While genecological studies suggest divergent selection on phenotypic traits for local adaptation to climate must be relatively strong (Howe et al. 2004; Savolainen et al. 2007; Alberto et al. 2013), population genetic studies suggest gene flow is high, as most widespread species show weak- to-moderate population differentiation (FST) for selectively neutral genetic markers (Kremer et al. 2012). How tree populations could diverge substantially for locally adaptive traits in the face of high levels of gene flow has been something of a puzzle (Savolainen et al. 2007). Theoretical modelling suggests that highly polygenic traits controlled by many co-varying loci of small effect can create phenotypic divergence under divergent selection despite high gene flow, but individual loci underlying such traits will have only weak divergence, and will be difficult to detect (Latta 2003; Le Corre and Kremer 2012; Savolainen et al. 2013). This genetic architecture presents a challenge for popula- tion studies to detect and adequately characterize local adaptation through genome scans

Aitken, S. N., & Bemmels, J. B. (2015). Time to get moving: Assisted gene flow of forest trees. Evolutionary Applications, doi:10.1111/eva.12293

Maybe I can solve a little piece of this puzzle with my PhD….

It is often assumed that forcing [for budburst] does not begin until after the chilling requirement has been met and this undoubtedly is what occurs naturally in boreal regions where extended periods of cold temperatures are never or rarely interrupted by warmer (forcing temperatures) until spring. We believe, however, that chilling and forcing can occur at the same time (in the temperature range where they overlap) and both systems are accumulating ‘‘time’’ over the dormant period. The systems involved in such accumulations (named the ‘‘memory of winter’’ by Amasino, 2004) are not understood.

From Harrington CA, Gould PJ, St.Clair JB: Modeling the effects of winter environment on dormancy release of Douglas-fir. Forest Ecology and Management 2010, 259:798–808.

The memory of winter

Inertia toward continued emissions creates potential 21st-century global warming that is comparable in magnitude to that of the largest global changes in the past 65 million years but is orders of magnitude more rapid.

From Diffenbaugh & Field 2013 in Science

Sentences to make your blood run cold

An additional challenge for parentage analysis is that it requires exhaustive sampling and so is practical only over small spatial scales (less than 10 km) and low densities. Even extraordinary examples of this type of work include only about 1000 trees in isolated populations (Lesser & Jackson 2013). The continental distributions of dense coniferous forests do not lend themselves to these methods.

In which I master the art of scientific understatement