A taxonomic revision of the genus Selaginella (Selaginellaceae) from Nepal

Abstract The present paper deals with the taxonomy of Selaginella from Nepal based on the examination of herbarium collections housed in major herbaria of Europe and Asia (with additional collections from virtual herbaria). A total of 25 species are recognised here, while Selaginella trichophylla and S. laxistrobila are two new records for the flora of Nepal, India (Sikkim) and Bhutan; Selaginella monospora var. ciliolata is synonymised to S. trichophylla; detailed descriptions, distribution and ecology and IUCN conservation status assessments (based on literature) are presented. For most of the species, illustrations of the leaves and strobili are provided for identification of the morphologically similar taxa.


Introduction
Selaginella P. Beauv. is the largest genus of lycophytes, with more than 700 species distributed all over the world but with highest diversity in the tropics (Jermy 1986, Zhou et al. 2015, PPG I 2016, Weststrand and Korall 2016. The Himalaya is one of the diversity centers of ferns and lycophytes of the World. Alston (1945) published the first account of Indian (including Nepalese) Selaginella P. Beauv. Earlier Don (1824), in his "Prodromus Florae Nepalensis", described seven species in Lycopodium L., including species of heterosporus Selaginella. Thapa (2002) listed 23 species of Selaginella. Fraser-Jenkins et al.'s (2015) revision of Nepalese Selaginella also recognised 23 species.
Description. Stems 5-15 cm, creeping. Rhizophores at intervals throughout the length of the creeping stem and branches, borne on dorsal side in axils of branches, densely hairy. Main stems anisotomously branched throughout, strongly dorsi-ventral in posi-tion, glabrous. Lateral branches arranged on main stem 0.5-1 cm apart, second branches simple or forked. Leaves spirally arranged on all sides stem and branches, more or less isomorphic, long linear-lanceolate, 0.8-2.3 mm excluding seta, 0.3-0.5 mm wide, margin shortly ciliolate, apex acuminate, in apex with long apical seta c. 1/5 as long as leaves.
Ecology. On rocks in dense forests at lower elevation. Alt. 250-1700 m. Distribution in Nepal. W, C, E. Nepalese threatened status: not available data. General distribution. BHUTAN, INDIA (Assam, Darjeeling, Uttarakhand, NE, C and S India), ARABIA, N AFRICA.

Selaginella remotifolia Spring
Ecology. Terrestrial, growing in paddy field or marshland or shady areas among the grasses with abundant water content. Restricted low altitude species of wet. Alt.   Chromosome number. 2n=18 (Manton 1950;Jermy et al. 1967). Selected specimens examined:
In both examined collections megaspores on the proximal and distal surfaces are covered with irregularly sized verrucae, the main surface is vermiculate, micro-sculptures are dense spinulose. Microspores on the proximal and distal surfaces are covered with irregularly sized verrucae, micro-sculptures are echinulate.
The molecular data also support the results of morphological studies. As a result, we consider the distribution of the species not only at low and medium altitudes but also in the highlands.