The Mediterranean is one of the major biodiversity hotspots of the world. It has been identified as the “core” of the speciation process for many groups of organisms. It hosts an impressive number of species, many of which are classified as endangered taxa. Climate change in such a diverse context could heavily influence community composition, reducing ecosystems resistance and resilience. This study aims at depicting the distribution of nine orchid species in the island of Sardinia (Italy), and at forecasting their future distribution in consequence of climate change. The models were produced by following an “ensemble” approach. We analysed present and future (2070) niche for the nine species, using Land Use and Soil Type, as well as 8 bioclimatic variables as predictors, selected because of their influence on the fitness of these orchids. Climate change in the next years, at Mediterranean latitudes, is predicted to results mainly in an increase of temperature and a decrease of precipitation. In 2070, the general trend for almost all modelled taxa is the widening of the suitable areas. However, not always the newly gained areas have high probability of presence. A correct interpretation of environmental changes is needed for developing effective conservation strategies.
Invasion by alien plant species may be rapid and aggressive, causing erosion of local biodiversity. This is particularly true for islands, where natural and anthropogenic corridors promote the rapid spread of invasive plants. Although evidence shows that corridors may facilitate plant invasions, the question of how their importance in the spread of alien species varies along environmental gradients deserves more attention. Here, we addressed this issue by examining diversity patterns (species richness of endemic, native and alien species) along and across roads, along an elevation gradient from sea-level up to 2050 m a.s.l. in Tenerife (Canary Islands, Spain), at multiple spatial scales. Species richness was assessed using a multi-scale sampling design consisting of 59 T-transects of 150 m × 2 m, along three major roads each placed over the whole elevation gradient. Each transect was composed of three sections of five plots each: Section 1 was located on the road edges, Section 2 at intermediate distance, and Section 3 far from the road edge, the latter representing the “native community” less affected by road-specific disturbance. The effect of elevation and distance from roadsides was evaluated for the three groups of species (endemic, native and alien species), using parametric and non-parametric regression analyses as well as additive diversity partitioning. Differences among roads explained the majority of the variation in alien species richness and composition. Patterns in alien species richness were also affected by elevation, with a decline in richness with increasing elevation and no alien species recorded at high elevations. Elevation was the most important factor determining patterns in endemic and native species. These findings confirm that climate filtering reflected in varying patterns along elevational gradients is an important determinant of the richness of alien species (which are not adapted to high elevations), while anthropogenic pressures may explain the richness of alien species at low elevation.