Shifts in climatic realised niches of Iberian species

Abstract

Climate change has strong effects on biodiversity. It causes shifts in the species' geographical range, towards other latitudes or elevations, while tracking its natural habitat. Here, the species maintains its realised niche stable (in the environmental space) and shifts its geographical range. Alternatively, a species might shift its realised niche through its fundamental niche, maintaining its geographical range stable, when tracking its natural habitat is not possible. Following this last hypothesis, we aimed to assess changes in species' environmental conditions based on their historical distribution. Within the environmental space, we compared the climatic realised niche of 300 species of several groups of flora and fauna between 1979 and 2013 in the Iberian Peninsula with ecospat R package, under the assumption of no distribution shift over time. We used the same species' distribution data in both periods. We used CHELSA yearly averaged time‐series data for 1979 and 2013. We analysed the differences in the climate between 1979 and 2013 with a Kruskal–Wallis test, by subtracting each pair of variables, and by subtracting the first three components of a PCA. For each species, we measured the realised niche similarity with Schoener's D index, the realised niche overlap with the stability, unfilling and expansion indices, and the distance between realised niche centroids. The climate between 1979 and 2013 changed in the Iberian Peninsula: climate variability reduces in 2013. Most of the species do not have equivalent realised niches. Although very few species had completely dissimilar niches, many species have shifted their realised niches to some degree. In only 35 years, it was already possible to observe how the realised niches of some species started to shift.