Distribution Patterns in Major Pteridophyte Taxa Relative to Those of Angiosperms

Whereas the distribution of the principal pteridophyte families over the major parts of the globe is quite similar to that of the principal angiosperm families, pteridophyte genera are in general considerably more widespread. Four possible explanations are discussed: greater age of fern genera and thus a longer period available for dispersal; slower evolution of ferns; greater dispersability through small size of diaspores; and non-equivalence of fern and angiosperm genera. Furthermore, primitive fern genera diverge in their distribution patterns from those of primitive angiosperms; they tend to occupy special habitats and/or to possess special growth forms, rather than being concentrated in geographical relict areas, as are angiosperms. Finally, the 'American Paradox' in the distribution of fern genera and sections, which is an imbalance between the Old and the New World, is briefly