Integrative species delimitation of the Selaginella sanguinolenta (Selaginellaceae) group with description of a new species, S. baodongii

Selaginella sanguinolenta group is widely distributed from the Himalayas to Siberia and the Russian Far East, including four to nine taxa. Despite progress in recent phylogenetic studies of the S. sanguinolenta group, the problem of species delimitation in this group remains. We revise the taxonomy of the S. sanguinolenta group based on an integrative approach considering morphological, molecular, and geographical evidence. The sampling for molecular analysis based on rbcL, psbA, and 26S nrDNA sequence data involved 71 individuals, covering the geographical range of this group. A total of 21 morphological traits from 103 specimens were explored using principal component analysis and linear discriminant analysis (LDA). The LDA results indicate that the combination of ventral leaf cilium length and ventral/dorsal leaf carinate characteristics enable a success rate of more than 90% in distinguishing between S. aitchisonii (western Himalayas to northern China), S. jacquemontii (western Himalayas to southwest China), and S. sanguinolenta (Russian Far East regions to northeast China). The phylogenetic analysis results of nuclear and plastid DNA markers further disclose the clear molecular differentiation. Selaginella nummularifolia, S. rossii, and S. sajanensis are well-defined species based on morphological and molecular evidence with narrow distribution ranges respectively. Based on molecular and morphological evidence, in combination with distribution information, we finally recognize seven species in the S. sanguinolenta group, including a new species, S. baodongii sp. nov. from the bordering regions of Russia and China in northeast Asia.