Habitat-related adaptive properties of plant cuticular lipids

Cuticular permeability is thought to be related to the biophysical properti es of cuticular waxes and, in turn, to the chemical composition of this bou ndary layer. However, thus far evidence for this relationship has been elus ive. We investigated possible correlations between habitat and inter- and i ntraspecific variations in two parameters likeley to affect crystallinity a nd transition melting temperatures of waxes. Three species from the family Cupressaceae (Austrocedrus chilensis, Fitzroya cupressoides, Pilgerodendron uviferm) were selected as a model system because they are closely related and form a continuum over 20 degrees of latitude in South America that incl udes important climatic differences. We found major divergence among the th ree species and more fine-scale population differentiation for A. chilensis and P. uviferum in weighted mean carbon number (N) and dispersion about th is mean (d). Broad-sense heritabilities, estimated from ramet-ortet regress ions and from analysis of variance among ortets of F. cupressoides were 0.9 2 for N and from 0.64-0.76 for d. Even in areas of close sympatry, species maintained their unique biochemical characteristics, thus supporting the ge netic basis of cuticular hydrocarbons. Both species and population patterns suggest that natural selection has favored cuticular hydrocarbon mixes tha t provide differential fitness in the face of habitat differences in water stress and temperature.