Seascape genomics reveals population isolation in the reef-building honeycomb worm, Sabellaria alveolata (L.)

Abstract

Background: Under the threat of climate change populations can disperse, acclimatise or evolve in order to avoid fitness loss. In light of this, it is important to understand neutral gene flow patterns as a measure of dispersal potential, but also adaptive genetic variation as a measure of evolutionary potential. In order to assess genetic variation and how this relates to environment in the honeycomb worm (Sabellaria alveolata (L.)), a reef-building polychaete that supports high biodiversity, we carried out RAD sequencing using individuals from along its complete latitudinal range. Patterns of neutral population genetic structure were compared to larval dispersal as predicted by ocean circulation modelling, and outlier analyses and genotype-environment association tests were used to attempt to identify loci under selection in relation to local temperature data. Results: We genotyped 482 filtered SNPs, from 68 individuals across nine sites, 27 of which were identified as outliers using BAYESCAN and ARLEQUIN. All outlier loci were potentially under balancing selection, despite previous evidence of local adaptation in the system. Limited gene flow was observed among reef-sites (F ST = 0.28 ± 0.10), in line with the low dispersal potential identified by the larval dispersal models. The North Atlantic reef emerged as a distinct population and this was linked to high local larval retention and the effect of the North Atlantic Current on dispersal. Conclusions: As an isolated population, with limited potential for natural genetic or demographic augmentation from other reefs, the North Atlantic site warrants conservation attention in order to preserve not only this species, but above all the crucial functional ecological roles that are associated with their bioconstructions. Our study highlights the utility of using seascape genomics to identify populations of conservation concern.

Specific niche requirements underpin multidecadal range edge stability, but may introduce barriers for climate change adaptation

“…These populations are perhaps even more vulnerable because they are likely to be genetically isolated. Population genetic analysis, whilst based on a single population from Galway Bay, shows that S. alveolata from Ireland are genetically differentiated from other European and North African populations (Muir et al., 2020). Genetic structure at the regional scale around Ireland has not yet been evaluated for this species, but hydrodynamic modelling studies suggest that barriers to dispersal could exist, most likely due to tidal fronts (Robins et al., 2013), restricting connectivity among discrete populations.…”

Applying landscape metrics to species distribution model predictions to characterize internal range structure and associated changes

“…As Earth's climate rapidly changes, individuals of a species must move, acclimate, adapt or die. Range shifts are therefore key to species persistence (Muir et al, 2020). Beyond range size and boundaries, internal range structure metrics are needed to adequately | 643 describe species' ranges and more accurately quantify how they will be affected in the future (Csergő et al, 2020), particularly for species with discontinuous distributions.…”

Population genetic and genomic approaches for the management of the blackfoot paua, Haliotis iris Gmelin 1791, within the genus context

“…Barriers to gene flow for many marine species have been detected using neutral markers (Wei et al, 2013;Schiavina et al, 2014;Silva et al, 2016;Silva & Gardner, 2016;Diopere et al, 2018;Singh et al, 2018). On the other hand, a higher number of significant associations are found between adaptive genetic variability and environmental variability that determines in situ natural selection on populations (Diopere et al, 2018;Muir et al, 2020;Boulanger et al, 2022;Papa et al, 2022). The relationship between environment and target species may be assessed via quick seascape genomics protocols and considered when managing the target species and/or marine resources within the marine community over time.…”