A Five Gene Phylogenetic Study of Fuireneae (Cyperaceae) with a Revision of Isolepis humillima

Cyperaceae tribe Fuireneae consists of six genera (Actinoscirpus, Pseudoschoenus, Fuirena, Bolboschoenus, Schoenoplectus, and Schoenoplectiella) and approximately 155 species distributed widely across all continents except Antarctica. Recent molecular analyses suggest that Fuireneae is paraphyletic with respect to Cypereae, but limited taxonomic sampling and low branch support have resulted in unresolved relationships among key genera. To address the potential paraphyly of Fuireneae as well as intratribal and intertribal relationships, thirty taxa representing major lineages from the six Fuireneae genera within Cypereae were sequenced for five coding and non-coding regions from the nuclear (internal transcribed spacer, ITS) and chloroplast (trnL intron/ trnL-trnF spacer; partial ndhF, rbcL and matK genes) genomes. Maximum parsimony, maximum likelihood and Bayesian analyses of the dataset strongly support Fuireneae as a grade of three clades: (1) Fuirena, (2) Bolboschoenus and (3) a group composed of Cypereae and the four remaining Fuireneae genera (Schoenoplectus, Schoenoplectiella, Actinoscirpus, and Pseudoschoenus). Individual and combined gene trees consistently position Isolepis humillima within a well supported clade consisting of species in Schoenoplectiella sect. Schoenoplectiella. Based on molecular evidence, we transfer Isolepis humillima to Schoenoplectiella humillima, and suggest that a large-scale revision of tribal limits is required to reflect the natural relationships of the genera currently treated in Fuireneae.