Homola Jared J, Loftin Cynthia S, Kinnison Michael T
School of Biology and Ecology University of Maine Orono ME USA.
Maine Cooperative Fish and Wildlife Research Unit U.S. Geological Survey Orono ME USA.
Ecol Evol. 2019 Oct 1;9(20):11799-11823. doi: 10.1002/ece3.5685. eCollection 2019 Oct.
Metapopulation-structured species can be negatively affected when landscape fragmentation impairs connectivity. We investigated the effects of urbanization on genetic diversity and gene flow for two sympatric amphibian species, spotted salamanders () and wood frogs (), across a large (>35,000 km) landscape in Maine, USA, containing numerous natural and anthropogenic gradients. Isolation-by-distance (IBD) patterns differed between the species. Spotted salamanders showed a linear and relatively high variance relationship between genetic and geographic distances ( = .057, < .001), whereas wood frogs exhibited a strongly nonlinear and lower variance relationship ( = 0.429, < .001). Scale dependence analysis of IBD found gene flow has its most predictable influence (strongest IBD correlations) at distances up to 9 km for spotted salamanders and up to 6 km for wood frogs. Estimated effective migration surfaces revealed contrasting patterns of high and low genetic diversity and gene flow between the two species. Population isolation, quantified as the mean IBD residuals for each population, was associated with local urbanization and less genetic diversity in both species. The influence of geographic proximity and urbanization on population connectivity was further supported by distance-based redundancy analysis and multiple matrix regression with randomization. Resistance surface modeling found interpopulation connectivity to be influenced by developed land cover, light roads, interstates, and topography for both species, plus secondary roads and rivers for wood frogs. Our results highlight the influence of anthropogenic landscape features within the context of natural features and broad spatial genetic patterns, in turn supporting the premise that while urbanization significantly restricts interpopulation connectivity for wood frogs and spotted salamanders, specific landscape elements have unique effects on these two sympatric species.
当景观破碎化削弱连通性时，集合种群结构的物种可能会受到负面影响。我们在美国缅因州一片面积超过35,000平方千米的区域内，对两种同域两栖物种——黄斑蝾螈（ ）和林蛙（ ），研究了城市化对其遗传多样性和基因流的影响，该区域包含众多自然和人为梯度。两种物种的距离隔离（IBD）模式有所不同。黄斑蝾螈在遗传距离和地理距离之间呈现出线性且相对较高方差的关系（ = 0.057， < 0.001），而林蛙则呈现出强烈的非线性且较低方差的关系（ = 0.429， < 0.001）。对IBD的尺度依赖性分析发现，对于黄斑蝾螈，基因流在距离达9千米时具有最可预测的影响（最强的IBD相关性），对于林蛙则在距离达6千米时具有最可预测的影响。估计的有效迁移表面揭示了两种物种之间遗传多样性和基因流高低对比的模式。种群隔离，以每个种群的平均IBD残差来量化，与当地城市化以及两种物种较低的遗传多样性相关。基于距离的冗余分析和随机化多重矩阵回归进一步支持了地理接近度和城市化对种群连通性的影响。抗性表面建模发现，两种物种的种群间连通性都受到已开发土地覆盖、轻型道路、州际公路和地形的影响，对于林蛙还受到二级道路和河流的影响。我们的结果突出了人为景观特征在自然特征和广泛空间遗传模式背景下的影响，进而支持了这样一个前提，即虽然城市化显著限制了林蛙和黄斑蝾螈的种群间连通性，但特定的景观要素对这两种同域物种具有独特影响。
