PHYLOGENETIC IMPLICATIONS FROM CUTICULAR WAX ANALYSES IN EPILOBIUM SECT. ZAUSCHNERIA (ONAGRACEAE)

Analysis of n-alkane constitutents of the leaf cuticle have been utilized to elucidate phylogenetic relationships within Epilobium section Zauschneria. Specimens representing 136 populations were greenhouse-grown under the same conditions. Crosses were made between representatives of all taxa within the section. The resulting F₁ generations were also grown under the same conditions. Cuticle samples were removed in chloroform, purified with column chromatography and analyzed using gas chromatography and mass spectrometry. Resultant data were computer analyed using discriminant function analysis. Based on percent composition of 12 n-alkanes, each population and taxon can be characterized by a distinctive wax profile. Results suggest that the tetraploids E. canum subsp. canum and E. canum subsp. latifolium have been derived from the anastomosis of two distinct diploid genomes, E. canum subsp. canum “angustifolium” and E. septentrionale. Biochemical evidence from extant populations of E. canum are in agreement with geographic positions and ranges of the diploid species involved. Greenhouse hybridizations between the respective diploids, E. canum subsp. canum “canum” and E. septentrionale, result in F₁ progeny possessing phenotypes similar to naturally occurring tetraploid E. canum populations. Wax compositions of the natural tetraploid populations are intermediate between diploids and vary depending on geographical proximity to diploid species. Past taxonomic treatments of the genus have placed the tetraploid Zauschneria arizonica within the species Z. californica (now E. canum). Analysis of wax compositions now suggets that Z. arizonica had an independent origin which involved, at least in part, the diploid species E. canum subsp. garrettii from Utah.