Putting Physcomitrella Patens on the Tree of Life: the Evolution and Ecology of Mosses

Physcomitrella patens is an important model system for studies of genetics and physiology, and with its newly sequenced genome, it is perfectly placed phylogenetically to serve as a point of comparison for angiosperms. This chapter addresses three main questions: (1) How typical of a moss is P. patens? It is rather atypical, given the reasons that it was selected as a model system, such as its rapid life cycle and reduced morphology, yet it is representative in many ways. (2) Where does it belong in the phylogenetic history of land plants? The mosses are monophyletic, and share a common ancestor with hornworts and tracheophytes, with P. patens nesting within the ‘true mosses’. (3) What are the special attributes of moss ecology and evolution that can lend special interest to the study of P. patens? When comparing P. patens with tracheophytes, it is important to understand both its similarities and differences with its larger cousins – we discuss how many processes influencing their physiology, ecology and evolutionary diversification seem to be quite different from the tracheophytes.