Cladopus yangjiangensis X. T. Liu, G. Di Chen & B. Hua Chen, 2024

Zhang, Miao, Liu, Xiu-Ting, Tian, Min, Chen, Zhang-Xue, Huang, Ying-Lin, Chen, Guo-Di & Chen, Bing-Hua, 2024, Cladopus yangjiangensis (Podostemaceae), a new species from Guangdong, South China, redefining the phylogenetic relationships within Cladopus, PhytoKeys 249, pp. 231-249 : 231-249

Cladopus yangjiangensis X. T. Liu, G. Di Chen & B. Hua Chen sp. nov.

Figs 4 , 5 , 6 , 7 , 8

Diagnosis.

Cladopus yangjiangensis shares certain similarities with C. fukienensis and C. austrosinensis , such as comparable ovary lengths, and analogous stigma and capsule shapes. However, it is distinguished by several unique traits. The leaves of C. yangjiangensis are markedly elongated, measuring 18.7–26.7 mm, which is substantially longer than those of C. fukienensis (1.3–5.0 mm) and C. austrosinensis (up to 6 mm). The flowering shoots of C. yangjiangensis also exceed those of other two species, ranging from 4.2 to 13.1 mm, compared to 3.5–6.0 mm in C. fukienensis and 1.6–3.5 mm in C. austrosinensis . Additionally, C. yangjiangensis produces a greater number of bracts, with counts ranging from 20 to 54, in contrast to 12–36 in C. fukienensis and 8–14 in C. austrosinensis . Finally, the root width of C. yangjiangensis is notably narrower, at about 0.4 mm, compared to 0.4–1.3 mm in C. fukienensis and 0.5–1.3 mm in C. austrosinensis (Table 3 ).

Type.

China • Guangdong: Yangjiang City Yangxi County, Tangkou Town, Tongyou village , elevation 200 m, 21°49'N, 111°28'E, 24 December 2023, XT Liu & GD Chen 0001 (Holotype FNU! barcode FNU 0041314 ; isotype FNU! barcode FNU 0041315 ) .

Description.

Perennial aquatic herb; roots narrowly ribbon-like, compressed, dorsiventral, succulent, ca. 0.4 mm width, 0.1–0.2 mm thick, adhere to the surface of underwater rocks, brick-red during winter, dark green during reproduction; stem short, arising from root branch axils (Fig. 4 ); flowering shoots obpyramidal, solitary, erect, 4.2–13.1 mm tall; leaves linear, in rosette on vegetative shoots, 3–8 in number, 18.7–26.7 mm long, deciduous at flowering; leaves on reproductive shoots palmate (also known as bracts), lobes 3–5 digitate, central lobe long, columns two, opposite, overlapping, bracts 20–54, upper leaves larger, diminishing towards apex, 1.5–1.9 × 1.1–2.0 mm, lobes rigid and coarse after water loss; flowers bisexual, solitary at fertile branch apex, enclosed in pale red spathe during early development; spathella globose, acumen short, 1.7 × 0.3 mm; tepals two, broadly linear, acuminate, 0.7–1.1 mm long; stamen single, 1.2–2.4 mm long; filament nearly cylindrical, slightly flattened, 0.9–1.3 mm long; anthers two, elliptical, yellow, ~ 0.6–0.9 mm long; Ovary single, pale yellow-green, ellipsoid, two-chambered, 1.2–1.7 × 0.9–1.1 mm; ovules ovate, 15–23 per chamber, attached to entire placenta (Figs 5 , 6 ); capsule brownish, globose, smooth, 1.1–1.4 mm long; fruit stalk 1.2–1.7 mm long; seeds small, yellow, narrowly ovoid, 0.3–0.5 × 0.1–0.3 mm (Fig. 7 ).

Distribution and habitat.

Many other plants grow in the surrounding habitat, whose tree layer includes Archidendron clypearia ( Fabaceae ), Engelhardia roxburghiana ( Juglandaceae ), Aporosa dioica ( Phyllanthaceae ), Zanthoxylum avicennae ( Rutaceae ), Sterculia lanceolata ( Malvaceae ) and others; the shrub layer includes Acronychia pedunculata ( Rutaceae ), Rhaphiolepis indica ( Rosaceae ), Rubus leucanthus ( Rosaceae , Ficus pyriformis ( Moraceae ), Glochidion lanceolarium ( Phyllanthaceae ), Garcinia oblongifolia ( Clusiaceae ), Melastoma sanguineum ( Melastomataceae ), Saurauia tristyla ( Actinidiaceae ), Adina pilulifera ( Rubiaceae ), Pavetta hongkongensis ( Rubiaceae ), and others; the vegetation layer includes Blechnopsis orientalis ( Blechnaceae ), Plenasium vachellii ( Osmundaceae ), Acorus gramineus ( Acoraceae ), Pandanus austrosinensis ( Pandanaceae ), Alpinia hainanensis ( Zingiberaceae ), Thysanolaena latifolia ( Poaceae ), Miscanthus floridulus ( Poaceae ), Pentasachme caudata ( Apocynaceae ) and others; and some exotic plants include Stauntonia obovatifoliola ( Lardizabalaceae ), Phanera erythropoda ( Fabaceae ), Rourea microphylla ( Connaraceae ) and others.

Phynology.

Flowering and fruiting season in November to February of the following year.

Etymology.

The Yang Jiang Chuan Tai Cao (阳江川苔草). The epithet yangjiangensis (阳江) refers to Yangjiang City, Guangdong Province, South China, where this new species was found.

Conservation status.

According to our investigation, Cladopus yangjiangensis was only found in a stream in Yangjiang City, Guangdong Province, China, and hence we suggest its placement in the Data Deficient category of IUCN (2022). In addition, according to the Updated List of National Key Protected Wild Plants (Decree No. 15) by the country’s State Forestry and Grassland Administration and the Ministry of Agriculture and Rural Affairs, all of the known genera of Podostemaceae found in China are classified as under national secondary protection. This new species should also be included on the national secondary protection list during the upcoming revision process.

Figures

Figure 4. Cladopus yangjiangensis A habitat (Photographed by Guo-Di Chen) B root with tufts of leaves, leaves linear, brick red in color C plants in bud adhering to rock surface D flowering shoot E top view of flower (red arrow pointing to the stamen) F mature fruits.

Figure 5. Cladopus yangjiangensis A flowering shoot on roots, inverted tower shape (reproductive leaves (a. k. a. bracts) imbricate, finger-like) a flower with 2 stigmas, a stamen (stamen clearly longer than ovary) B stamens, arrow points to two tepals, fused to ovary C gynoecia, arrow points to reddish, ribbon-shaped stigmas D stamen and tepals (tepals attached to filament bases on either side) E stamen F gynoecium with ellipsoid ovary, no bracts G longitudinal ovary section H ovules. Scale bars: 2 mm (A); 500 μm (A, B, C, D, E, F, G); 200 μm (H).

Figure 6. Cladopus yangjiangensis A vegetative shoot B tufts of leaves on root (clustered, roots subterete, linear leaves) C abaxial and adaxial views of the upper leaves of reproductive shoots D leaves with some lobes markedly long at the base of vegetative shoots. Scale bars: 5 mm (A, B); 1 mm (C, D).

Figure 7. Cladopus yangjiangensis A fruiting shoots on root B stalked capsule, tan, globose, smooth C fertile seeds and ovules in a mature fruit D fertile seeds E, F adaxial and lateral views of placenta. Scale bars: 2 mm (A); 400 μm (B); 200 μm (C, D, E, F).

Figure 8. Illustration of Cladopus yangjiangensis A tufts of leaves on root B flowering shoot on roots C leaves with some lobes markedly long at the base of vegetative shoots D abaxial and adaxial views of leaves on the upper part E flower with 2 stigmas, a stamen and 2 tepals F gynoecium without bracts, ovary ellipsoid G stamen H longitudinal section of the ovary I adaxial view of the placenta J stalked capsule, globose, smooth K seeds.