This special issue of the journal PhytoKeys contains a working checklist of accepted taxa worldwide. This is vital in achieving the goal of developing an online flora of all known plants by 2020 as part of the Global Strategy for Plant Conservation. The authors here present the first-ever worldwide checklist for liverworts (Marchantiophyta) and hornworts (Anthocerotophyta) that includes 7486 species in 398 genera representing 92 families from the two phyla. The checklist has far reaching implications and applications, including providing a valuable tool for taxonomists and systematists, analyzing phytogeographic and diversity patterns, aiding in the assessment of floristic and taxonomic knowledge, and identifying geographical gaps in our understanding of the global liverwort and hornwort flora. The checklist is derived from a working data set centralizing nomenclature, taxonomy and geography on a global scale. Prior to this effort a lack of centralization has been a major impediment for the study and analysis of species richness, conservation and systematic research at both regional and global scales. The success of this checklist, initiated in 2008, has been underpinned by its community approach involving taxonomic specialists working towards a consensus on taxonomy, nomenclature and distribution.
Introduction 3
Ecological and biological significance of liverworts and hornworts 4
Species numbers 5
Major historical works 6
Contemporary resources 8
Structure and format of the checklist 9
Taxon confidence levels 10
Methodology 11
Summary statistics 13
Concluding remarks 13
Taxonomic synopsis 14
Taxonomic list 27
Names in genera not currently accepted 507
Alphabetic list of accepted taxa 513
Acknowledgements 667
References 668