Allocheilos rubroglandulosus W.H. Chen & Y.M. Shui, 2020

Chen, Wen-Hong, Guo, Shi-Wei, Wu, Jian-Yong, Chen, Li & Shui, Yu-Min, 2020, Two new species of Allocheilos (Gesneriaceae) from the karst regions in Yunnan, China, PhytoKeys 157, pp. 155-166 : 155

Allocheilos rubroglandulosus W.H. Chen & Y.M. Shui sp. nov. Figs 4 , 5

Diagnosis.

The new species is similar to A. maguanensis W.H.Chen & Y.M.Shui with three major staminodes and style longer than ovary, but differs in its elliptic bracts (vs. broadly ovate to rounded), triangular calyx lobes awny at the apex (vs. elliptic and beaked at the apex), and lateral staminodes with red glands (vs. without red glands).

Type.

China. Yunnan province, Mengzi county, Shuitian community, 23°08'35"N, 103°21'46"E, on the cliffs of a limestone sink-hole, elev. ca. 1410 m, in flower, 6 November 2017, Y. M. Shui et al. B2017-1287 (holotype KUN; isotype PE).

Herb perennial. Rhizome short, 6-7 mm in diam., stem absent. Leaves 8-12 in mature individuals, basal, rosette; petiole 9.4-11.6 cm long, densely brown-red villous; blade herbaceous, round or broadly ovate, 4.5-13 × 3.6-9.8 cm, base obliquely cordate, apex round or obtuse, margin shallowly crenulate, slightly reflected, adaxially densely depressed white pubescent, abaxially densely brown-red villous especially along the nerves; venation palmate, lateral veins 4-7 on each side of midrib, adaxially slightly depressed and abaxially prominent. Inflorescences axillary, 10-16-flowered cymes; peduncles 8-10 cm long, densely brown-red villous; bracts 2, opposite, elliptic, 5.6-6.4 × 2.3-2.6 mm, adaxially subglabrous, abaxially sparsely brownish hispid, margin obscurely and irregularly crenulate and ciliate above the middle, apex acute; bracteoles 2, oblong-lanceolate, ca. 5 × 2 mm, adaxially subglabrous, abaxially densely brownish hispid; pedicel 0.6-1.8 cm long, brown-red hispid. Calyx actinomorphic, 5-parted to the base, segments lanceolate or triangular, 4.5-5.2 × 2.1-2.2 mm, apex acuminate or caudate, margin entire, abaxially densely white pubescent and brown-red villous, adaxially glabrous. Corolla white or pinkish at the base, broadly campanulate, zygomorphic, ca. 1.1 cm long, ca. 0.4 cm wide at the throat, outside white glandular pubescent, inside glabrous, tube 3.2-3.5 mm long; limb 2-lipped; adaxial lip 8.8-9.2 × 8.8-9.5 mm, slightly swollen at the base, ca. 6 mm high, ca. 7 mm wide, slightly longer than abaxial lip, 4-lobed, lobes triangular, 3.1-3.3 × 1.4-1.6 mm, apex obtuse, middle lobes 2 symmetric, lateral lobes 2 oblique; abaxial lip narrowly triangular, undivided, 8.1-8.5 × 2.5-2.9 mm, apex acute. Stamens 2, adnate ca. 2 mm above base; anthers 2, coherent laterally; filaments sparsely puberulent, base slightly swollen, 7-8 mm long; staminodes 3, lateral 2 red on the top, ca. 1.5 mm long, adnate to ca. 1.5 mm above base, middle white on the top, ca. 3.1 mm long. Disc ring-like, yellow, 0.7-0.8 mm high, margin entire. Pistil 1.4-1.6 cm long; ovary oblong, 3-4 mm long, sparsely pubescent; style 7-8 mm long, sparsely pubescent; stigma 1, capitate. Dry capsule straight, elliptic, 7-8 × 2.1-2.3 mm, dehiscing loculicidally, valves 2.

Phenology.

Flowering is from October to November (June to July in the greenhouse).

Etymology.

The epithet refers to the red glands on the top of lateral staminodes, which is an indicator to lead the pollinators to find the nectar. Hitherto, the character was first observed in Gesneriaceae ( Weber 2004).

Distribution and ecology.

The new species is only distributed in Mengzi county, Yunnan, southwestern China. It grows in deep limestone sinkholes. The adjacent habitat has been disturbed by local people for the purpose of planting corn. The main accompanying plants are Begonia laminariae Irmscher in Begoniaceae , Impatiens apalophylla J.D.Hooker in Balsaminaceae , Pteris deltodon Baker in Pteridiaceae , Thalictrum ichangense Lecoyer ex Oliver in Ranunculaceae .

Provisional conservation status.

Based on observations around the locality, this new species was found only in one limestone sinkhole with around 30 mature individuals on the cliffs in three smaller populations. Thus, as the above new species, its further exploration should be conducted while an urgent project is needed for this rare species with extremely small populations ( Ma et al. 2013). So far, the species can be provisionally considered as Critically Endangered, CR: B1b (v) + 2b (v). ( IUCN 2012; IUCN Standards and Petitions Subcommittee 2017)

Additional examined specimens.

China. Yunnan province, Mengzi county, Shuitian community, elev. ca. 1410 m, fruits dry, 6 November 2017, Y. M. Shui et al. B2017-1296 (KUN); ibid, Y. M. Shui et al. B2017-1298 (KUN).

Discussion.

At the background of the white flowers, two red glands at the top of staminodes are an important indicator for the pollinators to visit the plants. It is obvious that nectars are hidden at the back of the indicator (Fig. 5C ).The discovery will provide us an opportunity to explore the diversity and evolution of staminodes of the genus in Gesneriaceae and the other groups endemic to the karst regions in China and the adjacent countries (Laos, Myanmar, Thailand and Vietnam).

Figures

Figure 4. Vegetative morphology of Allocheilos rubroglandulosus W. H. Chen & Y. M. Shui, sp. nov. (From holotype, photographed by S. W. Guo and Y. M. Shui) A habitat and plants B adaxial surface of the round leave, arrow indicating the overlapped leaf blade at base C abaxial surface of the round leave, arrows indicating the reflected margin D adaxial surface of the broadly ovate leave with overlapped basal lobes of the leave annotated by arrow E abaxial surface of the broadly ovate leave, arrow indicating the reflected margin F hairs of petiole and main nerves on the abaxial surface of the round leaves G margin and hairs on the adaxial surface of the round leave H margin and hairs on the abaxial surface of the round leaf, arrow indicating the reflected margin.

Figure 5. Flower morphology of Allocheilos rubroglandulosus W. H. Chen & Y. M. Shui, sp. nov. (From holotype, photographed by S. W. Guo and Y. M. Shui) A inflorescence B right part of the inflorescence C left part of the inflorescence D lateral view of the leaf part of the inflorescence E face view of the flower F face view indicating 3 staminodes, middle white and lateral 2 red on the top G lateral view of flower indicating stamens H opened corolla indicating the stamens and staminodes and the swollen nodes at the base of filaments. Notes: at anther, br bract; cx calyx lobe, dc disc, fm filament, gl glandular, sd staminode, sl style, sm stigma, sn swollen nodes at base of filament.