Cladistic analyses based on chloroplast protein coding genes rbcL and rps4, and the chloroplast encoded trnL (UAA) intron were conducted (1) to investigate phylogenetic relationships among basal peristomate mosses, especially the nematodontous mosses (Tetraphidaceae and Polytrichaceae), and the arthrodontous mosses with pleated endostomes (Buxbaumiaceae and Diphysciaceae), and (2) to make inferences on evolution of the peristome. A combined data matrix included 46 taxa and 2206 characters of which 619 were parsimony informative. The results indicate that the basal peristomate mosses, particularly the Tetraphidaceae, Polytrichaceae and Buxbaumiaceae, are paraphyletic. Sister group relationships between the following taxa are newly suggested: Tetraphidaceae and all peristomate mosses; Polytrichaceae and the clade consisting of Buxbaumiaceae, Diphysciaceae, diplolepideous and haplolepideous mosses; Buxbaumiaceae and the clade consisting of Diphysciaceae, diplolepideous and haplolepideous mosses. The following novel inferences on peristome evolution are also suggested: the plesiomorphic condition of the endostome of the arthrodontous peristome was pleated; the pleated endostome has been transformed into a keeled endostome in the diplolepideous/haplolepideous clade; the similarity in cell divisions preceding deposition of secondary peristomial wall material in peristome development is a synapomorphy in the peristomate mosses. The exostome has been independently lost or reduced in the Diphysciaceae, and the diplolepideous/haplolepideous clade.

Communicating Editor: Alan T. Whittemore