Does current-driven dispersal explain local benthic diversity in the Mediterranean basin?

Local pattern of biodiversity depends on several factors. When examining the diversity of benthic species found on artificial substrates (initially free of life) that were deployed on the seabed, the colonization phase consists in the establishment of various species inhabiting different habitats from adjacent areas or from distant regions thanks to current-driven larval dispersal. This work focuses on the “colonization” step; we hypothesized that earlier colonization is mainly influenced by two interacting factors: the variety of habitats patches (both nearby the artificial structure as well as in remote locations) and the diversity of origins of colonists, which can be brought to the artificial structure by highly variable marine currents. When colonizers potentially come from a diversity of spatial origins, characterized by various habitats, species/genetic diversity is expected to be higher, everything else being equal. We tested this hypothesis in a pilot study in the NW Mediterranean coast, using Automated Reef Monitoring Structures (the structures to be colonized), photo-analyses (method to assess species diversity) and dispersal modelling combined with habitat map. The only results that presented a significant result in the present study ( p <0.05 ) was the Z-Score Shannon Index when considering the surveyed sites separately. Finally the present study suggests that that current-driven dispersal of propagules and habitat patchiness control to a certain degree the spatial structure of benthic populations. Other factors, such as local environmental conditions and trophic interactions, were discussed but neglected here despite the fact they could also play a role in the stabilisation of biodiversity patterns when the substrate is saturated with species.