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J. Jpn. Bot. 92(2): 119–122 (2017)

Kenji SuetSugua,* and Takuto Shiratab: A New Color Variant of the Slipper Orchid Cypripedium debile

aDepartment of Biology, Graduate School of Science, Kobe University, 1-1, Rokkodai, Nada-ku, Kobe, 657-8501 JAPAN;bGraduate School of Life and Environmental Sciences, Tsukuba University, 1-1-1, Tennodai, Tsukuba, 305-8571 JAPAN*Corresponding author: kenji.suetsugu@gmail.com

Summary : We descr ibe a new form of Cypripedium debile whose lip excepting basal area, column, stigma, and staminode is lacking in purple coloration in Kiso County, Nagano Pref., Japan The ecological significance of the new form Cypripedium debile f. shinanoense is also discussed.

T h e l a d y ’s s l i p p e r s s u b f a m i l y (Cypripedioideae), which is distributed throughout the northern temperate zone and some of the tropics, is often regarded as a model lineage for food-deceptive orchids. The Cypripedioideae contains five genera comprising a total of 158 species (Pridgeon et al. 2001). One of the distinguishing features of this group is the one-way trap design of their flowers, which facilitates efficient pollination. Visiting insects pass through the flower entrance into the labellum and then proceed to exit through one of the pairs of basal orifices that are formed by the staminode that block the opening at the bottom of the labellum (Li et al. 2008).

The genus Cypripedium is a group of lady’s slippers orchids that contains ca. 50 species found throughout northern temperate zones (Cribb 1997, Pridgeon et al. 2001). Although species belonging to this genus are generally considered to be bee pollinated (Sugiura et al. 2001, Sugiura et al. 2002, Bänziger et al. 2005, Suetsugu and Fukushima 2014, but also see Ren et al. 2011), it has been suggested that one species, Cypripedium debile Rchb. f., might utilize its mushroom-like odour to attract fungivorous flies (Stoutamire 1967).

Cypripedium debile Rchb. f. is a widespread

and locally common species found in China, Taiwan, and Japan (Cribb 1997). It can be distinguished from other species in its genus by its glabrous habit, its paired heart-shaped leaves that are borne well above the soil surface, and its pendent inflorescence that bear small green and dark purple-veined flowers that are subtended by a linear bract (Cribb 1997). The current study describes a new form of C. debile that has lips lacking the dark purple veins.

Taxonomic treatmentCypripedium debile Rchb. f. f. shinanoense

Suetsugu & Shitara, f. nov. [Fig. 1]The newly discovered specimens differ from

Cypripedium debile Rchb. f. f. debile in that the lip excepting basal area, column, stigma, and staminode is lacking in purple coloration.

Type: JAPAN. Honshu. Nagano Pref., Kiso County, Agematsu Town. 4 June 2016, Masayuki Matsui 160604-1 (KPM–holotype).

Japanese name: Shinano-ko-Atsumorisō. Note: In this habitat, approximately 200

flowering individuals of C. debile f. shinanoense were found growing on the floor of the coniferous forest dominated by Chamaecyparis obtusa (Siebold et Zucc.) Endl. and Abies firma Siebold et Zucc. None of C. debile f. debile are distributed in the habitat. Similar color variants have also been discovered, though the mutant has not been formally described with a type specimen (Mitsuhashi 1988). In addition, a previously recognized mutant is somewhat distinct from C. debile f. shinanoense because the flower of the previously recognized

120 植物研究雑誌　第 92巻　第 2号 2017年 4月

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April 2017 TheJournal of Japanese Botany Vol. 92 No. 2 121

color variant is completely lacking in purple coloration including the basal area of the lip and lateral petal, which is still purple in C. debile f. shinanoense (Mitsuhashi 1988). In addition, as far as we know, a color variant of C. debile that is completely lacking purple coloration in the flower often co-occurs at very low frequency with normal colored C. debile populations, while as many as 200 C. debile f. shinanoense flowering individuals occur without C. debile f. debile. These facts may indicate that C. debile f. shinanoense is ecologically distinct from the color variant of C. debile, which is completely lacking purple coloration in the flower. It should be noted that Mitsuhashi (1988) also noted that the color variant of C. debile that is completely lacking purple coloration in flower can be seen without C. debile f. debile in a population. However, unfortunately, the population Mitsuhashi (1988) indicated has been lost due to illegal collection (Mitsuhashi personal communication).

Cypripedium debile Rchb. f., is believed to utilize its mushroom-like odour to attract fungivorous flies (Stoutamire 1967). In addition to their mushroom-like odour, the dark purple veins on the lips of C. debile flowers bear a striking resemblance to the gills of mushrooms, which suggest that this species utilizes not only olfactory mimicry to attract pollinators but also visual signals. Indeed, Policha et al. (2016) has shown that the mushroom-like, ‘gilled’ labellum of the orchid Dracula lafleurii can enhance pollinator attraction by exploiting the visual/chemosensory perceptual bias of fungivorous drosophilid flies. Given the apparent importance of this phenomenon, it would be interesting to investigate whether the absence of the purple veins on the lips of the newly discovered form of C. debile affects the frequency of pollinator visits or the diversity of its pollinator assemblage in comparison to C. debile f. debile.

We thank Masayuki Matsui for his discovery. We also thank Masayuki Matsui, Kenichi

Hashiba, Michiko Mineta, and Sadayoshi Mineta for their assistance in the field study. We also thank Masayuki Sato for providing typical C. debile f. debile samples to utilize in the comparative study. This work was supported by JSPS KAKENHI Grant Number 15K18470.

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Stoutamire W. 1967. Flower biology of the Lady’s Slipper (Orchidaceae: Cypripedium). Michigan Botanist 6: 159–175.

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Sugiura N., Goubara M., Kitamura K. and Inoue K. 2002. Bumblebee pollination of Cypripedium macranthos var. rebunense (Orchidaceae); a possible case of floral mimicry of Pedicularis schistostegia (Orobanchaceae). Plant Syst. Evol. 235: 189–195.

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末次健司 a，設楽拓人 b：ラン科コアツモリソウの色彩変異　コアツモリソウ Cypripedium debile Rchb. f.（ラン科）の唇弁には，通常，顕著な暗紫色の脈を生じるが，この脈を生じない個体が新たに見つかったので，新品種シナノコアツモリソウ Cypripedium debile Rchb. f. f. shinanoense Suetsugu & Shitara として記載した．タイプ産地では，およそ 200個体すべてが暗紫色の脈を生じない個体で，通常の個体とは混生していなかった．コア

ツモリソウは，キノコに似た匂いとキノコのヒダに似た唇弁の脈により，菌食性の昆虫を送粉者として利用していると考えられている．よって，脈を生じない新品種において，母種と送粉様式に違いがあるかは興味のあるところである．

（a神戸大学理学研究科，b筑波大学生命環境科学研究科）