Biodiv Sci ›› 2021, Vol. 29 ›› Issue (12): 1607-1619.DOI: 10.17520/biods.2021273

• Original Papers:Plant Diversity • Previous Articles     Next Articles

Species delimitation of the Selaginella delicatula group in China

Menghua Zhang1,2, Xianchun Zhang1,*()   

  1. 1 State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093
    2 University of Chinese Academy of Sciences, Beijing 100049
  • Received:2021-07-09 Accepted:2021-11-03 Online:2021-12-20 Published:2021-12-16
  • Contact: Xianchun Zhang

Abstract:

Aims: Species delimitation of Selaginella remains largely based on morphological characters, however, many closely related species are morphologically indistinguishable from each other. This study aims to (1) explore phylogenetic relationships within the S. delicatula group; and (2) evaluate the utility of nuclear and chloroplast DNA markers for the classification of Selaginella.
Methods: A total of 73 individuals were sampled, covering the geographical distribution and morphological variation of this group. We sequenced three chloroplast markers (rbcL, psbA, and atpI) and two nuclear markers (26S nrDNA and pgiC) to infer the phylogenetic relationships and haplotype network.
Results: We detected incongruence within S. delicatula-S. picta clade between chloroplast and nuclear phylogenies. The chloroplast dataset indicated S. delicatula is not monophyletic, with S. delicatula B sister to S. delicatula A-S. picta. In contrast, nuclear dataset discovered the monophyly of all three species, with S. delicatula sister to S. picta and S. wallichii sister to the S. delicatula-S. picta clade. Morphological characters, including main stem and branches, sporophylls, sterile leaves (ventral, dorsal, and axillary leaves) and spores were carefully observed and assessed. Morphological comparisons indicated that the samples of S. delicatula A and B clades are only distinct in branch patterns and the micromorphology of megaspores surface, not differential in morphology of leaves, strobili and microspores.
Conclusion: As a result of available evidence, three taxa were recognized in the S. delicatula group. It is necessary to perform further studies with cytological evidence and more samples of S. delicatula from type locality in order to obtain a better understanding of the species delimitation. We suggested that the taxonomic work of Selaginella should focus on the closely related species and multiple lines of evidence should be considered, including morphological characters, cytological evidence, molecular data (nuclear and chloroplast DNA markers), and geographical distribution.

Key words: 26S nrDNA, pgiC, chloroplast markers, lycophytes, Selaginella delicatula group