USDA Forest Service Rocky Mountain Research Station, Moscow, ID, USA.
Ecology, Evolution and Behavior, University of Minnesota, Saint Paul, MN, USA.
J Evol Biol. 2018 Sep;31(9):1284-1299. doi: 10.1111/jeb.13301. Epub 2018 Aug 14.
Growth rhythm that is well synchronized with seasonal changes in local climatic conditions is understood to enhance fitness; however, rapid ongoing climate change threatens to disrupt this synchrony. To evaluate phenotypic selection on growth rhythm under expected warmer and drier future climate, seedlings from 49 populations of whitebark pine (Pinus albicaulis Engelm.) were grown and measured over more than 10 years in two common garden field experiments on sites that approximate the projected future climate of the seed origins. Selection on growth rhythm was assessed by relating individual plant fitness to timing and rate of shoot elongation. Differential survival clearly evidenced selection on growth rhythm. We detected directional and stabilizing selection that varied in magnitude between experimental sites and among years. The observed phenotypic selection supports the interpretation of clinal variation among populations within tree species as reflecting adaptive variation in response to past natural selection mediated by climate. To the extent that growth rhythm is heritable, results of the present study suggest evolution of whitebark pine toward a more distinct timing of shoot elongation and generally more rapid elongation in the immediate next generation under ongoing climate change in environments similar to the study sites.
与当地气候条件的季节性变化同步良好的生长节律被认为可以提高适应性；然而，正在发生的快速气候变化可能会破坏这种同步性。为了评估在预期更温暖和更干燥的未来气候下生长节律的表型选择，我们在两个共同的田间实验中种植了来自 49 个白皮松（Pinus albicaulis Engelm.）种群的幼苗，并在接近种子起源地未来气候的地点进行了 10 多年的测量。通过将单个植物的适应性与芽伸长的时间和速度联系起来，评估了生长节律的选择。明显的生存差异证明了生长节律的选择。我们检测到定向选择和稳定选择，其大小在实验地点和年份之间有所不同。观察到的表型选择支持了这样的解释，即在树种内的种群之间存在梯度变化，这反映了对过去由气候介导的自然选择的适应性变化。在生长节律具有遗传性的程度上，本研究的结果表明，在类似于研究地点的环境中，在持续的气候变化下，白皮松在下一代中更明显地定时进行芽伸长，并且通常会更快地伸长。
