PREMISE Defense investment in plant reproductive structures is relatively understudied compared to the defense of vegetative organs. Here the evolution of chemical defenses in reproductive structures is examined in light of the optimal defense, apparency, and resource availability hypotheses within the genus Cornus using a phylogenetic comparative approach in relation to phenology and native habitat environmental data. METHODS Individuals representing 25 Cornus species were tracked for reproductive phenology over a full growing season at the Arnold Arboretum of Harvard University. Floral, fruit, and leaf tissue was sampled to quantify defensive chemistry as well as fruit nutritional traits relevant to bird dispersal. Native habitat environmental characteristics were estimated using locality data from digitized herbarium records coupled with global soil and climate data sets. RESULTS The evolution of later flowering was correlated with increased floral tannins, and the evolution of later fruiting was correlated with increased total phenolics. Leaves were found to contain the highest tannin activity, while inflorescences contained the highest total flavonoids. Multiple aspects of fruit defensive chemistry were correlated with fruit nutritional traits. Floral and fruit defensive chemistry were evolutionarily correlated with aspects of native habitat temperature, precipitation, and soil characteristics. CONCLUSIONS Results provide tentative support for the apparency hypothesis with respect to both flower and fruit phenology, while relative concentrations of secondary metabolites across organs provide mixed support for the optimal defense hypothesis. The evolution of reproductive defense with native habitat provides, at best, mixed support for the resource availability hypothesis.

中文翻译：

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山茱萸属花卉和果实组织化学防御的进化权衡

前提 与植物器官的防御相比，对植物生殖结构的防御投资的研究相对较少。在这里，使用与物候学和原生栖息地环境数据相关的系统发育比较方法，根据山茱萸属内的最佳防御、外观和资源可用性假设，检查了生殖结构中化学防御的演变。方法 在哈佛大学阿诺德植物园，对代表 25 种山茱萸物种的个体进行了整个生长季节的生殖物候追踪。对花、果实和叶组织进行采样，以量化防御化学以及与鸟类传播相关的果实营养特征。使用来自数字化植物标本馆记录的地方数据以及全球土壤和气候数据集来估计本地栖息地环境特征。结果晚花的进化与花单宁含量的增加有关，而晚果的进化与总酚类物质的增加有关。发现叶子含有最高的单宁活性，而花序含有最高的总黄酮类化合物。水果防御化学的多个方面与水果营养特性相关。花卉和果实防御化学与原生栖息地温度、降水和土壤特征等方面在进化上相关。结论 结果为关于花和果实物候的表观假说提供了初步支持，而跨器官的次级代谢物的相对浓度为最佳防御假设提供了混合支持。原生栖息地的生殖防御进化至多为资源可用性假说提供了混合支持。