CEFE, Univ Montpellier, CNRS, EPHE, IRD, Montpellier, France.
J Anim Ecol. 2022 Aug;91(8):1627-1641. doi: 10.1111/1365-2656.13740. Epub 2022 Jun 1.
Urbanisation is a world-wide phenomenon converting natural habitats into new artificial ones. Environmental conditions associated with urbanisation represent great challenges for wildlife. Behaviour and stress tolerance are considered of major importance in the adaptation to novel urban habitats and numerous studies already reported behavioural and stress response phenotypes associated with urbanisation, often suggesting they represented adaptations, while rarely demonstrating it. The main goal of this study was to test the adaptive nature of urban shifts in behavioural and stress-related traits, and by adaptive we mean phenotypic change favouring traits in the same direction as selection. Using 7 years of monitoring of urban and forest great tits, we first tested for differences in exploratory behaviour, aggressiveness and breath rate, between both habitats. Second, we performed habitat-specific analyses of selection on the three former traits using (a) reproductive success and (b) survival estimated via capture-mark-recapture models, as fitness estimates, to determine whether shifts in these behavioural and stress-related traits were aligned with patterns of ongoing selection. We found that urban birds displayed higher exploratory behaviour and aggressiveness, and higher breath rate, compared to forest birds. Selection analyses overall revealed that these shifts were not adaptive and could even be maladaptive. In particular, higher handling aggression and higher breath rate in urban birds was associated with lower fitness. Higher exploration scores were correlated with lower survival in both habitats, but higher reproductive success only in forest males. Overall, differences in patterns of selection between habitats were not consistent with the phenotypic divergence observed. Taken together, these results highlight that phenotypic shifts observed in cities do not necessarily result from new selection pressures and could be maladaptive. We hypothesise that divergences in behavioural traits for urban birds could result from the filtering of individuals settling in cities. We thus encourage urban evolutionary scientists to further explore the adaptive potential of behavioural traits measured in urban habitats (a) by replicating this type of study in multiple cities and species, (b) by implementing studies focusing on immigrant phenotypes and (c) by measuring selection at multiple life stages.
城市化是一种全球性现象，将自然栖息地转化为新的人工栖息地。与城市化相关的环境条件对野生动物构成了巨大挑战。行为和应激耐受性被认为是适应新的城市栖息地的重要因素，许多研究已经报道了与城市化相关的行为和应激反应表型，这些表型通常被认为是适应的，但很少有研究证明这一点。本研究的主要目的是测试行为和与应激相关的特征在城市变化中的适应性，适应性是指有利于朝着与选择相同方向的特征的表型变化。使用 7 年对城市和森林大山雀的监测，我们首先测试了这两个栖息地之间的探索行为、攻击性和呼吸率的差异。其次，我们使用（a）繁殖成功率和（b）通过捕获-标记-重捕模型估计的存活率作为适应度估计值，对这三个前体性状进行了特定栖息地的选择分析，以确定这些行为和与应激相关的性状的变化是否与正在进行的选择模式一致。我们发现，与森林鸟类相比，城市鸟类表现出更高的探索行为、攻击性和呼吸率。选择分析总体上表明，这些变化不是适应性的，甚至可能是适应性不良的。特别是，城市鸟类的更高处理攻击性和更高呼吸率与较低的适应度相关。在两个栖息地中，更高的探索得分与更低的存活率相关，但仅在森林雄性中与更高的繁殖成功率相关。总体而言，栖息地之间选择模式的差异与观察到的表型趋异不一致。综上所述，这些结果强调了城市中观察到的表型变化不一定是由新的选择压力引起的，并且可能是适应性不良的。我们假设，城市鸟类行为特征的差异可能是由于定居在城市中的个体的过滤所致。因此，我们鼓励城市进化科学家进一步探索在城市栖息地中测量的行为特征的适应性潜力（a）通过在多个城市和物种中复制这种类型的研究，（b）通过实施关注移民表型的研究，以及（c）通过测量多个生命阶段的选择。
