Argyreia subrotunda Q.R.Liu & M.L.Zhang, 2023

Zhang, Mao-Lin, He, Yi & Liu, Quan-Ru, 2023, A new species of Argyreia (Convolvulaceae) from Yunnan, China, PhytoKeys 225, pp. 199-209 : 199

publication ID	https://dx.doi.org/10.3897/phytokeys.225.100646
persistent identifier	https://treatment.plazi.org/id/4B08EF65-8DC3-503A-AEC0-BAB7CC79B2B4
treatment provided by	PhytoKeys by Pensoft
scientific name	Argyreia subrotunda Q.R.Liu & M.L.Zhang
status	sp. nov.

Treatment

Argyreia subrotunda Q.R.Liu & M.L.Zhang sp. nov.

Figs 1 View Figure 1 , 2 View Figure 2

Type.

China. Yunnan Province: Malipo County, Xinzhai Village , 22°57'48.01"N, 104°46'31.11"E, along roadside, 1300 m elev., 27 Aug 2021, fl. M. L. Zhang BNU2021YN074 (holotype: BNU0053319!; isotypes: BNU!) GoogleMaps .

Diagnosis.

A. subrotunda is unique, a small-flowered type with an entire or shallowly lobed corolla as well as exserted stamens and pistils (included in dry specimens), smaller elliptic bracts, and outer sepals ovate-circular. It is similar to A. wallichii in indumentum features (whitish tomentose) and fruit types (red globose berry), but differs by its smaller elliptic bracts (vs. ovate-oblong), lax flat-topped cymes (vs. compact capitate) and shorter corolla tubes (2-2.5 cm vs. 4-5 cm). Additionally, A. subrotunda is similar to A. fulvocymosa in leaf shape (broadly ovate-circular to nearly circular) and inflorescence (flat-topped cymes), but the latter is covered with densely yellowish villus and has a distinctly 5-lobed corolla, which is very easy to distinguish (Table 1 View Table 1 ).

Description.

Climbing lianas; stem woody at base, herbaceous above, the former puberulent, the latter covered with whitish trichomes. Leaves simple, alternate; petiole 6-10 cm long, tomentose; leaf blades broadly ovate to rounded, 13-16 × 12-15 cm; base truncate or slightly cordate, occasionally oblique, margins entire, apex acute or obtuse, sometimes slightly emarginate; adaxially green, sparsely whitish velutinous only along leaf veins, abaxially paler, densely shining tomentose; secondary veins 13-15 on either side, curved to edge, veins slightly raised adaxially, more prominently raised abaxially. Inflorescences flat-topped cymes, axillary or terminal; peduncle 2-5 cm long, tomentose, angulate, secondary and tertiary peduncle 6-12 mm long; bracts small, elliptic, 8-10 × 4-8 mm, obtuse, hairy outside, veined; pedicels 5-7 mm long, up to 10 mm in fruit. Flowers diurnal; sepals unequal, 2 outer ovate-circular, 8-9 × 6-7mm, 3 inner elliptic, 6-7 × 3-5 mm, apex obtuse, abaxially whitish tomentose, adaxially glabrous, veined, enlarged in fruit, rose-red, shiny. Corolla tubular-funnelform, 2-2.5 cm long, pink, densely whitish villous outside on mid-petaline bands, otherwise glabrous, limb entire or shallowly lobed. Stamens exserted; filaments filiform, 14-15 mm long, attaching to the site of ca. 5 mm from stamens base, expanded at attachment points and densely whitish hairy there; anthers oblong, 3-4 mm long; pollen globose, pantoporate, with spines, 90-101 μm in diameter. Pistil exserted; disc ringlike, glabrous, ca. 1 mm high; ovary glabrous, ovoid, 2-3 mm high; style filiform, glabrous, 20-22 mm long; stigmas capitate, 2-lobed. Fruit enclosed in persistent, accrescent calyx, 2 outer fruiting sepals enlarging to 10-11 × 7-8 mm, 3 inner sepals 8-10 × 5-6 mm; berry subglobose, 7-10 mm in diam., purple-red, glabrous, exocarp leathery shiny, with obvious stomata under a magnifier, wrinkled when dry. Seeds 1-2, subglobose or hemispherical, 3.5-4 × 4-4.5 × 2.5-3 mm, black, glabrous, surface not smooth; hilum subcordate, brown, basal, margin with sparsely whitish hairy.

Phenology.

Flowering from August to November; fruiting in November to February.

Distribution and habitat.

Distributed in Yunnan and Gaungxi Province (Fig. 3 View Figure 3 ), occurring at elevations of ca. 650-1300 m, distributed at open and sunny places such as roadsides, thickets, edges of mingled forest.

Preliminary conservation status.

Least Concern (LC). At present, five populations have been collected in Malipo County, Maguan County and Napo County. Each population is large with high flowering rates, and the number of mature individuals in the population is more than 50. According to the IUCN (2019) red list categories and criteria, A. subrotunda should be categorized as a 'Least Concern (LC)' species, which needs further investigation and research to more fully assess the conservation status.

Etymology.

The specific epithet refers to the leaf shape, which is near-round.

Chinese name.

近圆叶银背藤 ( Jìn Yuán Yè Yín Bèi Téng).

Additional specimens examined.

China, Guangxi Province: Napo County, Baisheng Township, Naen Reservoir , 26 Nov. 2013, fr. B. Y. Huang et al. 451026131126017LY (GXMG!) ; Yunnan Province: Malipo County, Bar-bu, 1000 m elev., 2 Feb. 1940, fr. C. W. Wang et al. 86509 (PE!); Malipo County , Wen-tian Road beside National Highway G 246, 650 m elev., 23 Nov. 2021, fr. X. B. Guo BNU2021YN081 (BNU!); Malipo County , Xinzhai Village , 1300 m elev., 23 Nov. 2021, fl. X. B. Guo BNU2021YN082 (BNU!) .

Pollen morphology

The observed pollen grains of A. subrotunda were monad, spheroidal to subspheroidal and radially symmetrical, with polypantoporate and echinate ornamentation (Fig. 4 View Figure 4 ). It was possible to divide into two types based on the pollen morphology as follows: the diameter of the pollen grain was less than 100 μm with shorter bottle-like spines (5-7 μm), such as A. wallichii and the new species A. subrotunda ; the diameter of pollen grains was over 100 μm with longer cone-shaped spines (≥ 10 μm), such as A. marlipoensis , which is endemic to Yunnan province, and the flower of which is first seen in this study.