| Summary: | This dissertation provides keys and concise descriptions of the genera, species and varieties of bryophytes known from the semi-arid steppe region of south-central British Columbia. Thirty-seven genera and seventy-seven species are included. Detailed illustrations are provided for selected species. Local distribution maps are included for all the taxa.
Four of the species included here are new to North America: Crossidium rosei, Phaseurn vlassovii, Pottia cf. wilsonii and Pterygonerum kozlovii. In addition, the genera Crossidium and Trichostomopsis as well as eight species and two varieties are new to Canada. Five additional species are reported for the first time from British Columbia.
Distributions of the taxa in the study area are discussed at local and world levels. Local distributions are influenced most by substratum type, aspect and elevational change, and effects of disturbance. Most of the taxa are terricolous and restricted to or with apparent preference to one of five soil types. Many taxa are saxicolous, but distributions with respect to rock type could not be determined.
The regional bryoflora is compared also to temperate dryland bryophyte floras globally. Surprisingly, the regional flora has very strong affinities, at both the species and genus levels, not only to dryland floras in the North American southwest but also with the arid regions of Eurasia and North Africa. Although some of the taxa in these areas are widespread throughout the Northern hemisphere, many species express disjunctions between the arid regions. Two contrasting causes, long-distance dispersal and vicariance, are discussed with respect to the origin of the disjunctive patterns. In most instances vicariance appears a more likely cause of the disjunction, although this conclusion is highly speculative. If vicariance is a cause, then the disjunct taxa are probably ancient and conservative. Bipolar disjunctions are also discussed. Long distance dispersal as well as hop dispersal appear to be more likely causes of this type of pattern than vicariance.
Many of the taxa require critical taxonomic revision. This reflects the lack of research in arid regions. Suites of genera that are problematic include Grimmia, Schistidium and Coseinodon, and Phaseurn, Pottia, Desmatodon and Tortula. Also, at least 41% of the species pose particular taxonomic problems. Some possible solutions for these problems are suggested here. === Science, Faculty of === Botany, Department of === Graduate
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