Marco Malavasi

Multifaceted Analysis of Patch-Level Plant Diversity in Response to Landscape Spatial Pattern and History on Mediterranean Dunes

Landscape structure is known to critically affect biodiversity. However, although the multi-facetted character of biodiversity is widely recognized, few studies have linked landscape spatial pattern and history simultaneously to multiple facets (taxonomic, functional, and phylogenetic) and spatial components (α, β, and γ) of plant diversity. We set out to reveal whether landscape parameters have specific effects on the separate diversity facets and components of plant diversity at a patch scale on coastal dune landscapes of Central Italy. For each landscape patch, we computed a set of patch-based metrics relying on multi-temporal land-cover maps. Based on a database of plant community plots, on functional traits from field measurements and on a dated phylogenetic tree, we calculated taxonomic (TD), functional (FD), and phylogenetic diversity (PD) within each patch at α, β, and γ level. Diversity measures were then related to the landscape metrics via linear mixed-effect models. Landscape pattern and transformations affected TD only moderately in coastal dune ecosystems. We found much stronger and contrasted effects on FD and PD. FD increased in patches surrounded by human-dominated habitats; PD was higher in fragmented patches, particularly in the Mediterranean macchia. Moreover, landscape pattern affected differently the single communities, the turnover among communities and the pool of species within the patch (α, β, and γ components). Our results call for the combined inclusion of FD and PD and their partitions into ecological analyses, being TD too crude to capture the comprehensive and contrasted response of plant diversity to landscape spatial pattern.

Multiple drivers of plant diversity on coastal dunes: A Mediterranean experience

In light of the global biodiversity loss, syntheses of the available knowledge about drivers of biodiversity are becoming increasingly important. However, despite the high number of studies analyzing patterns of plant species diversity, few attempts have been made to synthesize findings within different ecosystems. In this work, the relative role of a wide set of predictors imputable to three conceptual-methodological domains (abiotic, human-mediated disturbance and landscape domain, hereafter AD, DD and LD) was simultaneously analyzed in 644 random plots distributed along the coastal dunes of Central Italy. Native species richness and focal species cover, both field-recorded, were used as response variables. Predictors pertaining to the three domains were derived from both field surveys and high-resolution remotely sensed imagery (LiDAR and orthophotos). To test how AD, DD and LD affect native species richness and focal species cover, a GLM and a linear model were fitted respectively. The three domains were then ranked according to their relative importance. Although the role of the three domains was always significant, they turned out to unequally contribute to the explanation of native species richness and focal species cover patterns. For Mediterranean coastal dune ecosystems, AD appears to be the key biodiversity driver, followed by DD and LD. Our results suggest that as long as human disturbance is limited, plant diversity will distribute according to species abiotic tolerances, regardless of habitat loss and fragmentation per se. Representing a first effort towards a synthesis of plant diversity drivers in coastal dunes, this work points to the importance, in Mediterranean coastal dune ecosystems, of zonation dynamics, whose occurrence should be addressed as a priority issue by efficient conservations strategies.

Applying diversity metrics to plastic litter ‘communities’: a first explorative and comparative analysis

In this explorative study we applied a set of uni- and bi-variate diversity metrics (α-diversity, Whittaker β-diversity, γ-diversity, Whittaker plot) to two sampled ‘communities’ of anthropogenic beach litter. Meso-litter represented the ‘species’ with the highest number of items. Comparing the two sampled sites, we observed different values in total number of items, in α-, β- and γ-diversity and in the shape of Whittaker plot: we think that these results might have implication for assessing the impact of marine litter and the necessary operation measures aimed to its removal: (i) the higher is the amount of litter, the higher the effort in its removal, (ii) the higher is the α- and γ-diversity, the higher the number of tools and equipment to differentiate it, (iii) Shannon index, evenness and β-diversity provide interesting information on, respectively, diversity of sources, their frequency distribution and turnover, so implying different impacts on specific sensitive targets in different sites and the necessity of oriented operational actions. Moreover, the higher is the β-diversity, the higher the heterogeneity of litter with implication on a possible change of resources and equipment involved. Although we highlighted some caveat in the use and misuse of diversity metrics in beach litter management, we suggest further application of these indices to beach litter ‘communities’ to build a general conceptual framework in this sense.