Trade-offs between photosynthesis and the costs of resource capture inform economic strategies of plants across environmental gradients and result in predictable variation in leaf traits. However, understudied functional groups like hemiparasites that involve dramatically different strategies for resource capture may have traits that deviate from expectations. We measured leaf traits related to gas exchange in mistletoes and their eucalypt hosts along a climatic gradient in relative moisture supply, measured as the ratio of precipitation to pan evaporation (P/E_p), in Victoria, Australia. We compared traits for mistletoes vs. hosts as functions of relative moisture supply and examined trait–trait correlations in both groups. Eucalypt leaf traits responded strongly to decreasing P/E_p, consistent with economic theory. Leaf area and specific leaf area (SLA) decreased along the P/E_p gradient, while C:N ratio, leaf thickness, N per area, and δ¹³C all increased. Mistletoes responded overall less strongly to P/E_p based on multivariate analyses; individual traits sometimes shifted in parallel with those of hosts, but SLA, leaf thickness, and N per area showed no significant change across the gradient. For mistletoes, leaf thickness was inversely related to leaf dry matter content (LDMC), with no relationship between SLA and mass-based N. In mistletoes, reduced costs of transpiration (reflecting their lack of roots) and abundant succulent leaf tissue help account for observed differences from their eucalypt hosts. Trait-based analysis of atypical functional types such as mistletoes help refine hypotheses based on plant economics and specialized adaptations to resource limitation.

光合作用与资源获取成本之间的权衡决定了环境梯度下植物的经济策略，并导致了叶片性状的可预测变化。但是，像半寄生虫这样的被研究不足的功能性群体涉及截然不同的资源捕获策略，其特性可能与预期背道而驰。我们沿着相对水分供应的气候梯度测量了槲寄生及其桉树寄主中与气体交换有关的叶片性状，以降水量与蒸发皿蒸发量之比（P / E _p），在澳大利亚维多利亚州。我们比较了槲寄生和寄主的性状作为相对水分供应的函数，并检验了两组的性状-性状相关性。符合经济理论，桉树叶片性状对P / E _p的降低反应强烈。叶面积和比叶面积（SLA）沿减小P / ë _p梯度，而C：N比，叶片厚度，单位面积N，和δ ¹³ C中的所有增加。杂音对P / E _p的整体反应较弱基于多元分析；个体性状有时会与寄主的性状平行移动，但SLA，叶片厚度和每面积N的变化在整个梯度上均无明显变化。对于槲寄生，叶片厚度与叶片干物质含量（LDMC）成反比，而SLA和基于质量的氮之间没有关系。在槲寄生中，蒸腾成本的降低（反映出它们缺乏根）和丰富的肉质叶片组织有助于解决问题。观察到与桉树寄主的差异。对非典型功能类型（例如槲寄生）的基于特征的分析有助于基于工厂经济学和对资源限制的专门调整来完善假设。