Dechaine Jennifer M, Johnston Jill A, Brock Marcus T, Weinig Cynthia
Department of Plant Biology, University of Minnesota, St Paul, MN 55108, USA.
New Phytol. 2007;176(4):874-882. doi: 10.1111/j.1469-8137.2007.02210.x.
Phenotypic plasticity, the ability of a genotype to express different phenotypes across environments, is an adaptive strategy expected to evolve in heterogeneous environments. One widely held hypothesis is that the evolutionary benefits of plasticity are reduced by its costs, but when compared with the number of traits tested, the evidence for costs is limited. Selection gradients were calculated for traits and trait plasticities to test for costs of plasticity to density in a field study using recombinant inbred lines (RILs) of Brassica rapa. Significant costs of putatively adaptive plasticity were found in three out of six measured traits. For one trait, petiole length, a cost of plasticity was detected in both environments tested; such global costs are expected to more strongly constrain the evolution of plasticity than local costs expressed in a single environment. These results, in combination with evidence from studies in segregating progenies of Arabidopsis thaliana, suggest that the potential for genetic costs of plasticity exists in natural populations. Detection of costs in previous studies may have been limited because historical selection has purged genotypes with costly plasticity, and experimental conditions often lack environmental stresses.
表型可塑性是指基因型在不同环境中表达不同表型的能力，是一种预计会在异质环境中进化的适应性策略。一个被广泛接受的假说是，可塑性的进化益处会因其成本而降低，但与所测试的性状数量相比，成本的证据有限。在一项使用芜菁重组自交系（RILs）的田间研究中，计算了性状和性状可塑性的选择梯度，以测试可塑性对密度的成本。在六个测量性状中的三个中发现了假定适应性可塑性的显著成本。对于一个性状，即叶柄长度，在两个测试环境中都检测到了可塑性成本；与在单一环境中表现出的局部成本相比，这种全局成本预计会更强烈地限制可塑性的进化。这些结果，与来自拟南芥分离后代研究的证据相结合，表明自然种群中存在可塑性遗传成本的可能性。在先前研究中成本的检测可能受到限制，因为历史选择已经清除了具有高成本可塑性的基因型，而且实验条件往往缺乏环境压力。
