The Forest School, Yale School of the Environment, Yale University, New Haven, CT 06511.
Smithsonian Tropical Research Institute Apartado Postal 0843-03092, Panama City, Panamá.
Proc Natl Acad Sci U S A. 2024 Jun 4;121(23):e2316971121. doi: 10.1073/pnas.2316971121. Epub 2024 May 29.
Assessing within-species variation in response to drought is crucial for predicting species' responses to climate change and informing restoration and conservation efforts, yet experimental data are lacking for the vast majority of tropical tree species. We assessed intraspecific variation in response to water availability across a strong rainfall gradient for 16 tropical tree species using reciprocal transplant and common garden field experiments, along with measurements of gene flow and key functional traits linked to drought resistance. Although drought resistance varies widely among species in these forests, we found little evidence for within-species variation in drought resistance. For the majority of functional traits measured, we detected no significant intraspecific variation. The few traits that did vary significantly between drier and wetter origins of the same species all showed relationships opposite to expectations based on drought stress. Furthermore, seedlings of the same species originating from drier and wetter sites performed equally well under drought conditions in the common garden experiment and at the driest transplant site. However, contrary to expectation, wetter-origin seedlings survived better than drier-origin seedlings under wetter conditions in both the reciprocal transplant and common garden experiment, potentially due to lower insect herbivory. Our study provides the most comprehensive picture to date of intraspecific variation in tropical tree species' responses to water availability. Our findings suggest that while drought plays an important role in shaping species composition across moist tropical forests, its influence on within-species variation is limited.
评估物种对干旱的响应内变异性对于预测物种对气候变化的响应以及为恢复和保护工作提供信息至关重要，但绝大多数热带树种的实验数据都缺乏。我们使用相互移植和常见的花园田间实验，以及对与抗旱性相关的基因流动和关键功能性状的测量，评估了 16 种热带树种在强降雨梯度下对水分可用性的种内变异性。尽管这些森林中的物种对干旱的抵抗力差异很大，但我们几乎没有证据表明干旱的种内变异性抵抗力。对于大多数测量的功能性状，我们没有发现显著的种内变异。在同种的较干燥和较湿润起源之间确实存在显著差异的少数几个性状，其表现出的与基于干旱胁迫的预期相反的关系。此外，来自较干燥和较湿润地点的同种幼苗在共同花园实验和最干燥的移植地点在干旱条件下表现同样良好。然而，与预期相反，在相互移植和常见花园实验中，在较湿润的条件下，较湿润起源的幼苗比较干燥起源的幼苗存活得更好，这可能是由于昆虫取食减少所致。我们的研究提供了迄今为止最全面的热带树种对水分可用性响应的种内变异性图片。我们的研究结果表明，尽管干旱在塑造湿润热带森林的物种组成方面起着重要作用，但它对种内变异性的影响是有限的。
