ECOTYPIC ADAPTATION IN AUSTROCEDRUS-CHILENSIS IN CUTICULAR HYDROCARBON COMPOSITION

An homologous series of hydrocarbons ranging from C-21 to C-37 was det ected in foliar cuticular waxes of Austrocedrus chilensis (D.Don) Pic. -Ser. & Bizz., by gas chromatography. Qualitatively, the chromatograms were similar for all individuals sampled from 29 natural populations in Chile and Argentina, showing C,, and C,, alkanes to be dominant. Qu antitatively, the chromatograms varied significantly among populations . Multivariate analyses showed that arid zone populations from mediter ranean Chile and the Patagonian steppe were different from one another and were distinct from mesic populations close to the Valdivian rainf orest vegetation zone. Mediterranean Chilean populations were characte rized by higher concentrations of the longer carbon-chain alkanes, but retained equal amounts of shorter-chain homologues as the mesic popul ations. A greater variation in chain lengths and higher concentrations of longer carbon chains in the mediterranean populations is consisten t with a model for the adaptation to reduced cuticular permeability. P artial Mantel matrix tests revealed significant climatic and inter-pop ulation distance effects with taxonomic distances based on multivariat e and univariate hydrocarbon data. Annual rainfall was overall the mos t significant factor, particularly in regressions with the shorter-cha in hydrocarbons. Annual mean temperature was most significant for the longer-chain hydrocarbons. This suggests, on the one hand, ecogenic ad aptation to both temperature and precipitation of cuticular hydrocarbo n composition, and, on the other hand, a weaker, but important effect of gene flow in determining hydrocarbon composition in this species. T he northernmost populations at San Felipe and San Gabriel were the mos t distinctive. This could result from the effects of random changes in allele frequencies and/or to founder effects in isolated and small po pulations. These populations shaw some East-Andean affinities presumab ly due to historic migration patterns.