Cuticular permeability is thought to be related to the biophysical properties of cuticular waxes and, in turn, to the chemical composition of this boundary layer. However, thus far evidence for this relationship has been elusive. We investigated possible correlations between habitat and inter- and intraspecific variations in two parameters likeley to affect crystallinity and 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° of latitude in South America that includes important climatic differences. We found major divergence among the three species and more fine-scale population differentiation for A. chilensis and P. uviferum in weighted mean carbon number (N) and dispersion about this mean (d). Broad-sense heritabilities, estimated from ramet-ortet regressions and from analysis of variance among ortets of F. cupressoides were 0.92 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 genetic basis of cuticular hydrocarbons. Both species and population patterns suggest that natural selection has favored cuticular hydrocarbon mixes that provide differential fitness in the face of habitat differences in water stress and temperature.
Corresponding Editor: T. Mousseau