Experimental approaches are based on the concept of common gardens and the decomposition of phenotypic variance observed in standardized environments into its genetic and environmental components. Choice of the phenotypic trait to examine is crucial and our research has focused on several different phenotypic traits related to the survival component of total lifetime fitness (e.g. growth, water-use efficiency, wood properties, cold tolerance & disease resistance). For conifers, common gardens that we use are constructed from seeds collected within natural populations, so as to form collections of half-sibling families (at least this is what we assume). From this collection of half-sibling families, we can estimate numerous quantitative genetic parameters such as heritability (i.e. the proportion of phenotypic variance explainable by genetic variance), QST (i.e. the proportion of additive genetic variance due to population identifiers), and the additive genetic value of maternal trees (e.g. maternal tree BLUPs). The latter forms the basis of the phenotypic data used to associate with genetic marker data using either population-based approaches, such as association genetics, or family-based approaches, such as quantitative trait locus mapping. The outcomes of these studies are genomic regions that are candidates for the genes or genomic regions comprising the genetic architecture for the phenotypic trait of interest. Along with the identity of the genomic regions comprising the genetic architecture of a trait, this approach also provides effect size estimates for each candidate region. A large fraction of our publications utilize data derived from common gardens, with the bulk of them dealing with the relationship between genotypes and phenotypes for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), foxtail pine (Pinus balfouriana Grev. & Balf.), and loblolly pine (Pinus taeda L.). Experimental approaches based on common gardens are also amenable to more detailed experimentation, such as application of treatments to specific families to test specific hypotheses or development into reciprocal transplantation studies (Kawecki and Ebert 2004). Although not yet implemented in most of our research, this is a natural extension once the groundwork has been laid using traditional common gardens.
- Alberto, F. J., S. N. Aitken, R. Alia, S. C. Gonzalez-Martinez, H. Hanninen, A. Kremer, F. Lefevre, T. Lenormand, S. Yeaman, R. Whettan, et al. 2013. Potential for evolutionary responses to climate change - Evidence from tree populations. Global Change Biology 19: 1645-1661.
- Eckert, A. J., A. D. Bower, B. Pande, K. D. Jermstad, K. V. Krutovsky, J. B. St. Clair and D. B. Neale. 2009. Association genetics of coastal Douglas fir (Pseudotsuga menziesii var. menziesii, Pinaceae). I. Cold-hardiness related traits. Genetics 182: 1289-1302.
- Eckert, A. J., J. van Heerwaarden, J. L. Wegrzyn, C. D. Nelson, J. Ross-Ibarra, S. C. González-Martínez and D. B. Neale. 2010. Patterns of population structure and environmental associations to aridity across the range of loblolly pine (Pinus taeda L., Pinaceae). Genetics 185: 969-982.
- Eckert, A. J., J. L. Wegrzyn, J. D. Liechty, J. M. Lee, W. P. Cumbie, J. M. Davis, B. Goldfarb, C. A. Loopstra, S. R. Palle, T. Quesada, C. H. Langley, and D. B. Neale. 2013a. The evolutionary genetics of the genes underlying phenotypic associations for loblolly pine (Pinus taeda, Pinaceae). Genetics 195: 1353-1372.
- Eckert, A. J., A. D. Bower, K. D. Jermstad, J. L. Wegrzyn, B. J. Knauss, J. V. Syring, and D. B. Neale. 2013b. Multilocus analyses reveal little evidence for lineage wide adaptive evolution within major clades of soft pines (Pinus subgenus Strobus). Molecular Ecology 22: 5635-5650.
- Fisher, R. A. 1930. The genetical theory of natural selection. Claredon Press, Oxford.
- He, T., J. G. Pausas, C. M. Belcher, D. W. Schwilk, and B. B. Lamont. Fire-adapted traits of Pinus arose in the fiery Cretaceous. New Phytologist 194: 751-759.
- Kawecki, T. J. and D. Ebert. 2004. Conceptual issues in local adaptation. Ecology Letters 7: 1225-1241.
- Neale, D. B. and O. Savolainen. 2004. Association genetics of complex traits in conifers. Trends in Plant Science 9: 325-330.
- Reznick, D. N. and R. E. Ricklefs. 2009. Darwin’s bridge between microevolution and macroevolution. Nature 457: 837-842.