Abstract Inter-plant variability (i.e., differences between individuals within population) may be a significant and rather neglected source of variation for addressing the occurrence of secondary sexual dimorphism in plants, especially in long-lived species. However, secondary sexual dimorphism (SSD) in plants is generally analyzed through the comparison of position metrics alone, mainly by the mean values of the male and female samples. Here we analyzed SSD in the dioecious tree Lithraea molleoides by a traditional comparison of position metrics and by taking into account inter-plant variability through a bootstrapping procedure i.e., by selecting randomly and one at a time, a female and a male from the sample and comparing them. This procedure was repeated several times and then the mean of those differences and the confidence intervals were calculated. Our results showed that inter-plant variability contribute to SSD, particularly in nutrient allocation to leaves and flowers. Some floral traits, on the other hand, were higher in males irrespective of inter-plant variability (i.e., flower number and flower mass). Accordingly, males produce more than twice as many flowers as females and their flowers had 22% more biomass than female’s flowers. On the other side, females had 20% more floral N concentration per unit dry mass (floral Nmass) and had more leaf N concentration per unit dry mass (leaf Nmass) than males when inter-plant variability was considered. This differences in nutrient concentration could lead to a higher herbivory in females than in males given a higher leaf nutritional quality. Thus, the quantification of inter-plant variability seems crucial for detecting inter-sexual differences, which may have important ecological and evolutionary implications.

中文翻译：

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雌雄异株树中的次生性二态性：植物间变异性问题？

摘要 植物间变异（即种群内个体之间的差异）可能是解决植物，尤其是长寿物种中发生次生性二态性的重要且相当被忽视的变异来源。然而，植物中的第二性二态性（SSD）通常仅通过位置指标的比较来分析，主要通过雄性和雌性样本的平均值进行分析。在这里，我们通过传统的位置指标比较和通过自举程序考虑植物间变异性来分析雌雄异株树 Lithraea molleoides 中的 SSD，即通过一次随机选择一个，从样本中选择一个雌性和一个雄性，比较它们。这个过程重复几次，然后计算这些差异的平均值和置信区间。我们的结果表明，植物间变异性有助于 SSD，特别是在叶和花的营养分配方面。另一方面，一些花性状在雄性中较高，而与植物间变异性（即花数和花质量）无关。因此，雄性开出的花是雌性的两倍多，而且它们的花比雌性花的生物量多 22%。另一方面，当考虑植物间变异性时，雌性每单位干质量（花 Nmass）的花氮浓度（花 Nmass）和每单位干质量（叶 Nmass）的叶片 N 浓度比雄性高 20%。考虑到更高的叶子营养质量，这种营养浓度的差异可能导致雌性比雄性更高的食草性。因此，植物间变异性的量化对于检测可能具有重要生态和进化意义的两性间差异至关重要。