Abstract
The Chocó region in Colombia harbours one of the wettest rainforests in the world. Isolated for about 3 million years, it is known for its high rate of endemism in flowering plants, birds and butterflies. Bryologically it is, however, very unsufficiently known. For this reason, a transect was investigated from sea level to 1800 elevation. Ten hectarplots were studied ar different altitudes. 125 species of mosses were identified, of which 45 are new records for the departments of Chocó or Risaralda and 17 are new records for Colombia. Holomitrium aberrands J.-P. Frahm is described as new. The floristic results allow a first evaluation fo the bryogeograpgical rôle of this region. With 3 endemic species, endemism of mosses in the Chocó region is not as high as in other groups of organisms. Bryologically, the special characteristic of the Chocó mossflora seems to be a meso american floristic element, to which 15% fo the species belong. Part of the endemic species of mosses occur also in Panama. It is therefore supposed that the Chocó phytogeographical element is not confined to northern Ecuador and Colombia but continues into the isthmus of Panama.
Based on a calculation of floristic discintinuities, three altitudinal belts could be recoginzed between sea level and 1800 m, the tropical lowland forest up to 200 m, the tropicla submontane forest between 300 and 1500 m and the lower tropical montane forest between 1500 and 1800 m. The delimitation of altitudinal belts agrees quite well with altitudinal studies of tropical rainforest based on bryoophytes in other parts of the world.
Serval effects could be observed which are probably due to the extreme high humidity: Terrestrial species were found growing on bark or corticolous species on leaves. The cover of epiphytic bryophyytes is higher than elsewhere, especially in the lowland forest which shows usually a low bryophyte cover. The percentage of mosses compared with that of hepatics is much lower than wlsewhere. Mosses form only about 10% of the bryophyte cover in contrast to 40-50% in the according elevation in other rain forest regions.