Department of Evolution and Ecology, University of California, Davis, California, USA.
Bodega Marine Laboratory, University of California Davis, Bodega Bay, California, USA.
Glob Chang Biol. 2022 Apr;28(8):2596-2610. doi: 10.1111/gcb.16080. Epub 2022 Jan 19.
Environmental change is multidimensional, with local anthropogenic stressors and global climate change interacting to differentially impact populations throughout a species' geographic range. Within species, the spatial distribution of phenotypic variation and its causes (i.e., local adaptation or plasticity) will determine species' adaptive capacity to respond to a changing environment. However, comparatively less is known about the spatial scale of adaptive differentiation among populations and how patterns of local adaptation might drive vulnerability to global change stressors. To test whether fine-scale (2-12 km) mosaics of environmental stress can cause adaptive differentiation in a marine foundation species, eelgrass (Zostera marina), we conducted a three-way reciprocal transplant experiment spanning the length of Tomales Bay, CA. Our results revealed strong home-site advantage in growth and survival for all three populations. In subsequent common garden experiments and feeding assays, we showed that countergradients in temperature, light availability, and grazing pressure from an introduced herbivore contribute to differential performance among populations consistent with local adaptation. Our findings highlight how local-scale mosaics in environmental stressors can increase phenotypic variation among neighboring populations, potentially increasing species resilience to future global change. More specifically, we identified a range-center eelgrass population that is pre-adapted to extremely warm temperatures similar to those experienced by low-latitude range-edge populations of eelgrass, demonstrating how reservoirs of heat-tolerant phenotypes may already exist throughout a species range. Future work on predicting species resilience to global change should incorporate potential buffering effects of local-scale population differentiation and promote a phenotypic management approach to species conservation.
环境变化具有多维性，局部人为压力源和全球气候变化相互作用，对物种地理分布范围内的种群产生不同的影响。在物种内部，表型变异及其成因（即局部适应或可塑性）的空间分布将决定物种对环境变化的适应能力。然而，人们对种群间适应性分化的空间尺度以及局部适应模式如何导致对全球变化压力源的脆弱性知之甚少。为了检验在海洋基础物种鳗草（Zostera marina）中，小尺度（2-12 公里）的环境压力马赛克是否会导致适应性分化，我们进行了一项跨越加利福尼亚州托马莱斯湾长度的三向互移植实验。我们的结果表明，所有三个种群在生长和存活方面都具有强烈的本土优势。在随后的共同花园实验和摄食实验中，我们表明，温度、光照可用性和引入食草动物的放牧压力的反梯度导致了种群之间的差异表现，这与局部适应一致。我们的研究结果强调了环境压力局部马赛克如何增加邻近种群的表型变异，从而提高物种对未来全球变化的恢复力。更具体地说，我们确定了一个位于中心的鳗草种群，它对类似于鳗草低纬度边缘种群所经历的极热温度具有预先适应能力，这表明耐热表型的储库可能已经存在于物种的整个分布范围内。未来预测物种对全球变化的恢复力的工作应该纳入局部种群分化的潜在缓冲效应，并促进以表型为基础的物种保护管理方法。
