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Aim Land-use change typically goes hand in hand with the introduction of exotic species, which mingle with indigenous species to form novel assemblages. Here, we compare the functional structure of indigenous and exotic elements of ground-dwelling arthropod assemblages across four land-uses of varying management intensity. Location Terceira Island (Azores, North Atlantic). Methods We used pitfall traps to sample arthropods in 36 sites across the four land-uses and collated traits related to dispersal ability, body size and resource use. For both indigenous and exotic species, we examined the impact of land-uses on trait diversity and tested for the existence of non-random assembly processes using null models. We analysed differences in trait composition among land-uses for both indigenous and exotic species with multivariate analyses. We used point-biserial correlations to identity traits significantly correlated with specific land-uses for each element. Results We recorded 86 indigenous and 116 exotic arthropod species. Under high-intensity land-use, both indigenous and exotic elements showed significant trait clustering. Trait composition strongly shifted across land-uses, with indigenous and exotic species being functionally dissimilar in all land-uses. Large-bodied herbivores dominated exotic elements in low-intensity land-uses, while small-bodied spiders dominated exotic elements in high-intensity land-uses. In contrast, with increasing land-use intensity, indigenous species changed from functionally diverse to being dominated by piercing and cutting herbivores. Main conclusions Our study revealed two main findings: first, in high-intensity land-uses, trait clustering characterized both indigenous and exotic elements; second, exotic species differed in their functional profile from indigenous species in all land-use types. Overall, our results provide new insights into the functional role of exotic species in a land-use context, suggesting that, in agricultural landscape, exotic species may contribute positively to the maintenance of some ecosystem functions. [ABSTRACT FROM AUTHOR]

Aims Human landscape disturbance can drive the degradation of natural environments, thereby contributing to indigenous (endemic and native non-endemic) species extinctions, facilitating the establishment of exotic species and ultimately resulting in more similar species compositions over time and space. We assessed whether similarities in epigean arthropod assemblages differ between indigenous and exotic species in an oceanic archipelago, and we also examined whether such assemblage similarities depend on the most dominant species, the island, the type of habitat, the degree of landscape disturbance or local environmental variables. Location Four oceanic islands in the Azores archipelago, Portugal. Methods We examined the degree of assemblage similarity and the effect of environmental variables and spatial disturbance to explain the epigean arthropod distributions for indigenous and exotic species. Results Exotic species increased overall assemblage similarity. Distinct arthropod assemblages occurred on the different islands and in the different habitats. Assemblage differences between the habitats depended on the island. This pattern was largely explained by the abundance patterns of the most abundant indigenous and exotic species (ten indigenous and ten exotic species accounted for 75% of total individuals). In comparison with the high explanatory capacity of the habitats and islands per se, local environmental variables and disturbance hardly explained the assemblage composition in both groups of species. Main conclusions We demonstrate that exotic species promote assemblage homogenization on these oceanic islands, and that such process is contingent and independent between islands and habitats. General habitat characteristics seemed to be the main driver of assemblage structure, independently of the different climatic conditions or disturbance levels. [ABSTRACT FROM AUTHOR]