Why is the rainforest lichen Methuselah’s beard (<i>Usnea longissima</i>) so rare in British Columbia’s inland temperate rainforest?

Coastal (CTR) and inland temperate rainforests (ITR) in western North America share a rich oceanic lichen flora. The distinctive Methuselah’s beard (Usnea longissima Ach.) is an exception to this pattern of shared distributions, with very few ITR locations. Does absence reflect dispersal limitations or climatic intolerance? To answer question, we transplanted U. thalli from the CTR three locations, assessing growth rates against reciprocal transplants. Canopy microclimate measurements provided concurrent data on conditions. Growth rate responses (length, mass, area) were evaluated after summer full-year Notwithstanding extended drought conditions during period, annual transplants at two locations supported comparable those source population, dewfall autumn rains being major hydration sources. Thalli third site (summer only) location transitional drier interior plateau lost both mass length. Based these findings, suggest that much reflects combined influence requirements for stands long continuity topographically induced wetting by dewfall.