The book provides a synthesis of population ecology, population genetics and plant physiology, applied to the question, which properties contribute to fitness of populations of Plantago species. Five species, P. major, P. lanceolata, P. media, P. maritima and P. coronopus were investigated for demographic and genetic structures. Ecophysiological data were obtained in the laboratory and in the field. Together with data on soils and micrometeorologic characteristics of the sites, an analysis of factors, contributing to fitness was carried out. Moreover, complex interactions as mycorrhiza, N-cycling in the rhizosphere and co-adaptation with parasitic fungi and animals are included.