No abstract

Little is known about dispersal in deep-sea sponges, yet understanding patterns of gene flow and connectivity is essential for their effective management. Given rising pressure from harmful anthropogenic activities, schemes that manage resource extraction whilst conserving species diversity are increasingly necessary. Here, we used ddRADseq derived SNPs to investigate the genetic diversity and connectivity for the deep-sea sponge Phakellia ventilabrum across the northeast Atlantic Ocean (from the Cantabrian Sea to Norway). The analysis of 166 individuals collected from 57 sampling stations were grouped into 17 different areas, including two MPAs, one SAC and other areas with different levels of protection. The 4,017 neutral SNPs we uncovered indicated high connectivity and panmixis amongst the majority of areas, spanning a ca. 2,500-kilometre range and depths of 99–900 m. This was likely due to the presence of strong ocean currents aiding larval transport, as supported by our migration analysis and also by 3D particle tracking modelling using information on the reproductive cycle of P. ventilabrum. We also observed significant genetic similarity between samples from the Cantabrian Sea and Roscoff (France) as compared to the remainder of the collection areas, likely arising from physical drivers such as prevailing current circulation patterns and topographic features, acting as barriers for gene flow. Despite this, our results suggest that all protected areas studied are well connected with each other. The relatively low genetic diversity observed in all areas, though, highlights the potential fragility of this species to changing climates, which might compromise resilience to future threats.

No abstract

Little is known about dispersal in deep-sea ecosystems, especially for sponges, which are abundant ecosystem engineers. Understanding patterns of gene flow in deep-sea sponges is essential, especially in areas where rising pressure from anthropogenic activities makes difficult to combine management and conservation. Here, we combined population genomics and oceanographic modelling to understand how Northeast Atlantic populations (Cantabrian Sea to Norway) of the deep-sea sponge Phakellia ventilabrum are connected. The analysis comprised ddRADseq derived SNP datasets of 166 individuals collected from 57 sampling stations from 17 different areas, including two Marine Protected Areas, one Special Area of Conservation and other areas with different levels of protection. The 4,017 neutral SNPs used indicated high connectivity and panmixis amongst the majority of areas (Ireland to Norway), spanning ca. 2,500-km at depths of 99–900 m. This was likely due to the presence of strong ocean currents allowing long-distance larval transport, as supported by our migration analysis and by 3D particle tracking modelling. On the contrary, the Cantabrian Sea and Roscoff (France) samples, the southernmost areas in our study, appeared disconnected from the remaining areas, probably due to prevailing current circulation patterns and topographic features, which might be acting as barriers for gene flow. Despite this major genetic break, our results suggest that all protected areas studied are well-connected with each other. Interestingly, analysis of SNPs under selection replicated results obtained for neutral SNPs. The relatively low genetic diversity observed along the study area, though, highlights the potential fragility of this species to changing climates, which might compromise resilience to future threats.