Weinig Cynthia, Stinchcombe John R, Schmitt Johanna
Department of Ecology and Evolutionary Biology, Box G-W, Brown University, Providence, Rhode Island 02912, USA.
Evolution. 2003 Jun;57(6):1270-80. doi: 10.1111/j.0014-3820.2003.tb00335.x.
Resistance and tolerance are widely viewed as two alternative adaptive responses to herbivory. However, the traits underlying resistance and tolerance remain largely unknown, as does the genetic architecture of herbivory responses and the prevalence of genetic trade-offs. To address these issues, we measured resistance and tolerance to natural apical meristem damage (AMD) by rabbits in a large field experiment with recombinant inbred lines (RILs) of Arabidopsis thaliana (developed from a cross between the Columbia x Landsberg erecta ecotypes). We also measured phenological and morphological traits hypothesized to underlie resistance and tolerance to AMD. Recombinant inbred lines differed significantly in resistance (the proportion of replicates within an RIL that resisted herbivory), and early flowering plants with tall apical inflorescences were more likely to experience damage. Tolerance (the difference in fitness between the damaged and undamaged states), also differed significantly among RILs, with some lines overcompensating for damage and producing more fruit in the damaged than undamaged state. Plastic increases in basal branch number, basal branch height, and senescence date in response to damage were all associated with greater tolerance. There was no evidence for a genetic trade-off between resistance and tolerance, an observation consistent with the underlying differences in associated morphological and phenological characters. Selection gradient analysis detected no evidence for direct selection on either resistance or tolerance in this experiment. However, a statistical model indicates that the pattern of selection on resistance depends strongly on the mean level of tolerance, and selection on tolerance depends strongly on the mean level of resistance. These observations are consistent with the hypothesis that selection may act to maintain resistance and tolerance at intermediate levels in spatially or temporally varying environments or those with varying herbivore populations.
抗性和耐受性被广泛视为对食草动物的两种替代性适应反应。然而，抗性和耐受性背后的性状在很大程度上仍然未知，食草动物反应的遗传结构以及遗传权衡的普遍性也是如此。为了解决这些问题，我们在一项大型田间试验中，利用拟南芥重组自交系（RILs，由哥伦比亚生态型和直立兰茨贝格生态型杂交培育而成），测量了对兔子自然顶端分生组织损伤（AMD）的抗性和耐受性。我们还测量了被认为是抗性和耐受性基础的物候和形态性状。重组自交系在抗性（一个RIL内抵抗食草动物的重复比例）方面存在显著差异，具有高顶端花序的早花植物更容易受到损伤。耐受性（受损状态和未受损状态之间的适合度差异）在RILs之间也存在显著差异，一些品系对损伤有超补偿作用，受损状态下比未受损状态产生更多果实。损伤后基部枝条数量、基部枝条高度和衰老日期的可塑性增加都与更高的耐受性相关。没有证据表明抗性和耐受性之间存在遗传权衡，这一观察结果与相关形态和物候特征的潜在差异一致。选择梯度分析在该实验中未检测到对抗性或耐受性的直接选择证据。然而，一个统计模型表明，对抗性的选择模式强烈依赖于耐受性的平均水平，而对耐受性的选择强烈依赖于抗性的平均水平。这些观察结果与以下假设一致：在空间或时间变化的环境或食草动物种群不同的环境中，选择可能会使抗性和耐受性维持在中等水平。
