On the diversity of land plants

To understand the current patterns of plant diversity, it is necessary to c onsider the various controlling factors within thr broad range of both spat ial and temporal scales. We briefly review historical and geographical evid ence for the evolutionary context. We concentrate on recent studies investi gating the processes that control plant diversity to outline am present kno wledge of plant diversity. Most of the research is drawn primarily, though not exclusively, from data collected in wetlands, although there are parall els to terrestrial systems. Future directions for the study and conservatio n of diversity are recommended.