Research Article |
Corresponding author: Tetsukazu Yahara ( tet.yahara@gmail.com ) Academic editor: Clifford Morden
© 2023 Tetsukazu Yahara, Shun K. Hirota, Seiko Fujii, Yasushi Kokami, Kengo Fuse, Hiroyuki Sato, Shuichiro Tagane, Yoshihisa Suyama.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Yahara T, Hirota SK, Fujii S, Kokami Y, Fuse K, Sato H, Tagane S, Suyama Y (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: 137-187. https://doi.org/10.3897/phytokeys.235.99140
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Japan has 16 native species of the genus Hosta Tratt. (Asparagaceae). A recent study on Hosta based on field surveys and molecular phylogenetic analyses resulted in the discovery of six unknown taxa in Kochi Prefecture, Shikoku Island, southwestern Japan. We aimed to identify these unknown taxa. Therefore, we constructed a finely resolved phylogeny for 320 Hosta samples collected from the Honshu, Shikoku, and Kyushu Islands using multiplex inter-simple sequence repeat genotyping by sequencing (MIG-seq). Based on this phylogenetic analysis and related morphological observations, we describe five new species, H. longipedicellata sp. nov., H. minazukiflora sp. nov., H. polyneuronoides sp. nov., H. samukazemontana sp. nov., and H. takiminazukiflora sp. nov. and one new subspecies, H. takiminazukiflora subsp. grandis subsp. nov. In addition, we propose two new status assignments, H. tardiva subsp. densinervia comb. and stat. nov. and H. scabrinervia stat. nov. We also propose classifying H. kikutii var. tosana as a species, H. tosana. Further studies that combine MIG-seq with careful morphological observations are needed for Hosta plants on all Japanese islands, which may result in the discovery of even more undescribed species.
anacladogenetic speciation, flowering season, MIG-seq, next generation sequencing, reproductive isolation, threatened species
The genus Hosta Tratt. (Asparagaceae) comprises 22–25 species endemic to East Asia and Russia (
Here, we examined the molecular phylogeny and taxonomy of Hosta on Shikoku Island, located east of Kyushu Island, which has the highest diversity of Hosta in Japan. According to
This study was initiated based on the findings of our previous research, which identified Hosta alata Hatus. ex Yahara of Kyushu Island as a new species (
To elucidate the taxonomy of Hosta plants previously identified as H. kikutii in Shikoku, we collected DNA samples of Hosta plants from Shikoku, Kyushu and Honshu. Following a previous study on H. alata (
We collected 320 DNA samples and voucher specimens from 70 localities for 30 taxa of Hosta in Japan (Suppl. material
Total DNA was extracted from the dried leaves using the CTAB method (
The Maximum Likelihood phylogeny of the Japanese species of Hosta based on SNPs was inferred for all samples using RAxML 8.2.10 (
Based on the results of phylogenetic analyses using MIG-seq, we reassessed the morphological traits utilized for classifying Hosta taxa in previous studies (
All raw MIG-seq data were deposited in the DDBJ Sequence Read Archive (DRA) under accession numbers DRA011621, DRA013286, and DRA015301.
A total of 96,556,838 raw reads (301,740 ± 10,362 reads per sample) were obtained from MIG-seq, and 79,861,049 reads (249,566 ± 8,620 reads per sample) were used for further analysis. After de novo SNP detection and filtering, 13,328 SNPs on 2,060 loci selected by R=0.3 were used for the phylogenetic reconstruction of all samples. Phylogenetic analyses of infrageneric groups and STRUCTURE analyses were performed using different SNP datasets selected by R=0.3 and R=0.5, respectively (see Suppl. material
In the following descriptions of the results obtained from phylogenetic analyses, we employ new names as determined by the conclusions of this study for five new species (H. longipedicellata sp. nov., H. minazukiflora sp. nov., H. polyneuronoides sp. nov., H. samukazemontana sp. nov., and H. takiminazukiflora sp. nov.), one new subspecies (H. takiminazukiflora subsp. grandis subsp. nov.), and two new taxonomic status assignments (H. tardiva subsp. densinervia comb. & stat. nov. and H. scabrinervia stat. nov.) (See the Taxonomy section for authorities of these new names). Hosta tardiva subsp. densinervia and H. scabrinervia are based on H. kikutii var. densinervia and var. scabrinervia, respectively (
In the Maximum Likelihood tree reconstructed using the MIG-seq dataset at R=0.3 (Fig.
In the full data set tree (Fig.
The overall topology of the Maximum Likelihood tree reconstructed using the MIG-seq dataset at R=0.5 (not shown) was identical to Fig.
The monophyletic relationship between H. tardiva subsp. tardiva and subsp. densinervia was supported by a 92% bootstrap value (Fig.
STRUCTURE analysis for Clade 1 indicated that ΔΚ was highest at K=3 (Fig.
Population genetic structure of Hosta Clade 1 and Clade 4 A, E changes of ΔΚ with K in Clades 1 and 4, respectively B a diagram showing the result of STRUCTURE analysis for Clade 1 at K=3 C a diagram showing the result of hierarchical STRUCTURE analysis for H. polyneuronoides and H. tardiva subsp. densinervia D diagrams showing the results of hierarchical STRUCTURE analysis for H. shikokiana and six related species at K=3 and 5 F diagrams showing the results of STRUCTURE analysis for Clade 4 at K=2, 3, and 8.
Clade 4 consisting of H. tosana was more fully examined (Fig.
STRUCTURE analysis for Clade 4 showed that ΔΚ was highest at K=3 and second highest at K=8 (Fig.
We observed five populations of H. tardiva subsp. densinervia at elevations from 90 m to 900 m (Fig.
Maps of collection locations for Hosta species A Shikoku Island (black) in relation to Japan B detail of Shikoku Island with population locations for some species and varieties C details of collection locations for H. polyneuronoides (solid circles) and H. scabrinervia (an open square), and approximate ranges (circles) of H. minazukiflora (M), H. longipedicellata (L), H. samukazemontana (Sa), H. shikokiana (Sh), and H. takiminazukiflora (T). Considering conservation concerns, we refrained from disclosing the precise collection locations of these five species. The contour map was reproduced from a webpage. (https://maps.gsi.go.jp/#11/33.726624/133.351364/&base=english&ls=english&disp=1&vs=c1g1j0h0k0l0u0t0z0r0s0m0f1&d=m) in accordance with the usage regulations of the Geospatial Information Authority of Japan.
Hosta polyneuronoides is morphologically similar to H. tardiva subsp. densinervia, but is distinguished by smaller inflorescence (3–10 flowers per inflorescence vs. more than 20 per inflorescence in H. tardiva subsp. densinervia) and shorter anther sacs (3.5–4 mm long vs. 5 mm long). Hosta polyneuronoides tends to flower earlier than H. tardiva subsp. densinervia: flowering specimens of H. tardiva subsp. densinervia were collected between August 13 and September 27, whereas flowering specimens of H. polyneuronoides were collected between July 25 and August 20 (see specimen records cited in the Taxonomy section). While H. tardiva subsp. densinervia was observed to grow on soil or rocks in open habitats along riverbanks, H. polyneuronoides was found to grow on wet rocks in shaded habitats along streams.
The type locality of H. scabrinervia (Fig.
Two specimens (MBK0319724 and MBK0179549) collected at an elevation of 200 m along the middle reach of the Yoshino River, at 7.5–9 km south of the type locality of H. scabrinervia, respectively, were morphologically identical to H. scabrinervia in the type locality (Fig.
In addition to H. scabrinervia, five other species (H. minazukiflora, H. longipedicellata, H. shikokiana, H. samukazemontana, and H. takiminazukiflora) are densely distributed within or near the range of Hosta polyneuronoides (Fig.
The type locality of H. minazukiflora (M in Fig.
A population of H. polyneuronoides is located at an elevation of 480 m at 7.5 km north of the type locality of H. minazukiflora (at an elevation of 280 m), both growing on rocks along the stream of a tributary of the Yoshino River (see M in Fig.
Measurements of 14 morphological traits in nine taxa of Hosta in Shikoku. Aspect ratio is defined as leaf length divided by leaf width.
H. t. densinervia | H. polyneuronoides | H. scabrinervia | H. minazukiflora | H. shikokiana | H. t. takiminazukiflora | H. t. grandis | H. longipedicellata | H. samukazemontana | |
---|---|---|---|---|---|---|---|---|---|
Leaf blade length | 12–23 cm | 7.5–28.5 | 16.6–32 | 11.8–17 | 8.1–9.3 | 11–26.5 | 22–25 | 13.4–30.2 | 7–22 |
Leaf blade width | 3.2–11.5 cm | 3.3–15.3 | 7.5–14.8 | 2.9–6.2 | 2.9–5.0 | 3.6–10.5 | 13–14 | 5.4–11.8 | 3.6–10.7 |
Aspect ratio | 2–3.6 | 0.9–2.9 | 1.6–3 | 2.4–4.3 | 1.9–2.9 | 2.1–3.3 | 1.7–1.8 | 2.2–3 | 1.8–2.9 |
Lateral veins | 6–11 pairs | 8–9 | 7–15 | 6–9 | 5–7 | 6–10 | 12–13 | 7–10 | 6–12 |
Petiole length | 9–36 cm | 5–40 | 5.5–47 | 8–19 | 6.5–8.5 | 3.4–22 | 35–38 | 15–34.3 | 3.2–14.5 |
Scape length | 27–44 cm | 15–51 | 28.5–45 | 18–37 | 20.5–29 | 8.6–28.5 | 31–36 | 26.5–32.5 | 20–43 |
Raceme length | 6–9 cm | 4.3–9 | 5–12 | 10–15 | 5.3–13 | 5.9–18.5 | 12–15.5 | 7.6–9 | 7–9 |
Flower number | 15–25 | 3–10 | 15–17 | 3–6 | 2–10 | 4–18 | 10–12 | 7–15 | 5–18 |
Floral bract length | 2–3 cm | 1.2–3.1 | 2–4.6 | 1.3–1.6 | 1.3–2.2 | 2–4.7 | 2.8–4.3 | 2–2.5 | 1.7–2.1 |
Floral bract width | 0.4 cm | 0.1–0.8 | 0.4–1.3 | 0.2–0.4 | 0.1–0.3 | 0.2–0.7 | 0.4–0.5 | 0.3–0.4 | 0.3–0.5 |
Pedicel length | 0.8–1.8 cm | 0.6–1.3 | 1.5–3.4 | 1.1–1.2 | 0.6–1.5 | 1.4–2.5 | 1.9–2.0 | 2.5–3.3 | 1–1.8 |
Perianth length | 3.9–5.3 cm | 4.5 | 5–6.8 | 4.1–4.7 | 4.4–5.0 | 4.0–5.7 | 3.8–4.9 | 4.4–6.4 | 4.5–5 |
Perianth lobe length | 1.1–2.0 cm | 0.7–1.2 | 0.8–1.6 | 1.2–1.4 | 1.4–1.7 | 1.2–1.8 | 1.2–1.3 | 1–1.5 | 1–1.3 |
Perianth lobe width | 0.4–0.8 cm | 0.4–1 | 0.5–1 | 0.6–0.8 | 0.8–1.0 | 0.5–1.0 | 0.7–0.8 | 0.6–0.9 | 0.7–0.8 |
Anther-sac length | 5 mm | 3.5–4 | 3 | 3 | 2.5–3 | 2–3 | 3 | 3 | 3 |
The type locality of Hosta takiminazukiflora was only 14 km west of that of H. minazukiflora (T and M in Fig.
A small population of H. takiminazukiflora subsp. grandis (JPN6487–89, JPN12518–12521) was found alongside a larger population of H. takiminazukiflora subsp. takiminazukiflora (JPN6483–86 and JPN6490), with the former growing upright from the soil between the rocks under the waterfall and the latter deflected from the wet cliff of the waterfall. Both subspecies were found in flower on June 24, 2021.
Hosta takiminazukiflora subsp. grandis (Fig.
The type locality of H. longipedicellata is located at 22.5 km west of that of H. takiminazukiflora and the two species are distributed in two mountain regions separated by an upper reach of the Yoshino River (L and T in Fig.
The type locality of H. samukazemontana (Sa in Fig.
Along the Kamegamori forest road, we collected both H. samukazemontana (JPN6325, with flower buds on June 22, 2021) and H. polyneuronoides (JPN6342 and 6361, without flower buds on June 22, 2021). The two populations were approximately 500 m apart along the road. Flowering specimens of H. samukazemontana were collected from Mt. Kanpu on June 19, July 24 and July 25 (see specimens cited in the Taxonomy section) and flowering specimens of H. polyneuronoides from Mt. Ishizuchi, located in the vicinity of Mt. Kanpu and the Kamegamori forest road, were collected on July 28 and August 7. Morphologically, H. samukazemontana is distinguished from H. polyneuronoides by deflected scapes upwardly curved at the tip (vs. straight) and anther sacs 3 mm long (vs. 3.5–4 mm long).
Two populations of the Kagami River lineage of H. tosana were observed on cliffs along the Kagami River in Kochi City. This location is 50 km SSW of the population of H. tosana var. tosana along the Monobe River. The specimen of the Kagami River lineage with flowers (Fig.
In the Befu Valley of Kami City, we collected H. tosana var. caput-avis from two populations: the upstream population (JPN6524–6526; Fig.
In Yanase, Aki-gun, the type locality of H. tosana var. caput-avis, we only found H. tosana var. caput-avis. Four samples from Yanase and an additional sample from its vicinity formed a clade with a bootstrap support of 100%. This clade was sister to another clade with a bootstrap support of 100%, comprising H. tosana var. caput-avis from Kami City and var. tosana from Kami City and three other localities including its type locality at Kajigamori (Fig.
Genetic divergence between taxa, measured by FST (Table
Genetic divergence between species or subspecies measured by FST. The abbreviations in the first line represent taxon names from H. t. densiflora (H. tardiva subsp. densiflora) to H. tosana var. tosana, and the last capu represents H. tosana var. caput-avis.
dens | poly | shi1 | shi2 | mina | grand | taki | samu | scab | long | Kaga | tosa | capu | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
H. t. tardiva | 0.16 | 0.15 | 0.29 | 0.32 | 0.33 | 0.38 | 0.27 | 0.30 | 0.23 | 0.31 | 0.44 | 0.40 | 0.40 |
H. t. densinervia | 0.07 | 0.18 | 0.18 | 0.18 | 0.25 | 0.16 | 0.16 | 0.12 | 0.19 | 0.37 | 0.34 | 0.33 | |
H. polyneuronoides | 0.14 | 0.12 | 0.12 | 0.18 | 0.14 | 0.10 | 0.09 | 0.15 | 0.30 | 0.29 | 0.28 | ||
H. shikokiana 1 | 0.17 | 0.22 | 0.30 | 0.19 | 0.24 | 0.18 | 0.24 | 0.41 | 0.36 | 0.36 | |||
H. shikokiana 2 | 0.27 | 0.38 | 0.17 | 0.31 | 0.17 | 0.24 | 0.50 | 0.40 | 0.41 | ||||
H. minazukiflora | 0.38 | 0.18 | 0.33 | 0.16 | 0.25 | 0.52 | 0.43 | 0.42 | |||||
H. t. grandis | 0.14 | 0.37 | 0.22 | 0.28 | 0.51 | 0.42 | 0.43 | ||||||
H. t. takiminazukiflora | 0.18 | 0.14 | 0.17 | 0.37 | 0.33 | 0.32 | |||||||
H. samukazemontana | 0.17 | 0.25 | 0.49 | 0.41 | 0.41 | ||||||||
H. scabrinervia | 0.17 | 0.38 | 0.34 | 0.33 | |||||||||
H. longipedicellata | 0.42 | 0.37 | 0.36 | ||||||||||
H. tosana Kagami River lineage | 0.15 | 0.16 | |||||||||||
H. tosana var. tosana | 0.10 |
Our phylogenetic analysis of Japanese Hosta species showed that H. tardiva subsp. densinervia and H. scabrinervia, previously classified as H. kikutii var. densinervia and var. scabrinervia by
Among taxa previously treated as varieties of H. kikutii, H. tardiva subsp. densinervia formed a clade with H. tardiva subsp. tardiva, supported by a bootstrap value as high as 99% (Fig.
Considering significant morphological differences, it is puzzling that the cluster of H. tardiva subsp. tardiva is a single offshoot of H. tardiva. Consequently, if H. tardiva subsp. tardiva is separated, H. tardiva subsp. densinervia cannot be considered monophyletic. The result of the STRUCTURE analysis provides a clue to explain this puzzling result. Ten samples of H. tardiva subsp. densinervia collected from the lower reach of the Niyodo River exhibit a mixture of two genetic identities: one identity is dominant in H. tardiva subsp. tardiva, and another identity is dominant in H. polyneuronoides, as well as in other samples of H. tardiva subsp. densinervia, including three samples from the type locality population in Tokushima Prefecture. In the Maximum Likelihood tree (Fig.
Hosta tardiva is likely an instance of anacladogenetic speciation, wherein a new species originates through budding, initially rendering the ancestral taxon paraphyletic. In such instances, it becomes necessary to acknowledge a paraphyletic subspecies when both derived and ancestral lineages display distinct diagnostic traits that set them apart (
Hosta tardiva subsp. densinervia and H. scabrinervia were initially described as H. kikutii var. densinervia and var. scabrinervia by
In the STRUCTURE analysis, H. scabrinervia exhibited a mixture of two genetic identities, one identity dominated in H. tardiva subsp. densinervia and another identity shared by seven species. This result seems to suggest a hybrid origin of H. scabrinervia. Among the seven species, H. takiminazukiflora subsp. takiminazukiflora is most similar to H. scabrinervia; however, it can be distinguished by several characteristics. It has purplish green or purple flower bracts instead of white or purplish white in H. scabrinervia, and its petioles are shorter (3–22 cm long as opposed to (20–)22–40 cm long). Hosta polyneuronoides is also similar to H. scabrinervia but can be distinguished by longer anther-sacs (3.5–4 mm long vs. 3 mm in H. scabrinervia). If H. scabrinervia originated from a hybridization, H. polyneuronoides and H. takiminazukiflora subsp. takiminazukiflora are most likely candidates of parental species. While available specimen records showed that H. polyneuronoides flowers earlier (July 25 to August 20) than H. scabrinervia (July 13 to July 25), these flowering records are close and two taxa may be able to hybridize in late July. However, at K=5 in the hierarchical STRUCTURE analysis, H. scabrinervia exhibited a unique genetic identity depicted by light blue, and did not exhibit another identity depicted by orange, which is dominant in H. takiminazukiflora subsp. takiminazukiflora. This result suggests that genetic variation accumulated after the origin of H. scabrinervia, even if it originated through a hybridization event between H. polyneuronoides and H. takiminazukiflora subsp. takiminazukiflora. In the SplitsTree, H. scabrinervia was separated from H. takiminazukiflora, which is closely related to H. longipedicellata, but connected with H. polyneuronoides. This relationship as well as the result of STRUCTURE analysis at K=3 suggest that H. scabrinervia is a species separated from H. takiminazukiflora and H. polyneuronoides, but could have a history of introgression with H. polyneuronoides.
Hosta polyneuronoides is closely related to H. tardiva, but its monophyly was supported by a bootstrap value of 82% (Fig.
Our phylogenetic analysis also indicated that another morphologically distinct species, H. shikokiana, belonged to Clade 1. Due to its morphological distinctiveness,
Our phylogenetic analyses, morphological observations, and field investigations have led to the discovery of three additional new species: H. samukazemontana, H. longipedicellata, and H. takiminazukiflora. Among them, H. samukazemontana occupies an intermediate position between a clade consisting of H. shikokiana, H. minazukiflora, and H. sp. 3, and another clade comprising H. tardiva subsp. tardiva, H. tardiva subsp. densinervia, and H. scabrinervia (Fig.
Hosta longipedicellata and H. takiminazukiflora formed a clade with a bootstrap support of 100%, and this clade, along with another clade comprising seven other species, originated at the base of Clade 1. This phylogenetic relationship supports the differentiation of H. longipedicellata and H. takiminazukiflora from the seven other species. We propose treating them as two distinct species, taking into account their genetic differences (Fig.
The divergence between the two sympatric subspecies of H. takiminazukiflora is intriguing. Hosta takiminazukiflora subsp. grandis is characterized by several distinct features including a cordate leaf base, a glaucous lower surface, green petioles and erect scapes without purple dots. These characteristics remain consistent under fertilized cultivation. In the Maximum Likelihood tree (Fig.
Notably, the FST values between H. takiminazukiflora subsp. grandis and the other species were relatively high, ranging from 0.22 to 0.51, while FST values between the two subspecies were as low as 0.09. This suggests that H. takiminazukiflora subsp. grandis may have originated through hybridization between an unknown species and a lineage of H. takiminazukiflora subsp. takiminazukiflora. Further investigations are necessary to test this hypothesis and elucidate the origin and taxonomic status of H. takiminazukiflora subsp. grandis.
While Clade 1 was classified into nine separate species, Clade 4 was considered to be a single species, H. tosana. Following the earlier classification proposed by
Additionally, we discovered another lineage designated as the Kagami River lineage, which was monophyletic and distinct from other lineages. The FST values between the Kagami River lineage and the two “varieties” were 0.15 and 0.16, respectively, indicating significant differentiation of the Kagami River lineage from the two “varieties”. It is likely that the Kagami River lineage can be distinguished as an infraspecific taxon. However, since H. tosana is widely recorded in the eastern part of Shikoku, further studies encompassing the entire range of H. tosana are needed to elucidate the taxonomic status of the Kagami River lineage.
Remarkably, seven species within Clade 1 (H. longipedicellata, H. minazukiflora, H. samukazemontana, H. scabrinervia, H. shikokiana, H. takiminazukiflora, and H. polyneuronoides) are densely distributed in the upper reaches and headwaters of the Yoshino River (Fig.
In the Taxonomy section, we provide a key to the taxa and update the taxonomy of Hosta species found on Shikoku Island, belonging to Clades 1 and 4. This update includes descriptions of six new taxa, encompassing five new species and one new subspecies, along with revised status for two existing taxa. However, we have refrained from revising the taxonomy of Clade 2, Clade 3, and Clade 6, pending further studies. Further comprehensive studies combining MIG-seq with meticulous morphological observations are necessary for these clades.
Below, we first treat H. tardiva subsp. tardiva and H. tardiva subsp. densinervia comb. & stat. nov., located on the top of the Maximum Likelihood tree for Clade 1 (Fig.
1 | Bracts ascending or spreading before flowering | Clade 2, 3, and 6; not treated below |
– | Bracts tightly closed before flowering | 2 |
2 | Scapes deflected and gently bent like a bow, curved upwards at the tip | 3 |
– | Scapes straight | 4 |
3 | Perianths 4.5–5 cm long, whitish. Flower bracts whitish purple, 1.7–2.1 cm long. | 8. Hosta samukazemontana |
– | Perianths 6.1–6.9 cm long, purple. Flower bracts whitish green, 2.2–5.2 cm long | 9. Hosta tosana |
4 | Leaf margin strongly undulated. Leaves with decurrent to winged petioles, lustrous below when dried | 4. Hosta shikokiana |
– | Leaf margin either not undulated or weakly undulated. Leaves not or only slightly decurrent to petioles, not lustrous below when dried | 5 |
5 | Perianths purple or lavender; inside veins distinct | 6 |
– | Perianths whitish; inside veins indistinct | 7 |
6 | Perianths purple; five distinct veins inside each lobe | 1A. Hosta tardiva subsp. tardiva |
– | Perianths lavender; three distinct veins inside each lobe | 5. Hosta minazukiflora |
7 | Anthers 3.5–5 mm long | 8 |
– | Anthers 2.5–3 mm long | 9 |
8 | Flowers more than 20 per scape. Anthers 5 mm long | 1B. Hosta tardiva subsp. densinervia |
– | Flowers 3–10 per scape. Anthers 3.5–4 mm long | 2. Hosta polyneuronoides |
9 | Leaf blades glaucous abaxially, broadly ovate | 6A. Hosta takiminazukiflora subsp. grandis |
– | Leaf blades light green abaxially, not glaucous, ovate or oblong-ovate | 10 |
10 | Flower bracts 2–2.5 cm long, withering during flowering. Leaf veins papillose on abaxial surface | 7. Hosta longipedicellata |
– | Flower bracts (2–)2.5–4.6 cm long, fresh during flowering | 11 |
11 | Flowers 15–20 per inflorescence. Flower bracts white or purplish white. Petioles (20–)22–40 cm long. Leaf veins papillose or smooth on abaxial surface | 3. Hosta scabrinervia |
– | Flowers 4–13 per inflorescence. Flower bracts purplish green or purple at anthesis. Petioles 3–22 cm long. Leaf veins smooth on abaxial surface | 6. Hosta takiminazukiflora subsp. takiminazukiflora |
Japan. Prov. Awa (Ehime Pref.): tractu Myōtō, in oppido Kamomyō, n.d., J. Nikai 1377 (holotype TI, n.v.).
August to September.
Japan (Shikoku Island). This species is widely distributed in Shikoku and typically thrives on herbaceous slopes near villages. It is cultivated in Honshu but often naturalized when it escapes cultivation.
Using criterion D1 for IUCN Red List categories (
Nankai-giboshi (
Japan. Kochi Pref.: Takaoka-gun, Kubokawa-cho, 8 Aug. 2001, Se. Fujii 8725 (JPN10003, FU!), ditto, 23 Aug. 2002, Se. Fujii 9271 (JPN10002, FU!); Cultivated at Makino Botanical Garden (32 specimens listed in the Suppl. material
In Shikoku, it usually grows near mountain villages, suggesting that its wild populations escaped from cultivation.
Hosta kikutii var. densinervia N. Fujita & M. N. Tamura, Acta Phytotax. Geobot. 59: 34 (2008); Tamura & Fujita in Iwatsuki et al., Fl. Jap. IVb: 143 (2016). Type. JAPAN, Shikoku: Tokushima Pref, Miyoshi-gun, Ikeda-cho, Shikino-kami Ferry, 27 Sep. 1965, with flowers, S. Takafuji 253 (holotype KYO!, isotype KYO!).
Hosta kikutii var. polyneuron sensu Fujita, Acta Phytotax. Geobot. 27: 80. 1976, p.p.
Mid-August to September.
Japan (Ehime, Kagawa, Kochi, and Tokushima Prefectures). This subspecies is distributed in the lower reaches of the Yoshino River, the middle and lower reaches of the Niyodo River, the headwater of the Shinjyo River (near the headwaters of the Shimanto River), and the lower reaches of the Shimanto River (Fig.
Using criterion D1 for IUCN Red List categories (
Sudare-giboshi (
Japan. Ehime Pref.: Kamiukena-gun, Omogokei, 13 Aug. 1970, N. Fujita 269, with flowers (KYO!); Saijyo City, 450 m elev., 6 Aug. 1971, H. Takahashi & N. Fujita 273 with young flower buds (KYO!); Nii-gun, 500 m elev., 30 Aug. 1955, G. Murata 9233 with flowers (KYO!). Kagawa Pref.: Mt. Otaki, 24 Sep. 1961, S. Sakaguchi s.n. with flowers (KYO!). Kochi Pref.: Agawa-gun, Niyodogawa-cho, Kuki, 80 m elev., 18 Aug. 2020, T. Yahara et al. JPN1255, 1258, 1263 with flowers (FU!); ditto, in the headwater of a tributary of Shinjyo River, 900 m elev., cultivated in Makino Botanical Garden, 8 Apr. 2021, T. Yahara et al. JPN3929 sterile (FU!); Agawa-gun, Ino-cho, Kashiki, 40 m elev., 20 Aug. 2020, T. Yahara et al. JPN1331–1333 with flowers (FU!); Takaoka-gun, Ochi-cho, Kataoka, 50 m elev., 20 Aug. 2020, T. Yahara et al. JPN1375–1377 with flowers (FU!); ditto, Tokoroyama, 13 Sep. 1962, G. Murata 17106 and 17107 with flowers (KYO!); Hata-gun, Nakamura-cho, along the Shimanto River, 20 Aug. 1913, Z. Tashiro s.n. with flowers (KYO!). Tokushima Pref.: Miyoshi City, Shikino-kami, 90 m elev., 11 Apr. 2021, sterile, T. Yahara et al. JPN4071, 4072, and 4075 (FU!); Ikeda-cho, along the Yoshino River, 16 Sep. 1971, C. Abe 43049 with flowers (KYO!); Miyoshi-gun, Minawa-mura, Kawasaki, along the Iya River, 8 Sep. 1958, T. Yamanaka 26270 with flowers (KYO!).
This subspecies is morphologically more similar to H. polyneuronoides, rather than to H. tardiva subsp. tardiva.
Hosta polyneuronoides is distinguished from H. tardiva subsp. densinervia in having 3–10 flowers per inflorescence (in contrast to 15–25 in subsp. densinervia) and anthers 3.5–4 mm long (compared to 5 mm long).
Herbs perennial. Leaves basal, spiral, long petiolate, 3–15 per ramet; blades ovate or oblong-ovate, 7.5–28.5 cm long, 3.3–15.3 cm wide, 0.9–2.9 times longer than width, thinly papery, glabrous on both surfaces, base cuneate to subcordate, apex acute to short acuminate, margin entire, veins 8–9 pairs, smooth on the lower surface; petioles 5–40 cm long, narrowly winged, 0.3–0.5 cm wide, glabrous. Scape 15–51 cm long, rachis terete, bract lanceolate, 4 cm long, 0.3–0.5 cm wide, light green, glabrous. Raceme 4.3–9 cm long, 3–10-flowered; flower bracts vivid (not withering) in anthesis, erect or diagonally spreading, whitish green, oblong-lanceolate, boat-shaped, 1.2–3.1 cm long, 0.1–0.8 cm wide, membranous, glabrous, apex acuminate. Flowers not fragrant, 5.7–6.0 cm long; pedicels 0.6–1.3 cm long, glabrous. Perianths white or very pale purple-white, funnel-form, 2.1–4.9 cm long, glabrous, 6-lobed; tube abruptly dilated from apical 2/3, lobes narrowly triangular, 0.7–1.2 cm long, 0.4–1 cm wide, apex acute. Stamens 6, 0.1–0.4 cm exerted from perianth; filaments white, free, 4.5–4.8 cm long, glabrous, anthers purple to yellow when fresh, dark blue-grey to light yellow when dried, 3.5–4 mm long. Ovary ellipsoid, 0.5 cm long, glabrous style 5.5–5.7 cm long, upwardly curved at the distal part, subequal to 1.5 cm exerted from perianth, glabrous, stigma capitate. Capsules or seeds not observed.
Flowering from July to August.
Japan (Kochi and Ehime Prefectures). Hosta polyneuronoides grows on open or shaded rocks and rock cliffs along rivers in the upper reaches and headwaters of the Yoshino River, and on the rocky ridgeline from Mt. Ishizuchi to Mt. Komochi-gongen and its vicinity.
This subspecies was named for its resemblance to H. tardiva subsp. densinervia identified as Hosta kikutii var. polyneuron by
Using criterion D1 for IUCN Red List categories (
Oku-sudare giboshi (new).
Japan. Ehime Pref.: Niihama City, Mt. Higashi-akaishi, 970 m elev., 21 Jun. 2021, T. Yahara et al. JPN6269–6271 sterile (FU!); ditto, 1040 m elev., 21 Jun. 2021, T. Yahara et al. JPN6153–6156 sterile (FU!); Mt. Ishizuchi, 28 Jul. 1972, S. Takafuji 799 with flowers (KYO!); Kamiukena-gun, Mt. Ishizuchi, 1600 m elev., 23 Jun. 2021, T. Yahara et al. JPN6390 sterile (FU!); ditto, 1980 m elev., 23 Jun. 2021, T. Yahara et al. JPN6407 sterile (FU!); Saijyo City, Mts. Ishizuchi, from Yoake-toge to Mt. Nishinokanmuri-dake, 1600 m elev., 7 Aug. 1971, H. Takahashi & N. Fujita 226 with flowers (KYO!). Kochi Pref.: Nagaoka-gun, Motoyama-cho, Along Asemi River, 480 m elev., 19 Aug. 2020, T. Yahara et al. JPN1327–1329 with flower buds (FU!); Tosa-gun, Okawa-mura, 570 m elev., 24 Jun. 2021, T. Yahara et al. JPN6493–6495 sterile (FU!); Tosa-gun, Ohkawa-mura, Kawasaki, 400 m elev., 24 Jun. 2021, T. Yahara et al. JPN6501–6503 with flower buds (FU!); Tosa-gun, Ohkawa-mura, Takano, 24 Jun. 2022, K. Fuse et al. JPN12529, 12530, 12532, 12535 sterile (FU!); Tosa-gun, Ohkawa-mura, near Okina Waterfall, 443 m elev., Jul. 25, 2023, Se. Fujii, FJW49-1, 2 with flowers (MBK!); Tosa-gun, Tosa-cho, 24 Jun. 2022, K. Fuse et al. JPN12506-12508 sterile (FU!); Agawa-gun, Ino-cho, 750 m elevation, 23 Jun. 2021, T. Yahara et al. JPN6449–6451 sterile (FU!); Agawa-gun, Ino-cho, 900 m elevation, 23 Jun. 2021, T. Yahara et al. JPN6446–6448 sterile (FU!); Agawa-gun, Ino-cho, Kamegamori Forest Road, 1650 m elev., 22 Jun. 2021, T. Yahara et al. JPN6342, 6361 sterile (FU!); ditto, Mt. Komochi-gongen, 29 Jun. 2022, K. Fuse et al. JPN12663, 12664 sterile (FU!); Agawa-gun, Ino-cho, Ohmori-gawa dam, 755 m elev., 3 May 2022, Se. Fujii JPN12427 sterile (FU!); Agawa-gun, Ino-cho, Terakawa-Ohdaru, 29 Jun. 2022, K. Fuse et al. JPN12666–12668 sterile (FU!). The sterile specimens were identified using MIG-seq.
Two specimens collected from Mt. Ishizuchi (S. Takafuji 799 and H. Takahashi & N. Fujita 226) were cited in the original description of H. shikokiana (
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.
Flowering in July.
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.
Using criterion D1 for IUCN Red List categories (
Zaratsuki-giboshi (
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!).
Japan. Ehime Pref., Mt. Higashi-akaishi, 7 Aug. 1957, T. Yamanaka 22475 (holotype KYO!).
Flowering in July and fruiting in August.
Japan (Ehime and Kochi Prefectures) (endemic). This species grows in open habitats on the rocky ridgeline of Mt. Higashi-akaishi and its surrounding areas on Shikoku Island.
Using criterion D1 for IUCN Red List categories (
Shikoku-giboshi (
Japan. Ehime Pref.: Mt. Higashi-akaishi, 15 Jul. 1952, T. Yamanaka 8901 with flowers (KYO!); ditto (as Mt. Akaishi), 9 Jul. 1928, G. Koidzumi s.n. with flower buds (KYO!); ditto, 1650 m elev., 21 Jun. 2021, T. Yahara et al. JPN6197, 6228, 6239, 6249, and 6252 with flower buds (FU!); ditto, 1640 m elev., 14 Jul. 1960, K. Tsuchiya 500 with flowers (KYO!); ditto, Mt. Hachimaki (a peak of Mts. Higashi-akaishi), 22 Jul. 2022, Se. Fujii JPN9953, 31 Jul. 2022, Se. Fujii JPN9954 with flowers (FU!); derived from Mt. Higashi-akaishi, cultivated in Makino Botanical Garden, 8 Apr. 2021, T. Yahara & Se. Fujii JPN3939–3942 sterile (FU!); between Mt. Higashiakaishi and Mt. Hutatsudake, 1600 m elev., 8 Sep. 1961, G. Murata 14981 with fruit (KYO!); ditto, cultivated stock of G. Murata 14981, G. Murata s.n. with flowers (KYO!). Kochi Pref.: Mt. Shiraga (cultivated stock), T. Yahara & Se. Fujii JPN3937, 8 Apr. 2021, sterile (FU!); ditto, Se. Fujii JPN9955, 23 Jul. 2021 with flowers (FU!).
The following specimens cited by
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).
Japan. Kochi Pref.: Nagaoka-gun, Motoyama-cho, Asemi River, 25 Jun. 2017, Se. Fujii & K. Yabe FOS-012016 with flowers (holotype MBK0318414!).
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.
Flowering from mid to late June and fruiting in August.
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.
The specific epithet was derived from the flowering season in June. Minazuki refers to June in Japanese.
Using criterion D1 for IUCN Red List categories (
Minazuki-giboshi (new).
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!).
Hosta minazukiflora is sister to H. shikokiana (Figs
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).
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!).
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).
Flowering in late June to early August.
Japan (Kochi Prefecture: Tosa County, endemic to Mt. Inamura, Mt. Higashikado, and the surrounding area). It grows on cliffs.
A specific epithet is derived from its habit of growing on rock cliffs (called ‘taki’ in Kochi dialect) and flowering in June (Minazuki).
Using criterion D1 for IUCN Red List categories (
Taki-minazuki-giboshi (new).
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!).
The clade comprising this species and H. longipedicellata is sister to all the other species in Clade 1 (Fig.
Hosta takiminazukiflora subsp. grandis is distinguished from subsp. takiminazukiflora in having scapes 31–36 cm long (compared to 8.6–28.5 cm long in subsp. takiminazukiflora), broader leaf blades (13–14 cm wide compared to 3.6–10.5 cm wide), cordate leaf base (vs. cuneate to obtuse), glaucous lower leaf surface, lateral veins 12–13 pairs (as opposed to 6–10 pairs), and petioles green, not dotted with purple.
Japan. Kochi Pref.: Tosa-gun, Tosa-cho, along Seto River, 24 Jun. 2021, T. Yahara et al. JPN6487 with flowers (holotype FU!).
Herbs perennial. Leaves basal, spiral, long petiolate, 3–5 per ramet; blades oblong-ovate, 22–25 cm long, 13–14 cm wide, 1.7–1.8 times longer than width, thinly papery, glabrous on both surfaces, base usually cordate, often decurrent, apex acuminate, margin entire, veins in 12–13 pairs, smooth or slightly papillose on the lower surface; petioles 35–38 cm long, narrowly winged, wing 0.3 cm wide, glabrous. Scape 31–36 cm long, terete. Raceme 12–15.5 cm long, 4–18-flowered; flower bracts vivid (not withering) in anthesis, erect, purplish light green, oblong-lanceolate, boat-shaped, 2.8–4.3 cm long, 0.4–0.5 cm wide, papery, glabrous, apex acuminate. Flowers not fragrant; pedicels 1.9–2 cm long, pale purple, glabrous; perianths 3.8–4.9 cm long, funnel-form, glabrous, 6-lobed, pale blue-purple outside, almost white to pale purple inside, midveins faintly purplish adaxially; tube dilated from apical 2/3, lobes oblong-triangular, 1.2–1.3 cm long, 0.7–0.8 cm wide, apex acute. Stamens 6, ca. 0.5 cm exerted from perianth; filaments 4.3–4.5 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 4.5–5.1 cm long, upwardly curved at the distal part, ca. 1 cm exerted from perianth, glabrous, stigma capitate. Capsules or seeds not observed.
Flowering in late June.
Japan (Kochi Prefecture) (endemic). This species grows on soil near waterfalls, whereas subsp. takiminazukiflora grows on rock cliffs.
The specific epithet is derived from its larger plant size rather than that of the typical subspecies.
Using criterion D1 for IUCN Red List categories (
Setogawa-giboshi (new).
Japan. Kochi Pref.: Tosa-gun, Tosa-cho, along Seto River, 24 Jun. 2021, T. Yahara et al. JPN6488–6489 with flowers (FU!); ditto, 24 Jun. 2022, K. Fuse et al. JPN12518–12521 with flowers (FU!).
In the type locality, subsp. grandis grows side by side with subsp. takiminazukiflora, and both subspecies flower simultaneously in late June, but the two subspecies are morphologically distinct and subsp. grandis formed a monophyletic group significantly separated from the sympatric population of subsp. takiminazukiflora. Therefore, subsp. grandis appears to be an evolutionary distinct lineage. This lineage is of particular interest as a research material for studying rapid speciation under disruptive selection and also serves as a valuable resource for breeding Hosta cultivars. Taking into account these characteristics, as well as its morphological distinctiveness, we distinguish it as a subspecies. Due to its limited population size, conservation measures are urgently necessary.
Hosta longipedicellata is similar to H. scabrinervia, but distinguished by its flower bracts 2–2.2 cm long, withering during flowering (compared to (2–)2.2–4.6 cm long, fresh during flowering), smaller and narrower leaf blades (compared to up to 25 ×15 cm), and the occurrence at elevations at 1700–1750 m (in contrast to at 90–550 m).
Japan. Kochi Pref.: Tosa-gun, Hongawa-mura, Mt. Tsutsujo, 1750 m elev., 1 Aug. 2006, S. Kobayashi & Y. Kurahashi FOK-077809 with flowers (holotype MBK0164413!).
Herbs perennial. Leaves basal, spiral, long petiolate, 3 per ramet; blades ovate or oblong-ovate, 13.4–30.2 cm long, 5.4–11.8 cm, 2.2–3 time longer than wide, thinly papery, glabrous on both surfaces, base rounded to subcordate, apex acute to short acuminate, margin entire, veins in 7–10 pairs, papillose on the lower surface; petioles 15–34.3 cm long, narrowly winged, wing 0.1–0.2 cm wide, glabrous. Scape 26.5–32.5 cm long, terete. Raceme 7.6–9 cm long, 7–15-flowered; flower bracts withering in anthesis, erect, purplish light green in the upper part, light green in the lower part, oblong-lanceolate, boat-shaped, 2–2.5 cm long, 0.3–0.4 cm wide, membranous, glabrous, apex acute. Flowers not fragrant; pedicels 2.5–3.3 cm long, glabrous; perianth 4.4–6.4 cm long, funnel-form, glabrous, 6-lobed, whitish purple outside in flower buds, almost white outside and inside when flowering, midveins purplish adaxially; tube dilated from apical 2/3, lobes triangular, 1.0–1.5 cm long, 0.6–0.9 cm wide, apex obtuse. Stamens 6, slightly shorter than perianth, not exerted; filaments 4.6–4.8 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 5.1–5.6 cm long, upwardly curved at the distal part, 1.1 cm exerted from perianths, glabrous, stigma capitate. Capsules or seeds not observed.
Flowering from late July to early August.
Japan (Kochi Prefecture). This species grows on rock cliffs at Mt. Tsutsujo, Mt. Tebako, Yasui Valley, and its vicinity in Kochi Prefecture on Shikoku Island.
The specific epithet is derived from the long pedicel.
Using criterion D1 for IUCN Red List categories (
Kamuro-giboshi (new).
Japan. Kochi Pref.: Tosa-gun. Hongawa-mura, Mt. Tsutsujo, 28 Jun. 2022, K. Fuse et al. JPN12637–12639, 12647, 12654 sterile (FU!); Agawa-gun, Niyodogawa-cho, 612 m elev., 3 May 2022, Se. Fujii JPN12425, 12426 sterile (FU!); Agawa-gun, Niyodogawa-cho, Yasui Valley, 470 m elev., 30 Jun. 2022, K. Fuse et al. JPN12674, 12676, 12680 sterile, JPN12675 with flower buds (FU!); Agawa-gun, Niyodogawa-cho, Miyagahira, 612 m elev., Jul. 22, 2023, Se. Fujii FJW48-1, 2, 3 with flowers (MBK!); cultivated at Makino Botanical Garden, derived from Mt. Tsutsujo, 1750 m elev., T. Yahara et al. JPN3927 sterile (FU!); cultivated at Makino Botanical Garden, derived from Mt. Tebako, 1700 m elev., T. Yahara et al. JPN3936 sterile (FU!).
The plant shown in Fig.
Hosta samukazemontana is distinguished from H. polyneuronoides by anther size (3 mm vs. 3.5–4 mm), and inflorescences (deflected and curved upward at the top in contrast to erect and straight). Hosta samukazemontana is also similar to H. tosana in having inflorescences deflected and curved upward at the top, but distinguished from H. tosana by whitish perianths 4.5–5 cm long (in contrast to purple perianths 6.1–6.9 cm long) and whitish purple flower bracts 1.7–2.1 cm long (as opposed to whitish green peraiths 2.2–5.2 cm long).
Japan. Kochi Pref.: Tosa County, Hongawa Village, Mt. Kanpu, 25 Jul. 1983, Y. Kokami M83-255 with flowers (holotype MBK0175579!).
Herbs perennial. Leaves basal, spiral, long petiolate, 2–6 per ramet; blades oblong-ovate, elliptic-ovate, ovate, 7–22 cm long, 3.6–10.7 cm wide, 1.8–2.9 time longer than wide, thinly papery, glabrous on both surfaces, base cuneate, rounded, cordate, decurrent, slightly folded, apex acuminate, margin entire, veins in 6–12 pairs, smooth on the lower surface; petioles 3.2–14.5 cm long, narrowly winged, wings 0.1–0.2 cm wide, glabrous. Scape 20–43 cm long, terete, deflected and curved upward at the top. Raceme 7–9 cm long, 5–18-flowered; flower bracts vivid (not withering) in anthesis, erect, whitish purple, oblong-lanceolate, boat-shaped, 1.7–2.1 long, 0.3–0.5 cm wide, membranous, glabrous, apex acuminate. Flowers 5–6 cm long; pedicels 1–1.8 cm long, glabrous. Perianths 4.5–5 cm long, purple-white outside, almost white inside, funnel-form, glabrous, 6-lobed, tube abruptly dilated from apical 2/3, lobes narrowly triangular, 1–1.3 cm long, 0.7–0.8 cm wide, apex acute, three veins distinct inside. Stamens 6; filaments 4.8 cm long, white, free, glabrous, almost as long as perianth, upwardly curved at the distal part, anthers purple when fresh, dark blue-grey when dried, 3 mm long. Ovary ellipsoid, 1 cm long, style 5 cm long, upwardly curved at the distal part, 0.5 cm exerted from perianth, glabrous, stigma capitate. Capsules green, cylindrical, 2.3–2.4 cm long, 0.4 cm wide, 3-angled. Seeds 2.2 mm long, with wings ca. 4 mm long, blackish brown.
Flowering in July, and fruiting in August.
Japan (Ehime and Kochi Prefectures) (endemic). This species grows on rock cliffs in the vicinity of Mt. Kanpu in the central part of the Kochi Prefecture on Shikoku Island.
The specific epithet was derived from the old name of the type locality (Mt. Samukaze).
Using criterion D1 for IUCN Red List categories (
Samukaze-giboshi (new).
Japan. Kochi Pref.: Agawa-gun, Ino-cho, along Kamegamori Forest Road, 1660 m elev., 22 Jun. 2021, T. Yahara et al. JPN6325 with flower buds (FU!). Ehime Pref.: Saijyo City, W slope of Mt. Kanpu, 1050 m elev., 20 Aug. 2020, T. Yahara et al. JPN1380–1382 with fruit (FU!); Saijyo City, Mt. Kanpu 1600 m, 24 Jul. 2022, Se. Fujii JPN15235 with flowers (FU!); Mt. Kanpu, June 19, 1943, S. Yamawaki s.n. with flowers (TI!).
This species was identified as H. shikokiana by
Hosta tosana F. Maek., J. Fac. Sci. Univ. Tokyo, Sect. 3, Bot. 5: 376. 1940. Type. Japan, Shikoku: Kochi Prefecture, Mt. Kajigamine (now called Kajigamori), T. Yoshinaga s.n. (unknown; not deposited in TI).
Hosta kikutii var. tosana (F. Maek.) F. Maek., Engei-daijiten 2:633. 1950; Tamura & Fujita in Iwatsuki et al. Fl. Jap. IVb: 143. 2016.
Hosta tosana var. caput-avis F. Maek., J. Jap. Bot. 22: 64. 1948. Type. JAPAN. Kochi Pref., Yanase, K. Yasui 332 (unknown; not deposited in TI).
Hosta caput-avis (F. Maek.) F. Maek. in Nakai, Iconogr. Pl. Asiae Orient. 5: 495. 1952.
Hosta kikutii var. caput-avis (F. Maek.) F. Maek., Engei-daijiten (Encycl. Hort.) 2: 633. 1950; Fujita, Acta Phytotax. Geobot. 27: 79. 1976.
Flowering in June to July.
Japan (Kochi and Tokushima Prefectures). This species grows on wet slopes, rocky cliffs, rocky riverbanks, and tree trunks in the elevations from 77 m to 1420 m.
Using criterion D1 for IUCN Red List categories (
Tosa-no-giboshi (
Morphs corresponding to “var. tosana ”:
Kochi Pref.: Locality not specified, cultivated in Tokyo, 1 Aug. 1943, Maekawa 7043 with flowers (TI; the cultivated plant may have been collected by T. Yoshinaga from the type locality, as this is the only specimen of this taxon deposited in TI, where Maekawa studied Hosta); Nagaoka-gun, Otoyo-cho, Mt. Kajigamori, 30 Apr. 2022, Se. Fujii JPN12424 sterile (FU!); Kami City, Monobe Town, O-dochi, 500 m elev., 25 Jun. 2021, T. Yahara et al. JPN6619–6620 with flowers (FU!); ditto, Go-o-do, 553 m elev., cultivated at Makino Botanical Garden, 8 Apr. 2021, T. Yahara & Se. Fujii JPN3931–3933 sterile (FU!); ditto, 600 m elev., 25 Jun. 2021, T. Yahara et al. JPN6614 & 6616 with flowers, JPN6611–6613, 6615 sterile (FU!); Miyanose, 400 m elev., T. Yahara et al. JPN6603 sterile (FU!); Befu, 550 m elev., cultivated at Makino Botanical Garden, 8 Apr. 2021, T. Yahara & Se. Fujii JPN3934 sterile (FU!); Befu Valley, 700 m elev., 25 Jun. 2021, T. Yahara et al. JPN6553–6555 with flowers (FU!); Aki City, 77 m elev., cultivated at Makino Botanical Garden, 8 Apr. 2021, T. Yahara & Se. Fujii JPN3935 sterile (FU!); Aki-gun, Kitagawa-mura, Shima, along the Nahari River, 28 May 2022, K. Fuse et al. JPN12653 sterile (FU!). Tokushima Pref.: Mt. Tsurugi, 14 Aug. 1931, Z. Tashiro s.n. with flowers (KYO!); ditto, below Minokoshi, 1400 m elev., 14 Aug. 1954, G. Murata 7977 with flowers (KYO!); ditto, 1420 m elev., 23 Jun. 2022, T. Yahara et al. JPN12821–12823 sterile (FU!); Higashiiyayama-mura, Inter Sugeoi et Minokoshi, 800 m elev., 12 Aug. 1954, G. Murata 7814 & 7816 with flowers and young fruits (KYO!); Naka County, Wajiki Town, 14 Jul. 1965, S. Takafuji 216 with flowers (KYO!); ditto, Kizawa Village, 24 Jul. 1980, S. Takafuji 1442 with flowers (KYO!); ditto, Riu-toge in Miyahama-mura, 2 Jul. 1952, G. Murata 5752 with flowers (KYO!); ditto, Kizu Village, 24 Jul. 1974, S. Takafuji 950 with flowers (KYO!).
Morphs corresponding to “var. caput-avis ”:
Kochi Pref.: Aki-gun, Yanase, 25 Jun. 2020, K. Fuse et al. 12536–12539 sterile (FU!); Kami City, Monobe Town, Befu Valley, 25 Jun. 2021, T. Yahara et al. JPN6524–6526 with flower buds, 6571 with flowers, 6572 with flower buds (FU!); Mt. Ishidate, 25 Jun. 2021, T. Yahara et al. JPN6585–6587, 6593–6596 with flower buds (FU!); on the river bank of Yanase, 1000 m elev., 20 Jul. 1958, S. Hatusima 22009A with wilted flowers (KAG056576!); transplanted from Yanase, 29 Jun. 1960, S. Hatusima s.n. with flowers (KAG056577!); ditto, 10 Jun. 1967, Hatusima s.n. with flowers (KAG056578!).
The Kagami River lineage:
Kochi Pref.: Kochi City, Tosayama, Hirose, 85 m elev., 3 Oct. 2008, Hamaguchi & N. Shintani PRC-00118 with fruits (MBK0208327!); ditto, 14 Jul. 2001, K. Hosokawa et al. FOK-001722 with flowers (MBK0104375!); Kuwao, 130 m elev., 14 Jul. 2013, A. Sakamoto FOS-004959 with flowers (MBK0247214!, MBK0247215!); from Kuwao to Tsuami, 27 Jul. 1968, N. Naruhashi & M.Wakabayashi 223 with flowers (KYO!); Namekawa, 30 m elev., 19 Aug. 2020, T. Yahara et al. JPN1265 with fruit, JPN1266 sterile, JPN1267 sterile, JPN1269 with fruit (FU!); Kajitani, 160 m elev., 29 July 2013, A. Sakamoto FOS-005031 with young fruits (MBK0247386!) and FOS-005032 with young fruits (MBK0247387!); Miyanokubo, 160 m elev., 14 Jul. 2013, A. Sakamoto FOS-004958 with flowers (MBK0247213!); ditto, 170 m elev., 14 Jul. 2013, A. Sakamoto FOS-004957 with fruits (MBK0247212!); Oh-ana Valley, 110 m elev., 19 Aug. 2020, T. Yahara et al. JPN1298 sterile, JPN1299 sterile, JPN1307 with flowers (FU!); Kagami-mura, Kawaguchi, along the Kagami River, 9 Jul. 1958, T. Yamanaka 25548 with flowers (KYO!).
The Kagami River lineage is sister to a clade comprising all other samples (Fig.
According to the MIG-seq tree, two genetically distinct lineages are distributed along the Monobe River in Kami City (Figs
While the two varieties appeared to lack distinction in Kami City, the population of Yanase, which serves as the type locality for H. tosana var. caput-avis, exhibited clear differentiation from the populations in Kami City. However, just like in the case of the Kagami River lineage, further studies using a larger sample size are necessary to definitively conclude about the Yanase lineage.
A lineage distributed in SE Kinki, Honshu (H. sp. 4 in Fig.
DNA samples and voucher specimens of Hosta spp. were collected in the protected areas of Ashizuri-Uwaumi National Park, Ishizuchi National (Kokutei) Park, Tsurugi National (Kokutei) Park, and Akaishi Mountains Nature Reserve, with permission from the Ministry of Environment, Ehime Prefecture, and Tokushima Prefecture. We thank Satoru Kinoshita and Yasushi Ibaragi for identifying the location of H. tosana in Tokushima Prefecture, and Shinji Fujii for providing DNA samples of H. densiflora subsp. densiflora (FJI17566) and H. sp. 3 (FIJ12268). We thank the Ministry of the Environment’s Rare Species Conservation Promotion Office and Saki Funamoto of Kyushu Open University for their assistance in obtaining collection permits. We are also grateful to the curators of FU, KAG, KYO, MBK, TI and VNMN for their help to access specimens for our studies.
The authors have declared that no competing interests exist.
No ethical statement was reported.
This study was supported by the Environment Research and Technology Development Fund (JPMEERF20204001 and JPMEERF20234001) of the Ministry of Environment, Japan.
Data curation: TY, SF. Formal analysis: YS, TY, SKH. Investigation: HS, KF. Resources: YK, KF, HS, SF. Writing - original draft: TY, ST. Writing - review and editing: TY.
Tetsukazu Yahara https://orcid.org/0000-0001-5105-7152
Shun K. Hirota https://orcid.org/0000-0002-6104-1119
Hiroyuki Sato https://orcid.org/0000-0001-6003-6492
Shuichiro Tagane https://orcid.org/0000-0002-1974-7329
Yoshihisa Suyama https://orcid.org/0000-0002-3136-5489
All of the data that support the findings of this study are available in the main text or Supplementary Information.
20 DNA samples and voucher specimens from 70 localities for 30 taxa of Hosta in Japan
Data type: xlsx
Sample sets
Data type: xlsx
Changes of ∆K with K in the samples of H. polyneuronoides and H. tardiva subsp. densinervia (A) and the other species of group 1 (B)
Data type: docx