Life history characteristics of two ecotypes of Plantago lanceolata L.

The life history of two populations of Plantago lanceolata L. from two different habitats is described, using standard demographical techniques. The first habitat is an open dune grassland on poor sandy substratum and grazed as a commonage for centuries. The vegetation occasionally suffers from drought. The second habitat is a closed hay meadow on organic substratum that is permanently waterlogged and mown once a year in July. The plantains in the dry site form small flat rosettes with many leaves and side rosettes. Small seeds are produced from many globular inflorescences on short ascending stalks late in the season (known as subvar. sphaerostachya f. minor). The plaintains in the wet site form few tall erect leaves and no side rosettes. Big seeds are produced from few long inflorescences on long stalks in the early season (known as subvar. latifolia). Seeds from the dry population show innate dormancy that shifts the main germination period of this population towards spring. The seeds require light and high temperatures for germination and form an appreciable seedbank. Seeds from the wet population show little dormancy and germinate readily in autumn at low temperatures and light intensities without forming a seedbank. Juveniles and adults share more or less equal risks in the dry site. Rosettes are short-lived and can flower in the second season even at small sizes. Seeds are produced at considerable costs. Juveniles are clearly more at risk in the wet site, where it takes several years to first flowering. Adults are long-lived and flower repeatedly, producing seeds at low costs. The results are discussed in connection with theoretical predictions from current life history theories.