The northern and southern polar regions differ substantially in topography, climate, terrestrial habitats and in their biota. The Arctic flora comprises around 900 flowering plants, 600–700 bryophytes and 2000 lichens. The Antarctic flora is depauperate by comparison with only two flowering plants, 100–120 bryophytes, and probably only around 200 lichens. Despite considerable taxonomic uncertainty, broad phytogeographic patterns can be outlined, with species having a Maritime Antarctic, Peninsula and Lesser Antarctic, Circum-Antarctic, and Disjunct distribution pattern. The extent of endemism in the flora is unclear. The origin of the Antarctic lichen flora appears ancient in pan, although there is ample evidence for post-Pleistocene or Holocene colonization and invasion.