Taxonomic revision of the genus Spiranthes (Orchidaceae) in Taiwan

Abstract

The taxonomy of Spiranthes is highly challenging due to its phenotypic plasticity, morphological convergence, and hybridization. This paper presents a re-evaluation of the genus Spiranthes (Orchidaceae) in Taiwan, with special reference to the taxonomic identity of S. suishaensis that has often been considered the earlier name of S. nivea or S. hongkongensis. Nonetheless, the floral dissection of the type specimen revealed that S. suishaensis has a well-developed rostellum that separates the stigma and pollinarium of each flower, in contrast to autogamous taxa such as S. nivea and S. hongkongensis. Given the morphological evidence and that only S. sinensis was collected in the S. suishaensis type locality, we concluded that S. suishaensis is neither an earlier name for S. nivea nor S. hongkongensis but a synonym of S. sinensis. During morphological comparisons of S. suishaensis with other taxa of S. sinensis complex, we also found that the taxon illegitimately described as “S. minutiflora” could be treated as a variant of S. nivea. Given that it is distinguishable from S. nivea var. nivea by its more densely pubescent rachis and ovaries (vs. sparsely pubescent rachis and ovaries), narrower sepals with white tinged with pink or purple at apex (vs. wider and entirely white sepals), and papillose labellum disc (vs. almost glabrous labellum disc), we described it as a new variety of S. nivea, which we propose to name S. nivea var. papillata T.C. Hsu & Suetsugu. Consequently, we concluded that three species (S. sinensis, S. hongkongensis, and S. nivea [including var. nivea and var. papillata]) and one hybrid, S. australis × S. sinensis, occur in Taiwan.

A revision of Orchidaceae from the Kimberley region of Western Australia with new species of tropical Calochilus and Dipodium

“…Notes: Delimitation of species within Spiranthes has been difficult to achieve due to widespread distributions, local variation, high phenotypic plasticity (Pierce & Cribb 2002;Chen et al 2009;Jones & Bates 2015;Pace & Cameron 2017;Tao et al 2018;Pace et al 2019) and hybridisation (Suetsugu et al (2020). Some species complexes are now being resolved using molecular data (Dueck et al 2014;Surveswaran et al 2017Surveswaran et al , 2018Frericks et al 2018;Fan & Huang 2019;Pace et al 2019).…”

Spiranthes hachijoensis (Orchidaceae), a new species within the S. sinensis species complex in Japan, based on morphological, phylogenetic, and ecological evidence

“…(Orchidaceae) includes approximately 50 species that are widely distributed across the tropical and temperate regions of the Americas, Eurasia, and Australia (Dueck et al 2014;Pace et al 2019;Surveswaran et al 2017Surveswaran et al , 2018. Nonetheless, the delimitation of closely related Spiranthes species based on morphology alone is hindered by phenotypic plasticity, convergent morphological features, and hybridization (Dueck et al 2014;Pace et al 2019;Suetsugu et al 2020;Surveswaran et al 2017Surveswaran et al , 2018Tao et al 2018). In particular, the systematics of the Old World S. sinensis (Pers.)…”

“…Our intensive herbarium and field surveys failed to provide evidence of the occurrence of S. flexuosa in Japan. Spiranthes sinensis can be characterized by its phenology (spring flowering) and glabrous rachis and ovaries (Hayakawa et al 2013;Pace et al 2019;Suetsugu and Hayakawa 2016). Meanwhile, S. australis can be characterized by its early summer or autumn flowering phenology and glandular pubescent rachis, stems, and ovaries (Hayakawa et al 2013;Pace et al 2019;Suetsugu and Hayakawa 2016;Tsukaya 1994Tsukaya , 2005.…”

“…Spiranthes sinensis can be characterized by its phenology (spring flowering) and glabrous rachis and ovaries (Hayakawa et al 2013;Pace et al 2019;Suetsugu and Hayakawa 2016). Meanwhile, S. australis can be characterized by its early summer or autumn flowering phenology and glandular pubescent rachis, stems, and ovaries (Hayakawa et al 2013;Pace et al 2019;Suetsugu and Hayakawa 2016;Tsukaya 1994Tsukaya , 2005. Finally, S. hongkongensis, with glandular pubescent rachis, floral bracts, ovaries, and sepals, can be distinguished from both S. sinensis and S. australis by its degenerated rostellum, pollinia without a viscidium, shorter column, and distinctly trilobed stigma (Hsu and Chung 2014;Hu and Barretto 1976;Suetsugu and Hayakawa 2019).…”

“…Our intensive herbarium and field surveys failed to provide evidence of the occurrence of S. flexuosa in Japan. Spiranthes sinensis can be characterized by its phenology (spring flowering) and glabrous rachis and ovaries (Hayakawa et al 2013 ; Pace et al 2019 ; Suetsugu and Hayakawa 2016 ). Meanwhile, S .…”