Bustos-Segura C, Fornoni J, Núñez-Farfán J
Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México, Distrito Federal, México.
J Evol Biol. 2014 Mar;27(3):488-96. doi: 10.1111/jeb.12307. Epub 2014 Jan 13.
Both theoretical and empirical works have highlighted the difference in the evolutionary implications of host resistance and tolerance against their enemies. However, it has been difficult to show evolutionary changes in host defences in natural populations; thus, evaluating theoretical predictions of simultaneous evolution of defences remains a challenge. We studied the evolutionary changes in traits related to resistance and tolerance against herbivory in a natural plant population using seeds from two collections made in a period of 20 years. In a common garden experiment, we compared defensive traits of ancestral (1987) and descendant (2007) subpopulations of the annual plant Datura stramonium that shows genetic variation for tolerance and to which the specialist herbivore Lema daturaphila is locally adapted. We also examined the effects of different plant genotypes on the herbivore for testing the plant genetic variation in resistance. Based on the response to the contemporary herbivore populations, results revealed a nonsignificant response in plant resistance traits (herbivore consumption, foliar trichomes and tropane alkaloids), but a significant one in tolerance. The survival of herbivores in laboratory experiments depended on the plant genotype, which suggests genetic variation in plant resistance. Although we cannot identify the selective agent for the change nor exclude genetic drift, the results are consistent with the expectation that when resistance fails to control herbivory, tolerance should play a more important role in the evolution of the interaction.
理论和实证研究均强调了宿主抗性和耐受性在抵御天敌方面的进化意义差异。然而，在自然种群中很难观察到宿主防御的进化变化；因此，评估防御同时进化的理论预测仍然是一项挑战。我们利用20年间采集的两个种子样本，研究了一个自然植物种群中与抗食草动物相关的抗性和耐受性性状的进化变化。在一个共同花园实验中，我们比较了一年生植物曼陀罗（Datura stramonium）祖先（1987年）和后代（2007年）亚种群的防御性状，该植物在耐受性方面表现出遗传变异，并且专食性食草动物曼陀罗叶甲（Lema daturaphila）对其具有局部适应性。我们还研究了不同植物基因型对食草动物的影响，以测试植物抗性的遗传变异。基于对当代食草动物种群的反应，结果显示植物抗性性状（食草动物取食量、叶毛和托烷生物碱）的反应不显著，但耐受性反应显著。实验室实验中食草动物的存活取决于植物基因型，这表明植物抗性存在遗传变异。虽然我们无法确定变化的选择因子，也不能排除遗传漂变，但结果符合这样的预期：当抗性无法控制食草动物时，耐受性在这种相互作用的进化中应发挥更重要的作用。
