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Disturbances, such as wildfires, are one of the main drivers of biodiversity dynamics, and their frequency and intensity are expected to increase due to global change. Such disturbances generate a mosaic of affected and unaffected patches that change landscape structure and, consequently, metacommunity networks. Therefore, to fully understand the consequences of such disturbances, a landscape perspective is required. In 2012, a wildfire burned 13 000 hectares in the NE Iberian Peninsula affecting a pond macroinvertebrate metacommunity. Communities were highly resilient to this disturbance, recovering after one hydroperiod. Their resilience was related to dispersal, being lower in species with weak dispersal abilities than those with strong dispersal abilities. This suggested that the metacommunity network played a major role in defining system resilience. In this context, we introduced a theoretical analysis based on this network in which we evaluated metacommunity resilience across several gradients of disturbance size and intensity incorporating species dispersal ability. Our study supports the empirical observation of a highly resilient metacommunity but also reveals that increased disturbance regimes might lead to a collapse of this resilience. Disturbance size and intensity interacted to determine the community recovery rate, which was high when both variables were low. Nevertheless, the transition from high to low resilience was sharp and depended on species dispersal. Diversity recovery was mostly driven by disturbance intensity, abruptly collapsing with its rise. This response highlighted the qualitative difference in the effect of size and intensity. These results not only illustrate the mechanisms shaping the studied metacommunity but also more generally stress the strong role of metacommunity mechanisms and landscape structure in biodiversity resilience. Finally, this study highlights the importance of using theoretical approaches rooted in empirical data to determine metacommunity dynamics and the need to preserve and build connected and heterogeneous landscapes to address future disturbance scenarios.

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.

The Mediterranean region has historically been affected by wildfires. However, studies addressing wildfire impacts have traditionally focused first on terrestrial systems and second on lotic systems. This bias has left a gap in knowledge related to wildfire effects on some of the emblematic habitats of the Mediterranean region such as temporary ponds. We hypothesise that temporary ponds will experience indirect consequences of wildfires like those of other aquatic systems (e.g. nutrient increases or trophic alterations). However, the fact that temporary ponds are dry during the summer, when most wildfires occur, could add a new path of disturbance such as an impact on organisms aestivating in the pond sediment due to their direct burning. Based on these hypotheses, the present study analyses wildfire impacts on faunal communities adapted to temporality, focusing on species traits related to expected indirect and direct impacts (i.e. dispersal ability, life history or feeding habits). We took advantage of a wildfire (summer 2012) that partially affected a Mediterranean temporary pond network, comparing the environmental and the faunal community responses from before and after the wildfire, and between the burned and unburned ponds during the subsequent hydroperiod. As hypothesised, our results indicated different wildfire effects. First, changes in abundances of some trophic groups from before and after the wildfire but also strong fluctuations at the beginning of the hydroperiod between burned and unburned ponds. Second, a decrease in abundance of organisms that remain in the pond sediment during drought in burned ponds, being probably affected directly by the wildfire. Only one hydroperiod appears to be sufficient for burned ponds to recover their similarity to unburned ponds, which highlights the high resilience of these communities. Despite their resilience, these communities could become compromised in the future since global change scenarios predict increase wildfire frequency and intensity in the Mediterranean region.

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Temporary rivers (TRs) dominate global river networks and are increasing in occurrence and spatiotemporal extent. However, few studies have investigated the communities that establish after rewetting events (i.e. the end of the dry phase), when local hydrological conditions can shape the communities through species sorting, and the spatial connectivity of sites can also influence colonisation. Here, we analysed the relative importance of both local hydrological conditions and spatial connectivity on the invertebrate communities of seven not impacted Mediterranean TRs after rewetting. We quantified the frequency and duration of drying events and the time since flow resumed. We also quantified spatial connectivity based on each site’s position in the river network (i.e. network connectivity) and the presence of nearby disconnected streams. Overall, we found that both hydrological conditions and network connectivity played a significant role in structuring aquatic invertebrate communities after rewetting. Taxonomic richness, functional richness and functional redundancy decreased with the frequency and duration of drying events and increased with time since the most recent rewetting. Network connectivity showed a significant unimodal relationship with taxonomic and functional metrics. In contrast, the presence of nearby disconnected streams was negatively related to functional richness and functional dispersion. Given that flow intermittence in Mediterranean areas is expected to intensify under future global change scenarios, our results can be helpful to guide future conservation and management actions.

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No abstract