Genecology is the study of intraspeciﬁc genetic variation in relation to environmental conditions. It reveals patterns of adaptation of populations to their environments that result from differences in natural selection among locations. Genecological studies are conducted for the practical purposes of: (1) determining how far seed can be moved from the collection site to a reforestation site without risking maladaptation of the trees to the planting site; (2) delineating geographic breeding zones for which a single breeding program would suffice; (3) selecting optimal provenances within the native range for nonnative (introduced) species; and, more recently, (4) predicting the ability of populations of forest trees to adapt to rapidly changing climates. To meet these objectives, seed is collected from different provenances (geographic origins) throughout all or a portion of a species range and planted in one or more ﬁeld or nursery common-garden experiments. The survival and growth of trees of different provenances are observed under the same set of environmental conditions, allowing for the separation of genetic and environmental effects.
[...] A full century before both Darwin's theory of evolution was published in On the Origin of Species, and Johann Gregor Mendel determined the mechanics of heredity, Carl von Linne (also known as Carolus Linnaeus, the father of modern taxonomy), reported in 1759 that yew trees (Taxus baccata) from France were less cold-hardy than those from Sweden. Around the same time, Henri Louis Duhamel du Monceau, Inspector-General of the French navy and noted botanist, established the ﬁrst forest genetic trials on record. [...]
[...] In species with intraspeciﬁc taxonomic structure, genetic differentiation resulting from both isolation and past adaptation can overlay and complicate the interpretation of variation resulting from adaptation to current or recent environments in continuously distributed populations. Hybridization resulting from secondary geographic contact between previously separated species can also produce strong geographic patterns of adaptive variation, for example, in the introgression zone between Picea glauca and P. sitchensis in the coastal mountains of British Columbia and Alaska. Genecological Methods Provenance Trials Traditional provenance trials require ﬁve steps: collection of seed; growing of seedlings; planting of a replicated experiment on multiple ﬁeld sites; measurement of traits; and analysis and interpretation of results. [...]
[...] For a number of species, superior provenances have been identiﬁed, trees from which have higher than expected growth rates and perform well above the norm for the genetic cline over a wide range of test environments. The second trend is that for many western North American species, the most rapidly growing genotypes with comparable survival and health to local provenances are from slightly milder environments than the test site, e.g., or 100–300m lower in elevation. This may reﬂect adaptational lag, that is, the local adaptation of populations to past rather than current environments, given the long generation interval of trees, or it may reﬂect a lack of extreme climatic events as agents of natural selection since the provenance trials were planted. [...]
[...] They can typically be completed in years, can involve more uniform environments and thus have a greater ability to detect genetic differences, can be located close to laboratory facilities for repeated observations or for assessment of time and equipment-intensive traits, and can allow the isolation, control, and testing of speciﬁc environmental factors such as temperature, moisture, photoperiod, and nutrients. Disadvantages include a lack of long-term information on survival and health in natural environments, and the inability to assess mature characteristics. [...]
[...] The majority of these tests have been in temperate forest regions in Europe and North America, with fewer published studies of tropical or boreal species. While these trials were initially established to generate information for operational forestry, they have been used for new applications in recent years, including predicting response to climate change, determining the underlying genetic basis of adaptive traits (i.e., ecological genomics) and testing evolutionary and ecological theories about factors limiting the evolution of species range. The extensive body of scientiﬁc literature on local adaptation in forest trees may well exceed that for any other type of organism. [...]
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