1. Strategies for forest gene conservation in BC

The long-term conservation of genetic diversity can be accomplished through a variety of approaches: 1) Populations can be maintained in situ - in parks, ecological reserves, and other protected areas; 2) Samples of seeds, individuals, or tissues can be collected and maintained ex situ, for example, in seed banks or clonal archives; and 3) The genetic materials being tested in provenance or progeny tests as part of breeding programs represent an additional genetic resource referred to as inter situ conservation. A robust gene conservation strategy combines different approaches and sets benchmarks for these approaches based on population genetic theory, species biology, availability of appropriate protected areas and knowledge of their populations, and whether a species is the subject of a breeding program.

We are fortunate in British Columbia to have an extensive network of protected areas accounting for approximately 12% of the land area of the province. These protected areas were selected at least in part to include all ecological units in the province, and form the backbone of our gene conservation strategy. Genetic resources in breeding programs for 10 conifers, as well as seed in long-term storage at the Ministry of Forests' Surrey Seed Centre, provide additional protection against loss of diversity. To evaluate whether these resources collectively are adequate to maintain genetic diversity for species evolution and adaptation, as well as tree breeding programs, and to guide additional conservation activities where needed, we initatiated projects to establish an overall strategy for gene conservation, to evaluate current levels of in situ conservation, and to guide additional ex situ collections, where needed.

Quick links to CFCG "Conservation Strategies" projects

Sampling strategies and geographic scale for capture of diversity and conservation of rare alleles

Ex situ conservation, through collection and storage of seed or cryogenic preservation of tissue cultures, is a very flexible tool and a good complement to in situ conservation. The vast majority of genetic diversity can be captured in relatively small in situ collections, however, rare alleles are much more challenging to comprehensively conserve. Populations in the core of a species range are likely to include high levels of genetic diversity, but peripheral or disjunct populations are more likely to contain alleles not found elsewhere. Dr. Washington Gapare conducted his PhD research on how best to allocate resources for sampling for ex situ gene conservation using Sitka spruce as a model species. He found that core and peripheral populations have strikingly different within-population genetic structure that requires different sampling strategies to fully capture. He also found that sampling strategy is not that important in core, high density populations, but becomes critical in disjunct, peripheral populations.

Funding: Forest Investment Account through Forest Genetics Council of BC
Publications: [Gapare]
Primary participants: [Gapare|Aitken|C. Ritland]

Adaptation and gene flow in central and peripheral populations

Peripheral populations are usually smaller and inhabit less optimal environments than core populations. Gene flow can accelerate local adaptation by providing genetic variation into peripheral populations, or it can inhibit local adaptation at range peripheries by introducing maladapted alleles. Disjunct peripheral populations may be 1) locally adapted due to selection and isolation or 2) severely maladapted due to small population size, low genetic diversity and inbreeding. Understanding how position within a species' range affects local adaptation will provide us with a guideline for better ex situ conservation strategies. We examined gamete pools of pollen, a major determinant of gene flow in wind-pollinated conifers, and evaluated some fitness-related quantitative growth traits in Sitka spruce to understand the evolutionary dynamics and fitness of peripheral populations. Paternity analysis using maximum likelihood methods estimated that outcrossing rate significantly decreased in peripheral populations compared to central populations. The estimated number of effective pollen donors per family ranged from 2.1 to 18.9, being highest in the central continuous population and lowest in the disjunct peripheral population. Multiple common garden experiments indicated that the disjunct peripheral populations did not have low average fitness despite high biparental inbreeding rates. Thus, these results suggest that wind-pollinated conifer species may, at least in the short term, show resilience to isolation and inbreeding because of their high fecundity and longevity, and isolation may even accelerate local selection. This implies that peripheral isolated populations of conifer species are potential sources of adaptive genes for extreme environments and for recovery of populations.

Funding: NSERC Discovery Grant, Forest Investment Account through Forest Genetics Council of BC, NSERC Industry Chair
Primary participants: [Mimura|Aitken]

Functional and population genomics of cold acclimation

Genecological studies in widely distributed tree species have revealed steep genetic clines along environmental gradients for traits related to adaptation to local climate. In the face of a changing climate, the ecological and economic importance of conifers necessitates an appraisal of how molecular genetic variation shapes quantitative trait variation. I am combining transcript profiling with association mapping to better understand the genomic architecture of adaptation to local climate in conifers, using Sitka spruce as a model. A microarray study during the fall hardening period revealed wholesale remodeling of the transcriptome within a population originating in the centre of the species range, and substantial variation in the autumn transcriptome was observed in populations from the northern and southern limits. I selected a suite of candidate genes, which were screened for single nucleotide polymorphisms (SNPs) in a panel of 24 individuals. A diverse array of biological processes were represented, including stress response, carbohydrate, lipid and phenylpropanoid metabolism, light signal transduction, and transcriptional and post-transcriptional regulation. Nucleotide diversity was approximately average for a conifer and linkage disequilibrium decayed rapidly. Tests of selective neutrality suggest widespread purifying selection within these candidate genes, though evidence for positive selection was detected within a few. I observed evidence for diversifying selection in 8% of the studied genes, which exhibited high population differentiation relative to the genome-wide average FST of 0.12. To identify genetic determinants of phenotypic variation in locally adaptive traits, an Illumina GoldenGate assay was used to genotype 768 SNPs in a mapping population comprised of 410 individuals from 12 populations collected across the species range. After correcting for population structure and relative kinship, associations were detected in 28 of the candidate genes, which cumulatively explained 28% and 34% of the phenotypic variance in cold hardiness and budset, respectively. Most notable among these associations were five genes putatively involved in light signal transduction, the key pathway regulating autumn growth cessation in perennials. This study represents a significant step toward the goal of characterizing the genomic underpinnings of adaptation to local climate in conifers, and provides a substantial resource for breeding and conservation genetics.

Funding: NSERC Discovery Grant, NSERC Industry Research Chair
Primary participants: [Holliday|Aitken]

Genetic mechanisms of local adaptation in a spruce hybrid zone

Populations will be locally adapted if they contain the appropriate genetic composition to survive and reproduce under current and local conditions. But environmental conditions do not remain constant, thus the appropriate genetic composition to survive and reproduce will change through time as environments change. If populations have increased genetic variation they have reduced risk of extinction in the face of future environmental stochasticity. Increased genetic diversity due to hybridization may result in a further capacity to adapt to changing environments. In this study we focus on the evolutionary mechanisms of gene flow and selection in characterizing the genetic structure of a Sitka-white spruce (Picea sitchensis x P. glauca) hybrid zone.

The broad goal is to identify the genetic consequences of introgression and the degree to which local adaptation in traits of economic value or those involved in adaptation to climate are exhibited across the hybrid zone using a variety of approaches; including molecular and quantitative trait analysis. While substantial genetic gains in growth and quality have been achieved using traditional methods, natural hybrid zones offer another valuable tool from which important genetic variation may be explored for future gains. The factors that drive natural selection and local adaptation in tree hybrid zones have broad ecological, conservation, and economic implications as both forest genetics and silviculture depend on understanding and managing genetic diversity in tree populations.

Funding: NSERC Discovery Grant, Genome BC

Primary participants: [Hamilton|Aitken]

Genetic structure and gene flow in natural and managed forest tree populations of the interior spruce hybrid zone

White spruce (Picea glauca) is a widely distributed and economically important tree species in Canada. In the southwestern part of its range, it hybridizes extensively with Engelmann spruce (Picea engelmanni) creating enormous hybrid swarms in a great part of British Columbia. The pattern and process responsible for hybrid zone maintenance as well as the influence of introgression between species is poorly understood. Because of their similarity in morphology, they have been treated as a complex, known as interior spruce. Although geographical (elevational) and environmental (climatic) differentiation have been well studied through multiple long-term provenance trials, the genetic composition of this zone and the effect of artificial selection on the genomic composition of interior spruce have never been thoroughly assessed.

This research focuses on characterizing the interior spruce complex by assessing the pattern and process responsible for the hybrid zone formation and maintenance, and by analyzing the effects of breeding and management on the genetic structure. Results will have implications in the management and conservation of the species complex and will be used to predict the adaptive potential of natural populations to climate change.

Funding: NSERC Discovery Grant, University Graduate Fellowship, Forest Investment Account through Forest Genetics Council of BC, Genome BC

Primary participants: [de la Torre|Aitken]

Development of a strategy for forest gene conservation

The long-term maintenance of genetic diversity is strongly affected by the effective sizes of populations, the spatial structuring of genetic diversity, numbers and frequencies of rare alleles, and selection/mutation/drift balance. While there is good general concensus on some issues, such as viable population sizes, there remains considerable debate over others, and our experience with species other than those in large breeding programs is limited. Strategies for the conservation and management of genetic diversity in the face of rapid climate change also need to be developed. We were extremely fortunate to be assisted by the late Dr. Gene Namkoong in developing the theoretical portion of this strategy, and will be producing a comprehensive document outlining both the theoretical and operational components of this strategy in the near future.

Funding: Forest Investment Account through Forest Genetics Council of BC
Participants: [Namkoong|Yanchuk|Aitken]

Develop marker-based methods of monitoring and managing coancestry in breeding populations

Multi-generational breeding programs require tools to monitor levels of genetic diversity over time in breeding and deployment populations. These monitoring tools can be theoretical, requiring input of population size and relatedness; or empirical, using genetic markers. Clones used in breeding programs will be assayed for highly informative microsatellite loci. Relatedness and pedigree structure will be estimated using patterns of allele identity and similarity. Alternative measures that incorporate multilocus patterns of relatedness and diversity will be considered. This information can then be integrated in designing breeding programs to optimize the joint objectives of maximizing both genetic gain and genetic diversity.

Funding: Forest Investment Account through Forest Genetics Council of BC
Published Papers: [Wellman et al. 2003, 2004]
Principal participants: [C. Ritland|K. Ritland|Wellman|El-Kassaby]

Genetic conservation can be accomplished in situ by maintaining wild populations in parks and protected areas, ex situ in seed banks, and for species with active breeding programs, inter situ in genetic common garden experiments. We have evaluated in situ conservation in British Columbia for all 50 tree species (Chourmouzis et al. 2009). Information from tens of thousands of botanical plots in the province has been integrated with spatial ecosystem and protected area data using geographic information systems. This information is being used to determine where additional information or additional in situ protection is needed.

On the In situ Cataloguing webpages we post:

Information on ecology, distribution, reproduction, demographics, in situ conservation, genetic structure, and/or resource management for individual species

The results of a GIS analysis cataloguing current levels of conservation of major and minor tree species based on BEC units.

A similar analysis has been conducted for in situ protection of the ten conifers in breeding programs for each Seed Planning Unit (Hamann et al. 2004). Data are also being compiled on ex situ conservation seed collections and inter situ common garden experiments by species and SPU in cooperation with the BC Ministry of Forests and Range.

Funding: Forest Investment Account through Forest Genetics Council of BC
Publications: [Hamann et. al. 2004 | Hamann et al. 2005)]
Primary participants: [Chourmouzis|Hamann|Yanchuk|Smets| Aitken]

For species of small tree stature, narrow distribution or little economic importance, information on the amount and distribution of genetic variation is generally lacking. However, these species may be important ecologically and may become important ecologically. Genetic knowledge is needed to guide seed transfer for ecological restoration. Furthermore, some of these species are threatened by introduced diseases or insects, or by climate change.

In order to prioritize individual species for genetic studies, we conducted a survey and workshop to summarize current knowledge and information needs for British Columbia's 'minor' tree species. Results from this workshop on prioritizing minor species for genetic conservation and research are available [sample extract - PDF 167 Kb]. To date, we have initiated research on four of the high-priority species: whitebark pine, Garry oak and Pacific dogwood.

Quick links to CFCG "Species" projects

• Whitebark pine (Pinus albicaulis)
• Garry oak (Quercus garryana)
• Pacific dogwood (Cornus nuttalli)
• Bigleaf Maple (Acer macrophyllum)

Other related links

• Whitebark pine in Western Canada - current research and management issues

Whitebark pine (Pinus albicaulis )

Whitebark pine is a keystone species in high-elevation ecosystems. It has been severely impacted by white pine blister rust an introduced disease caused by the fungus Cronartium ribicola, and is at risk of local extirpation in some areas. In an earlier CFCG study (Krakowski et. al. 2003), we studied the mating system of whitebark pine in two British Columbia populations and found a lower level of outcrossing then typical for wind-pollinated conifers. For his Ph.D. project, Andy Bower has conducted a seedling common garden study to assess rangewide genetic variation in quantitative traits that may reflect local adaptation. This information will be useful in developing seed transfer guidelines for restoration plantings to avoid maladaptation. Andy has also used isozyme analysis to: 1) confirm the mating system of whitebark pine for a larger number of populations; and 2) to determine if significant inbreeding depression can be detected in quantitative traits by comparing the family mean inbreeding coefficient, calculated from the parental outcrossing rate, with family mean performance of the seedlings; and 3) determine if levels of inbreeding differ among age cohorts (seedling, sapling and mature) or among sites with different levels of blister rust infection across 14 populations. His results confirm that whitebark pine has a mixed mating system, but the outcrossing rate is higher in more southern (U.S.) populations than previously found in BC, and the mean outcrossing rate is close to the mean of other conifers (tm = 0.86). Significant inbreeding depression was only detected in one trait: total seedling biomass. There was evidence of inbreeding in seedlings, saplings and mature trees, but when the level of rust is low, the heterozygote deficiency decreases with age. When the level of rust is high, however, there is some evidence that more homozygous individuals are more likely to survive, possibly due to recessive resistance genes being expressed in more inbred individuals.

More information can be found in the following documents by Krawkowksi [MSc Thesis, published papers] and by Bower [poster presentations: WFGA 2003, Alisomar 2004; published papers].

Funding: Forest Investment Account through Forest Genetics Council of BC
Principal participants: [Krakowski|Bower|Aitken| El-Kassaby|Yanchuk]

Garry oak (Quercus garryana)

Garry oak is a deciduous tree endemic to Western North America. It is confined within Canada to only a few isolated locations in southwestern BC. Although accounting for less than 0.3% of BC’s entire land coverage, Garry oak-associated ecosystems support tremendous biodiversity and are home to a large number of rare species. It is estimated that only 1-5% of pre-European Garry oak ecosystems remain uncompromised in BC 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 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, while cold hardiness was strongly correlated with temperature differential 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 BC and elsewhere.

Funding: Forest Investment Account through Forest Genetics Council of BC
Principal participants: [Huebert|Aitken]

Pacific dogwood (Cornus nuttalli)

The cumulative findings of this study suggest that low genetic diversity is ubiquitous throughout the native range of Pacific dogwood. Although genetically depauperate species are often of great conservation concern, results suggest this species may have a relatively long history of low diversity. This observation may illustrate the ambiguous correlations of neutral diversity, quantitative trait variation and adaptability. Although some species are capable of thriving following a bottleneck it is dangerous to assume this would be the case for all genetically depauperate species. It would be advisable for baseline data to be collected regarding population sizes and densities, in the event that Pacific dogwood should show signs of decline in the face of climate change or new or intensified biotic challenges. This is especially true for the southern populations, which have been shown to have the highest contributions to both total diversity and allelic richness. Without anywhere to go, these southern high elevation populations (> 1000m) would be forced to adapt or face elimination. The weak phylogeographic structure and low levels of among population differentiation suggest Pacific dogwood possesses great capacity for long distance dispersal. In the face of a rapidly changing climate, this feature would advantageous as it appears predisposed to move quickly into new, climatically favorable habitats. This genetic study is the first of its kind for Pacific dogwood and there is still much to be learned.

Project Poster

Funding: Forest Investment Account through Forest Genetics Council of BC
Principal participants: [Keir|Aitken|C. Ritland]

Bigleaf Maple (Acer macrophyllum)

In the coastal forests of southern BC, bigleaf maple is an important hardwood in a region dominated by conifers. In the Lower Mainland and on southern Vancouver Island, the habitat of this species has been fragmented by agriculture, forestry and urbanization. Mohammed Iddrisu has conducted his PhD research on the population, quantitative and conservation genetics of this species. The final portion of this research on the effects of population fragmentation on spatial genetic structure and diversity were conducted under the auspices of the CFCG.

Funding: Commonwealth Scholarship, NSERC Industry Chair in Population Genetics, Forest Investment Account through the Forest Genetics Council of BC
Publications: [Iddrisu and Ritland 2004; posters:WFGA 2004, UBC Faculty Research 2005]
Principal participants: [Iddrisu|K. Ritland|Aitken]

Populations of forest trees will be challenged in the coming century by the need to adapt or migrate in response to climatic warming. The mountain pine beetle epidemic has provided an early warning signal of the speed and magnitude with which climate-related disturbances can strike. Climate change needs to be considered in all aspects of forest genetic resource management, whether in anticipating the likelihood of persistence of conservation populations in protected areas, evaluating the potential for human facilitated migration of populations, or choosing seed sources for reforestation given climatic uncertainty. The Centre for Forest Gene Conservation is involved in research related to all of these areas.

A key milestone in our climate change related research was the development of ClimateBC, a scale-free climate model for BC. Predictions from this model have been used to project the future distributions of current bioclimatic envelopes for both ecosystems and species, to evaluate forest tree population persistence in protected areas given climate change, and to estimate population-specific temperature response curves for lodgepole pine using provenance trial data. A recent Vancouver Sun article features output ClimateBC (open pdf). Ongoing projects in the area of climate change and forest genetics include the analysis of climatic factors influencing interannual variation in radial growth of lodgepole pine provenance and the development of population temperature response functions for lodgepole pine and interior spruce based on seedling growth under varying temperature, moisture and carbon dioxide treatments in controlled growth chamber experiments. See "Predicting BC's future climate and forests: An animated presentation" for a brief overview (open slide show).

Quick links to "Climate Change" related projects described below

• ClimateBC and ClimateWNA
• ClimateBC and Bioclimatic Envelope Modelling
• Growth Response of Lodgepole pine to Climate
• Seedling Growth Response of Lodgepole Pine and Interior Spruce to Climate
• Radial Growth Responses in Lodgepole pine
• Conserving whitebark pine in a changing climate

ClimateBC

ClimateBC and ClimateWNA utilizes historical weather station data for the past century and global circulation model regional predictions to project climate means in BC over the next century.

Funding: NSERC Strategic Grant, BIOCAP Canada Foundation, FIA through Forest Genetics Council of BC, NSERC Industry Chair

Participants: [Wang|Hamann|Spittlehouse|Aitken]

ClimateBC and Bioclimatic Envelope Modelling

Using ClimateBC derived climate variables, Andreas Hamann and Tongli Wang have modelled the current climate envelopes of BC tree species and BEC zones. Under various climate change scenerios they analyze how these climate envelopes will shift in the future. BEC zone are predicted to change dramatically. Sub-boreal and montane zones are expected to be largely outside of their climate envelopes within 50 years. The IDF, ICH, PP and BG zones are expected to rapidly expand into most of BC's interior and into parts of the boreal forest. Some of BC's trees species are expected to gain potential habitat at about a 100 km per decade. While species like Douglas-fir, Ponderosa pine and many small broadleaves are expected to benefit, some commercial species and many high elevation or boreal species are expected to loose substantial portions of suitable habitat/climate. For more information see Hamann and Wang 2006.

Funding: NSERC Strategic Grant, BIOCAP Canada Foundation, FIA through Forest Genetics Council of BC

Primary participants: [Wang|Hamann]

Growth Response of Lodgepole pine to Climate

Understanding the response of tree populations to climate is critical for formulating new seed deployment strategies to adapt to climate change. Growth response functions have been developed for lodgepole pine populations based on observations from a comprehensive provenance trial. Results of this study suggest: 1) the importance of using a reliable climate model in genecology to avoid misleading conclusions; 2) new analytical methods developed by the CFCG improve growth response functions; 3) populations from furthere south are not necessarily a good choice for future climates; 4) populations with broad adaptability can be identified; and 5) the potential of optimizing seed source selection to mitigate climate change is substantial. For more information see Wang et al 2006.

Funding: Forest Investment Account through Forest Genetics Council of BC, NSERC Industry Chair

Primary participants: [Wang|Aitken|Yanchuk|Hamann|O'Neill]

Seedling Growth Response of Lodgepole Pine and Interior Spruce to climate

Global climate is warming rapidly and populations of long-lived trees may be unable to adapt quickly enough. Mitigation through genetic resource management requires knowledge of the relative response of populations to climate change. Existing provenance trials covering a range of climatic conditions can provide a first approximation. Extrapolation beyond this range requires seedling experiments in controlled climate chambers. We are undertaking such experiments evaluating the responses of lodgepole pine and interior spruce populations to temperature, and also exploring the effects of C02 enrichment and drought on these responses. The methodology will be useful to predict the response for those species lacking extensive provenance trials.

Funding: Forest Investment Account through Forest Genetics Council of BC

Primary participants: [Smets|Aitken]

Radial Growth Responses in Lodgepole pine

The Bioclimatic Envelope Model (BEM) created by Hamann and Wang (2005) forecasts dramatic changes in the latitudinal and elevational distributions of the climatic envelopes of forest trees throughout British Columbia over the next eight decades. While BEMs provide tremendously valuable information regarding potential future range distributions, field studies are needed to determine the actual biological responses of forests to changes in climate. Sierra Curtis-McLane's research will evaluate predictions from British Columbia BEMs compared to germination, survival and fitness of conifers planted outside of their native climatic ranges. Current research examines how climate patterns affect annual growth in populations of lodgepole pine (Pinus contorta). While baseline growth differential data have confirmed strong genotype by environment interactions, our research addresses the question of how annual ring widths vary among populations within a site and among sites for a given population. Wood cores were sampled in sixteen lodgepole pine common gardens that were established in 1974. Annual growth trends will be analyzed in conjunction with weather data, thereby shedding light on fitness responses of varying genotypes to current climate trends. Future field and growth chamber research will examine the germination and growth potential of different conifer genotypes relative to climate conditions at the margin of the species ranges. This information will be used to assess the extent to which adaptation by selection is taking place, and compared to seedling plantation data for seed transfer and conservation purposes.

Poster presentation: 2006
Funding: Forest Investment Account through Forest Genetics Council of BC
Primary participants: [Curtis-McLane|Aitken]

Conserving whitebark pine in a changing climate

Bioclimatic envelope models show a large discrepancy between the current realized and current and future predicted species range for whitebark pine (Pinus albicaulis Engelm.). Large areas in the northwest portion of BC that are projected to become primary refuges for the species under climate change scenarios are hypothetically also potentially habitable under current climate conditions, which begs the question of why whitebark pine doesn't grow in those areas already. A series of projects have been designed to evaluate the biotic and abiotic limiting factors associated with recruitment at the northwest margin of the species range, and the potential for whitebark pine populations to successfully recruit beyond the current species border. Common garden plantings were established within and north of the current northwest species range (50.1° to 59.7° latitude) using seeds from 10 open pollinated families from each of 7 whitebark pine populations (44.3° to 54.9° latitude). Of the 18 common garden sites, six are within the current species range, six are approximately 0.5°, 1.7° and 4.9° north of the current northwest species boundary in locations shown to be habitable under both 1970-2000 normal and 2055 projected climate regimes, and six are parallel to the latter but outside of the modeled range. The common gardens have a 20-year permit from the Ministry of Forests and Range, with the expectation that they will be renewed into the indefinite future. Additionally, the same 70 families will be subjected to five temperature regimes in growth chambers. The results will be used to refine current and future species distribution projections in order to more accurately predict the fundamental niches of threatened species under climate change scenarios. The project will also lend fodder to the current scientific and ethical controversy regarding whether it is acceptable to facilitate the migration of a species threatened by extirpation within its current range.

Poster presentation: 2008
Funding: Forest Investment Account through Forest Genetics Council of BC and BCMFR Research Branch
Primary participants: [Curtis-McLane|Aitken]