Rhododendron sohayakiense var. koreanum Y.Watan. & T.Yukawa, 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. koreanum Y.Watan. & T.Yukawa var. nov. Figs 1 , 5 , 8

Diagnosis.

This variety is similar to Rhododendron sohayakiense var. sohayakiense Y. Watan. & T. Yukawa and R. sohayakiense var. kiusianum Y. Watan., T. Yukawa & T. Minamitani, but is distinguished by its large leaf size. Further, it differs from the former through its raised lateral nerves on the abaxial leaf surface and from the latter through its shorter corolla tube and by its longer style exserted from the corolla.

Type.

SOUTH KOREA. Gyeongsangnam-do: Hamyang County, Mt. Wolbong, 35°44'51.31"N, 127°42'33.99"E, on slope of the mountain, 1000 m, 15 June 2017 (fl), Y. Watanabe, S. Hwang and N. Yun Wol06 (holotype: TNS; isotypes: TNS, KB).

Additional specimens examined.

SOUTH KOREA. Jeollabuk-do: Namwon City, Mt. Gonam, 35°28'27.74"N, 127°30'00.82"E, 800 m, 15 Jun 2017 (fl), Y. Watanabe, S. Hwang and N. Yun Gom01 (TNS); Mt. Jirisan, Banyabong peak, 1700 m, 20 Aug 1982 (fr), T. Yamazaki & F. Yamazaki 3294 (KYO); Gyeongsangnam-do: Mt. Gayasan, 23 Aug 1935 (fr), G. Koidzumi (KYO).

Description.

Spring leaves scattered or crowded on upper branchlets; petioles 0.5-1 mm long; blade thick chartaceous, oblong, 10-35 mm long (25-35 mm long at maximum within each individual), 5-15 mm wide, apex acute and terminating in a gland, base acute, strigose on both surfaces; midrib prominent abaxially; lateral nerves pinnate, 1-3 paired, raised abaxially. Summer leaves oblanceolate, 6-20 mm long, 1-8 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, openly tubular-funnelform, 8-12 mm long and wide, dissected 1/2 corolla length into 4 lobes; tube 2-3 mm long, ca. 2 mm wide, glabrous outside, pilose on upper inside; lobes elliptic to oblong, rounded, 3-5 mm long, 2-4 mm wide. Stamens 4, subequal, 6-9 mm long, exserted; filaments densely pilose on lower three-quarters; anthers yellow, oblong, ca. 1 mm long. Ovary ovoid, densely soft strigose, ca. 2 mm. Style 5-6 mm long, exserted, glabrous. Capsule ovoid, 3-4 mm long, 2.5 mm wide, densely strigose.

Distribution.

SOUTH KOREA: Jeollabuk-do, Gyeongsangnam-do.

Ecology.

The plants inhabit mountain ridges and slopes at altitudes over 800 m above sea level. Flowering specimens have been collected from June to August; fruiting specimens have been collected from October. Honeybees are frequent visitors to the flowers, suggesting that they are pollinators of the variety.

Etymology.

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

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 8. Rhododendron sohayakiense var. koreanum. 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, S. Hwang and N. Yun Wol 01 (holotype, TNS).