Ecological drivers of plant diversity patterns in remnants coastal sand dune ecosystems along the northern Adriatic coastline

Abstract

Coastal sand dunes represent one of the most fragile ecosystems in the Mediterranean basin. These habitats naturally suffer the action of several limiting factors such as sand burial, marine aerosol and low soil fertility; on the other hand, they often host species of high conservation value. Over the last decades, they have also experienced a high level of biological invasion. In this study, we sampled psammophilous vegetation in two sites in the northern Adriatic coast belonging to the Natura 2000 network to describe diversity patterns and to identify the main ecological drivers of species diversity. Plant species richness and their abundance were assessed in each plot. Differences in species composition for native and alien species were compared via PERMANOVA analysis. Species complementarity was explored by partitioning beta diversity in its spatial components (richness and replacement). A Generalized Linear Model was also computed to assess the main environmental factors that may promote invasiveness in these ecosystems. For the investigated area, our results highlight the strong differentiation in community composition both in alien and native species: in particular alien species showed on average a lower complementarity among habitats compared to native species. Specifically, communities seem to be more diversified when larger spatial scales were considered. Beta diversity in both groups appears to be more dominated by the richness component with respect to the replacement component. Furthermore, in these habitats, the occurrence of alien species was shown to be related to geomorphological predictors more than climatic variables.

Functional Divergence Drives Invasibility of Plant Communities at the Edges of a Resource Availability Gradient

“…The most interesting pattern emerging from our data is that invasive species displayed, on average, higher functional niche dissimilarity in both sampling sites, though Site 2 showed lower β0 (see Site 2 in Figure 2, Table 2), in agreement with the hypothesis that native and invasive species pools need to have a certain degree of differentiation in order to coexist in highly invaded communities [71]. Although both sampling sites displayed similar IAS richness, coastal areas were clearly more invaded, in line with previous studies in north-eastern Italy [45,72] as well as on a global scale [46]. The greater community invasibility in Site 2 may be explained by pulses of resources associated with reduced competition ('fluctuating resource theory', [73]) along with constant propagule pressure from adjacent environments subjected to anthropic disturbances, which might act as invasion epicenters.…”

“…In stress-prone ecosystems such as coastal dunes and saltmarshes, plant communities tolerate strong limiting factors (e.g., sand burial, salinity, and drought; [44,45]), which probably act as filter selecting only those IAS which are able to withstand them. As a consequence, the greater niche overlap observed in such stressful environments (both in terms of total overlap than of P N component) is not completely surprising, as well as the larger range of the CWMs (see for instance C, δ 13 C, and LMA), probably due to the mosaic of different habitats present in this site in a relatively restricted space, which often host rare and endemic species with peculiar functional attributes [82].…”

“…Coastal environments such as sand dunes are characterized by a steep ecological gradient in a relatively restricted space due to the presence of harsh abiotic conditions such as marine aerosol, sand blast, and lower levels of nutrients which strongly shape local plant communities [44]. In addition, coastal areas are experiencing high levels of invasion across the world [45,46]. Both sites are subjected to anthropogenic disturbances (e.g., tourism, proximity to urban areas), even though greater effects are observable in the coastal site.…”

Temperature-Dominated Driving Mechanisms of the Plant Diversity in Temperate Forests, Northeast China

“…Numerous models between climate and plant richness have been established, indicating that temperature and precipitation significantly affect richness patterns [23,30,31,55,71,86]. Strong positive relationships between the plant richness and the annual mean temperature were observed in our results.…”

Effect of Invasive Alien Species on the Co-Occurrence Patterns of Bryophytes and Vascular Plant Species—The Case of a Mediterranean Disturbed Sandy Coast

“…Invasive alien species (IAS) are recognized as an important threat to biodiversity worldwide [22] and especially in rare and extreme environments (such as alpine zone or isolated islands, [23][24][25]). On dune ecosystems, in particular, IAS alter the structure of native communities in different ways: reducing functional, phylogenetic and taxonomic diversities and excluding closely related and ecologically similar taxa [26][27][28][29][30].…”