Research Article |
Corresponding author: Tetsukazu Yahara ( tet.yahara@gmail.com ) Academic editor: Sandy Knapp
© 2022 Shun K. Hirota, Tetsukazu Yahara, Kengo Fuse, Hiroyuki Sato, Shuichiro Tagane, Shinji Fujii, Tadashi Minamitani, 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:
Hirota SK, Yahara T, Fuse K, Sato H, Tagane S, Fujii S, Minamitani T, Suyama Y (2022) Molecular phylogeny and taxonomy of the Hydrangea serrata complex (Hydrangeaceae) in western Japan, including a new subspecies of H. acuminata from Yakushima. PhytoKeys 188: 49-71. https://doi.org/10.3897/phytokeys.188.64259
|
According to the contemporary classification of Hydrangea native to Japan, H. serrata is a polymorphic species including six varieties. We discovered a plant identified as H. serrata, but morphologically distinct from previously known varieties, in Yakushima island where approximately 50 endemic species are known. To determine the relationship of this plant with previously known varieties, we examined morphology and constructed a highly resolved phylogeny of H. serrata and its relatives using three chloroplast genomic regions, rbcL, trnL intron, psbA-trnH, and two nuclear genomic regions, ITS1 and ITS2, and Multiplex ISSR genotyping by sequencing (MIG-seq). Based on these morphological and phylogenetic observations, we describe Hydrangea acuminata subsp. yakushimensis subsp. nov. as a newly discovered lineage in Yakushima, Japan and propose Hydrangea minamitanii stat. nov. and Hydrangea acuminata subsp. australis stat. nov. which were previously treated as varieties of H. serrata.
cpDNA, DNA barcoding, F ST, island, ITS, MIG-seq, threatened plants
Hydrangea L. s. lat. is a genus of Hydrangeaceae, comprising approximately 200 species distributed in East and Southeast Asia and the New World (
In 2005, we discovered a plant of the genus Hydrangea from a mountain-top area of the Yakushima Island, a small island with an area of 504.88 km2 and a maximum peak of 1,936 m in elevation, part of which is designated as a UNESCO Man and the Biosphere Reserve (
The newly discovered plant is morphologically identified as Hydrangea serrata in having ovate-oblong petals, distinct peduncles, and oblong leaves, based on the key and description of
A previous molecular phylogenetic study was performed on H. serrata and its relatives using rbcL, matK, and Random Amplified Polymorphic DNA (RAPD) markers (
Our new molecular phylogenetic analysis covered all the lineages distributed in Kyushu, including the newly discovered lineage from Yakushima, H. serrata var. acuminata , var. australis , and var. minamitanii from western Japan, as well as var. angustata (Franch. & Sav.) H. Ohba and var. serrata s. str. from eastern Japan. The results supported the treatment of the former three varieties as H. acuminata subsp. acuminata, H. acuminata subsp. australis, and H. minamitanii, respectively, and treating the newly discovered lineage as a new subspecies of H. acuminata.
We carried out field studies in Yakushima Island of Kagoshima Prefecture and five additional prefectures, including Fukuoka, Miyazaki, Kochi, Mie, and Shizuoka. In total, we collected 24 samples consisting of 10 species with five infraspecific taxa of Hydrangea for DNA isolation (Table
Scientific name | Voucher ID | Locality | Coordinates |
---|---|---|---|
Hydrangea (Dichroa) sp. | V8372 | Bidoup Nui Ba, Vietnam | 12.16016944, 108.5364333 |
Hydrangea acuminata [Shikoku lineage] | TGK0472 | Ino, Kochi | 33.781458, 133.188252 |
Hydrangea acuminata [Shikoku lineage] | JPN3301 | cultivated, Fukuoka | 33.55545001, 130.1939861 |
Hydrangea acuminata ssp. acuminata | JPN0330 | Mt. Ihara, Fukuoka | 33.48363400, 130.2638410 |
Hydrangea acuminata ssp. acuminata | JPN0433 | Mt. Raizan, Fukuoka | 33.48293333, 130.2204444 |
Hydrangea acuminata ssp. acuminata | JPN2336 | Mt. Oyaji, Miyazaki | 32.77326944, 131.3367306 |
Hydrangea acuminata ssp. acuminata | JPN2063 | Mt. Shiraiwa, Miyazaki | 32.56233100, 131.1113540 |
Hydrangea acuminata ssp. australis | JPN0908 | Mt. Karakuni, Miyazaki | 31.93438888, 130.8600000 |
Hydrangea acuminata ssp. australis | JPN3192 | Miyakonojyo, Miyazaki | 31.78877222, 130.9603278 |
Hydrangea acuminata ssp. yakushimemsis | JPN1708 | Yakushima, Kagoshima | 30.372031, 130.504266 |
Hydrangea acuminata ssp. yakushimemsis | JPN1799 | Yakushima, Kagoshima | 30.34255555, 130.4810000 |
Hydrangea davidii | V4997 | Fansipan, Vietnam | 22.34225, 103.7764167 |
Hydrangea grosseserrata | JPN0528 | Yakushima, Kagoshima | 30.34619444, 130.3918750 |
Hydrangea grosseserrata | JPN0652 | Yakushima, Kagoshima | 30.26264444, 130.5800944 |
Hydrangea hirta | JPN2415 | Mt. Amagi, Shizuoka | 34.86201944, 139.0215139 |
Hydrangea indochinensis | V4959 | Fansipan, Vietnam | 22.34755555, 103.7721944 |
Hydrangea kawagoeana | TG00879 | Suwanose-jima, Kagoshima | 29.62290600, 129.69778900 |
Hydrangea luteovenosa | JPN0378 | Mt. Ihara, Fukuoka | 33.48294444, 130.2541972 |
Hydrangea luteovenosa | JPN0901 | Mt. Karakuni, Miyazaki | 31.93438888, 130.8600000 |
Hydrangea luteovenosa | JPN1982 | Mt. Osuzu, Miyazaki | 32.29758800, 131.4459520 |
Hydrangea macrophylla | JPN3302 | cultivated, Fukuoka | 33.55545001, 130.1939861 |
Hydrangea macrophylla | JPN3303 | cultivated, Fukuoka | 33.55545001, 130.1939861 |
Hydrangea minamitanii | JPN1983 | Mt. Osuzu, Miyazaki | 32.29758800, 131.4459520 |
Hydrangea minamitanii | TG01200 | Aya, Miyazaki | 32.03053900, 131.21502800 |
Hydrangea scandens | JPN1980 | Mt. Osuzu, Miyazaki | 32.29758800, 131.4459520 |
Hydrangea scandens | JPN2931 | Kihoku, Mie | 34.18644999, 136.1858528 |
Hydrangea serrata var. angustata | JPN2404 | Izu City, Shizuoka | 34.96862800, 138.8459450 |
Hydrangea serrata var. serrata | JPN2980 | Osugi-dani, Mie | 34.21346388, 136.1650250 |
Localities of Hydrangea acuminata subsp. acuminata (including Shikoku lineage), subsp. australis , and subsp. yakushimensis where DNA samples and voucher specimens were collected in this study. The map was produced from Chiriin Chizu Vector (https://maps.gsi.go.jp/vector/).
Total DNA was extracted from the dried leaves using the cetyl trimethyl ammonium bromide (CTAB) method (
Maximum likelihood phylogeny based on SNPs was inferred using software RAxML 8.2.10 (
The chloroplast and nuclear genomic regions were sequenced using the next generation sequencing (NGS) technique (
The sequences of the five regions were determined using Claident pipeline (
Multiple alignments of the chloroplast and nuclear genomic regions were performed using the program MAFFT 7.313 (
Using the specimens listed in Table
Taxa | Specimen ID | Herbaria |
---|---|---|
Hydrangea acuminata ssp. acuminata | KAG161334, KAG161335, KAG161336, KAG161337, KAG161338, KAG161344, KAG161345, KAG161348, KAG161349, KAG161350 | KAG |
Hydrangea acuminata ssp. acuminata | Fujii 117037 | KYO |
Hydrangea acuminata ssp. australis | KAG023305, KAG083840, KAG083882, KAG086731, KAG161312, KAG161315, KAG161327, KAG161377 | KAG |
Hydrangea acuminata ssp. australis | Fujii 18200, Fujii 178001 | KYO |
Hydrangea acuminata ssp. yakushimensis | Yahara et al. 791, 792, 793–1, 793–2, 793–3, 793–4, 1103, 1104, 1105, JPN1799 | FU |
All raw MIG-seq data were deposited at the DDBJ Sequence Read Archive (DRA) with accession number DRA011509. The demultiplexed raw reads of ITS and cpDNA regions were deposited at the DDBJ Sequence Read Archive (DRA) with accession number DRA011510. All sequences of ITS and cpDNA regions were registered to DNA Data Bank of Japan (DDBJ) under accession nos. LC657594–LC657817.
A total of 22,106,838 raw reads (789,530 ± 47,627 reads per sample) were obtained, and after quality control, 20,944,147 reads (748,005 ± 45,296 reads per sample) remained. After de novo SNP detection and filtering, the dataset had 1,746 SNPs from 685 loci.
In the MIG-seq tree (Fig.
The degree of genetic differentiation measured by FST (Table
Hirtae | Chinenses | Macrophyllae | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
H. grosseserrata | H. kawagoeana | H. luteovenosa 1 | H. scandens | H. luteovenosa 2 | H. minamitanii | H. acuminata ssp. acuminata | H. acuminata ssp. australis | H. acuminata ssp. yakushimensis | Shikoku lineage | H. serrata | H. macrophylla | ||
Hirtae | H. hirta | 0.739 | 0.696 | 0.700 | 0.693 | 0.624 | 0.724 | 0.511 | 0.654 | 0.720 | 0.637 | 0.715 | 0.814 |
Chinenses | H. grosseserrata | – | 0.395 | 0.580 | 0.632 | 0.616 | 0.749 | 0.590 | 0.705 | 0.769 | 0.711 | 0.735 | 0.808 |
Chinenses | H. kawagoeana | – | – | 0.473 | 0.561 | 0.524 | 0.768 | 0.578 | 0.697 | 0.736 | 0.695 | 0.734 | 0.792 |
Chinenses | H. luteovenosa 1 | – | – | – | 0.544 | 0.510 | 0.729 | 0.574 | 0.681 | 0.728 | 0.687 | 0.702 | 0.775 |
Chinenses | H. scandens | – | – | – | – | 0.551 | 0.722 | 0.574 | 0.684 | 0.759 | 0.695 | 0.711 | 0.787 |
Chinenses | H. luteovenosa 2 | – | – | – | – | – | 0.501 | 0.454 | 0.594 | 0.679 | 0.565 | 0.598 | 0.720 |
Macrophyllae | H. minamitanii | – | – | – | – | – | – | 0.340 | 0.470 | 0.546 | 0.439 | 0.480 | 0.657 |
Macrophyllae | H. acuminata ssp. acuminata | – | – | – | – | – | – | – | 0.251 | 0.316 | 0.257 | 0.317 | 0.452 |
Macrophyllae | H. acuminata ssp. australis | – | – | – | – | – | – | – | – | 0.437 | 0.405 | 0.441 | 0.606 |
Macrophyllae | H. acuminata ssp. yakushimensis | – | – | – | – | – | – | – | – | – | 0.453 | 0.514 | 0.652 |
Macrophyllae | Shikoku lineage | – | – | – | – | – | – | – | – | – | – | 0.364 | 0.585 |
Macrophyllae | H. serrata | – | – | – | – | – | – | – | – | – | – | – | 0.553 |
A total of 111,216 reads (3,972 ± 299 reads per sample, ITS1) and 81,988 reads (2,928 ± 155 reads per sample, ITS2) were obtained. After gaps were trimmed, the total length of the sequences was 635 bp (ITS1: 267 bp, ITS2: 368 bp). In the ITS tree (Fig.
A total of 20,290 reads (725 ± 68 reads per sample, rbcL), 18,724 reads (669 ± 68 reads per sample, trnL intron), and 20,194 reads (721 ± 72 reads per sample, psbA-trnH) were obtained. After gaps were trimmed, the total length of the sequences was 1,354 bp. The sequenced lengths of each region were 222 bp and 227 bp (read 1 and 2 of rbcL), 228 bp and 228 bp (read 1 and 2 of trnL intron), and 226 bp and 223 bp (read 1 and 2 of psbA-trnH). In the cpDNA tree reconstructed using these sequences (Fig.
Morphologically, H. acuminata subsp. yakushimensis is similar to subsp. acuminata in having blue-colored flowers: fertile flowers with blue-colored petals, stamens, and sterile flowers with blue-colored calyces (Fig.
Measurements for nine morphological traits of H. acuminata ssp. acuminata , ssp. australis , ssp. yakushimensis, and H. minamitanii.
H. a. ssp. yakushimensis | H. a. ssp. acuminata | H. a. ssp. australis | H. minamitanii | |
---|---|---|---|---|
Leaf length | 12.5±1.5 (10.2–14.4) cm | 10.4±2.8 (10.4–15.6) cm | 13.4±1.6 (10.1–15.4) cm | 12.6±1.1 (12–14) cm |
Leaf width | 6.2±0.9 (4.6–7.5) cm | 4.3±1.1 (2.8–6.2) cm | 7.7±1.4 (5.4–9.7) cm | 6.2±0.9 (5.0–6.9) cm |
Petiole length | 2.8±1.0 (1.2–5.3) cm | 2.1±0.8 (0.9–3.5) cm | 2.8±1.3 (0.9–5.0) cm | 3.0±1.2 (2.2–4.5) cm |
Leaf apex length | 1.7±0.5 (1.0–2.4) cm | 1.8±0.7 (0.9–2.9) cm | 1.7±0.5 (0.7–2.5) cm | 1.5±0.5 (0.8–1.9) cm |
Leaf teeth length | 2.8±1.1 (1.0–5.0) mm | 1.8±0.6 (1.0–2.9) mm | 3.0±1.0 (1.0–5.0) mm | 3.1± 0.8 (2.2–4.2) cm |
No of teeth | 28.5±7.1 (15–42) | 21.2±6.1 (9–27) | 28.5±7.1 (15–42) | 28.8±4.9 (23–35) |
Corymb length | 4.3±1.5 (2.0–7.0) cm | 4.1±1.5 (1.9–6.3) cm | 5.8±2.2 (3.0–9.2) cm | 5.1±0.9 (4.5–6.3) cm |
Corymb width | 6.7±2.7 (3.9–11.8) cm | 5.5±1.9 (3.2–8.7) cm | 8.9±2.5 (6.2–12.8) cm | 7.9±0.9 (7.2–9.2) cm |
Capsule length | 2.4±0.2 (2.2–2.7) mm | 3.9±0.6 (3.2–5.1) mm | 4.3±0.4 (3.8–4.9) mm | 4.6±1.0 (3.9–5.3) mm |
Phylogenetically, H. acuminata subsp. yakushimensis is sister to subsp. australis. Morphologically, H. acuminata subsp. yakushimensis is similar to subsp. australis in having leaves larger than subsp. acuminata but distinguished with leaves glabrous adaxially except veins (vs. sparsely hairy in subsp. australis; Table
Morphological comparison between H. acuminata ssp. acuminata , ssp. australis , ssp. yakushimensis, and H. minamitanii.
H. a. ssp. yakushimensis | H. a. ssp. acuminata | H. a. ssp. australis | H. minamitanii | |
---|---|---|---|---|
Upper surface of lamina | glabrous | sparsely hairy | sparsely hairy | glabrous |
Upper surface of veins | hairy | hairy | hairy | hairy |
Lower surface of lamina | glabrous | sparsely hairy | densely curled hairy | glabrous |
Lower survace of veins | glabrous or glabrescent | sparsely hairy | densely curled hairy | glabrous or glabrescent |
Axils of lateral veins | hairs densely tufted | hairs not densely tufted | hairs not densely tufted | hairs densely tufted |
Petiole | glabrous | hairy | densely hairy | glabrous |
Young shoot | glabrous | hairy | densely hairy | glabrous |
Calyx of showy flower | blue | blue | blue | pink or white |
The discovery of H. acuminata subsp. yakushimensis is surprising because Yakushima is a well-botanized island, and H. acuminata subsp. yakushimensis has conspicuous, blue-colored flowers. This discovery illustrates that botanical surveys in the mountain-top area of Yakushima still remain insufficient, most likely because of its steep topography. In fact, our recent surveys resulted in the discovery of not only H. acuminata subsp. yakushimensis but also an additional new taxon of Stellaria (Caryophyllaceae) (
Using RAPD and the sequences of rbcL and matK,
In contrast, the FST between H. acuminata subsp. acuminata and subsp. australis (0.251) is lower than the above values (0.340 to 0.657) observed between the species, supporting the treatment as two subspecies. Similarly, the FST between H. acuminata subsp. acuminata and subsp. yakushimensis was 0.316, which is considered to be at the subspecies level, and the FST between subsp. australis and subsp. yakushimensis (0.437) was slightly higher. Differences between H. acuminata subsp. acuminata and subsp. australis are smaller, not only genetically, but also morphologically: JPN0908 collected at 1700-m elevation on Mt. Karakuni was identified as subsp. australis in the MIG-seq tree, but is morphologically very similar to subsp. acuminata, suggesting hybridization or intergradation between subsp. acuminata and subsp. australis.
In the MIG-seq tree (Fig.
The MIG-seq tree (Fig.
The MIG-seq tree (Fig.
It is notable that H. luteovenosa 1 and H. luteovenosa 2 were not sister to each other in both MIG-seq and ITS trees. In the MIG-seq tree which has a higher resolution than the ITS tree, H. luteovenosa 2 (JPN1982 collected from Mt. Osuzu, Miyazaki Pref.) was basal to a clade including H. scandens, H. luteovenosa 1 (JPN0378 collected from Mt. Ihara, Fukuoka Pref.), H. kawagoeana, and H. grosseserrata. It is likely that H. luteovenosa contains two cryptic species. To test this possibility, further studies with more samples of H. luteovenosa are needed.
This study demonstrated the usefulness of MIG-seq to obtain finely resolved phylogenetic trees for closely related species and infraspecific taxa in taxonomically complicated groups such as Hydrangea. Compared with the ITS and cpDNA trees, where only a few branches were supported by bootstrap values larger than 90%, most branches in the MIG-seq tree were supported by bootstrap values larger than 90%. In the ITS tree, the monophyly of H. acuminata subsp. yakushimensis was supported by the 97% bootstrap value, but the monophyly of H. acuminata subsp. acuminata and subsp. yakushimensis was ambiguous; the cluster of H. acuminata subsp. acuminata and H. minamitanii with the bootstap value 88% was weakly consistent with the MIG-seq tree topology. The resolution of the MIG-seq tree is even higher than that of the RAPD tree for the H. serrata complex obtained by
1 | Calyces of marginal showy flowers, petals of fertile flowers, and stamens always pink or white | 2 |
– | Calyces of marginal showy flowers, petals of fertile flowers, and stamens light blue when flowering | 3 |
2 | Leaves glabrous adaxially except veins and glabrous abaxially except for tufted hairs at axils of lateral veins. Distributed in Kyushu | H. minamitanii |
– | Leaves more or less hairy adaxially and abaxially. Distributed in Honshu | H. serrata |
3 | Leaves glabrous adaxially except veins. Capsules 2.7 mm or shorter | H. acuminata subsp. yakushimensis |
– | Leaves hairy adaxially. Capsules 3.2 mm or longer | 4 |
4 | Leaves usually sparsely hairy abaxially, hair not curled. Leaf width less than 6.2 cm | H. acuminata subsp. acuminata |
– | Leaves usually densely hairy abaxially, hair curled. Leaf width often 6.2 cm or larger | H. acuminata subsp. australis |
Hydrangea acuminata Siebold & Zucc., Fl. Jap. 1: 110, t. 56, 57-I (1839); Ohba & Akiyama in Bull. Natl. Mus. Nat. Sci., Ser. B, 39: 178 (2013).
Japan, Higo Province, Kyushu (L0043373, the lectotype designated by
Hortensia serrata var. acuminata (Siebold & Zucc.) H. Ohba & S. Akiyama, J. Jap. Bot. 91: 347 (2016).
Hydrangea macrophylla var. acuminata (Siebold & Zucc.) Makino, Ill. Fl. Nippon: 484, f. 1451 (1940), nom. tant.
Sawa-ajisai, Nishino-yama-ajisai.
Hydrangea acuminata subsp. acuminata is widely distributed on the main island of Kyushu, and usually grows on the soil near streams and often on cliffs, and sometimes in disturbed habitats.
Hydrangea acuminata subsp. yakushimensis is different from subsp. acuminata in that it has smaller capsules, 2.2–2.7 mm long with calyx tube 1.2–1.4 mm long and projected apical part including persistent style 1.0–1.3 mm (vs. capsules 3.2–5.1 mm long with calyx tube 1.6–3.4 mm and projected apical part including persistent style 1.5–2.0 mm), a larger infructescence attaining to 7 × 12 cm (vs. attaining to 6.3 × 8.7 cm), leaves glabrous adaxially except veins (vs. hairy) and glabrous or only slightly hairy abaxially except for tufted hairs at axils of lateral veins (vs. hairy overall on abaxial surface).
Japan. Kagoshima Pref.:Yakushima Migitani, on cliff along stream, 30.34255555°N, 130.48100000°E, 1520 m elevation, 9 September 2020, with fruits, K. Fuse JPN1799 (holotype: KYO!).
Shrubs 1–1.5 m tall. First year’s twigs green when fresh, with dark purple lenticels, glabrous, terete. Old twigs pale brown; bark not peeled off. Leaves opposite; petioles purplish green, 1.7–3 cm long, glabrous; leaf blade adaxially green, abaxially light green when fresh, pale green when dried, elliptic, 9–12 × 4.6–6.4 cm, papery, adaxially glabrous except veins which are covered with minute hairs, abaxially glabrous or only sparsely hairy except for tufted hairs at axils of lateral veins, secondary veins 6–9 on each side of midvein, adaxially slightly sunken, abaxially slightly elevated, base broadly cuneate, apex long acuminate, margin serrate, teeth 2–3 mm high, 13–31 along each side of the margin. Inflorescences corymbose cymes, 2–7 cm long, 4–12 cm in diam., densely pubescent, apex flat to slightly arcuate, 3–5-branched; the longest internode of each branch 1.5–2.5 cm long, densely pubescent; infructescence attaining to 7 × 12 cm. Marginal showy flowers light blue, on pedicel 1–2 cm long; sepals 3 to 5, rhomboid-elliptic, 0.8–1.4 × 0.5–1.1 cm, glabrous, apex obtuse, base rounded to cuneate, margin entire. Fertile flowers protandrous, light blue. Male-stage flowers on pedicel 1–1.8 mm long; calyx tube funnel-shaped, ca. 1 mm long, 0.8 mm in diam., lobes 5, triangular, 0.5 × 0.4 mm, apex acute; petals 5, light blue, elliptic, 2–2.2 × 1 mm, glabrous, apex acute; stamens 10, light blue, subequal, filaments 1.5–3 mm long, glabrous, anthers white, globular, 0.6 mm in diam.; ovary nearly 1/2 superior, style 3, connate at base, slightly spreading, dark blue, ca. 0.7 mm long, stigma flat. In female-stage flowers, petals and stamens fallen off; ovary nearly 1/2 superior; calyx tube light blue, ca. 1 mm long; style darker blue, spreading, ca. 1 mm long; capsules 2.2–2.7 mm long; calyx tube subglobose, 1.2–1.4 mm long, 1.5–2 mm in diam., projected apical part including persistent styles 1.5 mm long. Seeds light brown, elliptic, 0.8 × 0.5 mm, not winged.
Yakushima-ruri-ajisai.
Flowers were collected in July and August, and fruits were collected in September.
Yakushima (Yaku Island), Japan (endemic). The distribution of H. acuminata subsp. yakushimensis is restricted to cliffs along streams at Yakushima. It mainly grows in the mountain-top area from 1520 to 1750 m, but one population occurs at an elevation of 575 m, along the Miyanoura River.
The specific epithet is derived from the type locality, Yakushima.
Endangered (EN) based on criterion D; the population size is above 50, but less than 250.
Japan. Kagoshima Pref., Yakushima: Mt. Nagata, on cliff, 30.343799°N, 130.492056°E, 1750 m elevation, 2 August 2005, with flowers, T. Yahara, S. Tagane, K. Fuse & T. Saito 0791 (FU!); Kamisamano-kubo, on cliff, 30.343799°N, 130.492056°E, 1750 m elevation, 2 August 2005, with flowers, T. Yahara, S. Tagane, K. Fuse & T. Saito 0792 (FU!); ditto, with flowers, T. Yahara, S. Tagane, K. Fuse, T. Saito 0793 (FU!); Nemachino-kubo, on cliff, 30.345465°N, 130.49468230°E, 1740 m elevation, 12 July 2006, sterile, S. Tagane & K. Fuse 1065 (FU!); Migitani, on cliff along stream, 30.34255555°N, 130.48100000°E, 1520 m elevation, 13 July 2006, with flowers, S. Tagane & K. Fuse 1103, 1104, 1105 (FU!); Sensuikyo, 30.372031°N, 130.504266°E, 575 m elevation, 31 August 2020, sterile, K. Fuse JPN1708 (FU!).
Hydrangea serrata var. australis T. Yamaz., J. Jap. Bot. 76: 175 (2001). Type. Japan. Kagoshima Pref., Mt. Takakuma, 11 August 1942, T. Yamazaki s.n. (TI).
Hortensia serrata var. australis (T. Yamaz.) H. Ohba & S. Akiyama in Ohashi et al., Wild Fl. Jap. rev. ed. 4: 166 (2017), comb. nud.
Nangoku-yama-ajisai.
Hydrangea acuminata subsp. australis is widely distributed at lower elevations in the Kagoshima Prefecture and the southern part of the Miyazaki Prefecture of the Kyushu Island and usually grows in disturbed places along the margins of evergreen forests or Cryptomeria plantations. JPN0908 was collected on a volcanic cliff at 1700 m elevation on Mt. Karakuni and was identified as subsp. australis in the MIG-seq tree (Fig.
Hydrangea acuminata subsp. australis is distinguished from subsp. acuminata mainly by its larger and wider leaves often exceeding 6.2 cm wide (vs. not exceeding 6.2 cm), having more serrations along margin (22–43 vs. 9–27) and dense curled hair on the lower surface of lamina. However, JPN0908, was identified as subsp. australis in the MIG-seq tree, which is morphologically similar to subsp. acuminata in having smaller leaves, fewer serrations, and sparser pubescence on the lower surface of the leaf. This specimen might be of hybrid origin between subsp. australis and subsp. acuminata.
Japan. Kagoshima Pref.: Kagoshima City, 22 July 2002, with flowers, K. Maruno s.n. (KAG 083840!); Shibushi City, 4 June 2002, with fruits, K. Maruno s.n. (KAG 083882!); Aira City, 11 July 2004, K. Maruno s.n. (KAG 086731!); Kimotsuki Town, 300 m elevation, 20 July 1986, with fruits, S. Hatusima 41199 (KAG 161312!); KHydrangeahima City, 450 m elevation, 22 November 1986, with fruits, S. Hatusima 41920 (KAG 161315!); Mt. Nokubi, 700 m elevation, 12 July 1987, with flowers, S. Hatusima 42447 (KAG 161327!).
Hydrangea serrata var. minamitanii H. Ohba in J. Jap. Bot. 64: 199 (1989); Ohba & Akiyama, Bull. Natl. Mus. Nat. Sci., Ser. B, 39: 179 (2013). Type. Japan. Miyazaki Pref., Saito City, T. Minamitani 26304 (TI).
Hortensia serrata var. minamitanii (H. Ohba) H. Ohba & S. Akiyama, J. Jap. Bot. 91: 347 (2016).
Hyuga-ajisai.
Hydrangea minamitanii and H. acuminata ssp. acuminata often grow close, within 100 m of each other, but the former grows on wet cliffs along streams, and the latter grows on soil along forest margin. Hydrangea minamitanii is distinct from H. acuminata in having leaves glabrous abaxially except tufted hairs at axils of lateral veins, glabrous petioles, and glabrous young shoots (Table
Japan. Miyazaki Pref.: Mt. Osuzu, 500 m elevation, 20 October 1960, with fruits, S. Sako 3285 (KAG 161375!); ditto, 500 m elevation, 28 July 1971, with flowers, S. Hatusima & S. Sako 32643 (KAG 161376!); ditto, 11 July 1976, with flowers, T. Minamitani 22630 (KAG 161378!); Aya Town, 73 m elevation, 24 October 2019, with fruits, S. Tagane 1200 (KAG 128616!).
We thank Toshihiro Saito for his help with our fieldwork in Yakushima. Specimens of H. acuminata subsp. yakushimensis were collected in the protected area of the Yakushima National Park with permission from the Ministry of Environment, Yakushima office of Forestry Agency, and Kagoshima office of Agency for Cultural Affairs. Specimens of H. minamitanii, H. luteovenosa, and H. scandens were collected in the protected area of Osuzu Prefectural Natural Park with permission from the Miyazaki Prefecture and Forestry Agency. In addition, specimens of other species were collected in the following national parks with permission from the Ministry of Environment and the prefectures for both Kokuritu and Kokutei Park and in the national forests with permission from the local offices of Forestry Agency: Mt. Shiraiwa of Kyushu-chuo-sanchi National (Kokutei) Park, Mt. Oyaji of Sobo-katamuki National (Kokutei) Park, Mt. Karakuni of KHydrangeahima National (Kokuritsu) Park, Osugi-dani of Yoshino-kumano National (Kokuritsu) Park, and Mt. Amagi of Fuji-hakone National (Kokuritu) Park. We thank the Ministry of Environment’s Rare Species Conservation Promotion Office for their help in obtaining collection permits. We would like to thank Editage (www.editage.com) for English language editing. This study was supported by the Environment Research and Technology Development Fund (JPMEERF20204001) of the Ministry of the Environment, Japan, and partly by JSPS KAKENHI grant number 21K06307.