Petrocodon ionophyllus F.Wen, S.Li & B.Pan, 2020

Petrocodon ionophyllus F.Wen, S.Li & B.Pan View in CoL , sp. nov. Figs. 1 View Fig & 2 View Fig

Petrocodon ionophyllus can easily be distinguished from other

species of Petrocodon by its purplish green to purplish brown

leaf blades. Additionally, it closely resembles P. integrifolius

in having ovate or broadly ovate leaf blades and purple

corolla with a long tube and narrowly triangular limb lobes,

but differs from it in having 3–5 flowers per cyme (vs. 8–

10[–12]), calyx lobes narrowly lanceolate to linear-lanceolate

(vs. triangular), position of upper corolla lobes close together

to nearly parallel (vs. spreading, positioned at over 80̊ angle)

and stamens eglandular puberulent (vs. puberulent and

glandular puberulent).

Type: CHINA, Guangxi Zhuangzu Autonomous Region, Jingxi City, Sanhe town, growing in crevices of rocks and cliff on limestone hills, in evergreen broad-leaved forests, rare, 780 m, 08.04.2013, flowering, Bo Pan et al. BP P0783 (holo IBK!; iso IBK!, KUN!).

Perennial herbs forming acaulescent rosettes. Rhizomes subterete, 0.5-1.2 cm long, 0.2-0.4 cm in diam. Leaves 4-8, clustered at apex of rhizome, opposite; petioles terete, 12–15 × 1.5-2 mm, dark green with a slightly pale purplish shading, densely pubescent; leaf blade purplish green to purplish brown, chartaceous when dried, often almost symmetrical, ovate or broadly ovate, 3.2-6.4 × 2.8- 4.8 cm, broadly cuneate at base, obtuse to acute at apex, margins entire, abaxial surface sparsely strigose, adaxial surface pubescent; lateral veins 2- 4 on each side of midrib, slightly prominent abaxially, slightly sunken adaxially. Cymes 1-2, rarely 4, usually 1-branched with 3-5 flowers; peduncles 5-9 cm long, 1.2-1.5 mm in diam., densely pubescent to pilose, green with a purplish shading; bracts 2, lanceolate, 6-10 × 1.5-1.8 mm, apex acuminate, margins entire, abaxially white puberulous, adaxially glabrous, usually caducous; pedicels 4.8-7 mm long, densely puberulent, white. Calyx 5-parted to the base; lobes narrowly lanceolate to linear-lanceolate, 6-8 mm long, c. 1 mm wide, abaxially puberulent, white, adaxially glabrous, brownish. Corolla purple, white puberulent outside, 2.5-3.2 cm long; tube infundibuliform, 1.6-1.8 cm long, c. 3 mm in diam. at middle, glabrous inside; orifice c. 5 mm in diam.; limb 2-lipped, adaxial lip 2-lobed, lobes c. 5 mm long, c. 4 mm in diam. at base, narrowly triangular; abaxial lip 3-lobed, lobes 6-8 mm long, c. 4.2 mm in diam. at base, narrowly triangular to narrowly lanceolate, apex attenuate-acuminate, three pale purple longitudinal stripes and puberulent-hairs along the abaxial lip lobes. Stamens 2, deflected to one side (left or right) at the throat of corolla but included, adnate at c. 9 mm above the corolla tube base; filaments c. 10 mm long, straight, eglandular puberulent; anthers fused by their entire adaxial surfaces, reniform, white, c. 2 mm long, glabrous. Staminodes 3, lateral ones adnate to corolla tube c. 7 mm above the base, 9-10 mm long; the central one adnate to corolla tube c. 5 mm above the base, c. 1.1 mm long, all glabrous. Ovary 5.5-6 mm long, 0.7-0.9 mm in diam., densely white puberulent; style 6.5-7 mm long, deflected to the other side away from stamens, densely white glandularpuberulent; disc annular, c. 1 mm in high, margins entire; stigma bilobed, lobes ovate, c. 0.6 mm long. Capsules linear, straight, 1.4-1.7 cm long, glabrous, 4-valved. Seeds spindle shaped, c. 0.3 mm long. without hair-like appendages, brown to brownish black.

Flowering & fruiting: Flowering from April to May and fruiting from June to August.

Habitat: Petrocodon ionophyllus is found growing mostly in crevices and on moist surfaces of limestone rock at elevation range of 740–780 m in an evergreen broad-leaved forest on a limestone hill.

Etymology: The characteristic purplish green to purplish brown leaves of this species are unusual in the genus and distinguishes it from other Petrocodon species. Thus, the specific epithet, “ ionophyllus ” is chosen, derived from the Greek “ ion- ” (meaning violet-coloured) and “- phyllus ” (leaves), referring to its purple-hued leaves.

Distribution: Petrocodon ionophyllus is only found in Jingxi city, China. The type locality is close to the border between China and Vietnam, hence the distribution of this species might extend into Vietnam.

Conservation status: Currently, only one location with three sub-populations of this new species are known in the wild, with a total of 200 mature individuals on three limestone mountains in Sanhe Town. The mountains do not belong to any of the protected areas or natural reserves, so this population is very vulnerable to local timber harvesting, road construction and other detrimental factors. Because only one location (with <250 mature plants) has been found so far, we recommend that this species should be provisionally treated as Endangered (EN) under category D for very small or restricted population ( IUCN, 2019). However, this status could be reassessed in the future fieldwork.

Notes: The expanded genus Petrocodon and the many new published species resulted in a genus with various flower shapes, stamen numbers and colours ( Weber et al., 2011; Lu et al., 2017a). The genus currently harbours almost 40 species and has its distribution centre in the mountainous area of southwestern and southern China ( Wen et al., 2019, 2014 onw.). Only four species have been found distributed outside China, namely Petrocodon coccineus (C.Y.Wu ex H.W.Li) Yin.Z.Wang and P. hispidus (W.T.Wang) A.Weber & Mich.Möller (both distributed in China and Vietnam), P. bonii (Pellegr.) Mich.Möller & A.Weber (distributed in Laos, Thailand and Vietnam, not in China) and P. flavus D.J.Middleton & Sangvir (endemic to Thailand) ( Burtt, 2001; Phuong, 2006; Weber et al., 2011; Middleton et al., 2015b).

The morphological variation between Petrocodon species is rather diverse, yet we identified this species mistakenly as P. integrifolius when this plant was discovered because of their morphological similarities. The new species, P. ionophyllus , occurs in Jingxi City of Guangxi and grows on the surfaces and in crevices of limestone rocks under forests up to an altitude of about 750 meters. However, P. integrifolius is distributed in Longzhou County of Guangxi, and only grows in deep caves at altitudes between 200 to 530 meters (Fig. 3). In their native habitat, the new species grows significantly smaller than P. integrifolius , the texture of the leaves is hard, chartaceous to nearly leathery, and the hairs on the leaves are rough. The leaves of P. integrifolius are thin like paper, and pubescent. Living plants from the type localities of of both species, Longzhou and Jingxi, were introduced to the greenhouses of GCCC. The differences observed in the filed between these species were found to be consistent even after 4 years of cultivation. In P. ionophyllus , exhibit reciprocal enantiostyly where the style is deflected to one side and the stamen to the other, which is perhaps to reduce autogamy (Jesson & Barrett, 2002, 2003) ( Table 1, Fig. 4 View Fig ).

This is similar to the mirror-image flowers described in Paraboea rufescens (Franch.) Burtt ( Gao et al., 2006) . Further, the florescence of the two species are different; the flowering period of Petrocodon ionophyllus is from April to May, whereas P. integrifolius begins to bloom from June onwards.