Forest Sciences and Centre for Forest Conservation Genetics, University of British Columbia, Vancouver, BC, Canada.
J Evol Biol. 2010 Feb;23(2):249-58. doi: 10.1111/j.1420-9101.2009.01910.x. Epub 2009 Dec 15.
High-dispersal rates in heterogeneous environments and historical rapid range expansion can hamper local adaptation; however, we often see clinal variation in high-dispersal tree species. To understand the mechanisms of the species' distribution, we investigated local adaptation and adaptive plasticity in a range-wide context in Sitka spruce, a wind-pollinated tree species that has recently expanded its range after glaciations. Phenotypic traits were observed using growth chamber experiments that mimicked temperature and photoperiodic regimes from the limits of the species realized niche. Bud phenology exhibited parallel reaction norms among populations; however, putatively adaptive plasticity and strong divergent selection were seen in bud burst and bud set timing respectively. Natural selection appears to have favoured genotypes that maximize growth rate during available frost-free periods in each environment. We conclude that Sitka spruce has developed local adaptation and adaptive plasticity throughout its range in response to current climatic conditions despite generally high pollen flow and recent range expansion.
在异质环境中，高扩散率和历史上的快速范围扩张会阻碍地方适应；然而，我们经常在高扩散率的树种中看到渐成变异。为了了解物种分布的机制，我们在范围广泛的范围内调查了 Sitka 云杉的地方适应和适应性可塑性，Sitka 云杉是一种风媒树种，在冰川消融后最近扩大了其范围。通过生长室实验观察了表型特征，该实验模拟了物种实际生态位极限的温度和光周期条件。芽物候在种群之间表现出平行的反应规范；然而，在芽萌发和芽设置时间上分别观察到了假定的适应性可塑性和强烈的分歧选择。自然选择似乎有利于在每个环境中可用无霜期内最大限度地提高生长速度的基因型。我们的结论是，尽管花粉流动普遍较高且最近的范围有所扩大，但 Sitka 云杉在其整个范围内已经发展出了对当前气候条件的地方适应和适应性可塑性。
