Horsetails and ferns are a monophyletic group and the closest living relatives to seed plants.

:Most of the 470-million-year history of plants on land belongs to bryophytes, pteridophytes and gymnosperms, which eventually yielded to the ecological dominance by angiosperms 90 Myr ago. Our knowledge of angiosperm phylogeny, particularly the branching order of the earliest lineages, has recently been increased by the concurrence of multigene sequence analyses. However, reconstructing relationships for all the main lineages of vascular plants that diverged since the Devonian period has remained a challenge. Here we report phylogenetic analyses of combined data--from morphology and from four genes--for 35 representatives from all the main lineages of land plants. We show that there are three monophyletic groups of extant vascular plants: (1) lycophytes, (2) seed plants and (3) a clade including equisetophytes (horsetails), psilotophytes (whisk ferns) and all eusporangiate and leptosporangiate ferns. Our maximum-likelihood analysis shows unambiguously that horsetails and ferns together are the closest relatives to seed plants. This refutes the prevailing view that horsetails and ferns are transitional evolutionary grades between bryophytes and seed plants, and has important implications for our understanding of the development and evolution of plants.

Pryer KM ，Schneider H ，Smith AR ，Cranfill R ，Wolf PG ，Hunt JS ，Sipes SD ... -  《NATURE》

Incongruence between primary sequence data and the distribution of a mitochondrial atp1 group II intron among ferns and horsetails.

Wikström N ，Pryer KM 《MOLECULAR PHYLOGENETICS AND EVOLUTION》

Horsetails are the sister group to all other monilophytes and Marattiales are sister to leptosporangiate ferns.

The "Monilophyte" clade comprising ferns, horsetails and whisk ferns receives unequivocal support from molecular data as the sister clade to seed plants. However, the branching order of its earliest emerging lineages, the Equisetales (horsetails), the Marattiales, the Ophioglossales/Psilotales and the large group of leptosporangiate ferns has remained dubious. We investigated the mitochondrial nad2 and rpl2 genes as two new, intron-containing loci for a wide sampling of taxa. We found that both group II introns - nad2i542g2 and rpl2i846g2 - are universally present among monilophytes. Both introns have orthologues in seed plants where nad2i542g2 has evolved into a trans-arrangement. In contrast and despite substantial size extensions to more than 5kb in Psilotum, nad2i542g2 remains cis-arranged in the monilophytes. For phylogenetic analyses, we filled taxonomic gaps in previously investigated mitochondrial (atp1, nad5) and chloroplast (atpA, atpB, matK, rbcL, rps4) loci and created a 9-gene matrix that also included the new mitochondrial nad2 and rpl2 loci. We extended the taxon sampling with two taxa each for all land plant outgroups (liverworts, mosses, hornworts, lycophytes and seed plants) to minimize the risk of phylogenetic artefacts. We ultimately obtained a well-supported molecular phylogeny placing Marattiales as sister to leptosporangiate ferns and horsetails as sister to all remaining monilophytes. In addition, an indel in an exon of the here introduced rpl2 locus independently supports the placement of horsetails. We conclude that under dense taxon sampling, phylogenetic information from a prudent choice of loci is currently superior to character-rich phylogenomic approaches at low taxon sampling. As here shown the selective choice of loci and taxa enabled us to resolve the long-enigmatic diversifications of the earliest monilophyte lineages.

Knie N ，Fischer S ，Grewe F ，Polsakiewicz M ，Knoop V ... -  《-》

Mosses share mitochondrial group II introns with flowering plants, not with liverworts.

Pruchner D ，Nassal B ，Schindler M ，Knoop V ... -  《-》

The earliest angiosperms: evidence from mitochondrial, plastid and nuclear genomes.

Qiu YL ，Lee J ，Bernasconi-Quadroni F ，Soltis DE ，Soltis PS ，Zanis M ，Zimmer EA ，Chen Z ，Savolainen V ，Chase MW ... -  《NATURE》