The Lady Fern is a very successful diploid species found throughout many areas of the northern hemisphere. It is characterized by a very wide ecological range from South to North and from lowlands to the alpine region both in North America and in Eurasia. In Europe it is mainly an outbreeding fern. In the North-South gradient there is evidence for ecotypic differentiation. The question I asked was, if there exists a clinal or ecotypic adaptation along an altitudinal gradient within the Alps. Preliminary isozyme studies revealed no correlation between genetic variability and altitude. Most of the genetic variation was seen within populations. In a wider context, however, a differentiation among populations from Switzerland, North Italy, and Spain could be observed. Common garden experiments, started in 1999, have so far shown no clear correlation between morphological characteristics and altitude (range 500-1800m) and are therefore in agreement with the enzyme data. The conclusion following from these results is that this species is characterized by physiologically very tolerant genotypes, which are capable to successfully grow under differing environmental conditions. Unfortunately a broader study including the whole distribution area planned by Charles Werth remains open. Investigations on breeding biology and interfertility among different taxa in the complex would help to understand speciation patterns. Enzyme and molecular systematic studies are needed to elucidate the biology, evolutionary history and the different phylogeographic processes of this successful species.

Key words: Athyrium, common garden experiment, diploid speciation, genetic variability