DNA variation within Juncaceae: comparison of impact of organelle regions on phylogeny

Abstract

A phylogenetic analysis of the Juncaceae was conducted to assess relationships among the genera Juncus, Luzula and five other small South American genera (Distichia, Marsippospermum, Oxychloe, Patosia and Rostkovia). We examined parallel datasets from organelles (mtDNA: atp1 gene, cpDNA: trnL intron, trnL-F intergenic spacer, rbcL gene) with respect to qualities relevant to the phylogenetic analysis of the Juncaceae. The main aim of our work was to produce a robust phylogeny of the Juncaceae validated by data from both organelles. Our data confirm the monophyly of the genus Luzula, but do not provide support for monophyly of the genus Juncus. The majority of taxa clustered within two subgenera, Agathryon and Juncus, morphologically supported by the presence or absence of bracteoles and cymose or racemose inflorescences, respectively. The subgenus Juncus is divided into two separate clades, the first closely related to the subgenus Agathryon and the second in the most basal part of the tree. Moreover, small South American genera clustered together with Juncus sect. Graminifolii and also with Juncus sect. Juncus. In fact, comparison of results from separate analyses of mitochondrial and plastome genes demonstrates that the general resolution of main topology of the atp1 tree is similar to the separate rbcL tree; the genus Juncus is better resolved, but the genus Luzula remains mainly polytomic.