Hosta scabrinervia Yahara & Se. Fujii 2023, stat. nov.
Creators: name: Yahara, Tetsukazu
name: Hirota, Shun K.
name: Fujii, Seiko
name: Kokami, Yasushi
name: Fuse, Kengo
name: Sato, Hiroyuki
name: Tagane, Shuichiro
name: Suyama, Yoshihisa
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Liliopsida
Asparagales
Asparagaceae
Hosta
Hosta scabrinervia

description: 3. Hosta scabrinervia (N. Fujita & M.N. Tamura) Yahara & Se.Fujii stat. nov.  
Fig. 10  
 Hosta kikutii var. scabrinervia N. Fujita & M. N. Tamura, Acta Phytotax. Geobot. 59: 34. 2008. Type: JAPAN. Tokushima Pref., Miyoshi-gun, Ohboke, along the river, 13 Jul. 1968, C. Abe 33197 (holotype KYO!).   
Hosta kikutii var. polyneuron sensu Fujita, Acta Phytotax. Geobot. 27: 80. 1976, p.p.  
Phenology.  
Flowering in July.  
Distribution and habitat.  
Japan (Tokushima and Kochi Prefectures). The typical lineage of this species grows in rock crevices in the open habitats of riverbanks along the middle reach of Yoshino River. The upstream lineage (JPN12523-12525, FJS00006, FJS00007) grows on the wet cliffs in the upper reaches of the Yoshino River.  
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.  
Zaratsuki-giboshi (Fujita and Tamura 2008).  
Additional specimens examined.  
 Japan. Kochi Pref.: Nagaoka-gun, Ohtoyo-mura, Isodani, along Yoshino River, 8 Sep. 1958, T. Yamanaka 26222 with fruit (KYO!); Nagaoka-gun, Ohtoyo-cho, Higashidoi, Yoshino River, 4 Jul. 2002, H. Sasaoka FOK-603540 with flowers (MBK0170549!); left bank of Yoshino River, Okubo, Ohtoyo-cho, Nagaoka-gun, 26 Nov. 2017, A. Sakamoto et al. FOS-017749 with fruit (MBK0319724!); ditto, 18 Jul. 2004, M. Matsumoto et al. FOK-067597 with flowers (MBK0087490!); Tosa-gun, Ohkawa-mura, Takano, 24 Jun. 2022, K. Fuse et al. JPN12523 -12525 (FU!); Tosa-gun, Ohkawa-mura, Kawasaki, Jul. 25, 2023, Se. Fujii FJW-50-1, 2 with flowers (MBK0342373!, MBK0342374!); Tosa-gun, Ohkawa-mura, Kogane Waterfall, 23 Jul. 2022, Se. Fujii JPN15231, 15232, with flowers (FU!); ditto, Jul. 25, 2023, Se. Fujii FJW-51-1-4 with flowers (MBK!); Nagaoka-gun, Motoyama-cho, in front of Kizenzan Park, 8 Aug. 1971, H. Takahashi & N. Fujita 214 with flowers and fruit (KYO!);. Tokushima Pref.: Miyoshi-gun, Oboke, 11 Apr. 2011, T. Yahara et al. JPN4080, 4082-4087 sterile (FU!); ditto, 22 Jul. 1967, C. Abe 33157 with fruits (KYO!).   
Note.  
 Fujita and Tamura (2008) distinguished var. Hosta scabrinervia scabrinervia from var. Hosta scabrinervia densinervia by the papillose lower surface of the lateral veins, but some plants of the type locality population have smooth lower lateral vein surfaces. Morphologically, H. scabrinervia is similar to H. tardiva subsp. densinervia but distinguished by the flowering season (July in contrast to August to September in the latter) and anther length (3 mm long vs. 5 mm long). The specimens collected from Kogane Waterfall (JPN15231, etc.) have exceptionally long pedicels (2.9-3.4 cm long), compared to 2-2.7 cm in other specimens. In this aspect, they are similar to H. longipedicellata, but can be distinguished by their flower bracts which remain fresh during flowering (unlike the withering flower bracts of H. longipedicellata). In the original description of H. kikutii var. scabrinervia, Fujita and Tamura (2008) cited specimens from Ehime and Kochi Prefectures, but further studies combining molecular analyses with subsequent morphological observations are required to confirm their identities. As far as examined, the range of H. scabrinervia is restricted to a narrow region in the middle reach of Yoshino River (Fig. 7).
description: Published as part of 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, pp. 137-187 in PhytoKeys 235 on page 137, DOI: 10.3897/phytokeys.235.99140