Hosta minazukiflora Se. Fujii & Yahara, 2023

Yahara, Tetsukazu, Hirota, Shun K., Fujii, Seiko, Kokami, Yasushi, Fuse, Kengo, Sato, Hiroyuki, Tagane, Shuichiro & Suyama, Yoshihisa, 2023, Molecular phylogeny and taxonomy of Hosta (Asparagaceae) on Shikoku Island, Japan, including five new species, one new subspecies, and two new status assignments, PhytoKeys 235, pp. 137-187 : 137

5. Hosta minazukiflora Se. Fujii & Yahara sp. nov.

Figs 12 , 13

Diagnosis.

Hosta minazukiflora is similar to H. longipedicellata in having leaves shorter than 20 cm, straight scapes shorter than 43 cm, and perianth lobes 0.6-0.8 cm wide. However, H. minazukiflora is distinguished from H. longipedicellata by its lavender flowers (vs. whitish), shorter pedicels (1.1-1.2 cm vs. 2.5-3.3 cm), narrower leaves (2.9-6.2 cm wide vs. (5.4-)9-12 cm wide) smooth on the lower surface (vs. papillose), and the occurrence at elevations of 270-280 m (vs. 1700-1750 m).

Type.

Japan. Kochi Pref.: Nagaoka-gun, Motoyama-cho, Asemi River , 25 Jun. 2017, Se. Fujii & K. Yabe FOS-012016 with flowers (holotype MBK0318414!) .

Description.

Herbs perennial. Leaves basal, spiral, long petiolate, 4-6 per ramet; blades oblong-ovate to oblong-lanceolate, 11.8-17.0 cm long, 2.9-6.2 cm wide, 2.4-4.3 times longer than width, thinly papery, glabrous on both surfaces, base cuneate, decurrent, slightly folded, apex acuminate, margin entire, veins in 6-9 pairs, smooth on the lower surface; petioles 8-19 cm long, narrowly winged, wing 0.1-0.3 cm wide, glabrous. Scape 18-43 cm long, terete. Raceme 10-15 cm long, 3-6-flowered; flower bracts vivid (not withering) in anthesis, erect, whitish purple, oblong-lanceolate, boat-shaped, 1.3-1.6 cm long, 0.2-0.4 cm wide, membranous, glabrous, apex acute. Flowers not fragrant, 5.2-5.9 cm long; pedicels 1.1-1.2 cm long, glabrous. Perianth whitish purple, funnel-form, 4.1-4.7 cm long, glabrous, 6-lobed; abruptly dilated from apical 2/3, lobes narrowly triangular, 1.2-1.4 cm long, 0.6-0.8 cm wide, apex acute. Stamens 6; filaments 4.6-5.4 cm long, white, free, glabrous, 0.5-0.7 cm exerted from perianth, upwardly curved at the distal part, anthers purple when fresh, dark blue-grey when dried, 3 mm long. Style 5.2-6.1 cm long, upwardly curved at the distal part, 1.1-1.4 cm exerted from the perianth, glabrous, stigma capitate. Ovary ellipsoid, 0.6 cm long, glabrous. Capsule green, cylindrical, 1.8-2.3 cm long, 0.3-0.4 cm wide, shallowly 3-angled. Seeds ellipsoid-ovoid, 2 mm long, with wings 4 mm long, black when dry.

Phenology.

Flowering from mid to late June and fruiting in August.

Distribution and habitat.

Japan (Kochi Prefecture). This species grows on rock cliffs along the Asemi River, a branch of the Yoshino River, in the central part of the Kochi Prefecture on Shikoku Island.

Etymology.

The specific epithet was derived from the flowering season in June. Minazuki refers to June in Japanese.

Conservation status.

Using criterion D1 for IUCN Red List categories ( IUCN 2012, IUCN 2022), we recommend that this species be classified as EN (Endangered) because its population is estimated to be between 50 and 250.

Japanese name.

Minazuki-giboshi (new).

Additional specimens examined.

Japan. Kochi Pref.: Nagaoka-gun, Motoyama-cho, Asemi River , 280 m elev., 19 Aug. 2020, T. Yahara et al. JPN1308 sterile, JPN1309 sterile, and JPN1310 with fruit (FU!) ; ditto, 13 Jun. 2004, Y. Yamashita et al. FOK-066868 with flowers (MBK0083845!) ; ditto, 23 May 2002, Y. Kokami et al. FOK-055767 with flower buds (MBK0146148!) ; ditto, 270 m elev., 25 Jun. 2017, Se. Fujii & K. Yabe FOS-012017 with flowers (MBK0318415!) .

Note.

Hosta minazukiflora is sister to H. shikokiana (Figs 2 , 3 ), but morphologically more similar to H. longipedicellata (see diagnosis) and H. scabrinervia . The type specimen Se. Fujii & K. Yabe FOS-012016 was first identified as H. kikutii var. scabrinervia . While the two species are distributed in the Yoshino River system, H. minazukiflora is easily distinguished from H. scabrinervia by its smaller leaves (12-17 cm long and 3-6 cm wide compared to 17-32 cm long and 7.5-15 cm wide in H. scarbrinervia ), lavender perianths (in contrast to whitish perianths), and earlier flowering season in June (rather than July).

Figures

Figure 2. A rooted Maximum Likelihood tree for Hosta Clade 1 reconstructed using MIG-seq data. Bootstrap values are indicated on internodes. Based on the Maximum Likelihood tree of 28 Japanese species (Fig. 1), H. gracillima is used as an outgroup.

Figure 3. A SplitsTree for Hosta Clade 1 reconstructed using MIG-seq data.

Figure 12. The type specimen of H. minazukiflora: Se. Fujii & K. Yabe FOS- 012016 (holotype MBK).

Figure 13. Flowering plants of H. minazukiflora. Photos taken in the type locality (on 25 Jun. 2017 by Se. Fujii; not collected). Scale bars: 20 cm (A); 2 cm (B).