Data from: Contemporary evolution of plant growth rate following experimental removal of herbivores

Herbivores are credited with driving the evolutionary diversification of plant defensive strategies over macroevolutionary time. For this to be true, herbivores must also cause short-term evolution within plant populations, but few studies have experimentally tested this prediction. We addressed this gap using a long-term manipulative field experiment where exclosures protected 22 plant populations from natural rabbit herbivory for <1 to 26 years. We collected seeds of Rumex acetosa L. (Polygonaceae) from our plots and grew them in a common greenhouse environment to quantify evolved differences among populations in individual plant growth rate, tolerance to herbivory, competitive ability, and the concentration of secondary metabolites (tannins and oxalate) implicated in defense against herbivores. In 26 years without rabbit herbivory, plant growth rate decreased linearly by 30%. We argue that plant growth rate has evolved as a defense against intense rabbit herbivory. In contrast, we found no change in tolerance to herbivory or concentrations of secondary metabolites. We also found no change in competitive ability, suggesting that contemporary evolution may not feed back to alter ecological interactions within this plant community. Our results combined with those of other studies show that the evolution of gross morphological traits such as growth rate in response to herbivory may be common, which calls into question assumptions about some of the most popular theories of plant defense.

植食动物被认为在宏进化时间尺度上推动了植物防御策略的演化多样化。若该结论成立，那么植食动物必然会在植物种群内引发短期演化，但目前鲜有研究通过实验验证这一预测。我们通过一项长期野外操控实验填补了这一研究空白：该实验利用植食排除围栏使22个植物种群免受自然兔类的植食作用，围栏设置时长从不足1年至26年不等。我们从各实验样地采集了酸模（Rumex acetosa L.，蓼科Polygonaceae）的种子，在统一温室环境下开展栽培实验，以量化不同种群在个体生长速率、耐植食性、竞争能力以及与植食动物防御相关的次生代谢物（单宁与草酸）浓度等性状上的演化差异。在持续26年无兔类植食的样地中，植物生长速率线性下降了30%。我们认为，植物生长速率已演化成为应对高强度兔类植食的防御策略。与之相反，我们未观测到耐植食性或次生代谢物浓度发生显著变化。我们同样未发现竞争能力存在改变，这表明当代演化可能不会通过反馈作用改变该植物群落内的生态互作关系。结合其他研究的结果，我们的研究表明，针对植食作用演化出生长速率这类整体形态性状的现象或较为普遍，这对部分主流植物防御理论的前提假设提出了质疑。