Environmental selection is a main driver of divergence in house sparrows (Passer domesticus) in Romania and Bulgaria

Both neutral and adaptive evolutionary processes can cause population divergence, but their relative contributions remain unclear. We investigated the roles of these processes in population divergence in house sparrows (Passer domesticus) from Romania and Bulgaria, regions characterized by high landscape heterogeneity compared to Western Europe. We asked whether morphological divergence, complemented with genetic data in this human commensal species, was best explained by environmental variation, geographic distance, or landscape resistance—the effort it takes for an individual to disperse from one location to the other—caused by either natural or anthropogenic barriers. Using generalized dissimilarity modeling, a matrix regression technique that fits biotic beta diversity to both environmental predictors and geographic distance, we found that a small set of climate and vegetation variables explained up to ~30% of the observed divergence, whereas geographic and resistance distances played much lesser roles. Our results are consistent with signals of selection on morphological traits and of isolation by adaptation in genetic markers, suggesting that selection by natural environmental conditions shapes population divergence in house sparrows. Our study thus contributes to a growing body of evidence that adaptive evolution may be a major driver of diversification.

中性演化与适应性演化过程均可引发种群分化，但二者的相对贡献迄今尚未明确。我们以罗马尼亚与保加利亚的家麻雀（Passer domesticus）为研究类群，探究了这两类演化过程在其种群分化中的作用；相较于西欧，这两个区域的景观异质性更为显著。针对这一与人伴生的鸟类类群，我们结合形态分化数据与遗传数据，旨在明确环境变异、地理距离以及由自然或人为屏障引发的景观阻力（即个体从一处扩散至另一处所需克服的代价）三者中，哪一项最能解释其种群分化模式。我们采用广义差异模型（generalized dissimilarity modeling）——一种将生物β多样性同时拟合于环境预测因子与地理距离的矩阵回归技术——开展分析，结果显示，少量气候与植被变量即可解释约30%的观测种群分化，而地理距离与景观阻力的解释贡献则相对微弱。本研究结果与形态性状受自然选择作用、遗传标记呈现适应性分化的信号相符，表明自然环境条件介导的选择塑造了家麻雀的种群分化。综上，本研究为“适应性演化可能是物种多样化的核心驱动力”这一论点提供了新的实证依据，相关领域的证据正持续积累。