Mediterranean ecosystems are increasingly threatened by disturbances such as wildfires. These disturbances are expected to shift the selective pressures that determine trait-dependent community assembly. In addition, the stochasticity in species assembly may decrease because of the introduction of strong selection regimes or may increase because of random variation in recruitment. However, these changes in the selection profile and stochasticity in disturbed communities have seldom been evaluated. We examined the relative roles of wildfire disturbance, local conditions and successional dynamics on the assembly of aquatic macroinvertebrate communities. We used the theory of community assembly by trait selection (CATS) to identify traits under selection and to estimate their dependence on wildfire disturbance and environmental gradients. We took advantage of a natural wildfire that partially burned a Mediterranean system of temporary ponds, which were surveyed before and after the wildfire, creating a natural before-after-control-impact design. Before the wildfire, the burned and unburned ponds did not show differences in the selected traits. After the wildfire event, species with larger body sizes and scrapers were favoured in the burned ponds, while collectors and active dispersers were underrepresented. Nonetheless, local environmental conditions and successional dynamics had greater relevance in the selection of traits than the wildfire. This suggests that assembly mechanisms were largely determined by seasonal successional changes regardless of wildfire disturbance. Finally, the relevance of the analysed traits diminished during the hydroperiod, suggesting more stochastic assemblages and/or a replacement in the set of selected traits. Despite the prominent role of seasonal succession over wildfire, this disturbance was associated with a change in the selection strength over specific traits related with feeding strategies and species life-histories. Both hydroperiod and wildfire highlighted a strong role of trait-mediated processes (i.e., niche assembly). Therefore, the predicted increase in the frequency and intensity of wildfires is likely to result in community functional shifts. Furthermore, stochasticity was also important for community assembly, particularly from the middle towards the end of the hydroperiod. Our results evidenced the strong relevance of successional changes in trait-mediated assembly mechanisms and its interplay with wildfire disturbance in temporary pond communities.

中文翻译：

---

应对临时池塘的性状选择模式以应对野火干扰和季节性演替

地中海生态系统越来越受到野火等干扰的威胁。预计这些干扰会改变决定依赖特性的社区集会的选择压力。此外，物种组装的随机性可能会因为强选择机制的引入而降低，或者可能会因为招募的随机变化而增加。然而，很少对受干扰社区的选择概况和随机性的这些变化进行评估。我们研究了野火干扰、当地条件和演替动态对水生大型无脊椎动物群落组装的相对作用。我们使用通过性状选择 (CATS) 进行的群落组装理论来识别选择下的性状并估计它们对野火干扰和环境梯度的依赖性。我们利用了部分燃烧地中海临时池塘系统的自然野火，在野火前后进行了调查，创造了一个自然的前后控制影响设计。在野火之前，燃烧和未燃烧的池塘在选择的性状上没有表现出差异。野火事件发生后，被烧毁的池塘中，体型较大和刮刀的物种受到青睐，而收集者和活跃的传播者人数不足。尽管如此，与野火相比，当地环境条件和演替动态在性状选择方面具有更大的相关性。这表明无论野火干扰如何，组装机制在很大程度上取决于季节性演替变化。最后，所分析性状的相关性在水文时期减弱，建议更多随机组合和/或所选特征集中的替代品。尽管季节性演替在野火中发挥着重要作用，但这种干扰与与饲养策略和物种生活史相关的特定特征的选择强度的变化有关。水期和野火都强调了性状介导过程（即生态位组装）的重要作用。因此，预计野火频率和强度的增加可能会导致社区功能发生变化。此外，随机性对于社区集会也很重要，特别是从中期到水期末期。