Early evolution of land plants: Phylogeny, physiology, and ecology of the primary terrestrial radiation

The Siluro-Devonian primary radiation of land biotas is the terrestrial equ ivalent of the much-debated Cambrian "explosion" of marine faunas. Both sho w the hallmarks of novelty radiations (phenotypic diversity increases much more rapidly than species diversity across an ecologically undersaturated a nd thus low-competition landscape), and both ended with the formation of ev olutionary and ecological frameworks analogous to those of modem ecosystems . Profound improvements in understanding early land plant evolution reflect recent liberations from several research constraints: Cladistic techniques plus DNA sequence data from extant relatives have prompted revolutionary r einterpretations of land plant phylogeny, and thus of systematics and chara cter-state acquisition patterns. Biomechanical and physiological experiment al techniques developed for extant plants have been extrapolated to fossil species, with interpretations both aided and complicated by the recent know ledge that global landmass positions, currents, climates, and atmospheric c ompositions have been profoundly variable (and thus nonuniformitarian) thro ugh the Phanerozoic. Combining phylogenetic and paleoecological data offers potential insights into the identity and function of key innovations, thou gh current evidence suggests the importance of accumulating within lineages a critical mass of phenotypic character. Challenges to further progress in clude the lack of sequence data and paucity of phenotypic features among th e early land plant clades, and a fossil record still inadequate to date acc urately certain crucial evolutionary and ecological events.