Pilea shizongensis 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 : 55-57

Pilea shizongensis A.K. Monro, C.J. Chen & Y.G. Wei sp. nov. Figs 3 C , 4 A-C , 5 A-D

Diagnosis.

Most similar to Pilea aquarum from which it can be distinguished by the shorter stem, serrate rather than dentate leaves, shorter stipules and glabrous pistillate tepals.

Type.

China. Yunnan: Shizong County, Feng Huang Gu gorge, 1200 m, 024°37'54.0"N, 104°14'43.9"E (DMS), 14 May 2010, A. K. Monro & Y. G. Wei 6727 (holotype: IBK; isotypes: BM001001216, MO, PE).

Description.

Herb to 20 cm, epipetric and terrestrial. Stems procumbent and erect, drying dark brown, maroon to dark green when fresh, pubescent, more densely so towards the shoot tips, the hairs 0.5 mm, erect or weakly appressed, curved or crooked, orange-brown peltate glandular, cystoliths absent, the internodes 4-38 × 1.5-2.0 mm, angulate in cross-section, striate. Stipules 2.5-3.0 mm, auriculate-cordiform, drying brown. Leaves petiolate, distichous; petioles at each node unequal by ratio 1:3-4.4, 3-20 mm, pubescent, the hairs 0.25-0.375 mm, erect, strongly curved to curved; laminae at each node equal or subequal, 11-35 × 7-17 mm, ovate to broad ovate, chartaceous; 3-nerved, the lateral nerves visible for less than 2/3 of the lamina length, secondary nerves 4-6 pairs, borne 45-60° to the midrib, straight or weakly curved; upper surface drying brown or dark brown, dark green with maroon nerves and green flushed maroon when fresh, sparsely pubescent, the hairs 0.50-0.675 mm, appressed, straight or weakly curved, cystoliths absent, midrib raised; lower surface drying grey-brown when fresh, nerves densely pubescent, the hairs 0.375 mm, weakly appressed, curved, orange-brown peltate glandular, midrib and lateral nerves raised, cystoliths fusiform, randomly scattered; base symmetrical, cuneate or obtuse; margin serrate, the basal 1/4 entire; apex symmetrical, subcus pidate or cuneate. Inflorescences 4-10 per stem, unisexual, staminate and pistillate inflorescences synchronous, born on separate stems; bracts 0.375 mm; bracteoles 0.3-0.5 mm. Staminate inflorescences solitary, 17.5-25 mm, bearing 7-16 flowers in a loose cyme; peduncle 1/4 or less inflorescence length, 0.5 mm in diameter, pubescent, cystoliths absent; pedicels 0.8-1.0 mm, glabrous. Staminate flowers 1.5 -2.0 × 1.5-1.8 mm immediately prior to anthesis, deep pink; tepals 4, imbricate, 1.75 mm, fused for their basal 1/4, ovate or elliptic, glabrous, the subapical appendage 0.375 mm, corniculate, glabrous; stamens 4. Pistillate inflorescences solitary, 2.0-2.5 mm, bearing 17-30 flowers in a compact cyme; peduncle 1/2 to 2/3 inflorescence length, 0.375 mm in diameter, glabrous, cystoliths absent; pedicels 0.25-0.375 mm, sparsely pubescent. Pistillate flowers 0.375-0.50 mm, tepals 3, unequal, glabrous, adaxial tepal 0.5 mm, oblong, the dorsal tepal appendage 0.375 mm, oblong, markedly thickened; the lateral tepals 0.25-0.375 mm, asymmetrically ovate. Infructescences not seen.

Distribution.

Yunnan Province, Feng Huang Gu gorge, ca 1200 m, in limestone karst, growing on the floor of the gorge in deep shade.

Etymology.

The species name refers to county of the locality of the only known collection of this species, Shizong.

Discussion.

Comparison of the holotype material with type specimens from the herbaria listed in the methods section recovered Pilea aquarum Dunn as most similar to Pilea shizongensis . It can be distinguished from Pilea shizongensis based on pubescence, leaf margin morphology and pistillate tepal and flower morphology as summarised in Table 3 .

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

There is some confusion over the delimitation of Pilea aquarum and this is relevant to the delimitation of Pilea shizongensis . It would appear that the relatively rare character trait of pubescent pistillate tepals has been overlooked by several authors and that Pilea aquarum sensu strictu encompass a relatively narrow range of morphological variation which would exclude the subspecies Pilea aquarum subsp. brevicornuta and Pilea aquarum subsp. acutidentata.

Conservation status.

Using IUCN criteria ( IUCN 2001) Pilea shizongensis is considered Endangered (E). Pilea shizongensis is known from a single locality (IUCN criteria D2, number of locations <5). At these localities the populations of this species comprises ca 100-200 mature individuals (IUCN criteria D1, number of mature individuals <250). Using the IUCN methodology our Global Conservation Assessment for Pilea shizongensis is Endangered (E) based on criteria D1 and D2: population size and number of locations combined with a plausible future threat that could drive this taxon to Endangered in a very short time. Plausible threats include the location of the only known population within a tourist site and close to the only path used by visitors to access the gorge bottom. Any expansion of the path, fire or dumping of refuse by visitors could destroy this population.

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 4. Pilea shizongensis. A Habit B Close up of pistillate inflorescence C Close up of a staminate flower. Based on Monro & Wei 6727.

Figure 5. Pilea shizongensis. A Habit B Shoot tip C Close up of a staminate flowers D Close up of pistillate inflorescence and flowers. Based on Monro & Wei 6727.