First species records of charophytes (Charophyceae, Characeae) from Laos with a description of new species Nitella laotica sp. nov. and lectotypification of Chara pseudohydropithys Imahori

Chara braunii C.C.Gmelin, C. pseudohydropithys Imahori, and Nitella laotica R.E.Romanov, V.Yu Nikulin, K.-G.Bernhardt & A.A.Gontcharov, sp. nov. are reported for Laos. These records seem to be the first species records of charophytes for the country. Chara pseudohydropithys is lectotypified here and described in detail. It is the first record for Southeast Asia, extending its distribution range from mainland China, Taiwan, India, and Brazil. We mention this first record of C. braunii which is a frequently reported species in well-studied regions of Southeast and East Asia, because of the complete absence of records of charophytes from Laos. Nitella laotica sp. nov. is described as a new species using integrative taxonomy. The plants of N. laotica sp. nov. are macrodactylous, homoclemous, with mostly two-furcated branchlets, some branchlets one-two- or two-three-furcated, with or without central secondary ray within the same thallus and the same whorl, without accessory branchlets originating from central secondary rays or any furcation of branchlets, with bicellular dactyls and conical and mucronate end cells, solitary conjoined gametangia at first and more frequently at second furcation of branchlets, with reticulate ornamentation on both oospore surface and low spiral striae. The formation of ripe oospore surface is tentatively outlined for N. laotica sp. nov. This species is similar to N. oligospira A.Braun, a species distinctly different in morphology, in rbcL and ITS rDNA data. Further studies of charophytes are essential for Laos because the three species found there do not correspond to the species richness that can be expected for charophytes in a tropical country with a humid climate.