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Macroevolution of defense syndromes in Ficus (Moraceae)
Ecological Monographs ( IF 6.1 ) Pub Date : 2020-09-04 , DOI: 10.1002/ecm.1428
Jin Zhao 1 , Simon T. Segar 2 , Doyle McKey 3 , Jin Chen 1
Affiliation  

Recursive adaptations and counter‐adaptations of plant‐feeding insects are thought to have driven chemical and physical diversity in plant defenses. Among existing theories on defensive diversity, the syndromes hypothesis predicts that plants may evolve suites of covarying defense traits along evolutionary arms races with herbivores. We use the large, phenotypically diverse angiosperm genus Ficus (Moraceae) to test the major predictions of this hypothesis: (1) plant species will form distinctive combinations of defensive traits; (2) these traits will be correlated within each syndrome. Trait combinations need not map well onto phylogenies because plant species can converge onto similar trait values, but strong phylogenetic signal driven by selection (as opposed to drift) suggests roles for escalation and coevolution. Finally, Ficus species with complementary combinations of defenses will be less susceptible to insect damage and harbor distinct insect communities. We quantified susceptibility to insect herbivory and nine leaf traits related to resource acquisition and defense in 36 Ficus species growing in a common‐garden setting in dry and wet seasons over 2 yr. We recovered a set of three syndromes defined by relatively small sets of trait combinations. Broadly speaking, these syndromes grouped fig species with different life forms. For example, epiphytic figs had nutrient‐poor, tough, tannin‐rich leaves, while free‐standing trees tended to have leaves covered in trichomes and full of alkaloid‐rich latex. When season and species identity were accounted for, the combination of two traits, higher C:N and higher latex tannin content, provided significantly stronger defense than did either trait taken singly. Several individual traits (C:N, latex tannin, and trichome density) were significantly negatively correlated with herbivore damage, while alkaloid content was positively correlated (perhaps as a result of feeding by adapted herbivores). Several defensive traits influenced insect herbivore community structure. Finally, traits followed different evolutionary trajectories. While latex tannin, C:N, and leaf tannin fit a Brownian‐motion model of evolution, the first two escalating across Ficus phylogeny, others appeared to have more limited phylogenetic signal or tended to de‐escalate. Overall, the patterns we detected support the concept of coordinated defense syndromes, demonstrating that evolutionary arms races can drive combinations of traits in this genus.

中文翻译:

榕(桑科)防御综合征的宏观进化

人们认为,以植物为食的昆虫的递归适应和反适应驱动了植物防御中的化学和物理多样性。在有关防御多样性的现有理论中,综合症假说预测植物可能会沿着具有食草动物的进化军备竞赛进化出一系列不同的防御性状。我们使用表型广泛的大被子植物植物(桑科)检验这一假设的主要预测:(1)植物物种将形成防御性状的独特组合;(2)这些特征将在每个综合症内相关。性状组合不需要很好地映射到系统发育上,因为植物物种可以收敛到相似的性状值,但是由选择驱动的强系统发生信号(与漂移相反)表明其在逐步升级和共同进化中发挥了作用。最后,具有互补防御组合的榕树物种将更不易受到昆虫的伤害,并拥有独特的昆虫群落。我们量化了对36种无花果对昆虫食草性和与资源获取和防御有关的9种叶片性状的敏感性在2年以上的干燥和潮湿季节以普通花园环境生长的树种。我们恢复了一组由相对较少的特征组合定义的三个综合症。从广义上讲,这些综合症将无花果物种分为不同的生命形式。例如,附生无花果的叶子营养欠缺,坚韧,单宁丰富,而独立式树种的叶子往往被三毛覆盖,并充满了富含生物碱的乳胶。当考虑季节和物种特性时,较高的C:N和较高的乳胶单宁含量这两个性状的结合提供了比单独采用的任一性状更强的防御力。几种个体性状(C:N,乳胶单宁和毛状体密度)与草食动物的伤害显着负相关,而生物碱含量呈正相关(可能是由于适应性草食动物进食的结果)。几种防御性状影响了昆虫食草动物的群落结构。最后,特征遵循不同的进化轨迹。乳胶单宁,C:N和叶单宁适合布朗运动的进化模型,但前两个逐步升级榕属系统发生,其他的则似乎具有较有限的系统发生信号或趋于下降。总体而言,我们检测到的模式支持协同防御综合症的概念,表明进化军备竞赛可以推动该属的性状组合。
更新日期:2020-09-04
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