Biogeographical analysis of the pteridophyte diversity of continental Argentina and Chile

The pteridophytes are represented by 116 native species (43 genera/20 families) in continental Chile, and by 346 native species (86 genera/27 families) in continental Argentina. Both countries share 89 species (41 genera/20 families). Lower pteridophyte diversity and the higher endemism in Chile (11.2%) than in Argentina (3.5%) are possibly related to historical extinctions and the actual geo-climatic isolation. However, the endemism in pteridophytes is five to six times lower than in angiosperms. The richest Argentinean genera are Thelypteris (34 species), Asplenium (32), Cheilanthes (21), Blechnum (19) and Hymenophyllum (16). The last two genera are also the most numerous in Chile (Hymenophyllum 18 species and Blechnum 10). In the two countries, pteridophyte diversity shows opposite latitudinal trends, with high species richness in three centers: two subtropical humid centers in northwestern and northeastern Argentina, and a temperate humid center in southern Chile and Argentina around 40degrees S. The three centers concentrate 93% of the species and 95% of the endemisms, sharing few species. In the subtropical centers, the families Aspleniaceae, Polypodiaceae, Pteridaceae, Thelypteridaceae and Selaginellaceae are the main components and share a large number of species with Bolivia and Brazil, respectively. The southern temperate center has a lower pteridophyte diversity, but a larger number of endemisms (77%) than the northern subtropical centers. However, adjacent regions of Chile and Argentina within the temperate center have high similarity and maintain a strong floristic interchange. Blechnaceae and Hymenophyllaceae are the most common families. Taxa with disjunct distribution patterns and with presence in the three centers indicate that the pteridophyte flora had a wider and continuous distribution in the past, and that their limits have receded as a consequence of the strong climatic and geomorphologic changes during the Tertiary and the Pleistocene.