Diversity and biogeography of the Antarctic flora

Aim To establish how well the terrestrial flora of the Antarctic has been sampled, how well the flora is known, and to determine the major patterns in diversity and biogeography. Location Antarctica south of 60 degrees S, together with the South Sandwich Islands, but excluding South Georgia, Bouvetoya and the periantarctic islands. Methods Plant occurrence data were collated from herbarium specimens and literature records, and assembled into the Antarctic Plant Database. Distributional patterns were analysed using a geographic information system. Biogeographical patterns were determined with a variety of multivariate statistics. Results Plants have been recorded from throughout the Antarctic, including all latitudes between 60 degrees S and 86 degrees S. Species richness declines with latitude along the Antarctic Peninsula, but there was no evidence for a similar cline in Victoria Land and the Transantarctic mountains. Multi-dimensional scaling ordinations showed that the species compositions of the South Orkney, South Shetland Islands and the north-western Antarctic Peninsula are very similar to each other, as are the floras of different regions in continental Antarctica. They also suggest, however, that the eastern Antarctic Peninsula flora is more similar to the flora of the southern Antarctic Peninsula than to the continental flora (with which it has traditionally been linked). The South Sandwich Islands have a flora that is very dissimilar to that in all Antarctic regions, probably because of their isolation and volcanic nature. Main conclusions The Antarctic flora has been reasonably well sampled, but certain areas require further floristic surveys. Available data do, however, allow for a number of robust conclusions. A diversity gradient exists along the Antarctic Peninsula, with fewer species (but not fewer higher taxa) at higher latitudes. Multi-dimensional scaling ordination suggests three major floral provinces within Antarctica: northern maritime, southern maritime, and continental. Patterns of endemism suggest that a proportion of the lichen flora may have an ancient vicariant distribution, while most bryophytes are more recent colonists.