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Mediterranean Bioconstructions Along the Italian Coast 93

investigate marine connectivity (Kool et al., 2012). Dispersal models repre-
sent a valid methodological approach to identify patterns of potential con-
nectivity among marine bioconstructions. Recently, a dispersal model
driven by satellite mapping of ocean currents was developed to evaluate
the potential connectivity between coralligenous assemblages of the central
Mediterranean Sea (Ingrosso et al., 2017a; Fig. 9). The model was param-
etrized using the distribution of coralligenous formations in different marine
subregions (Fig. 9A) along with information on the dispersal capacity of the
Mediterranean scleractinian coral C. caespitosa, as a typical coralligenous bio-
constructor species. The model proved to be efficient in summarizing some
important features of the coralligenous network: high internal connectivity
was detected in the Eastern-Central Tyrrhenian, South Adriatic and Sardinia
Sea, whereas, considering the amount of propagule exchanged among
marine zones, the Strait of Sicily and the Northern Tyrrhenian Sea were
the main sink and source sites, respectively. The South-Eastern Tyrrhenian
Sea emerged as a critical stepping stone area within the general connectivity
network (Fig. 9C), on the contrary the North Adriatic Sea was the most iso-
lated and poorly connected. These preliminary results were just indicative
and must be confirmed by in situ genetic data.

3.2.3 β-Diversity of Bioconstructions
β-Diversity, the spatial turnover of species composition across latitudinal and
environmental gradients, was first introduced to formally link local (α)to
regional (γ) species richness (Whittaker, 1960). β-Diversity can be seen as
the contribution to regional species richness that comes from spatial hetero-
geneity within the same habitat or from species accumulation across habitats.
This concept is receiving increasing interest because it captures fundamental
processes that maintain biodiversity at multiple scales. For example, at local
scales, β-diversity may be promoted by habitat specialization and strong
biotic interactions, whereas, at larger scales, such as along environmental
and latitudinal gradients, β-diversity may reflect habitat filtering and dispersal
limitation (Anderson et al., 2011; Gaston et al., 2007a,b; Kraft et al., 2011;
Myers et al., 2013; Tuomisto et al., 2003).
β-Diversity also offers insights into how species assemblages respond to
anthropogenic influences (Socolar et al., 2016). Habitat fragmentation, spe-
cies introductions and the establishment of protected areas may increase or
decrease β-diversity depending on the prevalence of processes that enhance
or reduce variation in species composition among sites. For example, human
interventions that increase species connectivity, such as the provision of