Ant (Hymenoptera: Formicidae) assemblages were sampled with pitfall traps in three different habitats associated with a rehabilitated mine district and in undisturbed forests in Tuscany, Italy. The four habitats were (1) open fields (3-4 years old); (2) a middle-age mixed plantation (10 years); (3) an old-age mixed plantation (20 years); and (4) an oak woodland (40 years) not directly affected by mining activities. The aim of the study was to analyze ant recolonization patterns in order to provide insights on the use of Mediterranean ant fauna as indicators of restoration processes. Species richness and diversity were not significantly different among the four habitats. However, multivariate analyses showed that the assemblages in the different habitats were clearly differentiated, with similarity relationships reflecting a successional gradient among rehabilitated sites. The observed patterns of functional group changes along the gradient broadly accord with those of previous studies in other biogeographic regions. These were (1) a decrease of dominant Dolichoderinae and opportunists; (2) an increase in the proportion of cold-climate specialists; and (3) the appearance of the Cryptic species in the oldest plantations, with a maximum of abundance in the woodland. In conclusion, the results of our study supported the use of Mediterranean ants as a suitable tool for biomonitoring of restoration processes, and in particular, the functional group approach proved a valuable framework to better interpret local trends in terms of global ecological patterns. Further research is, however, needed in order to obtain a reliable classification of Mediterranean ant functional groups.

1. The organisation of an ant assemblage inhabiting an olive orchard in central Italy was analysed and patterns of dominance among ant species were described in order to assess (i) the relationship between thermal dependency and degree of behavioural dominance, and (ii) the relationship between dominance and discovery ability. 2. Activity patterns of the most abundant species on trees were examined in a sample of 120 trees during spring and summer. The degree of behavioural dominance and the ability of different species to discover new food sources were assessed using tuna baiting on a subset of 80 trees. 3. Different ant species showed contrasting patterns of activity. Some species (such as Lasius lasioides, Camponotus lateralis, and Camponotus piceus) were most active during the warmer part of the day, while others restricted their activity to the cooler hours (Camponotus aethiops and Plagiolepis pygmaea). Some species (such as Crematogaster scutellaris) were active irrespective of the time of day. 4. No clear relationship was observed between temperature of maximal activity and degree of behavioural dominance. There was, however, a positive relationship between behavioural dominance and thermal range of activity. A positive relationship between dominance and ability to find resources, with the most behaviourally dominant and aggressive species being most efficient in finding food items, was also observed. 5. The results support the idea that the temperature–dominance relationship is much more complex in Mediterranean‐type habitats than in other ecosystems. Of particular interest is the positive dominance–discovery relationship. This finding contrasts with previous investigations, which reported a negative relationship between dominance and discovery ability and suggested that this pattern plays a role in promoting the coexistence of species in ant communities.

1 Stable isotopes signatures ( ␦ 13 C and ␦ 15 N) of the most important tree-dwelling ants in an olive orchard were examined, together with the signatures of the most common herbivores, predators and sap-sucking insects. The olive orchard consists of separate subunits (trees) surrounded by a matrix of grasses or bare ground, and the role of ants in such a system is not fully understood. 2 None of the selected ant species was exclusive to the olive trees because they were also observed foraging on vegetation (mainly thistle) under the tree crowns. Hence, the relative contributions of these two sources of energy (olive trees versus herbs/grasses) were assessed by comparing the ␦ 13 C of ants with the signatures of plants and those of other arthropods collected on the trees and on nearby thistles. Next, the trophic level occupied by the ants and their ecological role within the olive food web were determined by examining the ␦ 15 N values and their relationship with indices of ecological performance measuring the potential pressure exerted by each species on the ecosystem. 3 The analysis of 13 C signatures revealed a different contribution of the two energy sources, olive trees versus herbs and grasses, with the former being more important for ants. The analysis of 15 N signatures suggested separate roles for different ant species: some ( Crematogaster scutellaris , Lasius lasioides ) occupied a higher trophic level, mostly involved in predation, whereas others ( Camponotus piceus , Camponotus lateralis ) occupied a lower level, probably involved more in homopteran tending. A fifth species ( Camponotus aethiops ) was in an intermediate position. Finally, the ␦ 15 N levels of the species were significantly correlated with indices of ecological performance.

1. The spatial arrangement of individuals and populations may have deep influences on all the biotic interactions within a community.2. The spatial distribution of nests of the ant Crematogaster scutellaris Olivier was analysed in an olive orchard in central Italy. As this species nests inside tree trunks, the regular structure of this simplified ecosystem may help to reduce the confounding effect of habitat heterogeneity on the spatial distribution of nests. In total, 531 trees were mapped and their shape (size and structure of the trunk) recorded. The presence of C. scutellaris nests in each tree was assessed in spring-summer and autumn 2006 and 2007. 3. The number of occupied trees changed in time, from a maximum of 129 (summer 2006) to a minimum of 60 (autumn 2007). Occupancy of tree was related to its shape, with larger trees being more frequently and more steadily occupied than smaller ones. 4. Nests were spatially aggregated, forming well-defined clusters, but aggregation was not explained by a corresponding clumping of larger trees. Nests belonging to the same cluster were usually not aggressive to each other, whereas aggression was more common between nests belonging to different clusters. The dynamic nature of the system coupled with the clustered distribution of nests, is consistent with a hypothesis of seasonal polydomy, and suggest that whereas some trees are steadily occupied (core) others are opportunistically colonised when new resources are discovered (satellites). 5. Clusters size distribution was shown to follow a truncated power-law, a finding consistent with the idea that clusters are self-organised structures dependent on local interactions. These results suggest that spatial self-organisation in ant colonies may in principle be more common than previously thought, although the mechanisms generating these patterns still need to be clarified.

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No abstract

Throughout the Mediterranean basin, the long-term interaction between human activities and natural processes has led to the formation of unique ecosystems whose biodiversity may be higher than that of the “original” systems. This is particularly true in the case of transformations of continuous stretches of closed forest into a complex mosaic of open and closed habitat over the course of centuries. In this study, we assessed the variation in diversity of ant assemblages in a typical patchy landscape, sampling ants in the three most important constituting habitats: olive plantation, harvested forest, and mature forest. In the study we used two different sampling methods—pitfall traps and observation at baits—which provided information on species presence at different temporal scales. The three habitats displayed different species assemblages, and considerable variation in species composition was observed at different times of the day, particularly in the harvested forest. Functional group analysis showed that the olive plantation, although the most artificial habitat, displayed the highest number of functional groups, suggesting a wider spectrum of available ecological niches for ant species within this habitat type. Overall, it was concluded that each of the three habitats contributes to enhance diversity at the landscape scale, which is greater than that expected from a more homogeneous habitat composition.

Parole chiave: analisi di comunità; avifauna; statistica multivariata; modelli predittivi.