Bothwell Helen M, Cushman Samuel A, Woolbright Scott A, Hersch-Green Erika I, Evans Luke M, Whitham Thomas G, Allan Gerard J
Environmental Genetics & Genomics Facility, Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, USA.
Rocky Mountain Research Station, United States Forest Service, Flagstaff, AZ, USA.
Mol Ecol. 2017 Oct;26(19):5114-5132. doi: 10.1111/mec.14281. Epub 2017 Sep 5.
Gene flow is an evolutionary process that supports genetic connectivity and contributes to the capacity of species to adapt to environmental change. Yet, for most species, little is known about the specific environmental factors that influence genetic connectivity, or their effects on genetic diversity and differentiation. We used a landscape genetic approach to understand how geography and climate influence genetic connectivity in a foundation riparian tree (Populus angustifolia), and their relationships with specieswide patterns of genetic diversity and differentiation. Using multivariate restricted optimization in a reciprocal causal modelling framework, we quantified the relative contributions of riparian network connectivity, terrestrial upland resistance and climate gradients on genetic connectivity. We found that (i) all riparian corridors, regardless of river order, equally facilitated connectivity, while terrestrial uplands provided 2.5× more resistance to gene flow than riparian corridors. (ii) Cumulative differences in precipitation seasonality and precipitation of the warmest quarter were the primary climatic factors driving genetic differentiation; furthermore, maximum climate resistance was 45× greater than riparian resistance. (iii) Genetic diversity was positively correlated with connectivity (R = 0.3744, p = .0019), illustrating the utility of resistance models for identifying landscape conditions that can support a species' ability to adapt to environmental change. From these results, we present a map highlighting key genetic connectivity corridors across P. angustifolia's range that if disrupted could have long-term ecological and evolutionary consequences. Our findings provide recommendations for conservation and restoration management of threatened riparian ecosystems throughout the western USA and the high biodiversity they support.
基因流是一个支持遗传连通性并有助于物种适应环境变化能力的进化过程。然而，对于大多数物种来说，关于影响遗传连通性的具体环境因素，或者它们对遗传多样性和分化的影响，我们知之甚少。我们采用景观遗传学方法来了解地理和气候如何影响一种基础河岸树种（窄叶杨）的遗传连通性，以及它们与全物种遗传多样性和分化模式的关系。在一个相互因果建模框架中使用多变量受限优化，我们量化了河岸网络连通性、陆地高地阻力和气候梯度对遗传连通性的相对贡献。我们发现：（i）所有河岸走廊，无论河流等级如何，都同样促进了连通性，而陆地高地对基因流的阻力是河岸走廊的2.5倍。（ii）降水季节性和最暖季度降水量的累积差异是驱动遗传分化的主要气候因素；此外，最大气候阻力比河岸阻力大45倍。（iii）遗传多样性与连通性呈正相关（R = 0.3744，p = 0.0019），这说明了抗性模型在识别能够支持物种适应环境变化能力的景观条件方面的效用。基于这些结果，我们绘制了一幅地图，突出显示了窄叶杨分布范围内的关键遗传连通走廊，如果这些走廊遭到破坏，可能会产生长期的生态和进化后果。我们的研究结果为美国西部受威胁的河岸生态系统及其所支持的高生物多样性的保护和恢复管理提供了建议。
