Byars Sean G, Parsons Yvonne, Hoffmann Ary A
Centre for Environmental Stress and Adaptation Research, Department of Genetics, Melbourne University, Parkville, Australia.
Ann Bot. 2009 Apr;103(6):885-99. doi: 10.1093/aob/mcp018. Epub 2009 Feb 10.
The persistence of plants inhabiting restricted alpine areas under climate change will depend upon many factors including levels of genetic variation in adaptive traits, population structure, and breeding system.
Using microsatellite markers, the genetic structure of populations of a relatively common alpine grass, Poa hiemata, is examined across three altitudinal gradients within the restricted Australian alpine zone where this species has previously been shown to exhibit local adaptation across a narrow altitudinal gradient.
Genetic variation across six microsatellite markers revealed genetic structuring along altitudinal transects, and a reduction in genetic variation at high and low altitude extremes relative to sites central within transects. There was less genetic variation among transect sites compared with altitudinal gradients within transects, even though distances among transects were relatively larger. Central sites within transects were less differentiated than those at extremes.
These patterns suggest higher rates of gene flow among sites at similar altitudes than along transects, a process that could assist altitudinal adaptation. Patterns of spatial autocorrelation and isolation by distance changed with altitude and may reflect altered patterns of dispersal via pollen and/or seed. There was evidence for selfing and clonality in neighbouring plants. Levels of gene flow along transects were insufficient to prevent adaptive changes in morphological traits, given previously measured levels of selection.
在气候变化的情况下，栖息于有限高山区域的植物能否存续将取决于许多因素，包括适应性状的遗传变异水平、种群结构和繁殖系统。
利用微卫星标记，对一种相对常见的高山禾本科植物——冬早熟禾（Poa hiemata）种群的遗传结构进行了研究，研究跨越了澳大利亚有限高山区域内的三个海拔梯度，此前已证明该物种在狭窄的海拔梯度上表现出局部适应性。
六个微卫星标记的遗传变异揭示了沿海拔样带的遗传结构，相对于样带中部的位点，在高海拔和低海拔极端位点的遗传变异减少。尽管样带之间的距离相对较大，但与样带内的海拔梯度相比，样带间位点的遗传变异较少。样带中部的位点比极端位点的分化程度低。
这些模式表明，相似海拔位点之间的基因流速率高于沿样带的基因流速率，这一过程可能有助于海拔适应性。空间自相关和距离隔离模式随海拔而变化，可能反映了通过花粉和/或种子的扩散模式改变。有证据表明相邻植物存在自交和克隆繁殖现象。鉴于之前测量的选择水平，沿样带的基因流水平不足以阻止形态性状的适应性变化。
