Shared and distinct patterns of genetic structure in two sympatric large decapods

Abstract

Aim: Comparing genetic structure in species with shared spatial ranges and ecological niches can help identify how dissimilar aspects of biology can shape differences in population connectivity. Similarly, where species are widely distributed across heterogeneous environments and major topographic barriers, knowledge of the structuring of populations can help reveal the impacts of factors which limit dispersal and/or drive divergence, aiding conservation management.Location: European seas of the northeast Atlantic and Mediterranean.Taxa: European clawed lobster (Homarus gammarus) and European crawfish (Palinurus elephas), two sympatric, heavily fished decapods with extensive dispersal potential.Methods: By RAD-sequencing 214 H. gammarus from 32 locations and 349 P. elephas from 15 locations, we isolated 6340 and 7681 SNP loci, respectively. Using these data to characterise contemporary population structuring, we investigate potential spatial and environmental drivers of genomic heterogeneity. Results:We found higher levels of differentiation among clawed lobsters than crawfish, both globally and within basins, and demonstrate where known hydrographic and topographic barriers generate shared patterns of divergence, such as a genetic break between the Atlantic and Mediterranean basins. Genetic structure not common to both species is principally apparent in the Atlantic portions of their range, where clawed lobster exhibits a genetic cline and increased differentiation towards range margins, while crawfish appear effectively panmictic throughout this region. Main Conclusions:We attribute the comparative lack of crawfish population structuring to their greater dispersal tendencies via a longer pelagic larval duration and sporadic adult movements. In contrast, genetic connectivity in clawed lobster is relatively restricted, with the correlation of site of origin and temperature to geographical heterogeneity at many divergent loci indicative of both neutral and adaptive processes.Our results help inform how contemporary management can account for likely demographic connectivity and marry the conservation of genomic variation with sustainable fisheries in these ecologically and economically important crustaceans.

Rare, long‐distance dispersal underpins genetic connectivity in the pink sea fan, Eunicella verrucosa

“…This suggests that between‐basin genetic differentiation may be driven by the same processes (i.e. stepping stone connectivity) occurring across the broader range of E. verrucosa rather than an oceanic barrier to gene flow, as is the case for several other species distributed across this region (Ellis et al., 2023 ; Patarnello et al., 2007 ; Riesgo et al., 2019 ). This aligns with differentiation detected in the DAPC (Figure 2a ), which showed the Tarragona population to cluster most closely with samples from Portuguese sites.…”

“…Isolated populations, for example, may rely on immigration from adjacent or distant populations to maintain a stable population size (demographic connectivity), or to introduce genetic diversity into a population via gene flow (genetic connectivity), which can mitigate the effects of genetic drift and inbreeding (Gagnaire et al, 2015;Lowe & Allendorf, 2010). The degree of genetic connectivity among benthic marine species' populations varies and can depend on the length of time that a species' larvae remain viable in the water column, a period known as the Pelagic Larval Duration (PLD) (Ellis et al, 2023;Weersing & Toonen, 2009).…”

“…Isolated populations, for example, may rely on immigration from adjacent or distant populations to maintain a stable population size (demographic connectivity), or to introduce genetic diversity into a population via gene flow (genetic connectivity), which can mitigate the effects of genetic drift and inbreeding (Gagnaire et al., 2015 ; Lowe & Allendorf, 2010 ). The degree of genetic connectivity among benthic marine species' populations varies and can depend on the length of time that a species' larvae remain viable in the water column, a period known as the Pelagic Larval Duration (PLD) (Ellis et al., 2023 ; Weersing & Toonen, 2009 ). In addition, a myriad of other factors including evolutionary history (such as re‐establishment from post‐glacial refugia (Jenkins, Castilho, et al., 2018 ), oceanographic barriers (Johannesson et al., 2018 ; Patarnello et al., 2007 ) and selection (Benestan et al., 2016 ; Lehnert et al., 2018 ) can shape genetic structure within marine taxa.…”

Ocean connectivity and habitat characteristics predict population genetic structure of seagrass in an extreme tropical setting

“…These concordances imply that oceanographic settings can have profound consequences on gene flow in seagrass, as has been documented in other studies (e.g., Jahnke et al, 2018; Ruiz‐Montoya et al, 2015). Populations may be geographically close to each other but could still be genetically isolated if the oceanographic setting prevents dispersal (e.g., Coolen et al, 2020; Jahnke et al, 2019); or geographically distant populations can be highly connected if currents facilitate dispersal among them (e.g., Ellis et al, 2023).…”

“…At a small spatial scale, within the dispersal range of the organism and in a system with multidirectional currents, a stepping‐stone model of dispersal, in which gene flow is limited only by geographic distance, is not likely to occur, as observed in the coral, Acropora spicifera , Houtman Abrolhos Islands (Thomas et al, 2015) and the whelk, Kelletia kelletii , Santa Barbara Channel (White et al, 2010). In contrast, the significant effect of geographic distance in limiting gene flow is often found at a larger spatial scale in marine systems, for example, in a series of local populations current along the coast (Couceiro et al, 2007; Ellis et al, 2023; Thiel & Haye, 2006).…”