Diplazium x kanayamaense K. Hori & H. Kanemitsu, 2021

Hori, Kiyotaka & Kanemitsu, Hironobu, 2021, Two new hybrids of the genus Diplazium (Athyriaceae) from Japan, PhytoKeys 172, pp. 39-55 : 39

Diplazium x kanayamaense K. Hori & H. Kanemitsu hyb. nov. Figure 3

Diagnosis.

Diplazium x kanayamaense has been determined to be similar to D. x toriianum in having 1-pinnate pinnatifid pinnae curved to an apex. However, lobes of D. x toriianum are obtuse at the apex and scales are more entire on the margin. In contrast, lobes of D. x kanayamaense are acute at the apex and scales show small projections on their margins.

Type.

Japan. Kyushu: Fukuoka Prefecture, Fukuoka City, Sawara-ku, Mt. Kanayama, 33°28'35.89"N, 130°19'23.57"E, alt. 700 m, semi-evergreen forest near streams containing Carpinus laxiflora (Siebold et Zucc.) Blume, Neolitsea sericea (Blume) Koidz., Quercus acuta Thunb and Stewartia pseudocamellia Maxim., on soil, 4 Jul 2020, H. Kanemitsu 3746 (holotype: KAG 151589).

Description.

Terrestrial summergreen fern. Rhizomes: creeping, non-branched, black, 10-15 × 0.5-0.8 cm in diam., closely set with roots and persistent, densely clothed with old stipe bases, glabrous; fronds: 2-5 per rhizome; stipes: purplish-green, 8-11 × 0.2-0.3 cm in diam., glabrous in middle to upper sections, sparsely clothed with dark brown scales (2.0-4.0 × 0.5-1.0 mm, with small projection on margin) of basal sections, lanceolate; blades: fresh green on adaxial surface, 1-pinnate pinnatifid, 1-pinnate at the apex, 15-26.5 × 8-23 cm, ovate; rachises: purplish-green, glabrous; pinnae: 9-10 pairs, ascending, lanceolate, alternate or opposite, petiolated (2-4 mm long), serrate to lobed, curved from base to apex, acute at the apex, sessile near the apex of blades, widely spaced, lowest pair slightly reduced or the same as second, second lowest pair usually largest, 15-17 cm × 1.5-3 cm; pinnules: alternate, 9-10 pairs on the basal sections of the blade, reduced distally, ovate to lanceolate, entirely to shallowly serrated, acute at apex in basal part of blade, obtuse at the apex in the middle section of blades, vein-free, single or double, close to or reaching to the margin, 5-7 pairs in the middle lobe; the most basiscopic pinnules on the lowest pinnae: occasionally absent, clearly short, independent from the costa, 2-10 mm × 1.5-4.0 mm; sori: long linear- or J-shaped, 1.0-3.0 mm long, on the middle of veinlets, 4-10 pairs per ultimate segment, persistent; indusia: cloudy white or brown, same shape as sori, entire, persistent; spores: absent or irregular-shaped, abortive.

Etymology.

The name derives from Mt. Kanayama, Sawara-ku, Fukuoka City, Fukuoka Prefecture, west Japan, where Diplazium x kanayamaense was initially found.

Specimens examined.

Japan. Kyushu: Fukuoka Prefecture, Fukuoka City, Sawara-ku, Mt. Kanayama, 33°28'35.89"N, 130°19'23.57"E, alt. 700 m, semi-evergreen forest near streams containing Carpinus laxiflora (Siebold et Zucc.) Blume, Neolitsea sericea (Blume) Koidz., Quercus acuta Thunb and Stewartia pseudocamellia Maxim., on soil, 15 Jul 2018, H. Kanemitsu 2883 (TNS1307641), H. Kanemitsu 2884 (TNS1307641), H. Kanemitsu 2906 (TNS1307645).

Distribution and ecology.

Diplazium x kanayamaense has been identified to be from Kyushu, western Japan (Figures 3 , 5 ). The species is observed on soil under semi-evergreen forest near streams. This hybrid is endemic to Japan and exists in a population of approximately 124 individuals with juveniles, although parents, D. chinense and D. deciduum , were both absent near its side.

Conservation status.

IUCN Red List Category. Based on estimates from GeoCAT, the EOO of D. x kanayamaense was 0.002 km2. AOO of D. x kanayamaense was 4.0 km2. There were only approximately 124 individuals in the type locality and the population size is not decreasing. According to IUCN (2012) criteria, this hybrid is endangered (EN). A formal evaluation of endangerment can be summarised by the following IUCN hierarchical alphanumeric coding system of criteria: EN D.

Figures

Figure 3. Diplazium x kanayamaense K. Hori & H. Kanemitsu A lower stipe scale B habit C detail of abaxial pinnule A-C from the holotype (KAG 151589 (illustration by K. Hori).

Figure 5. Map showing the known distribution in Japan of D. x kanayamaense = Red circle and D. x tsukushiense = Blue circle.