Vaucheria lii Rieth, 2024

Vishnyakov, Vasily S., 2024, Validation of the name Vaucheria lii (Xanthophyceae, Vaucheriaceae), with a new distributional record, Phytotaxa 634 (2), pp. 183-186 : 185

Vaucheria lii Rieth , sp. nov.

Vaucheria lii Rieth 1959 , Zeitschrift für Botanik, 47(3): 224, nom. inval. (descr. angl.); V. lii Rieth 1963 , Archiv für Protistenkunde, 106(4): 590, nom. inval. (descr. lat., sine typo).

Holotype, indicated here: — GEORGIA. Adjara: Kobuleti municipality, Ispani bog area , ephemeral pool in the Shavi Ghele River floodplain, 41.86324°N, 41.78962°E, on damp soil in a community of Persicaria thunbergii (Siebold & Zucc.) H. Gross. , water conductivity 38 µS, Vishnyakov 283, 9 April 2023; Algal Herbarium of the Komarov Botanical Institute RAS, Saint Petersburg ( LE AW000045 ).

Isotype: —a part of the gathering, Herbarium of the Institute of Botany, Ilia State University, Tbilisi ( TBI 1000172 ) .

Filaments monoecious, 8–39 µm in diameter. Fruiting branches born laterally on filaments or may terminate them; bearing gametangia separated from the filament by emptied space. Fruiting branch consists of 1 or 2 oogonia borne laterally to 1 antheridium. Antheridia circinate-cylindrical, born on erect and distally circinate pedicels. Oogonia erect, ellipsoid-reniform to ovoid, clearly beaked, face the antheridium, 44–80.5 µm length, 31–57 µm in diameter. Oogonial pore single. Oospores ellipsoid to reniform, 44–73 µm length, 40–52 µm in diameter; forming in proximal part of the oogonium and leaving circinate distal cavity. Oospore wall smooth, 1.5–2 µm thick. Asexual reproduction unknown.

Vaucheria lii differs from other species in V. sect. Racemosae due to a septum in the fruiting branch that separates gametangia and leads to emptied space ( Fig. 1–5 ). The oogonial pedicel remains attached to the oogonium ( Figs. 4, 5 ) and falls off as the oospore matures ( Fig. 3 ). Among the species having beaked oogonia with a distal cavity, V. lii can be delineated by the shape of the cavity, which is circinate-conical ( Fig. 4 , see also comparative table in: Entwisle, 1988). From V. riethii Simons (1978: 397) , the most related species, V. lii separates by a single pore at the apex of the oogonial beak.

The holotype of V. lii marks the first record of the species in the flora of the South Caucasus. In West Asia, the species is known only from the Caucasus, with the nearest find in the Republic of North Ossetia — Alania, Russia ( Vishnyakov et al. 2020). Vaucheria lii is typically found on muddy banks of ponds and streams, in drainage ditches, and on saltmarshes, where it can tolerate salinity up to 4.5‰. In Georgia, V. lii was collected in a temporary aquatic habitat, a shallow flow near the Ispani percolation bog, in spring. The water in the holotype locality is ultra-fresh, as indicated by low water conductivity (see above). The patches of Vaucheria filaments were associated with bare soil trodden by cattle. The species was not found in winter and summer collections from the same place, which was terrestrial, nor in many other collections from West Georgia. These observations confirm the rarity of V. lii in the region.

“ Vaucheria lii var. bipora ” ( Rieth 1978: 383) is considered an invalid name because the species’ name to which it was assigned was not validly published (ICN Art. 35.1), and it did not meet the requirements of ICN Art. 44. The same year, however, the name based on a different type, V. riethii , was validly published ( Simons 1978). Later, Rieth (1980: 72) acknowledged the identity of his “ Vaucheria lii var. bipora ” and V. riethii , so there is no need to validate the variety name . Here, I support the view that V. lii and V. riethii are separate species, although some intermediate specimens identified as V. lii were recently found in materials from Central Russia ( Vishnyakov et al. 2020). The latter are likely belong to V. riethii . As of today, this species is known only from Europe, while V. lii is semi-cosmopolitan.

Figures

FIGURES 1–5. Morphology of Vaucheria lii from the holotype: 1—fruiting branch with undifferentiated gametangia, the septum is absent; 2–5—fruiting branches with septa, emptied space and differentiated gametangia. Symbols: a—antheridium, dc—distal oogonial cavity, es—emptied space, o—oogonium, op—oogonial pedicel, s—septum. Scale bars: 1–3—50 µm, 4, 5—30 µm.