Phylogeny and systematics of the New World Selaginellaceae in a global context

In recent years, there has been a surge of interest in Selaginellaceae including treatments in regional floras and the description of new species, but a comprehensive review of the phylogeny and taxonomy of the New World taxa is still lacking. Here we assembled a dataset of one plastid and five nuclear markers of 610 accessions representing ca. 338 species to reconstruct a global phylogeny with a focus on the New World taxa (291 accessions representing ca. 160 species). Our major results include: (1) Sinoselaginelloideae are resolved as sister to Pulviniella + (Lycopodioidoideae + Selaginelloideae), different from previous results, illustrating the difficulty in resolving the affinities of Sinoselaginelloideae, (2) Selaginella schaffneri, included in a large-scale phylogeny for the first time, is resolved as the third earliest-diverging lineage in the family and a new genus, Mexiselaginella, and a new subfamily, Mexiselaginelloideae, are proposed, (3) there are ~319 (excluding four introduced/naturalized) species in 10 genera and six subfamilies in the New World and the New World is lacking 10 out of the 20 major clades (genera and/or subfamilies) in Selaginellaceae, (4) ca. 98% of the species diversity in the New World is found in Selaginelloideae and Gymnogynoideae, 69% of the species diversity is found in Selaginella s.s. alone, and ca. 96% of the species diversity is found in three genera, Selaginella s.s., Bryodesma, and Gymnogynum, (5) Selaginella rzedowskii is confirmed to have dorsal rhizophores and transferred to Lepidoselaginella, and (6) a list of species, genera, and subfamilies in Selaginellaceae from the New World is compiled and provided and a key to genera and subfamilies in the New World is given.