The Rhacomitrium heterostichum complex in British Columbia consists of four species and five varieties: R. "laxum", R. heterostichum, R. heterostichum var. affine, R. sudeticum, R. sudeticum var. macounii, R. brevipes, R. brevipes var. "laevis", var. "eramulosum" and var. "microcarpiformis". Within each of these taxa minor variations occur. R. sudeticum tends to be confined to sub-alpine and alpine localities and R. heterostichum to lower elevations, while R. "laxum" and R. brevipes show no altitudinal limitations. There appears to be a positive correlation between nature of branching and details of leaf apex structure to moisture conditions: short branches, abbreviated hair point and shorter leaf cells in the leaf apex being commoner in specimens of wet sites than in specimens of dry sites. Experimental evidence is needed to determine phenotypic plasticity in these characters, since they are widely used to distinguish among the various taxa of the R. heterostichum complex. / Science, Faculty of / Botany, Department of / Graduate

Investigation of morphology, karyotype, isozymes, cultivation, geography and habitat confirmed differences between Limbella tricostata (Sull.) CM. and Sciaromium fryei Williams. Significant differences were observed experimentally in branch bud frequency, leaf insertion angle, leaf areolation, chromosome length, mobility of superoxide dismutase and shoot orientation. Sciaromium fryei is considered a subspecies of Limbella tricostata. Chromosome numbers of both subspecies is n=11. L. tricostata ssp. tricostata has a Bryum type sporeling and a hypnaceous peristome, and is thought to have derived from L. pachyloma (Mont.) C.M. or its antecedent after long-distance dispersal from South America to Hawaii no later than the mid-Tertiary. L. tricostata ssp. fryei is thought to have derived from L. tricostata ssp. tricostata after long-distance dispersal from Hawaii to North America in the mid- to late Tertiary. / Science, Faculty of / Botany, Department of / Graduate

This thesis describes a study of six North American, dioicous Brachytheeium species possessing a rough seta. The phenetic variability of the six species was analysed in order to clarify the relationships, between species and to provide .simpler, more reliable means of identifying specimens. As a consequence of this investigation, the taxonomic identities of B. asperrimum (Mitt. ex. C. Muell.) Sull. and B. frigidum (C. Muell.) Besch, have been established through numerical analyses of the variation in the gametophytic features of the two species. Two types of analyses were used: a principal components analysis and a cluster analysis. The phenetic variation and habitat specificity of each species were analysed and documented and synonymy and ranges presented. A. test of the features considered diagnostic for the two species has been performed and the results of this test used to devise a reliable key. The relationships of the two species to the other North American dioicous species possessing rough setae were determined using a principal components analysis and. a cluster analysis. B. asperrimum (Mitt. ex. C. Muell.). Sull is shown to be closely related to B. bolanderi (Lesq.) Jaeg. and Sauerb.. B. frigidum (C. Muell.) Besch. is shown to be closely related to B. rivulare B.S.G. and B. nelsonii Grout. A dendrogram and discussion of the hypothetical, cladistic relationships of the six species are provided. / Science, Faculty of / Botany, Department of / Graduate

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Thesis (BSci. Hons.) -- University of Technology, Sydney, 2008.

The microorganisms colonizing plants can have a significant effect on host phenotype, mediating such processes as pathogen resistance, stress tolerance, nutrient acquisition, growth, and reproduction. Research regarding plant-microbe interactions has focused almost exclusively on vascular plants, and we know comparatively little about how bryophytes -- including mosses, liverworts, and hornworts -- are influenced by their microbiomes. Ceratodon purpureus is a dioecious, cosmopolitan moss species that exhibits sex-specific fungal communities, yet we do not know whether these microbes have a differential effect on the growth and physiology of male and female genotypes. Using a common-garden design, we reared ten axenic genotypes of C. purpureus in a controlled environmental chamber. Clonal C. purpureus replicates, with and without the addition of a microbial inoculation, were used to test the effect of a mixed microbial community on vegetative growth, sex expression, photosynthetic efficiency (Fv/Fm and ETR), and chlorophyll content (CFR) for male and female mosses. We found that microbes had a negative impact on the growth and photosynthesis efficiency of C. purpureus, and this effect varied among genotypes of C. purpureus for ETR and growth. Microbes also had a positive, sex-specific effect on chlorophyll content in C. purpureus, with males exhibiting lower CFR values in the absence of microbes. C. purpureus sex expression was marginally negatively affected by microbe addition, but gametangia production was low overall in our experiment. We also conducted preliminary surveys using direct counts from moss ramets to assess the community composition of epiphytic algae associated with our microbe addition and control C. purpureus. These surveys identified three algal morphospecies in association with the microbe addition C. purpureus genotypes, as well as cyanobacteria, nematodes, rotifers, and testate amoeba. No algae, cyanobacteria, or micro-fauna were observed in the control plants. Transplantation of a mixed microbial community from field-to-laboratory conditions may be applied to other bryophyte species under varying environmental conditions to provide insight into how these diminutive yet important ecosystems will respond to environmental perturbation.

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