petaloid travertine formation, Locality for Monro & Wei 6715.

Figure 6. Pilea guizhouensis. A Habitat B close-up of pistillate inflorescence C close-up of a pistillate flower. Based on Monro & Wei 6715.

Figure 7. Pilea guizhouensis. A Habitat B close-up of pistillate inflorescence C close-up of a pistillate infructescence. Based on Monro & Wei 6715.