Stellaria alsine Grimm subsp. nana K. Fuse & Yahara, 2021

Yahara, Tetsukazu, Hirota, Shun K., Fuse, Kengo, Sato, Hiroyuki, Tagane, Shuichiro & Suyama, Yoshihisa, 2021, A new subspecies of Stellaria alsine (Caryophyllaceae) from Yakushima, Japan, PhytoKeys 187, pp. 177-188 : 177

Stellaria alsine Grimm subsp. nana K. Fuse & Yahara subsp. nov.

Fig. 4

Diagnosis.

Stellaria alsine subsp. nana differs from the typical subspecies in its shorter stem (2.5-6 cm vs. 15-30 cm), smaller lamina (0.5-1 cm × 1-3 mm vs. 0.5-2 cm × 2-4 mm), shorter pedicels (0.1-0.6 cm long vs. 0.5-2 cm long), as well as chasmogamous flowers with 3 stamens and 2 styles (vs. 5 stamens and 3 styles) that are usually solitary (vs. usually 3-5 on a terminal or axillary cyme).

Type.

Japan. Kagoshima Prefecture: Yakushima, along a path to Mt. Nagata , on rocks along streams, 30°20'28.96"N, 130°28'37.22"E, 1500 m elevation, 21 July 2020, with cleistogamous flowers, T. Yahara, H. Sato, K. Fuse, Y. Higashi JPN0573 (holotype: FU!, isotype: KYO!) .

Description.

Herbs possibly biennial. Stems caespitose, 2.5-6 cm long, glabrous, erect in upper and middle parts, prostrate in lower parts. Leaves deciduous, sessile; blade oblong-obovate or narrowly obovate, 0.5-1 cm × 1-3 mm, glabrous, single-veined, base attenuate, apex acute, margin entire. Flowers solitary or 2-3 flowers in an axillary or terminal cyme with a ca. 6 mm scape. Pedicel 1-6 mm long, slender, glabrous. Sepals ovate-lanceolate, ca. 2.5 mm long in chasmogamous flowers, ca. 2.0 mm long in cleistogamous flowers, glabrous, apex acute. Petals of chasmogamous flowers 5, ca. 2.6 mm long, 2-cleft nearly to base; lobes oblanceolate, apex obtuse; petals absent in cleistogamous flowers. Stamens of chasmogamous flowers 3, 0.8 mm long; filaments ca. 0.4 mm long, glabrous, anthers globular, 0.4 mm in diam. Styles 2, glabrous. Capsule obovoid, 2.5 mm long, as long as sepals when mature, 2-loculated. Seeds dark brown, reniform, ca. 0.7 mm long, slightly flattened, tuberculate with raised papillae, without an appendage.

Phenology.

Chasmogamous flowers were observed in May, cleistogamous flowers and immature fruits were observed in July, and mature fruits and seeds were observed in September.

Distribution and habitat.

Yakushima, Japan (endemic). At present, this subspecies has been identified in two populations growing on rocks along streams at 1500 m elevation in the vicinity of Mt. Nagata.

Etymology.

The subspecific epithet is derived from its dwarf habit.

Conservation status.

Vulnerable (VU). The population size was estimated to be between 250 and 1000 mature individuals. The habitat is located within the protected area of Yakushima (Island) National Park and no threats are detected at present.

Additional specimens examined.

Japan. Kagoshima Prefecture: Yakushima, along a path to Mt. Nagata , 30°20'28.96"N, 130°28'37.22"E, 1500 m elevation, 4 September 2020, with fruits, K. Fuse, T. Saito JPN1791 (FU!); a gorge N of Mt. Nagata, 30°20'39.7"N, 130°29'28.5"E, 1700 m elevation, 3 May 2021, with chasmogamous flowers, K. Fuse, T. Saito JPN4891 (FU!) .

Figures

Figure 4. Stellaria alsine subsp. nana K. Fuse & Yahara A a living stem of K. Fuse & T. Saito JPN 4891 bearing a chasmogamous flower B the chasmogamous flower of A C Living stems of the holotype, T. Yahara et al. JPN 0573, bearing cleistogamous flowers D a fruit of K. Fuse & T. Saito JPN 1791. Scale bars: 1 cm (A, C); 1 mm (B); 2 mm (D).