Isoetes yuhangensis X. Liu & Y.C. Chen

Liu, Chenlai, Yu, Xiaolei, Song, Xiaoli, Shao, Jingjing, Chen, Yuchu & Liu, Xing, 2024, Two new diploid species of Isoetes (Isoetaceae: Lycopodiopsida) from Southeastern China based on morphological and molecular evidence, Phytotaxa 642 (1), pp. 37-49 : 42-43

publication ID	https://doi.org/ 10.11646/phytotaxa.642.1.3
DOI	https://doi.org/10.5281/zenodo.13213310
persistent identifier	https://treatment.plazi.org/id/038987CA-C053-7F7E-FF44-F89FFD957C47
treatment provided by	Felipe
scientific name	Isoetes yuhangensis X. Liu & Y.C. Chen
status	sp. nov.

Treatment

Isoetes yuhangensis X. Liu & Y.C. Chen View in CoL , sp. nov. ( Figure 2 View FIGURE 2 )

Diagnosis: — Isoetes yuhangensis differs from I.taiwanensis by its rugulate megaspores with fibrous perispores (vs tuberculate megaspores), velum absent (vs velum rudimentary), semicircular labium (vs reniform labium), and the megaspore muri connected on the distal surface (vs megaspore muri rarely connected).

Type:— CHINA. Zhejiang Province, Hangzhou City, Yuhang District , Huanghu Town , Cibi Village , elevation 81 m, 30°26′52″ N; 119°50′22″ E, 27 September 2021, X. Liu, WH2021092702 (holotype WH!) GoogleMaps .

Description: —Plants aquatic, amphibious, growing among paddy field drainage ditch. Corm 3-lobed. Roots conspicuous, dichotomously branched. Leaves white basally, green above, 1.1–2.3 mm wide at middle, 12–32 cm long, 5.7–10.6 mm wide at the base, erect to ascending, apex acute to attenuate. Ligule triangular. Labium present, semicircular. Sporangium 9.4–11.4 mm long, 4.2–5.8 mm wide, basal, oblong, the surface of sporangium with white, and membranous. Velum absent ( Figure 2G and 2H View FIGURE 2 ). Megaspores, 270–324 µm in diameter (N = 30 +/- SD 14.0 µm); proximal surface rugulate; equatorial ridges thin and corrugate, radial ridges thick and smooth; distal surface rugulate and densely covered with fibrous perispores ( Figure 2A–C View FIGURE 2 ). Microspores, 16–26 µm in length (N = 30 +/- SD 2.3 µm), monolete, proximal and distal surface sharp-tipped echinate ( Figure 2D and 2E View FIGURE 2 ). Chromosomes: 2n = 22 ( Figure 2F View FIGURE 2 ).

Etymology: —The specific epithet refers to the type locality Yuhang district, Zhejiang, where this species is endemic.

Distribution and Habitat: — Isoetes yuhangensis is only known from one locality, Cibi village ( Figure 6 View FIGURE 6 ). The plants are located at the bottom of the mountain ( Figure 2I View FIGURE 2 ), which are dominated by Metasequoia glyptostroboides Hu & W. C. Cheng , and associated with Alisma canaliculatum A. Braun & Bouché , Limnophila sessiliflora (Vahl) Blume , Lysimachia clethroides Duby , etc. Isoetes yuhangensis is a rare and endangered species in China. We have found only one site in the Yuhang district. It is vital to protect the populations of these new Isoetes species, and there is an urgent need to find additional populations.