The neophitization of the habitats and their impact on the vegetation and the Entomofauna of the North Adriatic Karst

This study was performed to examine the community composition of carabid beetles (Coleoptera: Carabidae) in native and non-native habitats in the North Adriatic Karst (North East Italy). More specifically we aimed to: (1) analyze the carabids community in the study area, (2) study the effects of some ecological variables (e.g. soil parameters and vegetation structure) on carabid assemblages, (3) compare the carabid beetles beta-diversity of native and non-native habitat types, (4) find possible characteristic species for the non-native habitats. Specifically, we addressed the following questions: (i) Does species beta-diversity of carabid beetles decrease from native to non-native habitats? (ii) What factors modulate species composition of carabid beetles between native and non-native habitats? As a first result we obtained that the habitat type, i.e. the gradient of vegetation, is the first driver of carabid assemblages among plots, with a clear open (thermophilous and grassland species), semi-open (sylvicolous thermophilous species), and close habitat type (sylvicolous and forest species). The second driver that was highlighted in the present research was A. altissima. This species is correlated to the highest number of carabid beetles observed in the study area, in accordance with many other studies describing more specific richness in degraded areas, due to the presence of generalist and opportunistic species. If we consider the species turnover, it is interesting to note that at this highest number of species correspond the lowest values of species beta-diversity, that means that A. altissima promote a local selection on species assemblages that induce their homogenization. Our results showed also a direct link between plant and carabid beetles communities, and the most important variables showing a determinant congruence across taxa (plants and carabid beetles) were again the habitat type and the structure of native vegetation. It is likely that when habitat type is changing, the native structure of vegetation would change too and, as a consequence, also carabid beetles assemblages may change. At the contrary, if we consider non-native plots, in correspondence of habitat type change, the structure of non-native vegetation and carabid beetles assemblages remain almost the same. The effect of vegetation can be considered as an indirect effect, since it is intrinsically influenced by environmental conditions combined with soil parameters. In this research, the highly complex interplay of environmental, soil and vegetation structure variables explain the cross-taxon congruence of the investigated carabid beetles and plant communities. The habitat type and the presence of A. altissima were the two important factors related to the distribution of functional traits among plots. The presence of A. altissima selected in its habitats more omnivorous and phytophagous species, dimorphic wings morphology species, xerophilic species and generalist species. Omnivorous, pterodimorphic, generalist species are known to be more abundant in disturbed and degraded areas. Only among native habitats we found a consistent difference in Functional Diversity (FD), that means that there were heterogeneous assemblage of traits composition from grassland to wood. Combining species richness and functional diversity data, in A. altissima woods even if the number of species was increasing, the Functional Diversity remained quite similar, meaning homogeneity in traits composition, whereas in A. altissima grassland we found an opposite result. In conclusion, A. altissima invasion induced changes in functional composition of carabid beetles by creating more heterogeneous community in grassland and more homogeneous community in wood, but increasing in both habitats the number of generalist and omnivorous species.