Variation in Lamium subg. Galeobdolon (Lamiaceae) -: insights from ploidy levels, morphology and isozymes

Lamium subg. Galeobdolon was investigated in Central Europe to evaluate karyological, morphological, and isozyme variations. Flow-cytometric analyses revealed three ploidy levels: diploid (corresponding to L. flavidum and L. galeobdolon), tetraploid (corresponding to L. argentatum and L. montanum), and triploid (very rare cytotype most probably of hybrid origin). Mixed samples comprising two or more cytotypes / taxa were repeatedly detected. An existence of hybrid individuals between both tetraploid taxa was also supported. Almost no variation at isozyme level was observed in L. argentatum originating from three European countries thus favouring a hypothesis of a monotopic origin. On the contrary, the pilot study detected high isozyme variability in the other taxa. Morphometric analyses confirmed clear separation between L. galeobdolon and L. montanum; bract characters and maximum number of flowers were selected as quantitative features with the highest discriminant power. Serious discrepancies between the original description of L. endtmannii and both karyological and morphological performance of the plants from localities attributed to this species were found. These results allow us to conclude that any taxonomic status of L. endtmannii is not justified.