UBC Theses and Dissertations
Biogeography of the montane moss flora of southwestern British Columbia and northwestern Washington State Spence, John R.
restricted species appear to have distributions coincident with the northern and southern limits of the Wisconsin ice sheets. The study area has the largest number of montane-restricted species of nine sites examined in western North America. The area may have served as a refugium for these species during glaciation. At the study area level, few distributions related to glaciation appear to exist. Most can be correlated with climate (especially precipitation) and habitat factors. A group of species with their centers of distribution in the more continental portions of interior western North America occur west of the Coast Ranges-Cascades crest in coastal areas. The largest concentration of these is in the dry northeastern Olympic Mountains. A combination of habitat restrictions, rarity, lack of sporangium production and disjunct distributions from the interior suggest that the majority of these species may have migrated into coastal areas during the Hypsithermal, with subsequent restriction to xeric sites (especially basic rock such as sandstone) during the cooler and wetter Neoglacial. Many of these species are concentrated in plant communities in the northeastern Olympic Mountains that are also suggested to be relictual.