Rhododendron sohayakiense var. kiusianum Y.Watan., T.Yukawa & T.Minamitani, 2019

Yoichi, Watanabe, Minamitani, Tadashi, Oh, Sang-Hun, Nagano, Atsushi J., Abe, Harue & Yukawa, Tomohisa, 2019, New taxa of Rhododendron tschonoskii alliance (Ericaceae) from East Asia, PhytoKeys 134, pp. 97-114 : 97

Rhododendron sohayakiense var. kiusianum Y.Watan., T.Yukawa & T.Minamitani var. nov. Figs 1 , 5 , 7

Diagnosis.

This variety is similar to Rhododendron sohayakiense var. sohayakiense Y. Watan. & T. Yukawa and R. sohayakiense var. koreanum Y. Watan. & T. Yukawa, but is distinguishable through its longer corolla tube and its shorter style included within the corolla. Further, it differs from the former through its raised lateral nerves on the abaxial leaf surface and from the latter through its small leaf size.

Type.

JAPAN. Kyushu: Kumamoto Pref., Kamimashiki County, Yamato Village, Mt. Mukosaka, 32°35'03.22"N, 131°06'19.30"E, on rocky ridge of the mountain, 1500 m, 23 July 2016 (fl), Y. Watanabe Mks04 (holotype: TNS; isotypes: TNS, KYO).

Additional specimens examined.

JAPAN. Kyushu: Ooita Pref., Mt. Katamuki, 2 Aug 1921 (fl), Z. Tashiro (KYO); Miyazaki Pref., Higashi-Usuki County, Shiiba Village, Mt. Eboshi, 1690 m, 18 Jul 2007 (fl), T. Minamitani (TNS); Miyazaki Pref., Higashi-Usuki County, Shiiba Village, Mt. Ougi, 1200-1661 m, 7 Jul 1994 (fl), T. Minamitani 049666 (TNS); Miyazaki Pref., Nishi-Usuki County, Hinokage Town, Mt. Goyou, 1570 m, 11 Aug 1990 (fr), T. Minamitani (TNS); Miyazaki Pref., Nishi-Usuki County, Hinokage Town, Mt. Katamuki, 1500 m, 25 Aug 1970 (fr), T. Minamitani (TNS); Miyazaki Pref., Nishi-Usuki County, Takachiho Town, Mt. Tengu, 1700 m, 24 Jun 1993 (fl), T. Minamitani (TNS); Miyazaki Pref., Nishi-Usuki County, Takachiho Town, Mt. Tengu, 1600-1700 m, 16 Aug 1992, T. Minamitani 44119 (TNS); Miyazaki Pref., Nishi-Usuki County, Takachiho Town, Mt. Shoji, 1600-1700 m, 16 Aug 1992, T. Minamitani 44128 (TNS); Miyazaki Pref., Nishi-Usuki County, Gokase Town, Mt. Mukosaka, Tsutsujigaoka, 1570 m, 12 Jul 1993 (fl), T. Minamitani (TNS); Miyazaki Pref., Nishi-Usuki County, Gokase Town, Mt. Mukosaka, Kita, 1550 m, 24 Sep 1996 (fl, fr), T. Minamitani B-T-052838 (TNS); Miyazaki Pref., Higashi-Usuki County, Kitakata Town, Mt. Hoko, 1100-1200 m, 26 Jun 1994 (fl), T. Minamitani (TNS); Miyazaki Pref., Higashi-Usuki County, Kitakata Town, Mt. Hoko, 1270 m, 23 Sep 1989 (fr), T. Minamitani (TNS); Miyazaki Pref., Nobeoka City, Kitakata, Mt. Ohkue, Kozumidaki, 1340 m, 6 Aug 1992 (fr), T. Minamitani (TNS); Kumamoto Pref., Kuma County, Mt. Ichifusa, 1700 m, 6 Aug 1960 (fl), M. Tagawa & K. Iwatsuki 3676 (KYO); Kumamoto Pref., Kuma County, Yunomae Town, Mt. Ichifusa, 26 Jul 1992 (fl), T. Minamitani 43478 (TNS); Kumamoto Pref., Kuma County, Mizukami Village, Mt. Ichifusa, 32°18'44.65"N, 131°06'03.50"E, on summit of the mountain, 1600 m, 24 July 2016 (fl), Y. Watanabe Ici02 (TNS).

Description.

Spring leaves scattered or crowded on upper branchlets; petioles 0.5-1 mm long; blade thick chartaceous, oblong-ovate, 10-20 mm long (at maximum within each individual), 5-10 mm wide, apex acute and terminating in a gland, base acute, strigose on both surfaces; midrib prominent abaxially; lateral nerves pinnate, 2-3 paired, raised abaxially. Summer leaves oblanceolate, 3-10 mm long, 1-5 mm wide, densely strigose on both surfaces. Calyx saucer-shaped, ca. 1.5 mm in diam., densely soft strigose, shallowly 4-lobed; lobes semiorbiculate, ca. 0.5 mm long. Corolla white, no blotches, tubular-funnelform, 7-13 mm long and wide, 4 lobes; tube 3-4 mm long, ca. 3 mm wide, glabrous outside, pilose on upper inside; lobes elliptic to oblong, rounded, 2-5 mm long, ca. 2 mm wide. Stamens 4, irregular, 3-5 mm long, as long as or shorter than corolla; filaments densely pilose on lower half; anthers yellow, oblong, ca. 1 mm long. Ovary ovoid, densely soft strigose, ca. 1.5 mm. Style 3-4 mm long, glabrous, shorter than corolla. Capsule ovoid, 3-4 mm long, 2.5 mm wide, densely strigose.

Distribution.

JAPAN: Kyushu.

Ecology.

The plants inhabit sunny and rocky mountain ridges and slopes at altitudes over 1000 m above sea level. Flowering specimens have been collected from July to August; fruiting specimens have been collected from October to November.

Etymology.

The specific epithet refers to ‘Kyushu’ where the new variety is distributed.

Note.

Although the style of this variety is included within the corolla, this part is exserted from the corolla in individuals from Mt. Ichifusa.

Figures

Figure 1. Photographs of flowers and leaves for the new taxa described in this study. A, B Rhododendron sohayakiense var. sohayakiense, Mt. Tsutsujo, Ehime Prefecture, Japan C, D Rhododendron sohayakiense var. kiusianum, Mt. Mukousaka, Kumamoto Prefecture, Japan E, F Rhododendron sohayakiense var. koreanum, Mt. Wolbong, Gyeongsangnam-do, South Korea. Photographs by Yoichi Watanabe.

Figure 5. Distribution of the Rhododendron tschonoskii alliance. Circles and squares showed locations of herbarium specimens (KYO, TNS).

Figure 7. Rhododendron sohayakiense var. kiusianum. A Flower, side view B Stamen C Pistil D Fruit E Abaxial and F adaxial sides of leaf. Scale bars: 1 mm (A-D); 3 mm (E, F). Drawings by Kumi Hamasaki from Y. Watanabe Mks 04 (holotype, TNS).