Phenotypic variation in clonal growth of Glaux maritima along an environmental cline

A population of Glaux maritima along an environmental cline from average to annual high water level was studied. Indications of ecotypic dilferentiation were found in previous field studies. In order to further investigate this, hibernacles sampled from different parts of the cline were cloned and subjected to different light intensities and inundation. Our hypotheses were that plants from the lower-meadow, where the vegetation is short and flooding frequent, ramify more and respond to inundation by increased height. Plants from central areas, with tall vegetation, were expected to ramify less. Upper-meadow plants were expected not to respond to inundation by height increment. Lower-meadow plants produced more but smaller vegetative offspring and flowered to a lower extent. There was also variation in response patterns to the treatments among plants of different origin. Lower-meadow plants responded less plastically to reduced light and inundation. The results add more evidence to the notion that ecotypic differentiation in vegetative and clonal behaviour is at hand. Some of this variation could be adaptive. The variability in vegetative offspring may be of importance for stability and persistence of clones as more different modes of responses to environmental hazards can be exhibited by each clone.