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Forest tree genetic conservation status report 1: In situ conservation status of all indigenous British Columbia species

Author(s) or contact(s): C. Chourmouzis, A.D. Yanchuk, A. Hamann, P. Smets, and S.N. Aitken
Source: Research Branch
Subject: Forest Genetics
Series: Technical Report
Other details:  Published 2009. Hardcopy is available.


The primary strategy for long-term conservation of British Columbia's biodiversity is through an extensive network of protected areas (pas). These parks and ecological reserves have been established in all of the major ecological units within the province. The driver behind such a "coarse filter" conservation approach is usually the conservation of species. Conservation of genetic diversity within species often receives relatively little attention, yet it is genetic diversity within populations that provides the capacity for native species to adapt to new environmental conditions. This is particularly important given the predicted rates of climate change for British Columbia in the next century.

In this document we evaluate how well British Columbia's protected areas meet the goal of conserving genetic diversity of all indigenous tree species in all major biogeoclimatic units (zones) in which they occur. Most tree species have high levels of genetic diversity but also show clinal variation with latitude, elevation, or distance to the ocean, which allows for adaptation to temperature and moisture conditions. Ensuring that several large populations are conserved within each major ecological unit should conserve high levels of genetic diversity and enable adaptation to rapidly changing conditions.

Thresholds for adequate conservation have been developed based on population genetic theory. This approach evaluates minimum effective population sizes needed to maintain current levels of genetic diversity indefinitely under an equilibrium between losing genetic variation due to genetic drift and gaining genetic variation via mutation. Population sizes presented in this document are estimates based on provincial botanical plot data extrapolated across ecological units, derived from species cumulative cover rather than population size (which is not directly measured during ecological data collection). We used the cumulative cover of species to estimate numbers of mature individuals; therefore, these estimates include unquantified errors and
do not fully reflect differences in tree stature and spatial distribution among species, ecosystems, and ages.

When we evaluated estimated sizes of populations protected in each biogeoclimatic zone against the thresholds determined for adequate conservation, many gaps in conservation became apparent. We focussed on clear conservation shortfalls within the core of species ranges; however, these are not the only places where protection may fall short. Many gaps occur at the margins of species ranges where species span ecological mapping units. This creates the impression that protection is scarce in ecological units where these species are uncommon. We took a pragmatic approach in evaluating such gaps and categorized them based on information beyond the botanical plot data. First, we identified gaps that are critical to a species' protection in ecosystems where the species is commonly found. Second, we identified potential gaps where estimates indicated that conservation populations may fall short of targeted sizes in ecosystems that are important to a species' provincial distribution, and recommended verification of population sizes using other sources of information (e.g., recent ecological mapping projects, expert knowledge, or ground truthing). Finally, we recognized the need to identify and conserve disjunct, marginal populations, which may contain unique genotypes. The current data were inadequate to address this need; therefore, the collective knowledge of field foresters, botanists, and ecologists, as well as other sources of data, will be required to identify disjunct populations. It is our hope that, through this prioritization process, critical gaps will be identified clearly and addressed first through additional conservation efforts. This is the first of what should be a series of analyses that will be updated at regular intervals.

The results of this study are summarized in Table 1, which shows in situ conservation priority rankings for all indigenous tree species across all biogeoclimatic ecosystem classification (BEC) zones in British Columbia. This is followed by a summary of in situ conservation priorities for tree species of conservation concern based on the results.

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Updated September 15, 2009