Aim Niche‐based species distribution models (SDMs) have become a ubiquitous tool in ecology and biogeography. These models relate species occurrences with the environmental conditions found at these sites. Climatic variables are the most commonly used environmental data and are usually included in SDMs as averages of a reference period (30–50 years). In this study, we analyse the impact of including inter‐annual climatic variability on the estimation of species niches and predicted distributions when assessing plant demographic response to extreme climatic episodes. Location Mediterranean basin, SE Iberian Peninsula. Methods We first characterized species niches with inter‐annual and average climate in the same environmental space. We then compare the respective capacities of climatic suitability obtained from averaged climate‐based and from inter‐annual variability‐based niches to explain population demographic responses to extreme drought. Furthermore, we assessed the relative increase in niche size when including climatic variability for a set of Mediterranean species exhibiting a wide range of distribution areas. Results We found that climatic suitability obtained from inter‐annual variability‐based niches showed higher explanatory capacity than average climate‐based suitability, especially for populations living in climatically marginal conditions, although both niches quantifications significantly explained species demographic responses. In addition, species with restricted distribution ranges increased relatively more their niche space when considering climatic variability, probably because in widely distributed species spatial variability compensates for temporal variability. Main conclusions The common use of climatic averages when characterizing species niches could lead to underestimations of species distribution and misunderstanding of demographic behaviour, with implications for conservation plans derived from SDMs, for example, overestimations of species extinction risk under climate change, or underestimations of alien species invasion’ risk. We highlight that including climatic variability in niche modelling can be particularly important when dealing with species with restricted distribution and populations at the margin of their species niche.

In recent decades, many forest die-off events have been reported in relation to climate-change-induced episodes, such as droughts and heat waves. To understand how these extreme climatic events induce forest die-off, it is important to find a tool to standardize the climatic conditions experienced by different populations during a specific climatic event, taking into account the historic climatic conditions of the site where these populations live (bioclimatic niche). In this study, we used estimates of climatic suitability calculated from species distribution models (SDMs) for such purpose. We studied forest die-off across France during the 2003 heatwave that affected Western Europe, using 2,943 forest inventory plots dominated by 14 single tree species. Die-off severity was estimated by Normalized Difference Vegetation Index (NDVI) loss using Moderate-resolution Imaging Spectroradiometer remote sensor imagery. Climatic suitability at the local level during the historical 1979-2002 period (HCS), the episode time (2003; ECS) and suitability deviance during the historical period (HCS-SD) were calculated for each species by means of boosted regression tree models using the CHELSA climate database and occurrences extracted from European forest inventories. Low HCS-SD and high mean annual temperature explained the overall regional pattern of vulnerability to die-off across different monospecific forests. The combination of high historical and low episode climatic suitability also contributed significantly to overall forest die-off. Furthermore, we observed different species-specific relationships between die-off vulnerability and climatic suitability: Sub-Mediterranean and Mediterranean species tended to be vulnerable in historically more suitable localities (high HCS), whereas Euro-Siberian species presented greater vulnerability when the hot drought episode was more intense.We demonstrated that at regional scale, past climatic legacy plays an important role in explaining NDVI loss during the episode. Moreover, we demonstrated that SDMsderived indexes, such as HCS, ECS and HCS-SD, could constitute a tool for standardizing the ways that populations and species experience climatic variability across time and space. K E Y W O R D Scanopy decay, climatic suitability, extreme climatic event, forest die-off, hot-drought, NDVI, species distribution models | 3135 MARGALEF-MARRASE Et AL.

High rates of climate change are currently exceeding many plant species' capacity to keep up with climate, leading to mismatches between climatic conditions and climatic preferences of the species present in a community. This disequilibrium between climate and community composition could diminish, however, when critical climate thresholds are exceeded, due to population declines or losses among the more mismatched species. Here, we assessed the effect of an extreme drought event on rich semiarid shrubland communities in the south-eastern Iberian Peninsula. Using a community climate framework, we compared the community climatic disequilibrium before and after the drought episode on three study sites with different levels of precipitation. Disequilibrium was estimated as the difference between observed reference climate and community-inferred climate, calculated as the mean climatic optimum for the species present, weighted by their abundances. We found that extreme drought embedded within a decadal trend of increasing aridity led to a significant reduction in community climatic disequilibrium, and that this reduction was positively related to water deficit (low P/PET values). In contrast, microhabitat variables such as vegetation cover or slope, did not emerge as significant predictors of changes in community climatic disequilibrium. Our study highlights that extreme drought events pushing communities in the same direction as climate trends may decrease community climatic mismatch, leading to communities more adapted to aridity through loss of drought-sensitive

Habitat suitability calculated from species distribution models (SDMs) has been used to assess population performance, but empirical studies have provided weak or inconclusive support to this approach. Novel approaches measuring population distances to niche centroid and margin in environmental space have been recently proposed to explain population performance, particularly when populations experience exceptional environmental conditions that may place them outside of the species niche. Here, we use data of co-occurring species' decay, gathered after an extreme drought event occurring in the southeast of the Iberian Peninsula which highly affected rich semiarid shrubland communities, to compare the relationship between population decay (mortality and remaining green canopy) and 1) distances between populations' location and species niche margin and centroid in the environmental space, and 2) climatic suitability estimated from frequently used SDMs (here MaxEnt) considering both the extreme climatic episode and the average reference climatic period before this. We found that both SDMs-derived suitability and distances to species niche properly predict populations performance when considering the reference climatic period; but climatic suitability failed to predict performance considering the extreme climate period. In addition, while distance to niche margins accurately predict both mortality and remaining green canopy responses, centroid distances failed to explain mortality, suggesting that indexes containing information about the position to niche margin (inside or outside) are better to predict binary responses. We conclude that the location of populations in the environmental space is consistent with performance responses to extreme drought. Niche distances appear to be a more efficient approach than the use of climate suitability indices derived from more frequently used SDMs to explain population performance when dealing with environmental conditions that are located outside the species environmental niche. The use of this alternative metrics may be particularly useful when designing conservation measures to mitigate impacts of shifting environmental conditions.