Geographic distance, water circulation and environmental conditions shape the biodiversity of Mediterranean rocky coasts

Abstract

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-

Nestedness and turnover unveil inverse spatial patterns of compositional and functional β‐diversity at varying depth in marine benthos

“…This is not surprising since the assemblages at the two depths shared about the 70% of species and dispersal potential should be very similar. Connectivity by currents at different depths, in addition, has been found to be quite correlated with turnover in species composition of marine benthos in the study area (Rattray et al, ). However, neither turnover nor the nestedness‐resultant component of functional dissimilarity correlated with geographic distance between islands at the two depths, suggesting little effect of connectivity potential on functional trait configuration of assemblages.…”

“…The assessment of spatial heterogeneity in species composition in the region of interest may assist the process of siting and spacing of marine reserves, in order to insure complementarity and increase inclusiveness of regional biodiversity in protected sites (Hewitt, Thrush, Halliday, & Duffy, 2005;Neigel, 2003). Also, modelling β-diversity in relation to geographic distance or connection by currents is essential to identify relevant scales of variation in community similarity and, thus, to plan networks of marine reserves that could maximize the potential for ecological connectivity (Rattray et al, 2016;Thrush et al, 2010;Watson et al, 2011).…”

Genomic evidence for global ocean plankton biogeography shaped by large-scale current systems

“…The travel time matrix we produced (measured in years) is available as Supplementary Table 15. Standard minimum geographic distance without traversing land 56 is available as Supplementary Table 16.…”

The spatial network structure of intertidal meiofaunal communities derived from environmental DNA metabarcoding surveys in Northwest Iberia

“…Pairwise geographic distances between sampling stations were calculated with a least-cost path approach, by using land areas (masked using the European Environment Agency coastline polygon 1:100000) as a barrier in distance calculations. This method allows for a more realistic evaluation of the effective spatial separation than the more commonly used Great Circle or Euclidean distances due to the complex geometry of coastlines in the study area (Rattray et al, 2016). We also considered the estuary affiliation to account for the estuary-level effects in determining the correlation structure among sampling stations.…”