Primulina linearicalyx F.Wen, B.D.Lai & Y.G.Wei, 2016

Wen, Fang, Lai, Bi-Dan, Zhao, Zhi-Guo, Wang, Bing-Mou & Wei, Yi-Gang, 2016, Primulina linearicalyx (Gesneriaceae), a new species from Guangxi, China, Phytotaxa 269 (1), pp. 41-46 : 42-45

Primulina linearicalyx F.Wen, B.D.Lai & Y.G.Wei , sp. nov. ( Figs. 1 & 2 )

Diagnosis: — Morphologically similar to Primulina linearifolia , P. pseudolinearifolia and P.longgangensis in leaf shape, but differs in having fewer flowers per cyme (1–3 flowers for P. linearicalyx vs. 8–24 flowers for P. linearifolia , 4–12 flowers for P. pseudolinearifolia and 2–15 flowers for P. longgangensis ; the same order hereinafter), longer calyx lobes (25–30 × 2.5–3 mm vs. 3.2–4 × 0.6–1.1 mm, 5–6 × ca. 1 mm and 5–8 × 0.9–1.5 mm), longer filaments (ca. 1.5 cm long vs. ca. 1 cm, 1–1.2 cm and ca. 1.5 cm long).

Type: — CHINA. Guangxi: Wuming County, Liangjiang Town, in crevice on the rock face, 23°26′26.61″N, 108°23′15.89″E, ca. 135 m, 23 May 2010, B.D.Lai 111016-1 (holotype: IBK!, isotype: IBK! ANU!).

Perennial herbs. Rhizomatous stem cylindrical to subterete, 3–10 cm long or longer, 1–2.2 cm in diam., often branched in the middle or at the base. Leaves 12–27, congested at apex, subsessile to sessile; leaf blade fleshy, linearoblong to linear-elliptical, 3.5–7.5 × 1–1.3 cm, with appressed white pubescence on both surfaces, apex obtuse to round, base attenuate to acute, margin entire and revolute, lateral veins 3–5 on each side, adaxially inconspicuous or conspicuous, abaxially conspicuously elevated. Cymes 3–5, axillary, usually simple, sometimes 1-branched, with 1–3 flowers; peduncle 4–5 cm long, 1.8–2.2 mm in diam., sparsely with brownish purple patent glandular and eglandular pubescence; bracts 2, free, opposite, lanceolate to broadly lanceolate, 8–11 × 4–5 mm, apex acute, margin entire, adaxially pubescent, abaxially glabrous, caduceus; pedicel 10–25 cm long, 1.5–2 mm in diam., sparely with glandular pubescence and almost appressed eglandular pubescence. Calyx 5-parted nearly to the base, all lobes slightly fused at base and swollen, lobes linear-lanceolate to linear, 25–30 × 2.5–3 mm, abaxially with brownish purple glandular pubescence, adaxially glabrous, apex attenuate and ended in a fine filamentous tip, margin entire. Corolla 3.5–4 cm long, purplish pink, upper part of the interior of the corolla with two yellowish brown short stripes, throat also with two yellow stripes, outside sparsely with transparent glandular short pubescence and purple eglandular puberulence, tube 2–2.5 cm long, 1.2–1.5 cm in diam. at the mouth; limb distinctly 2-lipped, adaxial lip 2-parted deeper to the proximal half, lobes broadly ovate to semicircular, margin repand when fresh, 6–8 × 7.5–8.5 mm, abaxial lip 3-lobed also deeper to the proximal half, lateral two lobes obliquely ovate, 10–12 × 8–10 mm, central lobe nearly rounded to oblong, 9–10 × 8.5–9.5 mm, lobe margins repand when fresh as the adaxial lip. Stamens 2, adnate 0.9–1.0 cm above the corolla base; filaments ca. 1.5 cm long, slightly geniculate near middle, glabrous; anthers coherent, nearly reniform, dorsifixed, densely bearded, ca. 3 mm long; staminodes 2, adnate to 1–1.1 cm above the corolla tube base, 6–6.5 mm long, apex capitate, glabrous. Disc ca. 1.5 mm in height, margin entire, glabrous. Pistil 3.5–5 cm long, ovary 2.5–3.5 cm long, 3–5 mm in diam., densely glandular-pubescent; style 1–1.5 cm long, 1.5–2 mm in diam., glandular-pubescent; stigma obtrapeziform, 4–5 mm long, apex 2-lobed. Mature capsule linear, 5–6 cm × ca. 3 mm, puberulent.

Distribution and habitat:— Primulina linearicalyx has only been found at the type locality, Liangjiang Township, Wuming County, Guangxi, China. Only one population was observed, with all individuals growing on dry and sunexposed rock surfaces of sedimentary rock at elevation of ca. 130 m.

Proposed conservation Red List category:—All the plants of Primulina linearicalyx , less than 300 mature individuals, are clustered together in a fairly small site at the foot of the Damingshan Mountain near a village. They grow on a big isolated sedimentary rock, which is surrounded by the local farm of cassava. It is so prone to the activities of local people that the category of ‘Critically Endangered’ (CR, B2a + E) is proposed here according to the IUCN red list criteria ( IUCN 2011).

Phenology:—This new species was observed flowering in late October to early November and fruiting in December.

Etymology:—The epithet is referring its very long and linear lanceolate calyx lobes, a diagnostic character in the genus Primulina .

Vernacular name:—Xiàn È Bào Chūn Jǜ Tái ("㩲º̊㤙ª).

Relationships:— Primulina linearicalyx is morphologically similar to P. linearifolia in vegetative characters and P. pseudolinearifolia in reproductive organs ( Table 1). It is interesting that the three species share similar habitat in usually exposed to sunlight on limestone outcrops (for P. linearifolia and P. pseudolinearifolia ) or conglomerate rocks (for P. linearicalyx ). The similarity in leaf morphology might be the adaptation to the sunlight exposure and arid soil and air in the dry season, which leads to reduced lamina area and thicker leaves for water storage as observed in many other xerophytes. These three species and P. longgangensis , another species with narrowly long and thick leaves, clustered into one clade in a phylogenetic study ( Kang et al. 2014 where P. pseudolinearifolia was identified being P. luochengensis as indicated in Xu et al. 2011 & 2012). This suggest a shared origin for the dry and sunny habitat adaptation, rather than convergent evolution of this trait.

Karyology:—In the concept and classification of Lima-de-Faria (1980), the chromosomes of Primulina are considered to be small in size with their range between 0.6–2.4 μm (Liu et al. 2012). The somatic chromosomes of P. linearicalyx at metaphase are illustrated in Figure 3 . It was identified the first time as diploid with chromosome number of 2n=36. The size of its chromosomes fell within the range of the genus, i.e. 0.8–1.0 μm while with only a slight variation in size within the complement ( Fig. 3 ). So far, almost all known chromosome numbers of Primulina including this new species represent a diploid number of 2n = 36 with a basic number of x = 18 ( Möller & Pullan 2015 onwards).

Figures

FIGURE 1. Primulina linearicalyx. A. Habit, B. Abaxial leaf surface showing the prominent veins, C. Opened corolla showing stamens and staminodes, D. Cyme, showing bracts, calyx lobes and pistil, E. Stigma.

FIGURE 2. Primulina linearicalyx. A. Type locality at the foot of the Damingshan Mountain, B. Habitat, C & D. Habit, E. Flowering plant in cultivation, F. Abaxial leaf surface, G. Bud and calyx lobes, H. Frontal view of flowers, I. Lateral view of corolla and calyx lobes, J. Top view of corolla and calyx lobes, K. Immature capsule, L. Mature and dehisced capsule.

FIGURE 3. Somatic chromosomes at metaphase of Primulina linearicalyx. A to F showing microphotographs from different cells with 2n=36, from roots of leaf cuttings of B.D.Lai 111016-1, IBK.