Abstract：
A major predicted constraint on the evolution of anti-herbivore defense in plants is the nonindependent expression of traits mediating resistance. Since herbivore attack can be highly variable across plant tissues, we hypothesized that correlations in toxin expression within and between plant tissues may limit population differentiation and, thus, plant adaptation. Using full-sib families from two nearby (<1 km) common milkweed (Asclepias syriaca) populations, we investigated genetic correlations among 28 distinct cardenolide toxins within and between roots, leaves, and seeds and examined signatures of tissue-specific divergent selection between populations by QST-FST comparisons. The prevalence, direction, and strength of genetic correlations among cardenolides were tissue specific, and concentrations of individual cardenolides were moderately correlated between tissues; nonetheless, the direction and strength of correlations were population specific. Population divergence in the cardenolide chemistry was stronger in roots than in leaves and seeds. Divergent selection on individual cardenolides was tissue and toxin specific, except for a single highly toxic cardenolide (labriformin), that showed divergent selection across all plant tissues. Heterogeneous evolution of cardenolides within and between tissues across populations appears possible due to their highly independent expression. This independence may be common in nature, especially in specialized interactions in which distinct herbivores feed on different plant tissues.
摘要：
植物抗草食动物防御进化的主要预测约束是介导抗性的性状的非独立表达。由于草食动物的攻击在植物组织中可以高度可变，我们假设植物组织内和之间的毒素表达的相关性可能会限制种群分化，因此，植物适应。使用附近两个（<1km）普通乳草（Asclepiassyriaca）种群的同胞家庭，我们调查了根内和根间28种不同的烯醇内酯毒素之间的遗传相关性，叶子和种子，并通过QST-FST比较检查了人群之间组织特异性差异选择的特征。患病率,烯醇二酸酯之间遗传相关性的方向和强度是组织特异性的，和个体的浓度在组织之间中等相关；尽管如此，相关性的方向和强度是特定于人群的。根中烯醇内酯化学的种群差异强于叶和种子。对单个烯醇内酯的不同选择是组织和毒素特异性的，除了单一的高毒性卡地内酯（拉的话），在所有植物组织中显示出不同的选择。由于其高度独立的表达，在群体中组织内和组织之间的烯醇二酸酯的异质进化似乎是可能的。这种独立性在本质上可能是常见的，特别是在特殊的相互作用中，不同的草食动物以不同的植物组织为食。
