The gene organization from rpoB to psbZ in analyzed ferns. The arrows correlate with the location, size and transcription direction of the corresponding genes. Dashed lines indicate direction of transcription does not change; solid lines mark putative local inversions. The complete version of the tree including statistical supports and branch lengths is shown in Additional file 1. *, the plastomes have been sequenced. The symbols of ycf66: green, complete gene; grey, pseudogene. Abbreviations: Z, psbZ; G: trnG-GCC; E: trnE-UUC; Y: trnY-GUA; D, trnD-GUC; M, psbM; N, petN; C, trnC-GCA; B: rpoB; Equisetum a, Equisetum arvense; Equisetum r, Equisetum ramosissimum.