Pattern di variazione spaziale in comunità biotiche appenniniche: modelli teorici e implicazioni conservazionistiche

The Apennines are characterized by the presence of a double stress gradient, with lowlands subject to high temperatures and pronounced aridity in summer, and high altitudes to very low temperatures in winter. This double stress gradient is expected to represent a strong environmental filter for biological communities. To test this hypothesis, we investigated how various aspects of plant communities, such as their functional traits, biogeographical groups, biological forms, and ecological preferences, varied with elevation in mountain areas of the Abruzzi Region. We also studied the influence of floral diversity and elevation (which reflects the environmental filtering mainly exerted by temperature) on butterfly communities. We also discussed the possible role of botanical gardens as sites to promote butterfly conservation (butterfly gardens) in natural areas. Finally, we used lichens to investigate the impact of air pollutants produced by the post-seismic reconstruction works in the city of L’Aquila, whose urban-rural gradient follows the elevational gradient. The study of plant functional traits showed that, as expected according to the double stress gradient hypothesis, the lowest and the highest elevations were the most selective. Also, the interspecific variation in plant traits was more important than the intraspecific one, a result of particular interest given the increasing impact of the climate change on mountains. The study of the biogeographical composition (chorotypes) of plant communities highlighted a prevalence of European and Euro-Asiatic species at intermediate elevations because of their preference for temperate climates, while Mediterranean species were strongly filtered by elevation, being particularly sensitive to the decrease of temperature. The analysis of biological forms showed that phanerophytes and geophytes prevailed at intermediate elevations occupied by beech woods, whereas hemicryptophytes increased with elevation due to their greater ability to cope with harsh environmental conditions at high elevations. Chamaephytes exhibited a U-shaped pattern due to their ability to cope with the harsh conditions at the two extremes of the gradient (strong aridity in the lowlands and intense cold on the mountaintops, respectively). The study of plant ecological preferences showed that the thermophilic character of the plant communities decreased with increasing elevation. At the extremes of the gradient (where open environments prevailed) plant communities were dominated by species that prefer sunny places and are capable of surviving on poor and dry soils, while communities at intermediate elevations (where forests prevailed) were dominated by species associated with shady places and which prefer rich and moist soils. The analysis of the relationships between butterfly and floral diversity (number of plant species with flowers at least potentially usable by butterflies) showed that plant richness was a much stronger predictor of butterfly abundance than elevation, while its effect on butterfly diversity was less important. This supports the hypothesis that butterflies are mainly generalist nectarivores, with availability of nectar sources and elevation acting in an opposite way on butterfly diversity. Our work on the use of botanical gardens as a tool for butterfly conservation allowed the development of a project that can represent a reference model to promote awareness of insect conservation, disseminate scientific knowledge, and perform research, also through citizen science programs. Finally, the study of lichens as bioindicators of air quality showed that lichen diversity decreased towards the center of the city of L'Aquila due to the atmospheric pollution produced by demolition and reconstruction works. This research suggests that lichens can be profitably used for air quality evaluation in other rural contexts subject to rapid urban expansion.