Matching genetics with oceanography: directional gene flow in a Mediterranean fish species

Genetic connectivity and geographic fragmentation are two opposing mechanisms determining the population structure of species. While the first homogenizes the genetic background across populations the second one allows their differentiation. Therefore, knowledge of processes affecting dispersal of marine organisms is crucial to understand their genetic distribution patterns and for the effective management of their populations. In this study, we use genetic analyses of eleven microsatellites in combination with oceanographic satellite and dispersal simulation data to determine distribution patterns for Serranus cabrilla, a ubiquitous demersal broadcast spawner, in the Mediterranean Sea. Pairwise population F_ST values ranged between ?0.003 and 0.135. Two genetically distinct clusters were identified, with a clear division located between the oceanographic discontinuities at the Ibiza Channel (IC) and the Almeria‐Oran Front (AOF), revealing an admixed population in between. The Balearic Front (BF) also appeared to dictate population structure. Directional gene flow on the Spanish coast was observed as S. cabrilla dispersed from west to east over the AOF, from north to south on the IC and from south of the IC towards the Balearic Islands. Correlations between genetic and oceanographic data were highly significant. Seasonal changes in current patterns and the relationship between ocean circulation patterns and spawning season may also play an important role in population structure around oceanographic fronts.     

Evidence of connectivity between continental and differentiated insular populations in a highly mobile species

Aim Genetically differentiated insular populations are candidates for independent units for conservation. However, occasional immigration to reduced island populations may occur and potentially have important consequences in their future viability and evolutionary potential. In this study, we investigate the conservation implications of population structure and connectivity of insular and continental populations of a migratory raptor as determined using genetic tools and satellite tracking. Location Western European populations in the Iberian Peninsula and two insular populations in the Mediterranean Sea (Balearic Islands) and Atlantic Ocean (Canary Islands). Methods We genotyped 22 microsatellite loci in 96 Egyptian vultures (Neophron percnopterus) from the Iberian Peninsula, 36 from Menorca (Balearic archipelago) and 242 (85% of the current population) from Fuerteventura (Canary Islands). We analysed genetic variation to estimate structure, gene flow, genetic diversity, effective size and recent demographic history of the populations. Additionally, 19 vultures were marked with satellite transmitters to track their migration routes. Results Insular populations were genetically differentiated from those of the mainland. We detected immigration in the insular populations and within the continental counterpart. We found similar levels of genetic variability between the continent and the islands, and a bottleneck analysis indicated recent sharp population declines in both archipelagos but not on the continent. Main conclusions Our study provides evidence that, in spite of significant differentiation, insular populations of highly mobile species may remain connected with the mainland. Conservation programmes should take into account population connectivity and integrate differentiated units of management within complex units of conservation that can best maintain processes and potential for evolutionary change.     

Multilocus Comparative Phylogeography of Two Aristeid Shrimps of High Commercial Interest (Aristeus antennatus and Aristaeomorpha foliacea) Reveals Different Responses to Past Environmental Changes

Phylogeographical studies can reveal hidden patterns in the evolutionary history of species. Comparative analyses of closely related species can further help disentangle the relative contributions of processes responsible for such patterns. In this work, the phylogeography of two aristeid species, Aristeus antennatus and Aristaeomorpha foliacea, was compared through multiple genetic markers. These marine shrimp species are of high commercial importance, and are exploited in the Mediterranean Sea (MED) and in Mozambique Channel (MOZ) where they occur in partial sympatry. Aristeus antennatus (N = 50) from Western and Eastern Mediterranean (WM and EM, respectively), Atlantic Ocean (AO) and MOZ, and Aristaeomorpha foliacea (N = 40) from WM, EM, MOZ North-Western Australia (AUS) were analyzed with two nuclear genes (PEPCK and NaK) and one mitochondrial (COI) gene. Within the study area differences were found between the two species in their phylogeographical patterns, suggesting distinct responses to environmental changes. Monophyly of Aristeus antennatus was found across its distributional range. This pattern contrasted by a deep evolutionary split within Aristaeomorpha foliacea where genetic diversity followed geography distinguishing MED-MOZ and AUS. We propose that the AUS lineage of A. foliacea warrants consideration as a distinct species, with consequent implications in systematics and resource management.     

Outlier SNP markers reveal fine‐scale genetic structuring across European hake populations (Merluccius merluccius)

Shallow population structure is generally reported for most marine fish and explained as a consequence of high dispersal, connectivity and large population size. Targeted gene analyses and more recently genome‐wide studies have challenged such view, suggesting that adaptive divergence might occur even when neutral markers provide genetic homogeneity across populations. Here, 381 SNPs located in transcribed regions were used to assess large‐ and fine‐scale population structure in the European hake (Merluccius merluccius), a widely distributed demersal species of high priority for the European fishery. Analysis of 850 individuals from 19 locations across the entire distribution range showed evidence for several outlier loci, with significantly higher resolving power. While 299 putatively neutral SNPs confirmed the genetic break between basins (F_CT = 0.016) and weak differentiation within basins, outlier loci revealed a dramatic divergence between Atlantic and Mediterranean populations (F_CT range 0.275–0.705) and fine‐scale significant population structure. Outlier loci separated North Sea and Northern Portugal populations from all other Atlantic samples and revealed a strong differentiation among Western, Central and Eastern Mediterranean geographical samples. Significant correlation of allele frequencies at outlier loci with seawater surface temperature and salinity supported the hypothesis that populations might be adapted to local conditions. Such evidence highlights the importance of integrating information from neutral and adaptive evolutionary patterns towards a better assessment of genetic diversity. Accordingly, the generated outlier SNP data could be used for tackling illegal practices in hake fishing and commercialization as well as to develop explicit spatial models for defining management units and stock boundaries.     

Climate variables explain neutral and adaptive variation within salmonid metapopulations: the importance of replication in landscape genetics

Understanding how environmental variation influences population genetic structure is important for conservation management because it can reveal how human stressors influence population connectivity, genetic diversity and persistence. We used riverscape genetics modelling to assess whether climatic and habitat variables were related to neutral and adaptive patterns of genetic differentiation (population‐specific and pairwise F_ST) within five metapopulations (79 populations, 4583 individuals) of steelhead trout (Oncorhynchus mykiss) in the Columbia River Basin, USA. Using 151 putatively neutral and 29 candidate adaptive SNP loci, we found that climate‐related variables (winter precipitation, summer maximum temperature, winter highest 5% flow events and summer mean flow) best explained neutral and adaptive patterns of genetic differentiation within metapopulations, suggesting that climatic variation likely influences both demography (neutral variation) and local adaptation (adaptive variation). However, we did not observe consistent relationships between climate variables and F_ST across all metapopulations, underscoring the need for replication when extrapolating results from one scale to another (e.g. basin‐wide to the metapopulation scale). Sensitivity analysis (leave‐one‐population‐out) revealed consistent relationships between climate variables and F_ST within three metapopulations; however, these patterns were not consistent in two metapopulations likely due to small sample sizes (N = 10). These results provide correlative evidence that climatic variation has shaped the genetic structure of steelhead populations and highlight the need for replication and sensitivity analyses in land and riverscape genetics.     

Echoes of a distant time: effects of historical processes on contemporary genetic patterns in Galaxias platei in Patagonia

Interpreting the genetic structure of a metapopulation as the outcome of gene flow over a variety of timescales is essential for the proper understanding of how changes in landscape affect biological connectivity. Here we contrast historical and contemporary connectivity in two metapopulations of the freshwater fish Galaxias platei in northern and southernmost Patagonia where paleolakes existed during the Holocene and Pleistocene, respectively. Contemporary gene flow was mostly high and asymmetrical in the northern system while extremely reduced in the southernmost system. Historical migration patterns were high and symmetric in the northern system and high and largely asymmetric in the southern system. Both systems showed a moderate structure with a clear pattern of isolation by distance (IBD). Effective population sizes were smaller in populations with low contemporary gene flow. An approximate Bayesian computation (ABC) approach suggests a late Holocene colonization of the lakes in the northern system and recent divergence of the populations from refugial populations from east and west of the Andes. For the southern system, the ABC approach reveals that some of the extant G. platei populations most likely derive from an ancestral population inhabiting a large Pleistocene paleolake while the rest derive from a higher‐altitude lake. Our results suggest that neither historical nor contemporary processes individually fully explain the observed structure and geneflow patterns and both are necessary for a proper understanding of the factors that affect diversity and its distribution. Our study highlights the importance of a temporal perspective on connectivity to analyse the diversity of spatially complex metapopulations.     

Comparative landscape genetics of pond‐breeding amphibians in Mediterranean temporal wetlands: The positive role of structural heterogeneity in promoting gene flow

Comparative landscape genetics studies can provide key information to implement cost‐effective conservation measures favouring a broad set of taxa. These studies are scarce, particularly in Mediterranean areas, which include diverse but threatened biological communities. Here, we focus on Mediterranean wetlands in central Iberia and perform a multi‐level, comparative study of two endemic pond‐breeding amphibians, a salamander (Pleurodeles waltl) and a toad (Pelobates cultripes). We genotyped 411 salamanders from 20 populations and 306 toads from 16 populations at 18 and 16 microsatellite loci, respectively, and identified major factors associated with population connectivity through the analysis of three sets of variables potentially affecting gene flow at increasingly finer levels of spatial resolution. Topographic, land use/cover, and remotely sensed vegetation/moisture indices were used to derive optimized resistance surfaces for the two species. We found contrasting patterns of genetic structure, with stronger, finer scale genetic differentiation in Pleurodeles waltl, and notable differences in the role of fine‐scale patterns of heterogeneity in vegetation cover and water content in shaping patterns of regional genetic structure in the two species. Overall, our results suggest a positive role of structural heterogeneity in population connectivity in pond‐breeding amphibians, with habitat patches of Mediterranean scrubland and open oak woodlands (“dehesas”) facilitating gene flow. Our study highlights the usefulness of remotely sensed continuous variables of land cover, vegetation and water content (e.g., NDVI, NDMI) in conservation‐oriented studies aimed at identifying major drivers of population connectivity.     

Range‐wide population structure of European sea bass Dicentrarchus labrax

The euryhaline European sea bass Dicentrarchus labrax L., inhabiting the coasts of the eastern Atlantic Ocean and Mediterranean Sea, has had many opportunities for differentiation throughout its large natural range. However, evidence for this has been incompletely documented geographically and with an insufficient number of markers. Therefore, its full range was sampled at 22 sites and individuals were genotyped with a suite of mapped markers, including 14 microsatellite loci (N = 536) and 46 neutral or gene‐linked single nucleotide polymorphisms (SNPs; N = 644). We confirm that the Atlantic and Mediterranean basins harbour two distinct lineages. Within the Atlantic Ocean no pattern was obvious based on the microsatellite and SNP genotypes, except for a subtle difference between South‐eastern and North‐eastern Atlantic sea bass attributed to limited introgression of alleles of Mediterranean origin. SNP genotypes of the Mediterranean lineage differentiated into three groups, probably under the influence of geographical isolation. The Western Mediterranean group showed genetic homogeneity without evidence for outlier loci. The Adriatic group appeared as a distinct unit. The Eastern Mediterranean group showed a longitudinal gradient of genotypes and most interestingly an outlier locus linked to the somatolactin gene. Overall, the spatial pattern fits those observed with other taxa of between‐basin segregation and within‐basin connectivity, which concurs well with the swimming capabilities of European sea bass. Evidence from a few outlier loci in this and other studies encourages further exploration of its regional connectivity and adaptive evolution.     

Structure and fragmentation of growling grass frog metapopulations

Metapopulations occur in fragmented landscapes, and consist of demographically-independent populations connected by dispersal. Nevertheless, anthropogenic habitat fragmentation may be fatal to metapopulations, as it disrupts dispersal and gene flow, and undermines the balance between population extinction and colonization. Understanding the extent to which particular land-use practices disrupt dispersal and gene flow is therefore crucial for conserving metapopulations. We examined the structure and fragmentation of metapopulations of the endangered growling grass frog (Litoria raniformis) in an urbanizing landscape in southern Australia. Population clustering analyses revealed three distinct genetic units, corresponding to the three wetland clusters sampled. Isolation-by-distance was apparent between populations, and genetic distance was significantly correlated with the presence of urban barriers between populations. Our study provides evidence that urbanization fragments metapopulations of L. raniformis. Managers of L. raniformis in urbanizing landscapes should seek to mitigate effects of urbanization on dispersal and gene flow.     

Asymmetrical gene flow of the recently delisted passerine black‐capped vireo (Vireo atricapilla) indicates source‐sink dynamics in central Texas

Habitat fragmentation can produce metapopulations or source‐sink systems in which dispersal in crucial for population maintenance. Our objective was to investigate connectivity among black‐capped vireo (Vireo atricapilla) populations in tandem with a demographic study (Biological Conservation, 2016, 203, 108–118) to elucidate if central Texas populations act as a source‐sink system. We genotyped 343 individuals at 12 microsatellite loci to elucidate the movement ecology of the black‐capped vireo in central Texas surrounding Fort Hood; the largest and most stable breeding population of black‐capped vireos inhabit Fort Hood. To gain insight into gene flow among populations, we analyzed genetic differentiation, migration rates, number of migrants, and parentage. We found statistically significant, but low levels of genetic differentiation among several populations, suggesting some limited restriction to gene flow. Across approaches to estimate migration, we found consistent evidence for asymmetrical movement from Fort Hood to the other central Texas sites consistent with source‐sink dynamics. Our results are complementary to black‐capped vireo demographic studies done in tandem showing that portions of Fort Hood are acting as a source population to smaller central Texas populations.     

New insights into the past and recent evolutionary history of the Corsican mouflon (Ovis gmelini musimon) to inform its conservation

Human-mediated species dispersal across the Mediterranean stretches back at least 10,000 years and has left an indelible stamp on present-day biodiversity. Believed to be a descendant of the Asiatic mouflon (Ovis gmelini gmelinii), the Corsican mouflon (O. g. musimon) was translocated during the Neolithic as ancestral livestock by humans migrating from the Fertile Crescent to the Western Mediterranean. Today, two geographically limited and disconnected populations can be found in Corsica. Whether they originated from distinct founders or one ancestral population that later split remains unknown, although such information is pivotal for the species’ management on the island. We genotyped 109 and 176 individuals at the Cytochrome-b gene and 16 loci of the microsatellite DNA, respectively, to gain insights into the natural history of the Corsican mouflon. We found evidence confirming that the Asiatic was the ancestor of the Corsican mouflon, which should thus be unvaryingly referred to as O. g. musimon, i.e. as a subspecies of the Asiatic mouflon. Haplotype divergence dating and the investigation of genetic structure highlighted a strong and ancient genetic differentiation between the two Corsican populations. Approximate Bayesian Computation pointed to the introduction of a single group of founders as the most reliable scenario for the origin of the entire Corsican population. Later, this ancestral stock would have decreased in number, facing genetic bottlenecks and eventually resulting in two divergent demes. Splitting most likely occurred several hundred years ago. Their shared past notwithstanding, we discuss whether the two relic Corsican mouflon populations should be now considered as distinct management units.

     

Microsatellite loci confirm a lack of population connectivity among globally distributed populations of the tope shark Galeorhinus galeus (Triakidae)

This study used 11 polymorphic nuclear microsatellite loci to determine the population connectivity of five geographically isolated populations of tope shark Galeorhinus galeus (Africa, Australia, North America, South America and western Europe). Genetic analyses revealed significant structure among all populations indicating a lack of population connectivity. These findings indicate that globally distributed populations of G. galeus are isolated and should be managed as distinct, independent stocks.     

Genetic consequences of past climate and human impact on eastern Mediterranean <Emphasis Type="Italic">Cedrus libani</Emphasis> forests. Implications for their conservation

Summary This study demonstrates the impact of natural factors and human activities on biodiversity at gene level on a keystone Mediterranean forest ecosystem species. We monitored the within and among population gene diversity of Cedrus libani, a forest tree species of the Eastern Mediterranean mountains. We used paternally inherited chloroplast microsatellites (57 haplotypes) and bi-parentally inherited isozymes (12 loci) to estimate allelic richness, heterozygosity, and differentiation in 18 natural and 1 planted populations from Turkey and Lebanon. We showed that there is a phylogeographic structure in C. libani, and that forests from Lebanon and Turkey constitute two genetically isolated groups which probably arose from distinct refugia after the last Quaternary glacial cycle. We found extensive gene flow and relatively low differentiation in Turkey, as well as little evidence of genetic drift within populations. However, one population we analyzed, which was planted more than 20 centuries ago, and is isolated from core populations in Turkey, demonstrated extremely low genetic diversity and deserves high conservation priority. In contrast, we found low gene flow, high differentiation and severe cases of genetic drift in Lebanon. As forests there are the remnants of millennia-long extensive deforestation, all deserve high conservation priority.     

Congruent population structure inferred from dispersal behaviour and intensive genetic surveys of the threatened Florida scrub-jay (Aphelocoma coerulescens)

The delimitation of populations, defined as groups of individuals linked by gene flow, is possible by the analysis of genetic markers and also by spatial models based on dispersal probabilities across a landscape. We combined these two complimentary methods to define the spatial pattern of genetic structure among remaining populations of the threatened Florida scrub-jay, a species for which dispersal ability is unusually well-characterized. The range-wide population was intensively censused in the 1990s, and a metapopulation model defined population boundaries based on predicted dispersal-mediated demographic connectivity. We subjected genotypes from more than 1000 individual jays screened at 20 microsatellite loci to two Bayesian clustering methods. We describe a consensus method for identifying common features across many replicated clustering runs. Ten genetically differentiated groups exist across the present-day range of the Florida scrub-jay. These groups are largely consistent with the dispersal-defined metapopulations, which assume very limited dispersal ability. Some genetic groups comprise more than one metapopulation, likely because these genetically similar metapopulations were sundered only recently by habitat alteration. The combined reconstructions of population structure based on genetics and dispersal-mediated demographic connectivity provide a robust depiction of the current genetic and demographic organization of this species, reflecting past and present levels of dispersal among occupied habitat patches. The differentiation of populations into 10 genetic groups adds urgency to management efforts aimed at preserving what remains of genetic variation in this dwindling species, by maintaining viable populations of all genetically differentiated and geographically isolated populations.     

Differential introgression from a sister species explains high FST outlier loci within a mussel species

Scanning genomes for loci with high levels of population differentiation has become a standard of population genetics. F_ST outlier loci are most often interpreted as signatures of local selection, but outliers might arise for many other reasons too often left unexplored. Here, we tried to identify further the history and genetic basis underlying strong differentiation at F_ST outlier loci in a marine mussel. A genome scan of genetic differentiation has been conducted between Atlantic and Mediterranean populations of Mytilus galloprovincialis. The differentiation was low overall (F_ST = 0.03), but seven loci (2%) were strong F_ST outliers. We then analysed DNA sequence polymorphism at two outlier loci. The genetic structure proved to be the consequence of differential introgression of alleles from the sister‐hybridizing species Mytilus edulis. Surprisingly, the Mediterranean population was the most introgressed at these two loci, although the contact zone between the two species is nowadays localized along the Atlantic coasts of France and the British Isles. A historical contact between M. edulis and Mediterranean M. galloprovincialis should have happened during glacial periods. It proved difficult to disentangle two hypotheses: (i) introgression was adaptive, implying edulis alleles have been favoured in Mediterranean populations, or (ii) the genetic architecture of the barrier to edulis gene flow is different between the two M. galloprovincialis backgrounds. Five of the seven outliers between M. galloprovincialis populations were also outliers between M. edulis and Atlantic M. galloprovincialis, which would support the latter hypothesis. Differential introgression across semi‐permeable barriers to gene flow is a neglected scenario to interpret outlying loci that may prove more widespread than anticipated.     

Distribution patterns of the Q and B biotypes of Bemisia tabaci in the Mediterranean Basin based on microsatellite variation

At least five of the biotypes described in the Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) complex are known to be present in the Mediterranean Basin area. Only two of them, however, are economically relevant, that is, biotypes B and Q. Biological and genetic differences between the two biotypes have been well studied, but less is known about their patterns of genetic variation and population structure. To address these issues, a study was undertaken based on variation at six microsatellite loci among a subset of nine B. tabaci populations (five belonging to the Q and four to the B biotype). The data obtained show that (i) these loci showed considerable polymorphism in the Q and B biotypes populations although the presence of null alleles can obscure the picture; (ii) the Iberian‐Q, Canarian‐Q, and Egyptian‐B populations exhibit heterozygosity excess as a result of bottleneck events; (iii) the low genetic differentiation between the Israeli, Iberian Peninsula, and Italian populations suggest that these populations share a common gene pool; (iv) the genetic distances between the Canarian‐Q population and the geographically close population from Morocco indicates spatial isolation and a limited gene flow; and finally (v) the microsatellite data for the B populations indicate that the whiteflies from Egypt and Israel have a close phylogenetic relationship, but the source of these biotype B invasions into the Mediterranean area remains unknown.     

Linking local movement and molecular analysis to explore philopatry and population connectivity of the southern stingray Hypanus americanus

Limited data pertaining to life history and population connectivity of the data-deficient southern stingray (Hypanus americanus) are available. To determine potential vulnerabilities of their populations, this study aimed to analyse their movement patterns and genetic variability. A population of southern stingrays encompassing nine sites around Cape Eleuthera, the Bahamas, has been monitored using mark-recapture, spanning a 2.5 year period. Out of 200 individual stingrays, more than a third were encountered again. The home range of the females appears to be restricted, which supports the notion of high site residency. As resident populations of stingrays could suffer from a lack of population connectivity and be predestined for genetic isolation and local extirpation, this study further investigated the genetic connectivity of four sample sites in the central and western Bahamas. A haplotype analysis from the mitochondrial D-loop region showed that no distinct population structure strictly correlated with the sample site. These findings were complemented by five microsatellite loci that revealed high degrees in genotypic variability and little population differentiation. The results suggest gene flow mediated by both males and females.     

Upwelling and eddies affect connectivity among local populations of the goldeye rockfish,Sebastes thompsoni (Pisces,Scorpaenoidei)

The goldeye rockfish, Sebastes thompsoni, commercial rockfish catch in the Northwest Pacific Ocean, may influence its population structure. To clarify the population genetic structure of Korean S. thompsoni and its degree of hybridization with the most close species, Sebastes joyneri, we analyzed a mitochondrial (mt) DNA control region and eleven polymorphic microsatellite (ms) loci. S. joyneri individuals were clearly distinguished from S. thompsoni by the mtDNA control region and ms loci results, with single interspecific hybridization between two species suggesting no impact on genetic structure of S. thompsoni. Analysis of mtDNA revealed no population structure within S. thompsoni, suggesting the survival of a single population in southern refugia during the glacial period. The ms loci results, in contrast, showed two genetically distinct clusters within S. thompsoni: One was predominant throughout Korean coasts (from the Yellow Sea, via the Korea Strait to the East Sea); the other was predominant at Dokdo Island in the East Sea; and both occurred in similar ratios at Wangdolcho Reef in the East Sea. A possible factor that restricts gene flow between Korean coastal and offshore populations in the East Sea may be related to the complex oceanic current patterns such as eddies and upwelling, which represent impermeable barriers to population connectivity for this species. Our findings highlight that these two populations might be representative of two separate stock within Korean waters and maintain their geographically related genetic structure.     

Genetic diversity and population structure in the Barrens Topminnow (<Emphasis Type="Italic">Fundulus julisia</Emphasis>): implications for conservation and management of a critically endangered species

The Barrens Topminnow (Fundulus julisia) has undergone a rapid and dramatic decline. In the 1980s, at least twenty localities with Barrens Topminnows were known to exist in the Barrens Plateau region of middle Tennessee; currently only three areas with natural (not stocked) populations remain. The long-term survival of the Barrens Topminnow will depend entirely on effective management and conservation efforts. Captive propagation and stocking of captive-reared juveniles to suitable habitats have successfully established a handful of self-sustaining populations. However, very little is known about the genetic composition of source and introduced populations including levels of genetic diversity and structuring of genetic variation. Here we use both mitochondrial sequence data and genotypes from 14 microsatellite loci to examine patterns of genetic variation among ten sites, including all sites with natural populations and a subset of sites with introduced (stocked) populations of this species. Mitochondrial sequence analysis reveals extremely low levels of variation within populations and fixed differences between drainages. Microsatellite genotype data shows higher levels of genetic variability and a molecular signature consistent with a recent history of population bottlenecks. Measures of genetic diversity at microsatellite loci including allelic richness are similar within source and introduced populations. Bayesian assignment tests and analysis of molecular variation (AMOVA) support two distinct populations, consistent with drainage boundaries. Results from AMOVA analysis also suggest low levels of genetic connectivity between isolated populations within the same drainage. Here we propose two distinct evolutionary significant units (ESUs) and two management units that reflect this population substructure and warrant consideration in future management efforts.     

Population genomics meet Lagrangian simulations: Oceanographic patterns and long larval duration ensure connectivity among Paracentrotus lividus populations in the Adriatic and Ionian seas

Connectivity between populations influences both their dynamics and the genetic structuring of species. In this study, we explored connectivity patterns of a marine species with long‐distance dispersal, the edible common sea urchin Paracentrotus lividus, focusing mainly on the Adriatic–Ionian basins (Central Mediterranean). We applied a multidisciplinary approach integrating population genomics, based on 1,122 single nucleotide polymorphisms (SNPs) obtained from 2b‐RAD in 275 samples, with Lagrangian simulations performed with a biophysical model of larval dispersal. We detected genetic homogeneity among eight population samples collected in the focal Adriatic–Ionian area, whereas weak but significant differentiation was found with respect to two samples from the Western Mediterranean (France and Tunisia). This result was not affected by the few putative outlier loci identified in our dataset. Lagrangian simulations found a significant potential for larval exchange among the eight Adriatic–Ionian locations, supporting the hypothesis of connectivity of P. lividus populations in this area. A peculiar pattern emerged from the comparison of our results with those obtained from published P. lividus cytochrome b (cytb) sequences, the latter revealing genetic differentiation in the same geographic area despite a smaller sample size and a lower power to detect differences. The comparison with studies conducted using nuclear markers on other species with similar pelagic larval durations in the same Adriatic–Ionian locations indicates species‐specific differences in genetic connectivity patterns and warns against generalizing single‐species results to the entire community of rocky shore habitats.