In plants, biomass and nutrient allocation often generate trade-offs between the different biochemical pathways conflicting the utilization of the common source among growth, reproduction and chemical defence. However, in dioecious plant species, these trade-off patterns could appear as a more contrasted problem between males and females due to the dissimilar reproduction investment. Generally, the growth ratio is higher in males than females, while females have a stronger defence than males. To understand the possible role of the sex-specific dissimilarities within the growth-defence conflict framework, we investigated the possible causes of the high variance of the essential oil yield in a dioecious evergreen species, Juniperus communis. Specifically, we tested the correlations between the essential oil yield with other individual-specific traits (e.g. sex, age), the presence of the growth-defence trade-off, and the differential growth and survival patterns between males and females through an extensive field survey with sample collection in three natural populations (Kiskunság National Park, Hungary). The individual-specific essential oil yield was also measured and served as a proxy to describe the degree of chemical defence. We found that the essential oil yield showed strong and consistent sex-specific patterns decreasing with age in adults. Contrary to the predictions, the males showed a consistently higher yield than the females. We also observed a growth-defence trade-off in males but not in females. Consistently with the growth-defence conflict hypothesis, the populations’ sex ratio was male-biased, and this pattern was more evident with ageing modifying the demographic structure due to the sexually dissimilar lifespan. Our juniper study revealed a contrasting and unique essential oil accumulation driven by the complex allocation trade-off mechanisms within individuals, which could be a flexible and adaptive defence response against the increasing biotic and abiotic environmental stresses exacerbated under global climate change.

中文翻译：

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杜松的性别差异：精油产量、生长-防御冲突和人口性别比

在植物中，生物量和养分分配通常会在不同的生化途径之间产生权衡，这会在生长、繁殖和化学防御之间对共同来源的利用产生冲突。然而，在雌雄异株植物中，由于繁殖投资的不同，这些权衡模式可能表现为雄性和雌性之间更具对比性的问题。一般来说，雄性的生长率高于雌性，而雌性的防御力比雄性强。为了了解性别特异性差异在生长-防御冲突框架中的可能作用，我们调查了雌雄异株常绿物种杜松（Juniperus Communis）中精油产量高差异的可能原因。具体来说，我们通过广泛的实地调查测试了精油产量与其他个体特定性状（例如性别、年龄）、生长防御权衡的存在以及雄性和雌性之间不同的生长和生存模式之间的相关性。三个自然种群（匈牙利基斯昆萨格国家公园）的样本采集。还测量了个体特定的精油产量，并作为描述化学防御程度的代表。我们发现，随着成年人年龄的增长，精油产量表现出强烈且一致的性别特异性模式。与预测相反，雄性的产量始终高于雌性。我们还观察到男性的生长防御权衡，但女性没有。与增长-防御冲突假说一致，人口的性别比例偏向于男性，这种模式在老龄化改变人口结构时更为明显，因为性别不同的寿命。我们的杜松研究揭示了由个体内部复杂的分配权衡机制驱动的对比而独特的精油积累，这可能是针对全球气候变化下日益加剧的生物和非生物环境压力的灵活和适应性防御反应。