Environmental response of Galium palustre s. lat. in a coastal area in Central Sweden

Abstract

Galium palustre s. lat. is a polymorphic taxon. The differences in morphology are correlated with the level of ploidy, but there is also a certain amount of phenotypic plasticity. The plasticity probably contributes to this taxon's successful colonization of a wide variety of habitats. The amount of plasticity was studied for plants from different kinds of habitats in Sweden, both for diploids (G. palustre s. str.) and octoploids (G. elongatum), which were cloned. This cloned material was then transplanted to three different localities in Sweden: a sunny exposed sea-shore, a ditch, and a shady alder swamp. The general pattern of morphology was similar for all material, independent of its origin and level of ploidy, with smaller plants (smaller in several vegetative characters) and a more abundant flowering on the exposed seashore than in the ditch, and the largest plants with a fairly sparse flowering in the alder swamp. The octoploid plants originating from the wooded wetland are the least plastic ones but are very variable within the localities. G. palustre var. balneum shows a similar variation pattern as the others, but there are also genetically fixed differences in some characters between it and G. palustre var. palustre. The changes in morphology of the plants in the different localities occur fairly rapidly (in one month), although the differences are more spectacular one year later.