Seascape Genomics Reveals Metapopulation Connectivity Network of Paramuricea biscaya in the Northern Gulf of Mexico

Abstract

The degree of connectivity among populations influences their ability to respond to natural and anthropogenic stressors. In marine systems, determining the scale, rate, and directionality of larval dispersal is therefore, central to understanding how coral metapopulations are interconnected and the degree of resiliency in the event of a localized disturbance. Understanding these source-sink dynamics is essential to guide restoration efforts and for the study of ecology and evolution in the ocean. The patterns and mechanisms of connectivity in the deep-sea (>200 m deep) are largely understudied. In this study, we investigated the spatial diversity patterns and metapopulation connectivity of the octocoral Paramuricea biscaya throughout the northern Gulf of Mexico (GoM). Paramuricea biscaya is one of the most abundant corals on the lower continental slope (between 1,200 and 2,500 m) in the GoM. The 2010 Deepwater Horizon oil spill (DWH) directly impacted populations of this species and thus are considered primary targets for restoration. We used a combination of seascape genomic analyses, high-resolution ocean circulation modeling, and larval dispersal simulations to quantify the degree of population structuring and connectivity among P. biscaya populations. Evidence supports the hypotheses that the genetic diversity of P. biscaya is structured by depth, and that larval dispersal among connected populations is asymmetric due to dominant ocean circulation patterns. Our results suggest that there are intermediate unsampled populations in the central GoM that serve as stepping stones for dispersal. The data suggest that the DeSoto Canyon area, and possibly the West Florida Escarpment, critically act as sources of larvae for areas impacted by the DWH oil spill in the Mississippi Canyon. This work illustrates that the management of deep-sea marine protected areas should incorporate knowledge of connectivity networks and depth-dependent processes throughout the water column.

Phylogeography of Paramuricea: The Role of Depth and Water Mass in the Evolution and Distribution of Deep-Sea Corals

“…biscaya, respectively. Lineage 1 was generally found deeper (mean depth 1,896 m) than lineage 2 (mean depth 1,454 m); however, these lineages co-occur at some intermediate-depth sites and 15% of assessed specimens had an admixed ancestry (see Figure 1 in Galaska et al, 2021). Interestingly, the morphology of the specimens examined in this study differs between these two lineages, with P. aff.…”

“…The need for robust species delimitation analyses is exemplified by a recent population genomic study of P. biscaya in the Gulf of Mexico, which utilized some of the same samples herein (Galaska et al, 2021). Based on >12K SNPs, Galaska et al (2021) found two lineages of P. biscaya, lineage 1 and lineage 2, represented in our study as P. cf. biscaya and P. aff.…”

“…Therefore, we likely included SNPs associated with conserved regions. In contrast, Galaska et al (2021) had three times as many SNPs from five times more specimens in just two sister lineages. Further investigation is needed to distinguish the degree of admixture from incomplete lineage sorting and elucidate the divergence process between these two groups.…”

“…Following Doughty et al (2014), Radice et al (2016) suggested that water masses are important conduits for promoting dispersal within depth bands while limiting dispersal across depth, a conclusion that is also supported by population genetic and larval dispersal studies of other North Atlantic species (e.g., Quattrini et al, 2015b;Bracco et al, 2019;Kenchington et al, 2019). More recently, seascape genomics (Galaska et al, 2021) and larval dispersal models demonstrated that populations of Paramuricea in the Gulf of Mexico are structured across depth; however, this structuring was observed within the same water mass (i.e., primarily North Atlantic Deep Water, > 1000 m). Paramuricea is an exemplar system to understand how oceanographic and other environmental conditions, both past and present, have influenced the diversification and distribution of deep-sea corals.…”

“…and explore the origin and diversification of species inhabiting the deep North Atlantic Ocean. Numerous studies have shown the effectiveness of RAD-Seq in differentiating populations and species and resolving phylogenetic relationships among closely-related species that have recently and/or rapidly diverged (Reitzel et al, 2013;Herrera et al, 2015;Herrera and Shank, 2016;Bracco et al, 2019;Quattrini et al, 2019;Galaska et al, 2021). We then used divergence dating, ancestral state reconstruction, and a dispersalextirpation-cladogenesis model to illuminate the biogeographic history of this genus.…”