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UBC Theses and Dissertations

The ecological and conservation genetics of Garry oak (Quercus garryana Dougl. ex Hook)) Huebert, Colin A.


Garry oak (Quercus garryana Dougl. Ex Hook) is a deciduous tree endemic to Western North America. It is confined within Canada to only a few isolated locations in southwestern British Columbia (B.C.). Although accounting for less than 0.3% of British Columbia’s entire land coverage, Garry oak-associated ecosystems support tremendous biodiversity and are home to a large number of rare species in B.C. Populations have, however, been declining since European settlement. It is estimated that only 1-5% of pre-European Garry oak ecosystems remain uncompromised in B.C. today. However, species distribution models predict the area climatically appropriate for Garry oak to triple in B.C. by the 2080’s. Using a common garden experimental design, data regarding growth and biomass partitioning, bud phenology and cold hardiness were collected for two years from a total of 1700 individuals from 15 populations representing the species’ entire range. Data were used to assess genetic diversity and geographic differentiation (QST) for these quantitative traits. Results indicate relatively weak population differentiation for most traits. However, significant genetic clines exist for height, germinant emergence date and cold hardiness. Height and germinant emergence were strongly correlated with environmental variables associated with summer aridity (mean summer precipitation, summer heat:moisture index, mean warmest month temperature), while cold hardiness was strongly correlated with temperature differential (the difference between mean warmest month temperature and mean coldest month temperature) and mean warmest month temperature. Estimates of population differentiation for traits (QST) were relatively low for growth related traits, bud burst and bud set (0.07-0.13) and moderate (0.30) for cold hardiness and germinant emergence. Results suggest Garry oak is a species closely adapted to conditions of intense drought and are used to recommend seed transfer guidelines and conservation strategies for current and future climates in B.C. and elsewhere.

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