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Given the sensitivity of mountain biodiversity to human pressure, it is essential to quantify changes in montane biological communities and contrast them with expectations based on potential drivers of change. This need is particularly pressing for biological groups representing important but little‐studied fractions of biodiversity, such as insects. We analyze the temporal changes (between 1998 and 2015) of leaf beetle communities in an altitudinal gradient in the Sierra de Ancares (NW Spain). Our results show temporal changes in the composition of local communities, with a tendency to assemblage thermophilization, as well as a homogenization of the spatial turnover pattern, mostly driven by an increased similarity between communities at the lower and intermediate altitudes. These temporal changes in community composition and in the spatial structure of biodiversity were associated with upward shifts of the upper altitudinal limit of warm‐adapted species and with downward shifts of the lower altitudinal limit of cold‐adapted species. While this upward shift is consistent with expectations of climate change effects, the observed downward shift suggests a land‐use change effect. Our results point to the joint effect of multiple factors (climate and land‐use change) behind temporal changes of these leaf beetle communities, which result in compositional reorganization and biotic homogenization, rather than a mere coherent displacement toward higher altitudes. More generally, we show that understanding temporal change of biodiversity requires assessing multiple community‐level metrics (e.g., variation in assemblage composition and/or changes in spatial turnover) for the detection of tendencies among the species‐specific signals (e.g., altitudinal range shifts). [ABSTRACT FROM AUTHOR]

Biological invasions constitute an opportunity to study the evolutionary processes behind species’ adaptations. The invasive potential of some species, like the Argentine ant (Linepithema humile), has likely been increasing because they show low intraspecific competition. However, multiple introductions over time or genetic divergence could increase the probability of intraspecific competition, constituting barriers for their dispersal and thus, decreasing invasive success. Here, we studied the genetic and behavioural variability of L. humile workers collected at six locations on the NW coast of the Iberian Peninsula, a possible scenario for multiple introductions and population divergence, due to its high level of maritime traffic and complex coastal geography. We analysed behaviours related to spatial navigation (exploration, wall-following), resources acquisition, and competition (inter and intraspecific aggressiveness) through two relevant seasons for the nest ecology: spring and autumn. Genetic analyses using microsatellites indicated that the nests studied belonged to the most spread supercolony in South Europe. However, we identified the existence of two genetically differentiated clusters in Galiza. Lethal interactions were found between workers from different and similar genetic clusters, but a trend suggests higher agonistic behaviours between the two genetic groups. Genetic differences were positively correlated with the geographical distance, but aggressiveness was not correlated with any of them. Ants from each of the tested nests expressed different behaviours with high plasticity through time. Ants from all nests showed more exploration and aggressiveness, less wall-following and faster detection of food in autumn than in spring, with no intraspecific aggressiveness observed in spring. Our findings suggest competition between nests of the same supercolony and behavioural seasonal variability, supporting the hypothesis of divergent evolutionary processes. The results of our work question the assumed unity of supercolonies of this species and offer insights for understanding the future adaptation of L. humile in the introduced areas. [ABSTRACT FROM AUTHOR]