Climate‐driven trends and ecological implications of event‐scale upwelling in the California Current System

Eastern boundary current systems are among the most productive and lucrative ecosystems on Earth because they benefit from upwelling currents. Upwelling currents subsidize the base of the coastal food web by bringing deep, cold and nutrient‐rich water to the surface. As upwelling is driven by large‐scale atmospheric patterns, global climate change has the potential to affect a wide range of significant ecological processes through changes in water chemistry, water temperature, and the transport processes that influence species dispersal and recruitment. We examined long‐term trends in the frequency, duration, and strength of continuous upwelling events for the Oregon and California regions of the California Current System in the eastern Pacific Ocean. We then associated event‐scale upwelling with up to 21 years of barnacle and mussel recruitment, and water temperature data measured at rocky intertidal field sites along the Oregon coast. Our analyses suggest that upwelling events are changing in ways that are consistent with climate change predictions: upwelling events are becoming less frequent, stronger, and longer in duration. In addition, upwelling events have a quasi‐instantaneous and cumulative effect on rocky intertidal water temperatures, with longer events leading to colder temperatures. Longer, more persistent upwelling events were negatively associated with barnacle recruitment but positively associated with mussel recruitment. However, since barnacles facilitate mussel recruitment by providing attachment sites, increased upwelling persistence could have indirect negative impacts on mussel populations. Overall, our results indicate that changes in coastal upwelling that are consistent with climate change predictions are altering the tempo and the mode of environmental forcing in near‐shore ecosystems, with potentially severe and discontinuous ramifications for ecosystem structure and functioning.     

Kinship analyses identify fish dispersal events on a temperate coastline

Connectivity is crucial for the persistence and resilience of marine species, the establishment of networks of marine protected areas and the delineation of fishery management units. In the marine environment, understanding connectivity is still a major challenge, due to the technical difficulties of tracking larvae. Recently, parentage analysis has provided a means to address this question effectively. To be effective, this method requires limited adult movement and extensive sampling of parents, which is often not possible for marine species. An alternative approach that is less sensitive to constraints in parental movement and sampling could be the reconstruction of sibships. Here, we directly measure connectivity and larval dispersal in a temperate marine ecosystem through both analytical approaches. We use data from 178 single nucleotide polymorphism markers to perform parentage and sibship reconstruction of the black-faced blenny (Tripterygion delaisi) from an open coastline in the Mediterranean Sea. Parentage analysis revealed a decrease in dispersal success in the focal area over 1 km distance and approximately 6.5% of the juveniles were identified as self-recruits. Sibship reconstruction analysis found that, in general, full siblings did not recruit together to the same location, and that the largest distance between recruitment locations was much higher (11.5 km) than found for parent–offspring pairs (1.2 km). Direct measurements of dispersal are essential to understanding connectivity patterns in different marine habitats, and show the degree of self-replenishment and sustainability of populations of marine organisms. We demonstrate that sibship reconstruction allows direct measurements of dispersal and family structure in marine species while being more easily applied in those species for which the collection of the parental population is difficult or unfeasible.     

Patterns and persistence of larval retention and connectivity in a marine fish metapopulation

Connectivity, the demographic linking of local populations through the dispersal of individuals, is one of the most poorly understood processes in population dynamics, yet has profound implications for conservation and harvest strategies. For marine species with pelagic larvae, direct estimation of connectivity remains logistically challenging and has mostly been limited to single snapshots in time. Here, we document seasonal and interannual patterns of larval dispersal in a metapopulation of the coral reef fish Amphiprion polymnus. A 3‐year record of larval trajectories within and among nine discrete local populations from an area of approximately 35 km was established by determining the natal origin of settled juveniles through DNA parentage analysis. We found that spatial patterns of both self‐recruitment and connectivity were remarkably consistent over time, with a low level of self‐recruitment at the scale of individual sites. Connectivity among sites was common and multidirectional in all years and was not significantly influenced by seasonal variability of predominant surface current directions. However, approximately 75% of the sampled juveniles could not be assigned to parents within the study area, indicating high levels of immigrations from sources outside the study area. The data support predictions that the magnitude and temporal stability of larval connectivity decreases significantly with increasing distance between subpopulations, but increases with the size of subpopulations. Given the considerable effort needed to directly measure larval exchange, the consistent patterns suggest snapshot parentage analyses can provide useful dispersal estimates to inform spatial management decisions.     

Biogeographic structure of the northeastern Pacific rocky intertidal: the role of upwelling and dispersal to drive patterns

Identifying the environmental conditions that drive biogeographic structure remains a major challenge of biogeography, evolutionary ecology and increasingly, conservation biology. Here, we use multivariate classification trees to assess the biogeographic structure of northeast Pacific (～ 26–58°N) rocky intertidal species (406 species of algae and invertebrates) from 102 field sites. Random forest analyses are used to assess the importance of 29 environmental variables, encompassing a broad range of potential drivers, to predict biogeographic structure. Analyses are repeated for species with different larval dispersal capabilities and by broad taxonomic categories (invertebrates and algae). Results show that overall biogeographic structure is in general agreement with classic classification schemes, but patterns are variable among species with different larval dispersal capabilities. Random forest models show a very high fit (pseudo r² > 0.94) and indicate that biogeographic structure can be predicted by a relatively modest subset of variables. Upwelling related variables are the best overall predictors of biogeographic structure (nutrient concentrations, sea‐surface temperature, upwelling/downwelling seasonal switch index), but the relative importance of predictors is geographically variable and top predictors are dependent on the type of larval dispersal. Upwelling related variables are more important to predict biogeographic structure for invertebrates with lower‐medium dispersal capabilities and algae, whereas species with high larval dispersal (planktotrophic) are better predicted by a different subset of variables (i.e. salinity, precipitation seasonality). Our results lend support to the influence of coastal upwelling in structuring biogeographic patterns and highlight the potential for climate change‐induced alterations of upwelling regimes to profoundly affect biodiversity at biogeographic scales.     

Mesoscale advection of Upogebia pusilla larvae through an upwelling filament in the Canaries Coastal Transition Zone (CTZ)

Larval transport has a strong influence on marine populations and ecosystem function. Traditional hypotheses establish that larvae of coastal species are swept offshore during strong upwelling periods producing low recruitment rates; however, recent studies have demonstrated that this hypothesis is not supported by larval distribution data. The present study examines the influence of upwelling filaments on larval advection and wastage. During August 1993, the transport of Upogebia pusilla was analysed in relation to an offshore filament off Northwest Africa. This mesoscale structure was generated by a trapped, quasi-permanent cyclonic eddy located between the Canary Islands and the African shelf and extended 150?km westward into the oligotrophic open ocean waters. The horizontal distribution depicted by U. pusilla larvae was strongly influenced by the oceanographic features of the Canaries Coastal Transition Zone (CTZ). Specifically, the larvae were closely associated with upwelling front and filament position, showing that these neritic larvae can be advected 10–100s of kilometres offshore through the filament. However, the low larval densities observed in the samples suggest that many larvae might remain close to the coast, thus avoiding seaward transport. This implies that filaments probably do not significantly affect the recruitment success of intertidal invertebrates such us U. pusilla in upwelling systems.     

Large‐scale,multidirectional larval connectivity among coral reef fish populations in the Great Barrier Reef Marine Park

Larval dispersal is the key process by which populations of most marine fishes and invertebrates are connected and replenished. Advances in larval tagging and genetics have enhanced our capacity to track larval dispersal, assess scales of population connectivity, and quantify larval exchange among no‐take marine reserves and fished areas. Recent studies have found that reserves can be a significant source of recruits for populations up to 40 km away, but the scale and direction of larval connectivity across larger seascapes remain unknown. Here, we apply genetic parentage analysis to investigate larval dispersal patterns for two exploited coral reef groupers (Plectropomus maculatus and Plectropomus leopardus) within and among three clusters of reefs separated by 60–220 km within the Great Barrier Reef Marine Park, Australia. A total of 69 juvenile P. maculatus and 17 juvenile P. leopardus (representing 6% and 9% of the total juveniles sampled, respectively) were genetically assigned to parent individuals on reefs within the study area. We identified both short‐distance larval dispersal within regions (200 m to 50 km) and long‐distance, multidirectional dispersal of up to ~250 km among regions. Dispersal strength declined significantly with distance, with best‐fit dispersal kernels estimating median dispersal distances of ~110 km for P. maculatus and ~190 km for P. leopardus. Larval exchange among reefs demonstrates that established reserves form a highly connected network and contribute larvae for the replenishment of fished reefs at multiple spatial scales. Our findings highlight the potential for long‐distance dispersal in an important group of reef fishes, and provide further evidence that effectively protected reserves can yield recruitment and sustainability benefits for exploited fish populations.     

Genetic population structure of the endemic fourline wrasse (Larabicus quadrilineatus) suggests limited larval dispersal distances in the Red Sea

The connectivity among marine populations is determined by the dispersal capabilities of adults as well as their eggs and larvae. Dispersal distances and directions have a profound effect on gene flow and genetic differentiation within species. Genetic homogeneity over large areas is a common feature of coral reef fishes and can reflect high dispersal capability resulting in high levels of gene flow. If fish larvae return to their parental reef, gene flow would be restricted and genetic differentiation could occur. Larabicus quadrilineatus (Labridae) is considered as an endemic fish species of the Red Sea and Gulf of Aden. The juveniles of this species are cleaner fish that feed on ectoparasites of other fishes. Here, we investigated the genetic population structure and gene flow in L. quadrilineatus among five locations in the Red Sea to infer connectivity among them. To estimate genetic diversity, we analysed 369 bp of 237 mitochondrial DNA control region sequences. Haplotype and nucleotide diversities were higher in the southern than in the northern Red Sea. Analysis of molecular variance (amova) detected the highest significant genetic variation between northern and central/southern populations (Phi(CT) = 0.01; P < 0.001). Migration analysis revealed a several fold higher northward than southward migration, which could be explained by oceanographic conditions and spawning season. Even though the Phi(ST) value of 0.01 is rather low and implies a long larval dispersal distance, estimates based on the isolation-by-distance model show a very low mean larval dispersal distance (0.44-5.1 km) compared to other studies. In order to enable a sustainable ornamental fishery on the fourline wrasse, the results of this study suggest that populations in the northern and southern Red Sea should be managed separately as two different stocks. The rather low larval dispersal distance of about 5 km needs to be considered in the design of marine protected areas to enable connectivity and self-seeding.     

Spatial and temporal patterns of larval dispersal in a coral‐reef fish metapopulation: evidence of variable reproductive success

Many marine organisms can be transported hundreds of kilometres during their pelagic larval stage, yet little is known about spatial and temporal patterns of larval dispersal. Although traditional population‐genetic tools can be applied to infer movement of larvae on an evolutionary timescale, large effective population sizes and high rates of gene flow present serious challenges to documenting dispersal patterns over shorter, ecologically relevant, timescales. Here, we address these challenges by combining direct parentage analysis and indirect genetic analyses over a 4‐year period to document spatial and temporal patterns of larval dispersal in a common coral‐reef fish: the bicolour damselfish (Stegastes partitus). At four island locations surrounding Exuma Sound, Bahamas, including a long‐established marine reserve, we collected 3278 individuals and genotyped them at 10 microsatellite loci. Using Bayesian parentage analysis, we identified eight parent‐offspring pairs, thereby directly documenting dispersal distances ranging from 0 km (i.e., self‐recruitment) to 129 km (i.e., larval connectivity). Despite documenting substantial dispersal and gene flow between islands, we observed more self‐recruitment events than expected if the larvae were drawn from a common, well‐mixed pool (i.e., a completely open population). Additionally, we detected both spatial and temporal variation in signatures of sweepstakes and Wahlund effects. The high variance in reproductive success (i.e., ‘sweepstakes’) we observed may be influenced by seasonal mesoscale gyres present in the Exuma Sound, which play a prominent role in shaping local oceanographic patterns. This study documents the complex nature of larval dispersal in a coral‐reef fish, and highlights the importance of sampling multiple cohorts and coupling both direct and indirect genetic methods in order disentangle patterns of dispersal, gene flow and variable reproductive success.     

USING ISOLATION BY DISTANCE AND EFFECTIVE DENSITY TO ESTIMATE DISPERSAL SCALES IN ANEMONEFISH

Robust estimates of dispersal are critical for understanding population dynamics and local adaptation, as well as for successful spatial management. Genetic isolation by distance patterns hold clues to dispersal, but understanding these patterns quantitatively has been complicated by uncertainty in effective density. In this study, we genotyped populations of a coral reef fish (Amphiprion clarkii) at 13 microsatellite loci to uncover fine‐scale isolation by distance patterns in two replicate transects. Temporal changes in allele frequencies between generations suggested that effective densities in these populations are 4–21 adults/km. A separate estimate from census densities suggested that effective densities may be as high as 82–178 adults/km. Applying these effective densities with isolation by distance theory suggested that larval dispersal kernels in A. clarkii had a spread near 11 km (4–27 km). These kernels predicted low fractions of self‐recruitment in continuous habitats, but the same kernels were consistent with previously reported, high self‐recruitment fractions (40–60%) when realistic levels of habitat patchiness were considered. Our results suggested that ecologically relevant larval dispersal can be estimated with widely available genetic methods when effective density is measured carefully through cohort sampling and ecological censuses, and that self‐recruitment studies should be interpreted in light of habitat patchiness.     

Larval Connectivity and the International Management of Fisheries

Predicting the oceanic dispersal of planktonic larvae that connect scattered marine animal populations is difficult, yet crucial for management of species whose movements transcend international boundaries. Using multi-scale biophysical modeling techniques coupled with empirical estimates of larval behavior and gamete production, we predict and empirically verify spatio-temporal patterns of larval supply and describe the Caribbean-wide pattern of larval connectivity for the Caribbean spiny lobster (Panulirus argus), an iconic coral reef species whose commercial value approaches $1 billion USD annually. Our results provide long sought information needed for international cooperation in the management of marine resources by identifying lobster larval connectivity and dispersal pathways throughout the Caribbean. Moreover, we outline how large-scale fishery management could explicitly recognize metapopulation structure by considering larval transport dynamics and pelagic larval sanctuaries.     

Sharp genetic breaks among populations of Haptosquilla pulchella (Stomatopoda) indicate limits to larval transport: patterns, causes, and consequences

To help stem the precipitous decline of coral reef ecosystems world-wide, conservation efforts are focused on establishing interconnected reserve networks to protect threatened populations. Because many coral reef organisms have a planktonic or pelagic larval dispersal phase, it is critical to understand the patterns of ecological connectivity between reserve populations that result from larval dispersal. We used genetics to infer dispersal patterns among 24 Indo-West Pacific populations of the mantis shrimp, Haptosquilla pulchella. Contrary to predictions of high dispersal facilitated by the strong currents of the Indonesian throughflow, mitochondrial DNA sequences from 393 individuals displayed striking patterns of regional genetic differentiation concordant with ocean basins isolated during periods of lowered sea level. Patterns of genetic structuring indicate that although dispersal within geographical regions with semicontiguous coastlines spanning thousands of kilometres may be common, ecologically meaningful connections can be rare among populations separated by as little as 300 km of open ocean. Strong genetic mosaics in a species with high dispersal potential highlight the utility of genetics for identifying regional patterns of genetic connectivity between marine populations and show that the assumption that ocean currents will provide ecological connectivity among marine populations must be empirically tested in the design of marine reserve networks.     

Genetic isolation by distance among populations of the netted dog whelk Nassarius reticulatus (L.) along the European Atlantic coastline

Estimates of the average distances by which marine larvae disperse are generally poorly described, despite the central role that larval dispersal plays in the demographic connectivity of populations across geographic space. Here, we describe the population genetic structure and average dispersal distance of the netted dog whelk Nassarius reticulatus (L.) (Mollusca, Gastropoda, Prosobranchia), a widespread member of European intertidal communities, using DNA sequence variation in a fragment of the mitochondrial gene cytochrome c oxidase subunit I (COI). An analysis of 156 individuals from 6 locations spread across approximately 1700 km of the European Atlantic coastline revealed weak and nonsignificant population structure (overall Phi(ST) = 0.00013). However, pairwise Phi(ST) values revealed a slight but significant increase in genetic isolation with geographic distance (IBD), suggesting that populations are not panmictic across the sampled geographic range. If we assume that the isolation by distance is maintained by a stable, stepping stone model of gene flow, then the slope of the IBD is consistent with an average larval dispersal distance of approximately 70 km per generation. The spatial scale of larval dispersal in N. reticulatus is consistent with the life cycle of the species (planktotrophic veliger lasting 30-60 days before competent to settle). A mismatch analysis of the COI sequences revealed a signature of an ancient demographic expansion that began 61 500-160,000 years ago, well before the most recent Pleistocene glaciation event. The greatest levels of genetic diversity occur within the middle latitudes of the whelk's geographic range, consistent with the notion that historic populations of N. reticulatus might have expanded northward and southward from the centrally located Bay of Biscay.     

Larval connectivity in an effective network of marine protected areas

Acceptance of marine protected areas (MPAs) as fishery and conservation tools has been hampered by lack of direct evidence that MPAs successfully seed unprotected areas with larvae of targeted species. For the first time, we present direct evidence of large-scale population connectivity within an existing and effective network of MPAs. A new parentage analysis identified four parent-offspring pairs from a large, exploited population of the coral-reef fish Zebrasoma flavescens in Hawai'i, revealing larval dispersal distances ranging from 15 to 184 km. In two cases, successful dispersal was from an MPA to unprotected sites. Given high adult abundances, the documentation of any parent-offspring pairs demonstrates that ecologically-relevant larval connectivity between reefs is substantial. All offspring settled at sites to the north of where they were spawned. Satellite altimetry and oceanographic models from relevant time periods indicated a cyclonic eddy that created prevailing northward currents between sites where parents and offspring were found. These findings empirically demonstrate the effectiveness of MPAs as useful conservation and management tools and further highlight the importance of coupling oceanographic, genetic, and ecological data to predict, validate and quantify larval connectivity among marine populations.     

Genetic Diversity and Local Connectivity in the Mediterranean Red Gorgonian Coral after Mass Mortality Events

Estimating the patterns of connectivity in marine taxa with planktonic dispersive stages is a challenging but crucial task because of its conservation implications. The red gorgonian Paramuricea clavata is a habitat forming species, characterized by short larval dispersal and high reproductive output, but low recruitment. In the recent past, the species was impacted by mass mortality events caused by increased water temperatures in summer. In the present study, we used 9 microsatellites to investigate the genetic structure and connectivity in the highly threatened populations from the Ligurian Sea (NW Mediterranean). No evidence for a recent bottleneck neither decreased genetic diversity in sites impacted by mass mortality events were found. Significant IBD pattern and high global F_ST confirmed low larval dispersal capability in the red gorgonian. The maximum dispersal distance was estimated at 20–60 km. Larval exchange between sites separated by hundreds of meters and between different depths was detected at each site, supporting the hypothesis that deeper subpopulations unaffected by surface warming peaks may provide larvae for shallower ones, enabling recovery after climatically induced mortality events.     

Predicting reef fish connectivity from biogeographic patterns and larval dispersal modelling to inform the development of marine reserve networks

Developing networks of no-take marine reserves is often hindered by uncertainty in the extent to which local marine populations are connected to one another through larval dispersal and recruitment (connectivity). While patterns of connectivity can be predicted by larval dispersal models and validated by empirical methods, biogeographic approaches have rarely been used to investigate connectivity at spatial scales relevant to reserve networks (10's–100's of km). Here, species assemblage patterns in coral reef fish were used together with an individual-based model of dispersal of reef fish larvae to infer patterns of connectivity in a ∼300 km wide region in the Philippines that included the Bohol Sea and adjacent bodies of water. A dominant current flows through the study region, which may facilitate connectivity among >100 no-take reserves. Connectivity was first investigated by analysing data on the presence/absence of 216 species of reef fish and habitat variables across 61 sites. Hierarchical clustering of sites reflecting species assemblage patterns distinguished a major group of sites in the Bohol Sea (Bray–Curtis similarity >70%) from sites situated in adjacent bodies of water (bays, channels between islands and a local sea). The grouping of sites could be partly explained by a combination of degree of embayment, % cover of sand and % cover of rubble (Spearman rank correlation, ρ_w = 0.42). The individual-based model simulated dispersal of reef fish larvae monthly for three consecutive years in the region. The results of simulations, using a range of pelagic larval durations (15–45 days), were consistent with the species assemblage patterns. Sites in the model that showed strongest potential connectivity corresponded to the majority of sites that comprised the Bohol Sea group suggested by hierarchical clustering. Most sites in the model that exhibited weak connectivity were groups of sites which had fish assemblages that were least similar to those in the Bohol Sea group. Concurrent findings from the two approaches suggest a strong influence of local oceanography and geography on broad spatial patterns of connectivity. The predictions can be used as an initial basis to organise existing reserves to form ecologically meaningful networks. This study showed that species assemblage patterns could be a viable supplementary indicator of connectivity if used together with predictions from a larval dispersal model and if the potential effect of habitat on the structuring of species assemblages is taken into consideration.     

Reduced genetic diversity and increased reproductive isolation follow population‐level loss of larval dispersal in a marine gastropod

Population‐level consequences of dispersal ability remain poorly understood, especially for marine animals in which dispersal is typically considered a species‐level trait governed by oceanographic transport of microscopic larvae. Transitions from dispersive (planktotrophic) to nondispersive, aplanktonic larvae are predicted to reduce connectivity, genetic diversity within populations, and the spatial scale at which reproductive isolation evolves. However, larval dimorphism within a species is rare, precluding population‐level tests. We show the sea slug Costasiella ocellifera expresses both larval morphs in Florida and the Caribbean, regions with divergent mitochondrial lineages. Planktotrophy predominated at 11 sites, 10 of which formed a highly connected and genetically diverse Caribbean metapopulation. Four populations expressed mainly aplanktonic development and had markedly reduced connectivity, and lower genetic diversity at one mitochondrial and six nuclear loci. Aplanktonic dams showed partial postzygotic isolation in most interpopulation crosses, regardless of genetic or geographic distance to the sire's source, suggesting that outbreeding depression affects fragmented populations. Dams from genetically isolated and neighboring populations also exhibited premating isolation, consistent with reinforcement contingent on historical interaction. By increasing self‐recruitment and genetic drift, the loss of dispersal may thus initiate a feedback loop resulting in the evolution of reproductive isolation over small spatial scales in the sea.     

Connectivity, sustainability, and yield: bridging the gap between conventional fisheries management and marine protected areas

A substantial shift toward use of marine protected areas (MPAs) for conservation and fisheries management is currently underway. This shift to explicit spatial management presents new challenges and uncertainties for ecologists and resource managers. In particular, the potential for MPAs to change population sustainability, fishery yield, and ecosystem properties depends on the poorly understood consequences of three critical forms of connectivity over space: larval dispersal, juvenile and adult swimming, and movement of fishermen. Conventional fishery management describes the dynamics and current status of fish populations, with increasing recent emphasis on sustainability, often through reference points that reflect individual replacement. These compare lifetime egg production (LEP) to a critical replacement threshold (CRT) whose value is uncertain. Sustainability of spatially distributed populations also depends on individual replacement, but through all possible paths created by larval dispersal and LEP at each location. Model calculations of spatial replacement considering larval connectivity alone indicate sustainability and yield depend on species dispersal distance and the distribution of LEP created by species habitat distribution and fishing mortality. Adding MPAs creates areas with high LEP, increasing sustainability, but not necessarily yield. Generally, short distance dispersers will persist in almost all MPAs, while sustainability of long distance dispersers requires a specific density of MPAs along the coast. The value of that density also depends on the uncertain CRT, as well as fishing rate. MPAs can increase yield in areas with previously low LEP but for short distance dispersers, high yields will require many small MPAs. The paucity of information on larval dispersal distances, especially in cases with strong advection, renders these projections uncertain. Adding juvenile and adult movement to these calculations reduces LEP near the edges in MPAs, if movement is within a home-range, but more broadly over space if movement is diffusive. Adding movement of fishermen shifts effort on the basis of anticipated revenues and fishing costs, leading to lower LEP near ports, for example. Our evolving understanding of connectivity in spatial management could form the basis for a new, spatially oriented replacement reference point for sustainability, with associated new uncertainties.     

Dispersal patterns of coastal fish: implications for designing networks of marine protected areas

Information about dispersal scales of fish at various life history stages is critical for successful design of networks of marine protected areas, but is lacking for most species and regions. Otolith chemistry provides an opportunity to investigate dispersal patterns at a number of life history stages. Our aim was to assess patterns of larval and post-settlement (i.e. between settlement and recruitment) dispersal at two different spatial scales in a Mediterranean coastal fish (i.e. white sea bream, Diplodus sargus sargus) using otolith chemistry. At a large spatial scale (～200 km) we investigated natal origin of fish and at a smaller scale (～30 km) we assessed "site fidelity" (i.e. post-settlement dispersal until recruitment). Larvae dispersed from three spawning areas, and a single spawning area supplied post-settlers (proxy of larval supply) to sites spread from 100 to 200 km of coastline. Post-settlement dispersal occurred within the scale examined of ～30 km, although about a third of post-settlers were recruits in the same sites where they settled. Connectivity was recorded both from a MPA to unprotected areas and vice versa. The approach adopted in the present study provides some of the first quantitative evidence of dispersal at both larval and post-settlement stages of a key species in Mediterranean rocky reefs. Similar data taken from a number of species are needed to effectively design both single marine protected areas and networks of marine protected areas.     

Rapid recovery of genetic diversity of stomatopod populations on Krakatau: temporal and spatial scales of marine larval dispersal

Although the recovery of terrestrial communities shattered by the massive eruption of Krakatau in 1883 has been well chronicled, the fate of marine populations has been largely ignored. We examined patterns of genetic diversity in populations of two coral reef-dwelling mantis shrimp, Haptosquilla pulchella and Haptosquilla glyptocercus (Stomatopoda: Protosquillidae), on the islands of Anak Krakatau and Rakata. Genetic surveys of mitochondrial cytochrome oxidase c (subunit 1) in these populations revealed remarkably high levels of haplotypic and nucleotide diversity that were comparable with undisturbed populations throughout the Indo-Pacific. Recolonization and rapid recovery of genetic diversity in the Krakatau populations indicates that larval dispersal from multiple and diverse source populations contributes substantially to the demographics of local populations over intermediate temporal (tens to hundreds of years) and spatial scales (tens to hundreds of kilometres). Natural experiments such as Krakatau provide an excellent mechanism to investigate marine larval dispersal and connectivity. Results from stomatopods indicate that marine reserves should be spaced no more than 50-100 km apart to facilitate ecological connectivity via larval dispersal.     

Highly Connected Populations and Temporal Stability in Allelic Frequencies of a Harvested Crab from the Southern Pacific Coast

For marine invertebrates with a benthic adult form and a planktonic larva phase, the connectivity among populations is mainly based on larval dispersal. While an extended larval phase will promote gene flow, other factors such as an intensive fishery and geographical barriers could lead to changes in genetic variability. In this study, the population genetic structure of the commercial crab Metacarcinus edwardsii was analyzed along 700 km of the Chilean coast. The analysis, based on eight microsatellite loci genotyped from megalopae and adult crabs, considered temporal and spatial patterns of genetic variation. The results showed no evidence of spatial patterns in genetic structure, suggesting high connectivity among the sampling sites. The temporal analysis showed no evidence of changes in allele frequencies and no evidence of a recent bottleneck. The lack of spatial structure and allele variation over time could be explained by the interaction of factors such as i) low reproductive variance due to the capability of females to store sperm in the seminal receptacle, which can be used for successive broods, ii) high larval dispersal and iii) high individual reproductive output. Using our data as priors, a genetic modelling approach coincided, predicting this temporal and spatial stability. The same analysis showed that a reduction in population size leads to the loss of genetic variability in populations, as well as of the genetic cohesiveness between populations, pointing out the importance management for species under exploitation, such as M. edwardsii.