Frankia from root nodules of nine different species of Ceanothus were characterized. DNA was amplified directly from nodular material using the polymerase chain reaction (PCR). The amplified region includes the 3' end of the 16S rRNA gene, the intergenic spacer (IGS), and a large portion of the 23S rRNA gene. Restriction enzyme digestions of PCR products allowed us to designate PCR-RFLP groups among the Ceanothus-infective Frankia tested. The groupings did not follow the taxonomic lines of the Ceanothus host species. Instead, the Frankia strains present followed a geographical pattern. This information was used to choose representative Ceanothus-infective Frankia for phylogenetic analysis. Full-length 16S rDNA sequences were amplified directly from the nodules of two Ceanothus species using the PCR. Sequences were determined using an automated sequencer, compared against GenBank, and assembled into consensus sequences. The sequences were aligned with other full-length Frankia 16S rDNA sequences available from the database. Phylogenetic trees were obtained from three different algorithms: neighbor joining, parsimony, and the maximum-likelihood method. These Ceanothus microsymbionts appear to be most closely related to the microsymbiont associated with Dryas drummondii using all three methods. / Graduation date: 1998

Thesis (Ph. D.)--Oregon State University, 1966. / Typescript. Includes bibliographical references (leaves 84-91). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 1987. / Typescript (photocopy). Includes bibliographical references (leaves 65-71). Also available online.

The evolutionary relationship between Frankia and actinorhizal plants was evaluated by reconstructing molecular phylogenetic trees from nifH, 16S rDNA, and rbcL nucleotide sequences. Subgroupings in Frankia phylogenetic trees reconstructed from nifH and from 16S rDNA sequences were consistent in terms of plant origins of Frankia strains. Although the branching order of Frankia 16S rDNA and plant rbcL trees were different, subgroupings of Frankia and of plants correlated well in terms of symbiotic partnership. Tree matching, estimated divergence times, and molecular clock hypothesis tests indicated that Frankia clades diverged more recently than plant clades and that actinorhizal symbioses originated more than three times after the plant clades diverged. A phylogenetic tree of Ceanothus species, which are symbiotic partners of Frankia, was reconstructed using ndhF gene sequences. The analysis identified two main clades corresponding to two subgenera: Ceanothus and Cerastes. The analysis also suggested that three monophyletic clades within the subgenus ceanothus can be delimited on the basis of vegetative characters. Based on rbcL sequences, the two subgenera diverged 18-39 million years ago whereas species within each subgenus diverged more recently. These results support the current division of Ceanothus into two monophyletic subgenera and agree with the postulated recent divergence of many species within each subgenus. Specificity between Ceanothus species and their Frankia microsymbionts was evaluated by analysis of DNA in nodules collected from three copopulations of Ceanothus species. Sequencing of the intergenic spacer region between 16S and 23S rRNA genes suggested that Ceanothus-microsymbiont Frankia are closely related. Nodules were further analyzed by genomic fingerprinting using repetitive sequences and PCR (rep-PCR). A newly designed, direct repeat sequence and a BOX sequence showed that Ceanothus-microsymbiont Frankia exhibited less diversity within each copopulation than among copopulations. Furthermore, geographic separation was a more important factor for divergence of Ceanothus-microsymbiont Frankia than host plant. The population of Ceanothus-infective Frankia in soils under stands of Ceanothus velutinus and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), a non-host plant, were compared. The population sizes were measured using plant bioassay methods with C. velutinus, C. sanguineus, and C. integerrimus as trap plants. Population size in soil under C. velutinus was about 10 times higher than that under the Douglas-fir. Nodulation capacities of the three trap plants were not significantly different. The diversity of Frankia nodulating trap plants was examined using rep-PCR. Results suggested that infective Frankia is not species-specific with regard to the three Ceanothus species used as trap plants and that although the degree of diversity was similar in both soils, the two populations consisted of different Frankia. / Graduation date: 1998

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 145-153).

Thesis (Ph. D.)--Oregon State University, 1998. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 45-54). Also available on the World Wide Web.

<p>Edaphic factors--those pertaining to the substrate or soil--are thought to play an important role in the diversification of flowering plants. Although edaphic factors are widely interpreted as causal agents in plant diversification, little is known about the evolutionary origin of most edaphic endemic plants, preventing inference of potential mechanisms by which substrate properties may influence speciation. The North American plant genus Ceanothus (Rhamnaceae) contains 9 edaphic-endemic species, taxa restricted to soils derived from specific geological materials. The three components of my dissertation research aim to improve understanding of how edaphic ecology has influenced the diversification of Ceanothus. First, I use DNA sequence data from the low-copy nuclear gene nitrate reductase to reconstruct the phylogeny of Ceanothus and elucidate diversification of this group into the California Floristic Province (CFP) of western North America, including the evolution of edaphic endemism. This research indicates that diversification of the two Ceanothus subgenera (Cerastes and Ceanothus) is centered on the CFP and is characterized by shallow divergence and phylogenetic relationships defined predominantly by geography. Divergence time estimation suggests that diversification of both Ceanothus subgenera began approximately 6 Ma. The nine edaphic-endemic taxa are not phylogenetically clustered in my analyses, suggesting that the origin of edaphic endemism has occurred on multiple occasions, including multiple examples of serpentine endemism. The second chapter of my dissertation uses soil chemistry data in combination with a more detailed examination of genetic variation in nitrate reductase to elucidate the evolution of a single edaphic endemic species.</p> / Dissertation

No description available.

Many fire-prone forests in western North America suffer from hazardous fuel conditions. Mechanical mastication is an increasingly common method of fuels treatment, but little is known regarding long-term effectiveness. A randomized block design at two sites (northern Sierras and southern Cascades) compared ladder fuels and overstory growth among treatments including mastication alone and mastication followed with prescribed fire or herbicide 10 or 11 years post-treatment. Subsequent herbicide application reduced ladder fuels in comparison to mastication alone or with prescribed fire. Prescribed fire further reduced ladder fuels at the southern Cascades site, however, in the northern Sierras postire ladder fuels were positively related to overstory absence. Mastication alone effectively released ponderosa pine at the southern Cascades site, whereas neither herbicide nor prescribed fire affected pine radial growth. This study demonstrates the feasibility of prescribed fire and herbicide for increasing treatment longevity of mastication, but also highlights potential limitations and important considerations.