Connectivity of sponge grounds in the deep sea: genetic diversity, gene
flow and oceanographic pathways in the fan-shaped sponge Phakellia
ventilabrum in the northeast Atlantic
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.