Van Zandt Peter A
Washington University, Department of Biology, I Brookings, Campus Box 1137, St. Louis, Missouri 63130, USA.
Ecology. 2007 Aug;88(8):1984-93. doi: 10.1890/06-1329.1.
The growth rate (GR) hypothesis relates the evolution of plant defense to resource availability and predicts that plants that have evolved in abiotically stressful environments grow inherently more slowly and are more constitutively resistant to herbivory than plants from more productive habitats. Stress-adapted plants are also predicted to have reduced inducibility, but this prediction has not been previously tested. To evaluate this hypothesis, I compared the growth of nine species of herbaceous plants from Missouri glade habitats to congeners from more productive non-glade habitats. I also conducted bioassays using larvae of the generalist herbivore Spodoptera exigua to estimate constitutive and inducible resistance in these congeners. Glade congeners tended to grow more slowly and have higher constitutive resistance and lower inducibility than non-glade species. However, none of these comparisons was statistically significant due to the conflicting response of one congeneric pair (Salvia azurea and S. lyrata). Analyses without this genus were consistent with the GR hypothesis, as were analyses that categorized congeners by relative growth rate. These results highlight the complexity in searching for factors that determine plant growth rates and resistance traits across multiple genera and support the hypothesis that both constitutive and induced resistance may be influenced by selection on traits that alter plant growth rates. Future studies should attempt to determine whether variation in inducibility is better explained by habitat or relative plant growth rates.
生长速率（GR）假说将植物防御的进化与资源可用性联系起来，并预测在非生物胁迫环境中进化的植物，其固有生长速度比来自生产力更高栖息地的植物更慢，并且对食草动物的组成型抗性更强。预计适应胁迫的植物诱导性也会降低，但这一预测此前尚未得到验证。为了评估这一假说，我比较了来自密苏里州林间空地栖息地的9种草本植物与其来自生产力更高的非林间空地栖息地的同属植物的生长情况。我还使用多食性食草动物甜菜夜蛾的幼虫进行了生物测定，以估计这些同属植物的组成型抗性和诱导抗性。与非林间空地物种相比，林间空地同属植物往往生长得更慢，具有更高的组成型抗性和更低的诱导性。然而，由于一对同属植物（天蓝鼠尾草和琴柱草）的反应相互矛盾，这些比较均无统计学意义。不包括该属的分析结果与GR假说一致，按相对生长速率对同属植物进行分类的分析结果也是如此。这些结果凸显了在多个属中寻找决定植物生长速率和抗性特征的因素的复杂性，并支持了组成型抗性和诱导抗性都可能受到对改变植物生长速率的性状选择影响这一假说。未来的研究应尝试确定诱导性的差异是由栖息地还是相对植物生长速率能更好地解释。
