Western larch (Larix occidentalis Nutt.) heartwood meals were successively extracted with five solvents of increasing polarity and finally with absolute ethanol. The total extractable material collected was 14.94%, oven dry (OD) wood basis. Compounds in each solvent fraction were seperated, mostly by column chromatography over silica gel, Sephadex A25 and Sephadex LH20. The identities of isolated compounds, after determining relevant physical and chemical properties were confirmed by comprison with standard compounds. Previously unreported compounds found in western larch heartwood included: Four resin acids (0.017% total yield) as sandaracopimaric, isopimaric, abietic and dehydroabietic from the petroleum ether (65° -80°) extract; pinocembrin (5,7 dihdroxy-flavanone) from the benzene extract (0.003% yield); and free L-arabinose from the water extract. Other compounds found were: β-sitosterol, β-sitosteryl palmitate, tristearin, esters of linolenic and arachidic acids, palmitic, palmitoleic, linoleic, linolenic and arachidic acids. Also found were dihydrokampferol, α-conidendrin, dihydroquercetin, quercetin and arabinogalactan (11.10% yield). Isolates were characterized by their IR and NMR spectra, various chrmatographic behaviours and comparison with standards. Physical and chemical properties of unidentified compounds are reported as a guide for future research. / Forestry, Faculty of / Graduate

The relative role of cospeciation and host switching in the phylogenetic history of ascomycete foliar symbionts is addressed in the orders Leotiales and Rhytismatales, fungi associated predominantly with Pinaceae (Coniferales). Emphasis is placed on comparing the evolution of the sister genera Pseudotsuga and Larix (Pinaceae) with that of the pathogenic and endophytic fungi in the genus Rhabdocline. Pinaceae evolved during the Mesozoic and divergence of all extant genera and several infrageneric lineages (esp. in Pinus) occurred prior to the Tertiary, with subsequent species radiations following climatic changes of the Eocene. The youngest generic pair to evolve from Pinaceae, Larix and Pseudotsuga, diverged near the Cretaceous-Tertiary boundary in East Asia or western North America. Rhabdocline is comprised of seven species and subspecies, six known from two species of Pseudotsuga and one, the asexual species Meria laricis, from three species of Larix. Evidence from host distributions and from nuclear ribosomal DNA suggests that Rhabdocline speciated in western North America and has been involved in several host switches. The ancestor of Meria laricis appears to have switched from P. menziesii to its current western North American hosts, L. occidentalis, L. lyallii, and very recently may have extended its host range to the European species, L. decidua. The occurrence of two lineages of R. weirii ssp. weirii on both North American species of Pseudotsuga is also probably the result of a recent host switch. Evidence of hostmediated divergence is seen in R. parkeri, which has different internal transcribed spacer types in the geographically isolated coastal and interior forms of P. menziesii. The wide host ranges of fungal genera closely related to Rhabdocline indicates that host switching is a prevalent pattern in the evolution of foliar symbionts in Leotiales and Rhytismatales. The prevalence of host switching in this group relative to other endosymbiotic organisms can probably be attributed to differences in dispersal mechanisms. Spores of foliar fungi are dispersed horizontally by wind and rain, rather than vertically from parent to offspring. Over evolutionary time, this provides more opportunities to shift to new hosts, particularly when the hosts are closely related and have overlapping distributions. / Graduation date: 1998

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