ABSTRACT. – Collembolan biodiversity was analyzed in the ecotone between water habitats and inland soils of two peat-bogs of Algeria. Four transects were sampled across the ecotonal zone of each peat-bog. Species diversity increased progressively from water to inland soils, and dominance of the most abundant species followed an inverse trend. These two descriptors had intermediate values in the ecotone. Collembolan abundances increased from water to inland in Thalah Boussaleh, with intermediate values for the ecotonal sample. But no clear pattern emerged for Khbouth. On the whole, the biodiversity patterns were the same in the two peatbogs, in spite of low similarities in species composition and species richness between them. Similarity between successive samples was always relatively low, with a slight decrease in the ecotonal zone as expected. It is postulated that biodiversity and dominance pattern of this kind is characteristic of asymmetrical ecotones, where adjacent habitats show high ecological contrasts and have very different levels of species richness.