Metapetrocosmea navicularis F. Wen, T. V. Do, Z. B. Xin & K. Tan, 2025

Li, Qi-Yang, Tan, Ke, Do, Truong Van, Xin, Zi-Bing, Bai, Xin-Xiang, He, Song-Tao & Wen, Fang, 2025, Metapetrocosmea navicularis, a new species of Gesneriaceae in Vietnam, PhytoKeys 261, pp. 87-98 : 87-98

publication ID	https://doi.org/10.3897/phytokeys.261.160454
DOI	https://doi.org/10.5281/zenodo.16762637
persistent identifier	https://treatment.plazi.org/id/FC3341FB-6E9A-5D9C-BB7E-5D0D2A467505
treatment provided by	PhytoKeys by Pensoft
scientific name	Metapetrocosmea navicularis F. Wen, T. V. Do, Z. B. Xin & K. Tan
status	sp. nov.

Treatment

Metapetrocosmea navicularis F. Wen, T. V. Do, Z. B. Xin & K. Tan sp. nov.

Fig. 1 View Figure 1

Type.

China • Guangxi: cultivated in Guilin Botanical Garden, introduced from Vietnam, Quang Tri Prov, Dak Rong Natural Reserve , on rock walls of a local waterfall, 15°40'41"N, 107°42'22"E, 190 m a. s. l., 10 Nov. 2024, Q. Y. Li & K. Tan 241110 (holotype: IBK! [ IBK 00470816 About IBK !]; isotypes: IBK! [ IBK 00470817 About IBK !], VNMN!) GoogleMaps .

Diagnosis.

Metapetrocosmea navicularis is similar to M. tamiana in macroscopic morphology, and phylogenetic analysis indicates that they are the closest relatives (Fig. 1 View Figure 1 ). But it is easy to distinguish the new species from M. tamiana by its leaf blade ovate to ovate-elliptic (vs. cordate to nearly round, the following comparisons follow the same order), leaf densely puberulent adaxial (vs. with mixture of long and short pubescence adaxial), bracts 6–9 mm long (vs. ca. 2 cm long), the ratio of corolla lobes length to corolla tube length consistently 1: 3 (vs. approximately 1: 1), 10–20 - flowered or more (vs. 4–6 - flowered), corolla tube gradually narrowed from mouth to base, subcylindrical-infundibulate (vs. wider in upper part, abruptly contracted towards base, distinctly infundibulate), filaments pubescent near the top (vs. glabrous), style puberulent (vs. pubescent), and stigma arcuate (vs. nutant) (Table 2 View Table 2 ).

Description.

Perennial herb. Rhizome subcylindrical, ca. 4 cm long, 6–8 mm in diameter, perennial-growing rhizomes exhibit distinct abscission scars following leaf abscission. Leaves 8–12 or more, petiolate; petioles 3–6 cm long, ca. 3 mm in diameter, pale green, puberulous; leaf blade alternate, ovate to ovate-elliptic, 6–8 × 2.5–4 cm, dark green to green adaxially with pale green veins commonly, pale green abaxially, apex acute, base obtuse, peltate, margin crenate, densely puberulent; venation penninerved, lateral veins 3–5 pairs, inconspicuously impressed adaxial veins, prominently raised abaxial. Inflorescence cymes, axillary, 10–20 - flowered or more. Peduncles densely pubescent, 6–12 cm long, ca. 4 mm in diameter; pedicels 1–3 cm long, ca. 2 mm in diameter, densely pubescent. Bracts 2, opposite, distinctly navicula, namely generally oblong-elliptic, base broader, apex attenuate being acuminate, resembling a small boat, 5–9 × 2–3 mm, margin entire but slightly reflexed, densely pubescent, deciduous, generally not persistent; calyx 5 - parted to the base, lobes nearly equal in length, ca. 8 × 2 mm, lanceolate, dark green, apex acute, outside villosulous, inside glabrous, margin ciliate. Corolla pale purple to white, ca. 3.5 × 2.5 cm, bilabiate; upper lip 2 - lobed, split to the midpoint of the corolla tube, lobes ca. 9 × 6 mm; lower lip 3 - lobed, central lobe more rounded than lateral lobes, lobes ca. 9 × 8 mm; corolla tube gradually narrowed from mouth to base, subcylindrical-infundibulate, with two dark purplish-blue lines that stretch from either side of the median lobe of the corolla down into the throat. Stamens 2, ca. 7 mm long, inserted at 8 mm from the base of the corolla; filaments linear, white, villous near the top, arcuate; anthers oblong, pale yellow, ca. 3 mm long, lanate; staminodes 2, ca. 4 mm long, ca. 1 mm in diamete, inserted at 8 mm from the base of the corolla, villous near the top, slightly curved. Disc annular, pale yellowish-green, ca. 1 mm high, glabrous. Pistil ca. 1.8 cm long; ovary linear, ca. 6 mm long, densely pubescent; style linear, ca. 1 cm long, white, densely puberulent; stigma obtrapeziform, emarginate. Capsule obliquely narrowly oblong, ca. 3 cm long, dehisces along the ventral suture; seed surface, longitudinal prominent ribs are further linked to become somewhat reticulate.

Phenology.

The peak flowering period occurs in December, with flowering from November to January and fruiting from February to March in the nursery of the botanical garden. Whether the natural flowering and fruiting periods of wild populations differ from those of cultivated populations in botanical garden requires long-term field observations for confirmation.

Vernacular name.

“Hình dáng gi ống thuy ền” (Understood as the bracts of this species are interpreted as naviculate shape). Its Chinese name is Chuán Bāo Dùn Yè Jù Tái (Chinese pronunciation); 船苞盾叶苣苔.

Distribution and habitat.

Metapetrocosmea navicularis is relatively common in moist with abundant populations and shaded habitats under evergreen broad-leaved forests at an altitude of approximately 190 m in its type locality. This species grows in moist rock crevices, with accompanying species mainly including some ferns and other herbaceous plants.

Additional examined specimens.

Metapetrocosmea tamiana , Vietnam • Vinh Phu Province, Tam Dao , 4 Nov. 1997, Soviet-Vietnamese Expedition 1986, No. 114. 19973431 * A (holotype: E!); Tam Dao, 1998, Soviet-Vietnamese Expedition 1986, No. 114. 15738 (E!); Tam Dao, 13 Jan. 1999, L. E. Skog & J. K. Boggan 7851 (US!). Metapetrocosmea navicularis , Vietnam • Quang Tri Province, Dak Rong Natural Reserve , growing on rocky cliffs by the side of the trail on the hill slope, 15°40'41"N, 107°42'22"E, 190 m a. s. l., 19 Mar. 2018, Van Truong Do et al. VMN-CN 1069 ( VNMN!) GoogleMaps .

Conservation status.

The species inhabits the Dak Rong Nature Reserve, Vietnam, an area of high biodiversity. Thanks to the favorable growing environment, the species has developed abundant populations here, resulting in a thriving population size. This richness in numbers is further supported by effective conservation and management efforts in the region. Following the IUCN Red List Categories and Criteria ( IUCN Standards and Petitions Committee 2024), our preliminary assessment result is Least Concern (LC).

Note.

It is very special because its bracts of this species are interpreted as naviculate shape, which is the first discovered in Metapetrocosmea . The character can also help distinguish it from all other species of Metapetrocosmea from Vietnam and China. From a macroscopic morphological perspective, this new species is indeed closest to M. tamiana , which is currently known to be distributed in Tam Dao National Park near Hanoi City in northern Vietnam. This represents a significant long-distance geographic isolation from the new species, which is distributed in southern Vietnam. We know that within subfam. Didymocarpoideae of Gesneriaceae , microenvironmental variations across different terrains and landforms can give rise to rich species diversity ( Tan et al. 2020). Among Chinese taxonomists, there’s even a widely circulated saying about the important characteristic of Gesneriaceae species diversity: “ one species per mountain ”, “ one species per gully ”, “ one species per cave ”, a point particularly prominent in the closely related genus Primulina ( Wei 2018; Wei et al. 2022, 2023). Considering the geographic isolation, there are also many readily discernible characteristics between this new species and Metapetrocosmea tamiana (Table 2 View Table 2 ). For example, the plant size and leaf size of the new species are 2 to 3 times larger than the latter and are very stable, maintaining this difference even under long-term common garden cultivation. After common garden cultivation, the new species can have more than 10 flowers per inflorescence, with the entire plant producing 60 or more flowers, densely clustered on the inflorescence (Fig. 1 B View Figure 1 ). In contrast, M. tamiana consistently has fewer than 10 flowers per inflorescence (around 4-6) and typically around 20 flowers per plant, with the flowers on the inflorescence being more scattered (Fig. 2 A View Figure 2 ). In wild populations of this new species, more than 90 % of individuals exhibit clear or indistinct white fishbone-patterned leaf veins (Fig. 1 A View Figure 1 ), while the latter has entirely green leaves without any white fishbone patterns (Fig. 1 C View Figure 1 ). However, since these traits are quantitative or semi-qualitative, they are not ideal for definitively distinguishing the two species. In contrast, the new species’ naviculate bract shape and the stable ratio of corolla lobe length to corolla tube length consistently being 1: 3, along with its pubescent filaments, are good qualitative characteristics for clearly differentiating the two species (Figs 1 F View Figure 1 , 2 D View Figure 2 ). In terms of flower size, the flowers of this new species are significantly larger in diameter than those of M. tamiana : measurements show that the flower diameter of the new species is usually around 2.5 cm, while that of M. tamiana is generally only ca. 2 cm (Figs 1 E View Figure 1 , 2 C View Figure 2 ). This size difference is clearly distinguishable to the naked eye. Turning to the blue-purple nectar guides on the inner surface of the corolla, although they appear similar, there are essential differences between the two species. The nectar guides of M. tamiana exhibit poor color stability: under high-temperature conditions in summer, their color fades gradually, eventually becoming extremely pale, almost white, and once this fading occurs, it is difficult to recover in a short period. In contrast, the nectar guides of the new species show extremely strong color stability; even in the same high-temperature environment, their blue-purple color remains vivid without fading or lightening. This characteristic also serves as an important diagnostic marker for distinguishing the two species (Figs 1 I View Figure 1 , 2 H View Figure 2 ). Moreover, in conjunction with phylogenetic analysis, we acquired the sequences of the type locality of M. navicularis and formed a fully supported clade in the phylogenetic tree (Fig. 3 View Figure 3 ).