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Aim: Species geographical range sizes play a crucial role in determining species vulnerability to extinction. Although several mechanisms affect range sizes, the number of biotic interactions and species climatic tolerance are often thought to play discernible roles, defining two dimensions of the Hutchinsonian niche. Yet, the relative importance of the trophic and the climatic niche for determining species range sizes is largely unknown. Location: Central and northern Europe. Time period: Present. Major taxa studied: Gall‐inducing sawflies and their parasitoids. Methods: We use data documenting the spatial distributions and biotic interactions of 96 herbivore species, and their 125 parasitoids, across Europe and analyse the relationship between species range size and the climatic and trophic dimensions of the niche. We then compare the observed relationships with null expectations based on species occupancy to understand whether the relationships observed are an inevitable consequence of species range size or if they contain information about the importance of each dimension of the niche on species range size. Results: We find that both niche dimensions are positively correlated with species range size, with larger ranges being associated with wider climatic tolerances and larger numbers of interactions. However, diet breadth appears to more strongly limit species range size. Species with larger ranges have more interactions locally and they are also able to interact with a larger diversity of species across sites (i.e. higher β‐diversity), resulting in a larger number of interactions at continental scales. Main conclusions: We show for the first time how different aspects of species diet niches are related to their range size. Our study offers new insight into the importance of biotic interactions in determining species spatial distributions, which is critical for improving understanding and predictions of species vulnerability to extinction under the current rates of global environmental change. [ABSTRACT FROM AUTHOR]

Aim: Our knowledge of Pleistocene refugia and post‐glacial recolonization routes of forest understorey plants is still very limited. The geographical ranges of these species are often rather narrow and show highly idiosyncratic, often fragmented patterns indicating either narrow and species‐specific ecological tolerances or strong dispersal limitations. However, the relative roles of these factors are inherently difficult to disentangle. Location: Central and south‐eastern Europe. Time period: 17,100 BP – present. Major taxa studied: Five understorey herbs of European beech forests: Aposeris foetida, Cardamine trifolia, Euphorbia carniolica, Hacquetia epipactis and Helleborus niger. Methods: We used spatio‐temporally explicit modelling to reconstruct the post‐glacial range dynamics of the five forest understorey herbs. We varied niche requirements, demographic rates and dispersal abilities across plausible ranges and simulated the spread of species from potential Pleistocene refugia identified by phylogeographical analyses. Then we identified the parameter settings allowing for the most accurate reconstruction of their current geographical ranges. Results: We found a largely homogenous pattern of optimal parameter settings among species. Broad ecological niches had to be combined with very low but non‐zero rates of long‐distance dispersal via chance events and low rates of seed dispersal over moderate distances by standard dispersal vectors. However, long‐distance dispersal events, although rare, led to high variation among replicated simulation runs. Main conclusions: Small and fragmented ranges of many forest understorey species are best explained by a combination of broad ecological niches and rare medium‐ and long‐distance dispersal events. Stochasticity is thus an important determinant of current species ranges, explaining the idiosyncratic distribution patterns of the study species despite strong similarities in refugia, ecological tolerances and dispersal abilities. [ABSTRACT FROM AUTHOR]

Aim: Climate change regulates autumn leaf senescence date (LSD), exhibiting a strong phenological control of plant carbon uptake. Unlike the delaying effect of daily mean temperature (Tmean) on LSD, the impact of warming asymmetry in daytime and nighttime, as evidenced by variations of the diurnal temperature range (DTR), remains elusive. The objectives of this study were to investigate physiological and ecological impacts of DTR on LSD using long‐term in situ observations and to predict the future trends of LSD under warming. Location: Europe. Time period: 1950–2015. Major taxa studied: Plant phenology. Methods: We used partial correlation analysis, multiple linear regression and ridge regression to explore the impacts of DTR on LSD. To quantify the importance of potential drivers of LSD, we trained random forest models and applied the SHapley Additive exPlanations method to isolate the marginal contributions of each predictor on LSD. For LSD modelling and projection, we first evaluated two temperature‐driven LSD models [i.e., cooling‐degree‐day (CDD, without DTR effect) and day–night‐temperature CDD (DNCDD, with DTR effect)], then applied them to predict future LSDs. Results: We found that observational increases in Tmean and DTR had contrasting effects on LSD. Increased Tmean delayed the LSD, whereas larger DTR overall had an advancing effect. Considering the DTR effect, the Tmean sensitivity of LSD was 14% lower than presently estimated (2.4 vs. 2.8 days °C−1). Warming asymmetry‐related drought stress and plant functional traits (i.e., plant isohydricity and water‐use efficiency) potentially explained the advancing effect of DTR on LSD. We found that current projections of future LSD are overestimated because the DTR effect is discounted, suggesting the need for an adequate understanding of how plant phenology responds to warming asymmetry. Main conclusions: Our findings highlight the importance of DTR in controlling LSD variations with an advancing‐dominant effect and call for the improvement of phenology modelling incorporating the DTR effect. Given that DTR showed a globally narrowing trend over the last several decades, more efforts are needed to understand the potential ecological impacts of warming asymmetry and vegetation response to climate change. [ABSTRACT FROM AUTHOR]

Aim: The amount of forest edges is increasing globally due to forest fragmentation and land‐use changes. However, edge effects on the soil seed bank of temperate forests are still poorly understood. Here, we assessed edge effects at contrasting spatial scales across Europe and quantified the extent to which edges can preserve the seeds of forest specialist plants. Location: Temperate European deciduous forests along a 2,300‐km latitudinal gradient. Time period: 2018–2021. Major taxa studied: Vascular plants. Methods: Through a greenhouse germination experiment, we studied how edge effects alter the density, diversity, composition and functionality of forest soil seed banks in 90 plots along different latitudes, elevations and forest management types. We also assessed which environmental conditions drive the seed bank responses at the forest edge versus interior and looked at the relationship between the seed bank and the herb layer species richness. Results: Overall, 10,108 seedlings of 250 species emerged from the soil seed bank. Seed density and species richness of generalists (species not only associated with forests) were higher at edges compared to interiors, with a negative influence of C : N ratio and litter quality. Conversely, forest specialist species richness did not decline from the interior to the edge. Also, edges were compositionally, but not functionally, different from interiors. The correlation between the seed bank and the herb layer species richness was positive and affected by microclimate. Main conclusions Our results underpin how edge effects shape species diversity and composition of soil seed banks in ancient forests, especially increasing the proportion of generalist species and thus potentially favouring a shift in community composition. However, the presence of many forest specialists suggests that soil seed banks still play a key role in understorey species persistence and could support the resilience of our fragmented forests. [ABSTRACT FROM AUTHOR]

Aim: The aims of this study were to evaluate the changes in the length of the time period between leaf‐out and flowering across temperate tree species, and associate these changes with potential physiological and environmental drivers to enhance mechanistic insight into these phenomena. Location: Central Europe. Time period: 1980–2016. Major taxa studied: Six temperate woody species. Methods: Statistical analyses were carried out based on long‐term ground observations of both spring leaf‐out and flowering across temperate tree species during 1980–2016, a period characterized by rapid warming. Results: The temperature sensitivity of flowering (−5.4 ± 0.04 days/℃, mean ± SE) was higher than that of leaf‐out (−4.6 ± 0.04 days/℃) across all species, regardless of whether leaf‐out occurred before or after flowering. This study postulates a hypothesis attributing the different temperature sensitivities to different thermal sensitivities, thermal requirements, and photoperiodic controls. Main conclusions: The larger temperature sensitivity of flowering than leaf‐out resulted in an extended time period between flowering and leaf‐out in species that bloom before leafing out, but a shorter time period between these phenophases in species with the opposite strategy. We would like to emphasize the importance of changes in time period between different phenophases, and we recommend conducting experimental research to reveal the underlying mechanisms of plant phenology response to climate change, and to explore its potential ecological implications. [ABSTRACT FROM AUTHOR]

Aim: We assessed the spatial distribution of four different types of avian specialization throughout Europe, identifying landscape features associated with specialization and quantifying where the Natura 2000 network intersects with areas of high avian specialization. Location: Europe. Time period: Present day. Taxa studied: European breeding birds. Methods: We used the European Atlas of breeding birds and four avian specialization measures (diet, foraging behaviour, foraging substrate and habitat). We calculated specialization richness and identified geographical hotspots for each of these ecological traits. We tested whether elevational gradient, landscape heterogeneity or dominant land use predicted each type of specialization richness. We determined which types of European protected areas are most associated with higher specialization richness. Results: Diet and foraging substrate specialists increased with elevation, whereas richness of foraging behavioural specialists decreased. There was a greater richness of dietary and habitat specialists in forests than in other environments. The Natura 2000 areas declared under Bird and both directives (Birds and Habitats) intersected with a high dietary, foraging substrate and habitat specialist richness. The richness of foraging behaviour specialists was high in Birds directive areas. Single and multiple hotspots of specialization were greater in protected than non‐protected areas. However, almost 30% of specialization hotspots did not intersect with protected areas. Main conclusions: Our findings suggest that higher levels of avian specialization in Europe are positively associated with elevation and forested land cover. Importantly, we found that the Natura 2000 network supports all types of avian ecological specialization, albeit mainly in areas declared under both directives. [ABSTRACT FROM AUTHOR]