Ecological connectivity is important for effective
marine planning and biodiversity conservation.
Our aim was to identify factors important in influencing
variation in benthic community structure on shallow
rocky reefs in 2 regions of the Mediterranean Sea with
contrasting oceanographic regimes. We assessed beta
(β) diversity at 146 sites in the littoral and shallow sublittoral
from the Adriatic/Ionian Seas (eastern region)
and Ligurian/Tyrrhenian Seas (western region) using a
null modelling approach to account for variation in species
richness. The distance decay relationship between
species turnover within each region and geographic
distance by sea was determined using generalised linear
models. Mantel tests were used to examine correlations
between β diversity and connectivity by ocean
currents, estimated from Lagrangian dispersal simulations.
Variation in β diversity between sites was partitioned
according to environmental and spatial components
using a distance-based redundancy approach.
Species turnover along a gradient of geographic distance
was greater by a factor of 3 to 5 in the western
region than the eastern region, suggesting lower connectivity
between sites. β diversity was correlated with
connectivity by ocean currents at both depths in the
eastern region but not in the western region. The influ-
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ence of spatial and environmental predictors of β diversity
varied considerably between regions, but was similar
between depths. Our results highlight the interaction
of oceanographic, spatial and environmental processes
influencing benthic marine β diversity. Persistent currents
in the eastern region may be responsible for lower
observed β diversity compared to the western region,
where patterns of water circulation are more variable.
