Towards a taxonomic revision of the lycophyte genus Selaginella (Selaginellaceae) in Guizhou, China: new species, new records and cryptic species

To clarify the taxonomic identities of newly-collected Selaginella specimens from Guizhou, south-western China, we briefly reviewed the Selaginella species recorded in Guizhou and conducted a study integrating morphological comparisons and phylogenetic analyses. The specimens from a total of 26 Selaginella populations which we collected in 2024 were grouped into 16 taxonomic entities, based on morphological comparisons, including ten species with established names and six taxa of uncertain identity. Phylogenetic analyses, based on plastid regions (rbcL, atpI, psbA) with broad sampling and plastid CDS with focused sampling, confidently placed 15 newly-collected specimens within the phylogeny: one specimen (S. davidii) within the Kungiselaginella clade and the remaining 14 distributed amongst three subclades of the Hypopterygiopsis clade. By integrating morphology and molecular evidence, we recognise one new species (S. dushanensis), one new provincial record (S. parachrysocaulos) to Guizhou and four cryptic species (S. amblyphylla, S. qingchengshanensis and two lineages of S. vaginata); where “cryptic species” denotes morphologically indistinguishable, but phylogenetically distinct lineages. Amongst these, S. amblyphylla and S. qingchengshanensis are also new records to Guizhou. The new species S. dushanensis is described and illustrated. It is morphologically very similar to S. monospora and S. submonospora, but differs mainly in median leaves with a long-aristate apex. As a result, the known diversity of Selaginella in Guizhou now records 43 species, including the four cryptic and one putative new taxon (S. cf. xipholepis). Further studies are needed to confirm the identities of the cryptic species and the remaining unidentified taxon.