Soil ciliates (protozoa, ciliophora) from Namibia (Southwest Africa), with emphasis on two contrasting environments, the Etosha Region and the Namib Desert

habitats of Namibia, Southwest Africa, one of the world's driest countries. The ciliate, respectively, their resting cysts, were re-activated from air-dried samples using the non-flooded Petri dish method. Species were determined by combining live observations, silver impregnation, and scanning electron microscopy. A total of 365 species were identified, of which 128 (35%) were undescribed, including a new order and suborder, three new families, and 34 new genera and subgenera. These new and many insufficiently known taxa, altogether more than 200 species and subspecies and over 300 populations, are described in the present monograph (see chapter 3.2.1 for a summary of names and nomenclatural acts); 800 type slides have been deposited in (LI). Further, ontogenesis was investigated in 20 species. The Namibian soil ciliate community shows some remarkable differences to the world community. Specifically, raptorious gymnostomatids and filamentous cyanobacteria feeding nassulids are over-represented, while hypotrichs and peritrichs are underrepresented. Nassulids obviously profit from the cyanobacteria covering wide areas of the Etosha region and the crust soils in the arid areas. Hypotrichs are more kthan r-selected and thus cannot develop optimally in the harsh Namibian climate. Likewise, the sandy soils are disadvantageous for sessile peritrichs. Generally, however, the Namibian soil ciliate biota are unexpectedly rich, that is, more diverse than those from central Europe, likely because they had at least 55 million years to evolve adapted populations and species. 200 of the 365 ciliate species identified occur at only one or two sites, showing a very patchy distribution of most species and a high proportion of possibly rare species. Most of the 11 most frequent (> 40%) species are common in soils globally, except for Exocolpoda augustini, which is adapted to hyperarid conditions by a special life cycle and an extraordinarily thick-walled (dormant) resting cyst. Using total species numbers and the proportions of undescribed species, four local ciliate diversity centres were discovered: Etosha region (19 samples with 216 species, of which 61 were undescribed); dune sea Namib Desert (15 samples with 150 species, of which 32 were undescribed); Aloe dichotoma forest and Bukaos River floodplain near the town of Keetmanshoop (2 samples each with 11 new species); road puddles in the Bambatsi Guest Farm (1 sample with 126 identified and 15 unidentified species, of which at least 40 were undescribed). We estimate that there are about 1000 soil ciliate species in Namibia, of which 350 are undescribed, including an unknown number of endemic species. Thus, our monograph contains only one third of the species actually living in the highly diverse terrestrial habitats of this country. We show that there must be many more free-living ciliate species globally than the 3000 estimated by FlNLAY. His estimation is flawed by biased literature evaluation, doubtful synonymies, unusual taxonomic practices and, partially, false theoretical concepts. Undersampling is the key to understanding protist diversity. K e y w o r d s : Adaptation, ciliate ecology, ciliate systematics, ciliate taxonomy, ciliate endemism, ciliate biodiversity, global number of free-living ciliates, neotypification, new species, ontogenesis, saline desert, dune desert, undersampling.