Antiherbivore defenses alter natural selection on plant reproductive traits

While many studies demonstrate that herbivores alter selection on plant reproductive traits, little is known about whether antiherbivore defenses affect selection on these traits. We hypothesized that antiherbivore defenses could alter selection on reproductive traits by altering trait expression through allocation trade-offs, or by altering interactions with mutualists and/or antagonists. To test our hypothesis, we used white clover, Trifolium repens, which has a Mendelian polymorphism for the production of hydrogen cyanide—a potent antiherbivore defense. We conducted a common garden experiment with 185 clonal families of T. repens that included cyanogenic and acyanogenic genotypes. We quantified resistance to herbivores, and selection on 6 floral traits and phenology via male and female fitness. Cyanogenesis reduced herbivory but did not alter the expression of reproductive traits through allocation trade-offs. However, the presence of cyanogenic defenses altered natural selection on ...

尽管已有诸多研究证实植食动物会对植物繁殖性状施加选择，但目前学界对于抗植食防御机制是否会同样作用于这类性状的选择仍知之甚少。本研究提出假说：抗植食防御机制可通过资源分配权衡改变性状表达，或是通过调控与共生生物和/或拮抗生物的互作关系，进而改变繁殖性状所承受的选择压力。为验证上述假说，我们选取了具有产氰化氢（hydrogen cyanide）——一种强效抗植食防御物质——孟德尔多态性的白三叶（*Trifolium repens*）作为实验材料。我们针对包含产氰型与非产氰型基因型的185个白三叶克隆家系开展了同质园实验。我们量化了植株的植食抗性，并通过雄性和雌性适合度，分析了6个花部性状与物候期所承受的选择压力。产氰作用虽降低了植株的植食受害程度，但并未通过资源分配权衡改变繁殖性状的表达水平。然而，产氰型防御机制的存在却改变了针对……的自然选择。