Endemic and alien vascular plant diversity in the small Mediterranean islands of Sardinia: Drivers and implications for their conservation

Abstract

Islands are of high interest for conservationists, due to their great biodiversity within discrete territories. Nonetheless, several mechanisms of plant diversity patterns are unknown, especially for continental islands. In this paper, we explored how endemic and alien vascular plant species richness and the compositional dissimilarity of small Mediterranean continental islands vary according to factors related to human activities, geography/landscape, and climate. Actions for endemic plant conservation were also prioritised according to both endemic and alien components. To this aim, data of endemic and alien plant species for forty islands of Sardinia were considered. Species-area residuals, which express the actual species composition free of area-effects, were modelled using 19 variables related to anthropogenic, geographic/landscape and climatic domains (group of factors). The geographic/landscape domain appeared to be important for both endemic and alien species richness and compositional dissimilarity, while the climatic one was especially relevant for alien species richness. The anthropogenic domain was mostly important for the compositional dissimilarity of aliens and for the endemic species richness. Actions for endemic plant conservation were of high priority for 14 islands; 11 of which are located off the northwest coast of Sardinia. Our research confirms that the Mediterranean small islands of Sardinia are plant endemism hotspots prone to alien invasion. Our findings suggest that removing anthropogenic disturbances is not sufficient to prevent plant invasions. Other factors related to climatic and geographic/ landscape domains are as or more important in determining endemic and alien plant composition.

Seed Germination Ecophysiology of Acacia dealbata Link and Acacia mearnsii De Wild.: Two Invasive Species in the Mediterranean Basin

“…Furthermore, when alien plant species are introduced to extremely sensitive habitats, in particular if they are already degraded and fragmented, the capacity for invasion may also be favoured by a high propagule pressure [6]. The Mediterranean Basin is one of the main biodiversity mega hotspots in the world and has a high sensitivity to biological invasions due to its biogeographic, climatic, and socio-economic conditions [7][8][9]. Mediterranean islands are particularly vulnerable to plant invasions and there is clear evidence of this phenomenon being intensified in recent years [9][10][11][12].…”

“…The Mediterranean Basin is one of the main biodiversity mega hotspots in the world and has a high sensitivity to biological invasions due to its biogeographic, climatic, and socio-economic conditions [7][8][9]. Mediterranean islands are particularly vulnerable to plant invasions and there is clear evidence of this phenomenon being intensified in recent years [9][10][11][12]. In Mediterranean ecosystems and habitats, a high percentage of invasive alien plants are woody species that have been intentionally introduced for ornamental, reforestation, and afforestation purposes [13][14][15].…”

Floristic and Vegetation Changes on a Small Mediterranean Island over the Last Century

“…This study has shown how the islet of Capo Passero has great floristic peculiarities and at the same time considerable vulnerability that can cause extinctions/decline of populations and reduction/alterations of habitats under stress. For this reason, it is important to plan and implement targeted conservation actions similar to what has been proposed for other small Mediterranean islands [ 4 , 85 ]. Already 50 years ago, considering the botanical interest of the Island of Capo Passero, Pirola [ 86 ] recommended its strict protection.…”

Spatial Phylogenetics, Biogeographical Patterns and Conservation Implications of the Endemic Flora of Crete (Aegean, Greece) under Climate Change Scenarios

“…The Mediterranean hosts several vulnerable species [ 34 ], with climate change projections expected to be more severely expressed on the Mediterranean islands and mountain ranges [ 33 ], which may have acted as refugia in the distant past [ 35 ]. Consequently, more plant extinctions are anticipated in these areas, even though very few have been documented thus far [ 36 , 37 ], despite intense anthropogenic pressure and plant invasions [ 38 ], acting in parallel with climate change.…”