Sedum kawaraense Takuro Ito & Kanemitsu, 2023

Ito, Takuro, Kanemitsu, Hironobu, Hoson, Taishi & Yahara, Tetsukazu, 2023, A new species of succulent plant discovered in limestone areas of Kyushu, Japan: Sedum kawaraense (Crassulaceae), Phytotaxa 587 (2), pp. 149-160 : 154

Sedum kawaraense Takuro Ito & Kanemitsu , sp. nov. ( Figs. 2 & 3 )

Type:— JAPAN. Kyushu, Fukuoka: Tagawa-gun , Kawara-machi , Mt. Kawara-dake , 16 May 2021, Hironobu Kanemitsu 4170 (holotype TUS!) .

Diagnosis:— Sedum kawaraense differs from its close relatives ( Table 2 ) in life history, rosulate and cauline leaf morphology, presence of stolons and bulbs at the leaf axil, flowering stem extension pattern, length, number of flowers, and habitat. Among these species, S. kawaraense is morphologically most similar to S. lipingense in the monocarpic life cycle, presence of rosette during anthesis and spatulate-oblanceolate cauline leaves, absent bulbs and stolons, and flowering stem extending from the rosette center and leaf axil, but differs in having larger spatulate rosulate leaves and more flowers per flowering stem ( Table 2 ).

Description:—Winter annual or biennial herbs, fleshy, glabrous. Rarely forms bulbils on leaf axils for vegetative propagation. Roots, fibrous, partially lignified. Rosettes 1.5–4.7 cm across; rosulate leaves alternate, reddish or greenish, sessile, thick, spatulate, entire, apex obtuse, base attenuated and shortly spurred, 0.7–2.4 cm long, 0.1–0.7 cm wide. Stem, single shoot emerging from rosette center, other shoots from the rosulate leaf axils, reddish or greenish, erect, 2.2–5.8 cm tall; cauline leaves mostly alternate, reddish or greenish, sessile, thick, spatulate to oblanceolate, entire, apex obtuse, base attenuated and shortly spurred, 0.3–1.6 cm long, 0.1–0.7 cm wide.; Flowering stems 1 to 7, fleshy, 2.0– 8.2 cm tall, base ca. 0.2 cm broad, reddish or greenish, erect. Inflorescences terminal, cymes, 2 to 3 branched, each branch usually 2–6 flowered. Bracts leaf-like, oblanceolate, apex obtuse, 0.3–1.6 cm long, 0.1–0.5 cm wide. Sepals 5, free, green, fleshy, subequal, lanceolate, 1–3 mm long, 0.8–1.2 mm wide, base shortly spurred, apex obtuse. Petals 5, blight yellow, lanceolate 4.5–6.5 mm long, 1.6–2.2 mm wide, apex acuminate, base slightly connate. Stamens 10, shorter than petals, 3.5–5.2 mm long, erect at flowering, 2–whorled; anthers oblong, ca. 0.5 mm long, red before dehiscence. Carpels 5, free, ascending, connate at the base, gibbous ventrally, 3.2–4.5 mm long. Fruits starshaped, follicle, ascending, 5.0– 6.5 mm long. Flowering in May to June.

This new species is categorized in sect. Sedum due to the presence of adaxially gibbous carpels ( Fu & Ohba 2001)( Fig. 3 ).

Etymology:—Epithet refers to the Japanese name of the type locality, Kawara-dake.

Distribution and habitat:—Endemic to Kawara-dake and its adjacent areas, Kyushu, Japan, on shady and mossy limestone rock.

Japanese common name:—Kawara-mannen-gusa (nov.).

Additional specimens examined (paratype):— JAPAN. Kyushu, Fukuoka: Tagawa-gun, Kawara-machi , Mt. Kawara-dake , Hironobu Kanemitsu 1121, 4163, 4164, 4165 ( TUS) , Hironobu Kanemitsu 4166, 4173 ( TNS) , Miyakogun, Miyako-machi, Ryu-ga-hana , Takuro Ito 7715, 7716, 7717 ( TUS) .

Conservation. IUCN Red List category:—Critically Endangered (CR). The distribution of S. kawaraense is restricted to limestone areas <10 km 2 (~ca. 0.056 km 2) in Kawara-dake and Ryu-ga-hana, Kyushu, Japan, and is anticipated to decline in the future because most of the distribution area of the species is privately owned, and limestone quarrying is still being carried out. Until now, one of the peaks of Kawara-dake has disappeared because of limestone mining activities. Based on Criterion B2 ( IUCN 2022), S. kawaraense qualifies as a CR. However, based on Criterion D1, S. kawaraense is qualified as NT because the populations in the two localities amount to ca. 2,400 mature individuals (ca. 1500 individuals in Kawara-dake and ca. 900 individuals in Ryu-ga-hana). Criterion B2 was adopted based on the precautionary principle.

Figures

FIGURE 2. The native habitats and habits of Sedum sp. (S. kawaraense). A. Kawara-dake, consists of three peaks. The first of the three peaks (Ichi-no-dake) has lost its upper half due to limestone mining. B. Habitat. On shady mossy limestone around the summit. C. Rosettes. D. Flower buds. E. Flowers. F. Fruits. [Photographed on 25 July 2022 (A & B), 29 August 2021 (C), 4 May 2021 (D), 16 May 2021 (E), 12 June 2022 (F) in Kawara-dake (A, B, E & F) and Ryu-ga-hana (C & D), Kyushu.]

FIGURE 3. The detailed morphology of Sedum sp. (S. kawaraense). A. Flower. B. Rosulate leaves. C. Cauline leaves. D. Young fruits. E. Mature fruit. Scale bars are 1 mm.