Primulina malipoensis mainly differs from P. maguanensis and P. lungzhouensis by its pale greenish-yellow flowers (vs. purple, with different colour patterns). This new species can further be distinguished from P. maguanensis by its greenish bracts (vs. white) and from P. lungzhouensis by its entire bracts margin (vs. denticulate).

CHINA. Guangdong Province, Guangzhou City, voucher from a cultivated plant at South China Botanical Garden, 29 July 2016 (flowering), Li-Hua Yang, YLH369 (holotype: IBSC!), introduced from Yunnan province, Malipo county, Xiajinchang town, growing on moist limestone rocks, Alt. 1500 m, 23°10'N, 104°49'E, 31 August 2013, Jun-lin Chen.

Perennial herbs. Rhizomatous stem subterete, 20–60 mm long, 5–15 mm in diameter. Leaves 8–12, basal or clustered at apex of stem, opposite decussate. Petiole flattened, 20–40 mm long, 8–10 mm wide, pubescent. Leaf blade slightly fleshy when fresh, thickly chartaceous when dried, ovate to broadly elliptic, 7–12 × 7–10 cm, adaxially densely pubescent, abaxially glabrescent and only puberulent along veins, apex subacute to obtuse, base cuneate, margin inconspicuously serrate; lateral veins 4 on each side, abaxially conspicuous. Cymes 3–5, axillary, 2–4 branched, 8–16-flowered; peduncles 15–27 cm long, ca. 2 mm in diameter, densely pubescent; bracts 2, sometimes with bracteoles (narrowly ovate, 8–12 × 4–7 mm), green, opposite, ovate, 16–25 × 8–13 mm, margin entire, apex acute, outside densely pubescent, inside sparsely pubescent. Pedicel 10–14 mm long, ca. 1 mm in diameter, densely glandular pubescent and puberulent. Calyx 5-parted to near base, lobes narrowly lanceolate, white, 7–9 × ca. 2 mm, outside densely glandular pubescent and puberulent, inside sparsely pubescent, margin entire. Corolla pale greenish-yellow, 24–32 mm long, outside glandular-pubescent and puberulent, inside glabrous; tube infundibuliform, 21–25 mm long, ca. 8 mm in diameter at mouth, ca. 5 mm in diameter at base; limb distinctly 2-lipped, adaxial lip 2-parted, lobes broadly ovate, 7–9 × 6–7 mm, apex rounded, abaxial lip 3-lobed, lobes oblong, 11–13 × 5–7 mm, apex rounded. Stamens 2, adnate to 10–13 mm above the corolla tube base; filaments linear, 9–11 mm long, pale greenish-yellow, geniculate near middle, sparely pubescent; anthers fused by the entire adaxial surfaces, ca. 2 mm long, abaxially densely covered with glandular hairs. Staminodes 3, lateral ones 6–7 mm long, adnate to 10–12 mm above the corolla tube base, middle one ca. 1.5 mm long, adnate to 6–8 mm above the corolla tube base. Disc annular, ca. 1.5 mm in height. Pistil 22–26 mm long; ovary cylindrical, 15–18 mm long, ca. 1.5 mm in diameter, densely glandular pubescent and puberulent; style ca. 7 mm long, densely glandular-pubescent and puberulent; stigma 1, its upper lobe lacking, lower lobe obtrapeziform, shallowly 2-lobed at apex, ca. 2 mm long, ca. 1.5 mm wide. Capsule linear, ca. 30 mm long, densely pubescent.

Figure 1. 

Primulina malipoensis. A habit B flower in front view C flower in side view D opened corolla, showing stamens and staminodes E fertile stamens F pistil and stigma G staminodes H bract. Drawn by Yun-Xiao Liu based on a cultivated individual collected from type locality.

Figure 2. 

Primulina malipoensis. A flowering plant cultivated in South China Botanical Garden B plant in natural habitat C flower in side view D opened corolla, showing stamens and staminodes E flower in front view F pistil and calyx G bracts. Photographs by Li-Hua Yang.

Figure 3. 

Primulina maguanensis (A, B), P. lungzhouensis (D, E), P. beiliuensis var. fimbribracteata (C, F), P. beiliuensis var. beiliuensis (G, H) and P. maculata (I, J). (A, C, D, G, J) habit, (B, E, F, H, I) flower. Photographs by Fang Wen (A–H) and Li-Hua Yang (I, J).

Primulina malipoensis is a narrowly endemic species restricted to a small area at both sides of the Sino-Vietnamese border (Xiajinchang Town, Malipo County, Yunnan Province, China. Khau La Village, Quyet Tien Community, Quan Ba District, Ha Qiang province, Vietnam.) (Figure 4). It grows on moist and shady limestone rocks, at ca. 1000–1500 m altitude.

Figure 4. 

Geographical distribution of Primulina malipoensis (triangle), P. lungzhouensis (cross), P. maguanensis (dot), P. maculata (pentagon), P. beiliuensis var. beiliuensis (square) and P. beiliuensis var. fimbribracteata (star).

Based on the field investigations, Primulina malipoensis is currently only known from three sites around the Sino-Vietnamese boundary. Each population possesses no more than 150 mature individuals. However, the type population, which grew close to a road, had disappeared in 2017 and thus, the primary reason why it disappeared is probably due to its destruction by human activities. Based on currently available information, P. malipoensis should be considered as Endangered (EN): B1b(iii,v)c(iv)+2b(iii,v)c(iv); C2b, following the IUCN Categories and Criteria (IUCN 2016).

This new species was observed flowering from June to July and fruiting from August to September.

The specific epithet is derived from the place, Malipo County in Yunnan province, China, where the new species was first found.

Primulina malipoensis (Figures 1 and 2) can be morphologically connected to P. maguanensis (Z. Yu Li, H. Jiang & H. Xu) Mich. Möller & A. Weber (Figure 3A–B) and P. lungzhouensis (W.T. Wang) Mich. Möller & A. Weber (Figure 3D–E) by its ovate or broadly elliptic leaf blade, with inconspicuously (or conspicuously) serrate margin, obvious bracts, white calyx lobes and infundibuliform corolla tube. However, it can easily be distinguished from the latter two species by the characters summarised in the diagnosis.

The authors’ molecular phylogenetic analyses illustrate that P. malipoensis, P. lungzhouensis, P. beiliuensis B. Pan & S.X. Huang (Pan et al. 2013) and P. beiliuensis B. Pan & S.X. Huang var. fimbribracteata. F. Wen & B.D. Lai (Lai and Wen 2015) form a monophyletic clade (Kong et al. 2017). However, their morphology and geographical distribution allow the assumption that P. maguanensis and P. maculata W.B. Xu & J. Guo (Guo et al. 2015) are also closely related to this group. Both P. maguanensis and P. maculata were compared to P. eburnea in the original protologue (Xu et al. 2008, Guo et al. 2015). Nevertheless, based on the observation of living plants, P. maguanensis seems most similar to P. lungzhouensis and P. malipoensis; P. maculata (Figure 3I–J) seems most similar to P. beiliuensis var. beiliuensis (Figure 3G–H) and P. beiliuensis var. fimbribracteata (Figure 3C–F). Further, the geographical distribution of P. maguanensis is adjacent to P. lungzhouensis and P. malipoensis (Figure 4) and the geographical distribution of P. maculata is adjacent to P. beiliuensis (Figure 4). Moreover, the results of the phylogenetical analysis in Guo et al. (2015) show that P. maculata is more closely related to P. lungzhouensis than P. eburnea. All of the above five species occur in nearly the same latitude zone of karst limestone areas from Southern China (from S-Yunnan to S-Guangdong), but with a disjunctive distribution (Figure 4). Therefore, these species perhaps represents a complex of longitudinal speciation, which may be caused by geographical isolation. Further studies are needed to confirm the phylogenetic relationship of this species complex and to determine its evolutionary mechanism of speciation.

Primulina malipoensis could also be related to other species by its yellow flowers. However, the phylogenetic results illustrate that P. malipoensis has a distant relationship with all yellow flowering species, such as P. lutea (Yan Liu & Y. G. Wei) Mich. Möller & A. Weber, P. alutacea F. Wen, B. Pan & B.M. Wang (Pan & al. 2016), P. pteropoda (W.T. Wang) Yan Liu, P. leprosa (Yan Liu & W.B. Xu) W.B. Xu & K.F. Chung and P. jiangyongensis X.L. Yu & Ming Li (Li et al. 2014) (cf. Kong et al. 2017). These yellow flowering species are distributed across different clades (Kong et al. 2017), which means that yellow flowers have independently evolved in different species. This result also suggests that flower colour can be used as an important character to differentiate species in Primulina.

CHINA. Yunnan Province, Malipo county, Xiajinchang town, Aotang, 23°07'45.41"N, 104°51'29.25"E, Alt. 1400 m, growing on moist limestone rocks near a road, 8 January 2010, Southeast Yunnan investigation team of DNA barcoding, GBOWS189 (KUN!). CHINA. Guangdong Province, Guangzhou City, voucher from a cultivated plant at South China Botanical Garden, 12 June 2016 (flowering), Li-Hua Yang, YLH350 (IBSC!), introduced from same locality and by the same people as the type. VIETNAM. Ha Qiang province, Quan Ba District, Quyet Tien Community, Khau La Village, Alt. 1100 m, growing on moist limestone rocks, 17 October 2017, Fang Wen et al. VMN-CN 874 (IBK!, VMN!).