First contribution to the diatom flora of the Amsterdam Island (TAAF)

Over 90 taxa have been observed in a first study on the terrestrial and fre shwater diatoms of the Amsterdam Island, in the southern Indian Ocean. The observed flora shows little resemblance with that of other subtropical isla nds (especially Mauritius, Reunion), but there are some similarities with t hat of subantarctic islands. The cluster analysis revealed 4 assemblages, m ost problably separated by moisture and pH. The Pinnularia borealis assembl age and the Luticola mutica assemblage prefer dry places. The Nitzschia fru stulum var. frustulum assemblages is found on wetter places such as an old block house. The last assemblage is characterized by the presence of many a cidophilic taxa and is only reported from the peat area on the central moun tain of the island.