Hosta takiminazukiflora 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

6. Hosta takiminazukiflora Se.Fujii & Yahara sp. nov.

Figs 14 , 15

Diagnosis.

Hosta takiminazukiflora is similar to H. longipedicellata and H. minazukiflora . It is distinguished from H. longipedicellata by leaves smooth on the lower surface (vs. papillose), pedicels 1.4-2.5 cm long (compared to 2.5-3.3 cm long), and flower bracts being fresh during flowering (in contrast to being withering), and from H. minazukiflora by perianths with a distinct midvein (as opposed to three distinct veins) and pedicels 1.4-2.5 cm long (compared to 1.1-1.2 cm long).

Type.

Japan. Kochi Pref.: Tosa County, Ookawa village, Mt. Higashikado-yama , 22 Jul. 2007, with flowers, N. Inagaki et al. FOK-080097 with flowers (holotype MBK0189902!) .

Description.

Herbs perennial. Leaves basal, spiral, long petiolate, 3-12 per ramet; blades oblong-ovate, 11-26.5 cm long, 3.6-10.5 cm, 2.1-3.3 times longer than wide, thinly papery, glabrous on both surfaces, base cuneate to obtuse, often decurrent, apex long acuminate, margin entire, veins in 6-10 pairs, smooth on the lower surface; petioles 3.4-22 cm long, narrowly winged, wing 0.1-0.6 cm wide, glabrous. Scape 8.6-28.5 cm long, terete. Raceme 5.9-18.5 cm long, 4-13-flowered; flower bracts vivid (not withering) in anthesis, erect, purplish light green, light bluish purple, ovate oblong-lanceolate, boat-shaped, 2-4.7 cm long, 0.2-0.7 cm wide, papery, glabrous, apex acute to acuminate. Flowers not fragrant; pedicels 1.4-2.5 cm long, glabrous; perianths 4-5.7 cm long, funnel-form, pale white-purple to light bluish-purple outside, almost white to light pale purple inside, midveins more or less purplish, glabrous, 6-lobed; tube dilated from apical 1/2, lobes triangular, 1.2-1.8 cm long, 0.5-1 cm wide, apex acute. Stamens 6, same or ca. 0.5 cm exerted from perianths; filaments 3.9-5.8 cm long, upwardly curved at the distal part, white, free, glabrous, anthers purple when fresh, dark blue-grey when dried, 3 mm long. Ovary ellipsoid, 0.6-0.7 cm long, style 4.5-6.5 cm long, upwardly curved at the distal part, up to 1 cm exerted from perianth, glabrous, stigma capitate. Young capsules 2.8 cm long (for MBK0087737).

Phenology.

Flowering in late June to early August.

Distribution and habitat.

Japan (Kochi Prefecture: Tosa County, endemic to Mt. Inamura, Mt. Higashikado, and the surrounding area). It grows on cliffs.

Etymology.

A specific epithet is derived from its habit of growing on rock cliffs (called ‘taki’ in Kochi dialect) and flowering in June (Minazuki).

Conservation status.

Using criterion D1 for IUCN Red List categories ( IUCN 2012, IUCN 2022), we recommend that this species be classified as VU (Vulnerable) because its population is estimated to be between 250 and 1000.

Japanese name.

Taki-minazuki-giboshi (new).

Additional specimens examined.

Japan. Kochi Pref.: Tosa County, Ookawa village, 900 m, 27 Jul. 2004, N. Inagaki et al. FOK-067742 with flowers and young fruits (MBK0087737!); Tosa County , Tosa Town , 620 m elev., 24 Jun. 2021, T. Yahara et al. JPN6478 - 6486, 6490 with flowers (FU!); Agawa-gun, Ino-cho, Mt. Inamura , 1390 m elev., 2 Aug. 2019, Y. Oohira 14695 with flowers (MBK0314655!); Agawa-gun, Ino-cho, north cliff of Mt. Inamura , 23 Jul. 2022, Se. Fujii JPN15229 , 15230 with flowers (FU!) .

Note.

The clade comprising this species and H. longipedicellata is sister to all the other species in Clade 1 (Fig. 2 ), and its morphological similarities to H. longipedicellata and H. minazukiflora are considered to be derived from a common ancestor.

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 14. The type specimen of H. takiminazukiflora: N. Inagaki et al. FOK- 080097 (holotype MBK).

Figure 15. A flowering plant of H. takiminazukiflora subsp. takiminazukiflora (JPN 6481, 24 Jun. 2021). Scale bars: 5 cm (A); 2 cm (B).