Population differentiation in Australian Cardamine. I. Variation in leaf characters

Abstract

Considerable variation in leaf shape and size was obseryed among populations of three reproductively isolated races of Cardamine collected from an altitudinal transect in southern New South Wales. The variation among populations was considerably greater in the alpine race than in the two other races occurring at lower altitudes. Some evidence of a relationship between altitude and the variation in size and shape of the leaf suggested that the differentiation of populations with respect to leaf characters was to some degree under the influence of natural selection. Furthermore, as correlations between the various leaf characters were, with the exception of one comparison, all significant, it is probable that these characters are determined, at least partly, by some common metabolic process. The influence of environmental diversity and the breeding system on the pattern of population differentiation in Cardamine is also discussed.