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A moss flora of Selkirk and Purcell Mountain Ranges, Southeastern British Columbia Tan, Benito Ching


The Selkirk and Purcell Mountain Ranges were chosen for a preliminary investigation of the moss flora because of the similarities of mean annual precipitation and vascular plant flora between the interior western hemlock zone and the coastal hemlock zone. Three summers (1976-78) were spent in this area intensively and extensively collecting moss specimens from various habitats' different vegetation zones and at all elevations. Close to 6000 collections have been analyzed including hundreds of specimens made by Macoun and MacFadden at the turn of the century. The total moss flora is conservatively established as 366 species belonging to 128 genera and 40 families. Several species either represent new records for the region or are significant extensions of previously local ranges. Others, like Hygroamblystegium noterophilum, Campylium radicale, Mnium arizonicum and Pohlia obtusifolia, are new to the province Scouleria marqinata is reported as new to Canada, and Physcomitrella patens, pichelyma pallescens and Pohlia lescuriana are new to western North America. Furthermore, Plagiothecium nemorale and Campylium calcareum are reported as new to North America. Based on the study, several new binomial combinations are proposed. Likewise, past taxonomic confusion involving species such as Dichodontium pellucidum -D. clympicum. Pohlia columbica, Barbula revoluta var. obtusula and Barbula convoluta -B. eustegia are explored in depth and resolved). Erroneous reports of species from the area were exposed by studying the original collections. A working manual with complete keys to the families, genera and species is presented. Important taxonomic or diagnostic features are given for each species, together with habitat and distribution information. A total of 176 distribution maps for various species are appended to illustrate the different patterns of distributions in the study area, in the province and in a few cases, western North America. The habitat conditions of each species were also observed and reported. The distribution of the mosses shows a pattern of distribution correlated with the prevailing local physical conditions such as precipitation and substrate pH. Hence, mosses of hygric and raesic habitats are found to be more abundant in kind and numbers of individuals in the northern Selkirk and Purcell Mountains, i.e., the wet and moist subzones of the interior western hemlock biogeoclimatic zone. Equally apparent is a concentration of calcicolous taxa in the vicinity of the Columbia Trench owing to the existence of calcareous substrata. Past and present collections of messes from the Halcyon Hotsprings have been compared to illustrate the drastic effects of logging and burning of the original forest cover on mosses. To elucidate the origin, possible migratory pathways and phytogeographical affinities of the local moss flora, the species composition is analyzed and grouped into several geographical and floristic elements. The groupings are made separately at various hierarchical levels: the province, North American continent and the world. The results show that nearly 80% of the species belong to widespread and common northern boreal taxa. Around 10% are restricted western North American endemics. There are more species (12%) that are more widespread south of the study area than north of it (5.5%). This is taken to suggest that the more important source of plant migration into the area under study after the last glaciation is from the unglaciated mountains and lowlands south of the Canadian border. Furthermore, there is a slightly higher percentage of continental moss species (12.5%) than oceanic ones (10.1%) in the two mountain ranges investigated, a reflection of the stronger influence of continental climate over the southeastern part of the province. No species new to science were discovered. Presumably, this indicates that the mountains were thoroughly glaciated and that no plant populations survived in situ during the glacial period. The interval since glaciation is probably too short for appreciable speciation to have occured. Routes for southward and eastward migrations of moss taxa from the Arctic and the Coast Mountains are also postulated and their contributions to the evolution of the moss flora of the study area are assessed to be minimal; westward expansion of moss species from the continental prairies is suggested to be effectively blocked by the Rocky Mountain Range. It is finally suggested that the association of many locally uncommon hygrophilic moss taxa with several active hotsprings in the study area is a phenomenon worth further investigation.

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