Pteridophyte richness in the NE Iberian Peninsula: biogeographic patterns

The richness and coexistence of pteridophyte species were studied at the me soscale level in the NE Iberian Peninsula (Catalonia and Andorra) using a g rid system with 10x10 km cell-size. The number of pteridophytes, the number of monolete and trilete ferns (two spore patterns), and the number of poly ploid and diploid ferns were studied in 371 of such units. The results sugg est: (a) a significant relationship of pteridophyte species richness with h igher-taxon richness (genera, family, order, class); (b) a significant rela tionship between pteridophyte richness and maximum altitude (positively rel ated), bedrock type (higher richness in siliceous types), and distance to t he coast (interacting with altitude); (c) a significant positive relationsh ip of monolete/trilete ratio with altitude (in the study area) and with lat itude (at the European scale); (d) a significantly higher polyploid/diploid ratio for monolete ferns than for trilete ferns, and a significant relatio n of this ratio with altitude. We conclude that at the scale studied, the d istribution of pteridophyte richness is mainly related to terrain and clima te parameters and that the monolete/trilete pattern may be explained by the higher polyploidy rate and better migration capacity in monolete species.