Data from: Regional variation in drivers of connectivity for two frog species (Rana pretiosa and R. luteiventris) from the U.S. Pacific Northwest

Comparative landscape genetics has uncovered high levels of variation in which landscape factors affect connectivity among species and regions. However, the relative importance of species traits vs. environmental variation for predicting landscape patterns of connectivity is unresolved. We provide evidence from a landscape genetics study of two sister taxa of frogs, the Oregon spotted frog (Rana pretiosa) and the Columbia spotted frog (R. luteiventris) in Oregon and Idaho, USA. Rana pretiosa is relatively more dependent on moisture for dispersal than R. luteiventris for dispersal, so if species traits influence connectivity, we predicted that connectivity among R. pretiosa populations would be more positively associated with moisture than R. luteiventris. However, if environmental differences are important drivers of gene flow, we predicted that connectivity would be more positively related to moisture in arid regions. We tested these predictions using eight microsatellite loci and gravity models in two R. pretiosa regions and four R. luteiventris regions (n = 1,168 frogs). In R. pretiosa, but not R. luteiventris, connectivity was positively related to mean annual precipitation, supporting our first prediction. In contrast, connectivity was not more positively related to moisture in more arid regions. Various temperature metrics were important predictors for both species and in all regions, but the directionality of their effects varied. Our results indicate that connectivity in R. pretiosa may be negatively impacted by reduction in mean annual precipitation. Overall, the pattern of variation in drivers of connectivity was consistent with predictions based on species traits rather than on environmental variation.

比较景观遗传学研究表明，在调控物种与区域间种群连通性的景观因子方面，存在广泛的变异。然而，在预测连通性景观格局时，物种性状与环境变异的相对重要性仍未明确。本研究基于美国俄勒冈州与爱达荷州的两种蛙类姊妹类群——俄勒冈斑蛙（Rana pretiosa）和哥伦比亚斑蛙（R. luteiventris）的景观遗传学研究，提供了相关证据。相较于哥伦比亚斑蛙，俄勒冈斑蛙的扩散活动对水分的依赖程度更高。因此若物种性状对连通性存在影响，我们预测俄勒冈斑蛙种群间的连通性与水分的正相关程度将高于哥伦比亚斑蛙。但若环境差异是基因流（gene flow）的主要驱动因子，则我们预测在干旱区域，种群连通性与水分的正相关程度会更高。本研究利用8个微卫星位点（microsatellite loci）和重力模型（gravity models），对俄勒冈斑蛙的2个区域与哥伦比亚斑蛙的4个区域（共1168只蛙类样本）的上述预测进行了验证。在俄勒冈斑蛙种群中，连通性与年平均降水量呈显著正相关，而哥伦比亚斑蛙种群则无此关联，这一结果支持了我们的第一项预测。与之相反，在更为干旱的区域中，连通性与水分的正相关程度并未显著提升。各类温度指标对两种蛙类的所有研究区域均为重要的预测因子，但其作用方向存在差异。本研究结果显示，俄勒冈斑蛙的种群连通性可能会因年平均降水量的减少而受到负面影响。总体而言，连通性驱动因子的变异模式与基于物种性状的预测相符，而非基于环境变异的预测。