Dactylostalix Reichenbach (1878:74)

Suetsugu, Kenji, Yagame, Takahiro, Yukawa, Tomohisa & Suyama, Yoshihisa, 2024, Taxonomic revision of the formerly monotypic orchid genus Dactylostalix, Phytotaxa 652 (2), pp. 83-99 : 86-89

Dactylostalix Reichenbach (1878:74)

Type:— Dactylostalix ringens Reichenbach (1878: 74) .

Rhizome creeping, pale brown. Scape arising from the rhizome, erect, glabrous, pale green, bearing one flower at the apex. Leaf solitary; leaf blade elliptic to ovate, pale green, obtuse at the apex, rounded or obtuse at the base; petiole broadly winged. Bract pale green. Ovary and pedicel pale green. Dorsal sepal oblanceolate to oblong, yellowish-green with or without reddish-purple spots around the base, apex obtuse or acute. Lateral sepals obliquely oblong to falcate, yellowish-green with or without reddish-purple spots around the base, apex obtuse or acute. Lateral petals oblanceolate to oblong, yellowish-green with or without reddish-purple spots around the base, apex obtuse or acute. Labellum protruding, reflexed at the apex, more or less 3-lobed, disc with 2 parallel keels; lateral lobes narrowly triangular to ovate, entirely white or white with a small reddish-purple spot at the apex of each lobe, or slightly obliquely semiorbicular, white with a large reddish-purple spot at the apex of each lobe; posterior portion of midlobe ovate to cordate, entirely white or white with randomly arranged small reddish-purple spots, or white with randomly arranged small reddish-purple spots and 2 larger reddish-purple dots at the base, margin slightly undulate and irregularly erose-denticulate. Column curved, semi-cylindrical with column wings at the lateral part of the apex and 1 appendage at the central part of the apex; rostellum well-developed; stigma located just below the rostellum. Anther hemispheric; pollinia 4, in 2 pairs, obovoid; viscidium rhomboid. Capsule obovoid.

Morphology:— The genus Dactylostalix is distinguished by its single flower, pollinarium featuring four stacked pollinia and a viscidium with a rudimentary stipe, the lack of a corm or pseudobulb, and a flat, non-plicate leaf within the subtribe Calypsoinae ( Freudenstein 1994; Freudenstein et al. 2005). The genus Dactylostalix encompasses two species ( D. ringens and D. uniflora ). Dactylostalix uniflora can be differentiated from D. ringens by its shorter scape, smaller flower, less spotted tepals, drooping sepals and lateral petals, a labellum with smaller, narrowly triangular to ovate lateral lobes, more pronounced keels on the adaxial surface of the lip, and a slender column with a less developed clinandrium.

Distribution:— The genus Dactylostalix is endemic to Japan and the Russian Far East (the Kuril Islands and Sakhalin Island) ( Freudenstein 1994; Freudenstein et al. 2005). Dactylostalix ringens is found over wider climate ranges, while D. uniflora is limited to the subarctic zone (high elevation areas in Honshu and Hokkaido). Even within sympatric populations, D. ringens tends to be found at lower elevations than D. uniflora populations. For instance, in Mt. Fuji, Dactylostalix ringens is found over a broader range of elevations (800–2200 m) while D. uniflora is typically found in the subalpine zone (2200–2400 m). However, further quantitative assessments are needed to accurately determine the distribution of both species.

Phylogeny:— The maximum likelihood phylogenetic analysis revealed that D. uniflora forms a distinct clade from D. ringens , supported by a 100% bootstrap value ( Fig. 5 ). Additionally, Neighbor-Net phylogenetic analysis indicated that D. ringens and D. uniflora represent at least two distinct genetic clusters ( Fig. 6 ). This analysis also suggests some genetic differentiation within D. uniflora ; however, morphologically, no clear differences were found between these two subgroups of D. uniflora based on our current dataset. Therefore, we conclude that it is appropriate to classify these as two distinct species, D. ringens and D. uniflora . Given that D. uniflora is distributed in high-altitude zones, these populations are likely prone to rapid differentiation.

Importantly, there was complete alignment between the morphological identification performed before obtaining genetic results and the genetic data. Thus, the diagnostic characteristics we employ are sufficiently robust to enable clear differentiation, ensuring that intraspecific variation does not compromise the classifications.

Figures

FIGURE 5. Phylogenetic tree of Dactylostalix ringens and D. uniflora reconstructed from MIG-seq data. Nodes supported by bootstrap values <50% are not shown. Branch length represents the average number of substitutions per site.

FIGURE 6. Neighbor-Net network of Dactylostalix ringens and D. uniflora reconstructed based on uncorrected p distance calculated from 6062 SNPs.