Systematic Studies in 'Schoenus' L. (Schoeneae, Cypearaceae)

Abstract

Infra- and suprageneric classification of 'Schoenus' is uncertain. Like other Cyperaceae, 'Schoenus' L. and allied genera have reduced vegetative and reproductive structures which have resulted in uncertain homologies and hence differences in opinion about its phylogenetic relationships. This study addresses the issues of phylogeny, species limits and usefulness of anatomical data in the genus. Phylogenetic analysis of 195 ingroup samples made up of 123 samples covering 74 species of 'Schoenus' and 72 samples across 56 species from 11 genera in tribe Schoeneae was conducted on a molecular sequence dataset from ITS nrDNA using maximum parsimony and Bayesian inference. Results indicated that 'Schoenus' is non-monophyletic, which corroborates small-scale previous molecular studies. 'Schoenus' subgen. 'Schoenus' had strongly supported lineages whereas S. subgen. 'Pseudomesomelaena', including 'S. grandiflorus', are embedded within other genera in Schoeneae and therefore not in core 'Schoenus'. The ITS data did not fully resolve relationships of 'Schoenus' at species level, but revealed numerous well supported terminal groupings and taxa allowing for further fine-scale study of the complexes to resolve limits and application of names. ... Taxonomic value of culm anatomy has been investigated using phenetic analysis. The results show culm anatomical features have taxonomic value in 'Schoenus' at and below species level and help to clarify patterns of variation at infra and interspecific level and to resolve species complexes. Phylogenetic analysis, however, indicated that the dataset had no power to resolve higher level relationships within 'Schoenus'. A new species has been distinguished from 'S. melanostachys' using morphology and integrating evidence from culm anatomy and scanning electron microscopy.