Data from: Herbivore-mediated interaction promotes the maintenance of trichome dimorphism through negative frequency-dependent selection

Natural plant populations exhibit genetic variation in defense traits against herbivores. Despite a growing body of evidence for herbivore-mediated selection on plant defenses, we still know little about how genetic variation persists in anti-herbivore defense traits. Here, we present field and experimental evidence for herbivore-mediated frequency-dependent selection that promotes the maintenance of trichome-producing (hairy) and trichomeless (glabrous) plants of Arabidopsis halleri subsp. gemmifera. First, in a natural population where the specialist leaf beetle Phaedon brassicae was prevalent, hairy plants were damaged less when frequency of neighboring glabrous plants increased. Furthermore, temporal variation in the frequency of the two plant morphs showed that rarer morphs increased in frequency at the scale of 1-m diameter patches between survey years. Using a mesocosm experiment, we demonstrated a rare-morph advantage for defense (leaf damage and herbivore abundance) and reproduction (flower and clone production) between hairy and glabrous plants in the presence of P. brassicae. However, this rare-morph advantage was not detected when beetles were absent, with glabrous plants having higher reproduction than hairy plants under these conditions, regardless of frequency conditions. These findings highlight the overlooked but potentially critical role of herbivore-mediated apparent interaction in maintaining plant defense polymorphism.自然植物种群在对抗植食性动物的防御性状上存在遗传变异。尽管关于植食动物介导的植物防御选择的研究证据日益增多，但我们对植食性防御性状的遗传变异如何得以维持仍知之甚少。本研究以球芽高山拟南芥（Arabidopsis halleri subsp. gemmifera）的产毛状体（多毛）与无毛状体（光滑）两种植株为研究对象，提供了植食动物介导的频率依赖选择可维持其防御性状多态性的野外与实验证据。首先，在专食性叶甲芸苔萤叶甲（Phaedon brassicae）大量发生的自然种群中，当邻近光滑植株的频率升高时，多毛植株的叶片受损害程度显著更低。此外，对两种植株形态的频率进行的时间动态监测结果显示，在两次调查的间隔年份中，以直径1米的斑块为尺度，稀有形态的频率会出现显著上升。通过中宇宙（mesocosm）实验，本研究证实：在芸苔萤叶甲存在的条件下，多毛与光滑植株在防御性状（叶片受损程度与植食动物种群丰度）和繁殖能力（开花与克隆繁殖）方面均存在稀有形态优势。但当无叶甲存在时，未观测到该稀有形态优势；此时无论频率条件如何，光滑植株的繁殖能力均高于多毛植株。上述研究结果凸显了此前被忽视、但可能在维持植物防御性状多态性中发挥关键作用的、由植食动物介导的表观相互作用。