MISHLER, Brent; Univ. of California, Berkeley: The evolution and ecology of desiccation tolerance in mosses

Bryophytes and tracheophytes adopted very different approaches to being a land plant; in general the bryophytes differ in most ways in their biology, ecology, and evolution from tracheophytes. One major difference is poikilohydry (the rapid equilibration of the plant’s water content to that of the surrounding environment) and desiccation tolerance (the ability of a plant to recover after being air-dry at the cellular level. Phylogenetic analyses suggest that desiccation tolerance was primitively present in the bryophytes (the basal-most living land plants), but has been lost in the evolution of tracheophytes. All bryophytes have these abilities to some extent, but they were lost in the elaboration of larger, more complex, and endohydric trachephytes. Desiccation tolerance has re-evolved in seeds and pollen and vegetatively in Selaginella, the ferns, and at least eight independent evolutions in the angiosperms. The moss Tortula ruralis is the best studied bryophyte — Oliver and colleagues have identified several genes that appear to be intimately involved in desiccation tolerance. We are using comparative approaches to find homologs among species of the Tortula ruralis complex and between bryophyte groups and the tracheophyte lineages. In particular we are targeting the exemplar species identified by the Deep Green collaboration, in a synthesis of a reconstructed phylogenetic tree for all land plants.