Genes or Environment? White spruce and the divergence effect at Alaska's northern treeline

基于树木年轮的气候重建的基础是假设树木生长对气候因子有稳定的响应。自20世纪70年代中期以来，在高纬度地区观测到基于树木年轮的温度重建与实测温度之间的偏差增加，称为“散度效应”。分化效应的一个原因可能是，特定种群中的一些树的生长速度加快，而另一些树的生长速度下降。拟议的项目解决了阿拉斯加林木线上的白云杉（Picea glauca）的这个问题。比较树木微卫星基因型与生长响应的两两相关性，将有助于阐明树木的不同行为是否由遗传和/或环境因素引起。如果确定了遗传成分，cp标记将用于测试气候响应的差异是1)由与黑云杉杂交的遗传渗入引起的，2)来自不同的冰川保护区，还是3)来自作为预选择适应的自然遗传变异，使物种能够以不同的方式应对不断变化的环境条件。这些发现将与树木气候学的实践以及我们对生态系统如何对全球气候变化作出反应的理解有关。

The basis of tree-ring based climate reconstruction is the assumption of a stable response of tree growth to climate factors. Since the mid-1970s, an increased off-set between tree-ring based temperature reconstructions and measured temperatures was observed at high latitudes, called “divergence effect”. One reason for the divergence effect might be that some trees of a given population react with enhanced growth, others show decreasing growth. The proposed project addresses this problem for white spruce (Picea glauca) at the treeline in Alaska. It will elucidate whether the different behavior of trees is caused by genetic and/or environmental factors, comparing pairwise relatedness of tree microsatellite genotypes with growth response. If a genetic component is identified, cp markers will be used to test whether the differences in climate response 1) are caused by genetic introgression by hybridization with black spruce, 2) origin from different glacial refugia, or 3) from natural genetic variation that acts as preselective adaptation and allows the species to respond to changing environmental conditions in different ways. The findings will bear relevance to the practice of dendroclimatology as well as our understanding of how ecosystems react to global climate change.