The leaf litter fauna of tropical forests harbours several groups of minute (0.2-2mm) staphylinoid beetles from four closely related families (Pselaphidae, Sydmaenidae, Staphylinidae and Ptiliidae). The former two groups each include a few thousand described species globally and are to various degrees associated with ants and termites. Tropical forest sites typically include a few dozen species, whose presence is highly sensitive to disturbance (including edge effects). Despite their high value as biodiversity indicator, their insufficiently known taxonomy precludes any wider comparisons beyond the count of morphospecies at local sites. We will use a combination of classical and molecular techniques to assesses species turnover, with focus on forest areas in northeastern Madagascar where river basins have recently been postulated to be constitute evolutionarily separated bioregions based on plant distribution. This will be the starting point for a universal global taxonomy of these groups, for comparisons at higher levels in the future. The study has wider implications for our understanding of the functioning of leaf litter and soil faunas. As the target groups fall in a size class much below that of other insect groups, the study will investigate how small body size affects species (beta) turnover and clade size (net species diversification), i.e. the link of macroecological and macroevolutionary factors.