Porembski, S. & Barthlott, W. (eds) (2000) Inselbergs: biotic diversity of isolated rock outcrops in tropical and temperate regions. Ecological studies 146, Springer-Verlag, Heidelberg, Germany. xxxi + 524 pp, figs, tables, colour plates, subject index, species index. Hardback: Price £103.00, US$149.00, sFr 257.00. ISBN 3 540 67269 9. This book appears at the 100th anniversary of the coining of the term ‘inselberg’, by the German geologist Wilhelm Bornhardt, to designate granitic outcrops present in East Africa. It comprises mainly a synthesis of research produced within a long-term research project of the Botanical Institute of the University of Bonn. In their introduction, the editors convincingly demonstrate that these very peculiar geological formations constitute natural laboratories to address some prevailing questions concerning the past and future of biotic diversity. Inselbergs appear as simplified systems compared to forests, especially in the tropics; they are scattered in all continents and are thus more suited for a worldwide comparative biodiversity analysis. Furthermore, they have generally escaped from human pressure. They offer models for quantitative analysis of species diversity and biotic communities within an almost uniform frame of physicochemical stresses. Moreover, the species that are adapted to these conditions belong generally to distinct phyletic lines, illustrating parallel evolution of morphofunctional traits. The insularity of the populations trapped on the outcrops also allows us to address issues concerning the population effects of fragmentation. Such a topic is interdisciplinary by definition, from geology to evolutionary biology through botany, zoology, population genetics and biogeography. Although the geological processes responsible for inselberg formation are still controversial, it is clear that they were shaped during a very long period. Bremer suggests that they probably began in a perhumid climate yielding intense weathering. Planational lowering with differential weathering could explain the isolation of outcrops elevated above the basal surface, as proposed by the French geographer Hurault in 1968, reference to which is omitted. Rock nature, atmospheric agents, and different kinds of weathering, create the conditions for the fine-scale differentiation of habitats. Microclimatic and vegetational differences from the surrounding environment justify consideration of inselbergs as ‘islands’ in the insularity perspective. Five contributions deal with the relationship between diversity, biological features and environmental constraints. Here, sound arguments demonstrate that the input of energy and matter to these peculiar ecosystems is formed by microorganisms: free cyanobacteria, cyanolichens and green algal lichens, primary agents capturing photonic energy, atmospheric CO2 and nitrogen, and weathering rock. The outcome of their activity is the possible colonization by plants. As noted, the vascular plants present on inselbergs belong to specialized types that are able to cope with nutrient deficiency or water shortage. Only 10 angiosperm families account for two-thirds of all inselberg specialists. Despite clear differences in their floristic composition between geographical and climatic regions, those plants share mechanisms of ecological adaptation to tolerate or avoid the action of stressing agents: short supply of water, high irradiance, high temperature, limitation in the availability of nutrients. Two main ‘strategies’ are considered: tolerance of desiccation and desiccation avoidance. Clearly, the adaptations represent outcomes of the pressure of several factors, which are often in opposition. For instance, a conflict between desiccation and starvation occurs whether the limitation of the water loss is based on the closure of stomata or the presence of an impermeable cuticle. In contrast to desiccation-tolerant plants, which survive by a drastic reduction of the life processes and are able to repair structures damaged by desiccation, the plants that avoid desiccation exhibit xeromorphic structures or metabolic means that decouple the photosynthesis machinery from the supply of CO2, so that the stomata can be open without danger of water loss during the night. The relative abundance of carnivorous species is also a sign of selection for adaptation to a deficiency of mineral nutrients. However, the need for water to achieve digestion could be related to their presence only in wet microhabitats (wet flushes). The past and future of these unique ecosystems are evoked. Past, because due to their old age they could give information about major climatic changes, and future, because they may be threatened by invasive alien weeds or uncontrolled access for tourism. The central part of the book offers a set of unevenly documented surveys of the flora present on inselbergs worldwide, gathering data that until now were scattered. The contribution on fauna, however, is so poorly documented, ignoring a large amount of references, that it might have been better left out of the book altogether. A set of high-quality colour plates illustrates the main landscape and floristic characteristics of inselbergs in several parts of the world. This book certainly provides a solid foundation for further studies on these ecosystems, studies which need interdisciplinary (hence international) research programmes and require institutional support if biodiversity conservation is to be taken seriously.