XVI International Botanical Congess

Pteridophytes have been found surprisingly habit-specific in their distribution within non-inundated rain forests in western Amazonia. The surprise comes from two sources: 1) soils in the area have proved more variable than is commonly thought, so there is a high diversity of available habitats, and 2) an unexpectedly high proportion of pteridophyte species show narrow edaphic preferences in the region. The distribution patterns of many species-rich genera (e.g., Adiantum, Polybotrya, Trichomanes) are such that congeneric species overlap geographically but not locally as they are confined to edaphically different habitats. Evolution of the Amazonian landscape and soils may hence have promoted evolution of edaphically specialized species.