Cyst Distribution and Hatching Pattern of Chirocephalus ruffoi (Crustacea,Anostraca) in an Experimental Undisturbed Pool

The pattern of cyst distribution in the absence of turbation and their hatching behaviour were studied in an outdoor artificial pool, where just differentiated adults of the anostracan Chirocephalus ruffoi (sex ratio 1:3) lived until it dried up. The horizontal and vertical distributions of cysts in the pool bed were determined. The comparison between cyst bank estimate (Mura , 2004) and the actual number of cysts counted in the pool bed revealed an estimate error of 20.9%. Resting eggs occurred only in the upper 2.5 cm thick soil sections and decreased within this section as depth increased. Peripheral areas of the pool contained significantly larger numbers of cysts than the central area. Multiway analysis on the results recorded in hatching success (nested ANOVA) revealed that the differences were significantly affected by initial soil conditions, treatment and vertical distribution of cysts. Among these factors, vertical distribution (sections nested in cores) was the most influential. Hatching success was significantly inversely related to depth. Differences in the timing of hatching depending on the above considered factors were also noted. A nearly synchronous hatching pattern was observed only for cysts from initially dry sediment of the uppermost layers. In all successively deeper layers, hatching showed multiple peaks and was increasingly delayed and erratic (already mentioned). ANCOVA within each of the experimental conditions revealed significant differences in hatching frequencies (time as covariate) depending on sediment depth. Within any given layer, ANCOVA revealed a significant influence of initial sediment conditions and treatment on the timing of hatching. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The adenosine triphosphate content of cysts of Globodera pallida and G. rostochiensis as a possible quantitative estimate of field populations

A rapid method is described for estimating the number of juveniles of Globodera pallida and G. rostochiensis in cysts collected from field soils. The technique uses a photometer to measure the adenosine triphosphate (ATP) content of the cysts by bioluminescence. Results for ten to twelve soil samples of 100 g taken from each of four fields showed that the number of juveniles that emerged when the samples were placed in potato root diffusate was significantly related to ATP content of a second series of cyst samples from these fields. Cysts from one field gave a higher ATP content per hatched juvenile than was recorded for the remaining three fields. There are several, untested, explanations of this discrepancy, but some evidence suggests that the hatching test and not the ATP method may have given an unreliable estimate of the viable egg content of cysts from this field. Further work may result in an enhanced precision and increased rapidity in estimating field populations of cyst nematodes by this technique.     

Structure and Functioning of the “Egg Bank” of a Fairy Shrimp in a Temporary Pool: Chirocephalus ruffoi from Pollino National Park (Southern Italy) as a Case Study

To investigate their distribution and total numbers, resting eggs of the anostracan Chirocephalus ruffoi were collected from the bed of a temporary pool in southern Italy. Samples were taken at 0.5 m intervals along six transects oriented at 30° from each other, by means of a cylindrical core sampler. The horizontal distribution of intact resting eggs was extremely patchy, with cyst number per core ranging from 191 to 1,400 (CV = 32.7%), corresponding to a mean of between 0.8 and 4.3 cysts cm⁻³. Differences observed were related to core position and transect orientation, total cyst numbers being markedly higher in the leeward area of the pool compared to the windward area. Marked variation was also evident in vertical distribution, a significant, though weak correlation was recorded between egg density and sediment depth. Cyst‐bank size (± 95% confidence limits) of the pool bed, estimated from the mean cyst number cm⁻³ obtained for the 6 transects, ranged between 1.0 × 10⁸ and 1.3 × 10⁸ cysts. Hatching in the laboratory was very erratic. Despite significant differences in hatching, the observed variation was unrelated to most of the variables considered (position within sections, cores and transects, pre‐incubation treatment) and was explained only by initial sediment conditions (moist/dry). In none of the experimental conditions tested was synchronous hatching obtained. Possible causal factors (mixing of the bottom sediments by cattle, egg age, storage conditions, differential exposure to environmental cues as well as variability in hatching response even at clutch level) are discussed. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Towards an optimal sampling strategy for Alexandrium catenella (Dinophyceae) benthic resting cysts

The study proposes methodological developments to optimize sampling strategy of resting cysts of Alexandrium catenella to estimate their abundance with a predefined error. This work also aims to provide information on spatial distribution of resting cysts in sediments. The distribution mode of A. catenella resting cysts related to the abundance variability was studied through sediment cores sampling on four different spatial scales and using Ludox CLX gradient density method. The quantification method underestimates by a factor of 2 the resting cysts abundance in one gram of sediment. Application of Taylor's power law allowed us to define a compromise between sampling effort and abundance estimation error. In the case of A. catenella resting cysts from Thau lagoon, the optimal sampling strategy consists of sampling 10 stations on a surface of 2 km² for a given coefficient of variability (C) of 15%, sampling 3 sediment cores at each station (C = 30%) and counting only one replicate by core (C = 18%). Results related to the application of Taylor's power law are closely dependent on resting cyst density and aggregation in a given sediment. In our area, A. catenella resting cysts are mainly observed in the upper 3 cm of sediment. Horizontally, their heterogeneity is lower on 10 cm² surface and tends to stabilize itself beyond a surface of 10 m². Each author has to carry out this pre-sampling effort for his own resting cysts-forming species, in his own area, in order to increase accuracy of resting cyst mapping.     

Spatial distribution of Heterodera trifolii in Chinese cabbage fields

Although Heterodera trifolii is commonly known as the clover cyst nematode, recently the nematode has been identified as a serious menace for Chinese cabbage growers in highland areas in Korea. Soil samples were collected from two Chinese cabbage fields highly infested with H. trifolii in highland areas of Korea, Jungsun and Samcheok, in 2014 and 2015, respectively. A total of 777 (2?×?2?m sampling area) and 414 (5?×?5?m area) soil samples were collected from Jungsun and Samcheok, respectively. The total cysts, cysts with eggs, number of eggs, and empty cysts were calculated for each sample. Distribution patterns for these variables were characterized using spatial analysis by distance indices (SADIE) and variogram model analysis. The aggregation index for cysts with eggs was higher in Jungsun (89.32) than Samcheok (3.63), which indicated that the cyst population density was higher. However, the spatial association of total cysts versus cysts with eggs was higher in Samcheok. The Gaussian model showed reasonable independent range of the nematode in Jungsun and Samcheok to be approximately 53.66?m and 48.54?m, respectively. The model suggested that each nematode sample should be taken at least 50?m apart in the given areas. Inclusion of this distribution pattern may significantly minimize the number of samples in future sampling methods, which could save time and labor, and initiate management practices by elucidating spatial variability factors that influence crop yield.     

QUANTITATIVE ANALYSIS OF VEGETATION AT THE RICHVALE VERNAL POOLS,CALIFORNIA

California vernal pools exhibit vegetation of mainly native, annual vascular plants that flower and set seed as standing water from the Mediterranean climate wet season evaporates. Deeper depressions often show concentric rings of color from the different species responding to progressive drying of the habitat. Vernal pool plant life was numerically analyzed in 1979 near Richvale, in the Sacramento Valley, by sampling in a regular grid pattern that covered both the pool and the adjacent annual grassland. Each species was measured once in all sample sites, all data were pooled and an importance value was determined for each of the 61 species. Species are discussed in relation to the high water line of a pool (maximum extent of standing water). Samples covering all regions of a plot showed there are “pool species” (e.g., Lasthenia fremontii) with nearly identical distributions almost totally within high water line. Four native species made up 75% of all the plants counted in the pool samples. In general, pool species had higher densities inside the high water line than the “non-pool species” had outside the high-water line. Non-pool species (e.g., Aira caryophyllea) tended to occur in the pool samples more than the pool species occurred outside the pool. Some species (e.g., Limnanthes alba) had roughly similar absolute and importance values for pool and non-pool areas; these were called “transition species,” and had less importance than either pool or non-pool species throughout the plots. The two study plots, 40 m apart, had similar rankings for the top pool, non-pool and transition species: importance of the species varied within each of these two neighboring pools.     

Physical characteristics influencing the utilization of pools by brown trout in an afforested catchment in Southern Ireland

Seasonal and spatial variation in brown trout Salmo trutta L. abundance, density and biomass were studied in 29 pools of varying size in an afforested catchment together with the physical characteristics of those pools. A movement of 0+ trout towards the pools as the year progresses was detected. Water volume of the pool accounted for a significant amount of the variation in metrics across all seasons. Cover provided by overhanging vegetation also explained a significant amount of variation, especially during the summer. Water velocity, percentage of undercut bank and substrate composition had little explanatory power in the distribution of trout in the pools. In all seasons significant relationships between both fish biomass (g m⁻²) and fish number and water volume in the pool were found. However, in summer and autumn there was also a significant correlation between both fish density (fish m⁻²) and biomass and water volume in the pool described by a power function with a coefficient >1. These relationships were consistent across the subset of pools studied over a 2-year period. Thus there was a proportionally greater number of fish in deeper pools than in the shallower ones in summer and autumn, suggesting that trout use the available habitat (i.e. the pool) as a three dimensional space in which an increase in the third dimension (depth) leads to a proportionally greater number of fish per unit area.     

Survey of aquatic macroinvertebrates and amphibians at Wupatki National Monument,Arizona, USA: An evaluation of selected factors affecting species richness in ephemeral pools

Ephemeral aquatic habitats in Wupatki National Monument vary from naturally formed pools in arroyos over 5000 years old, to constructed catchment basins with ages estimated at 60–1000+ years old, and borrow pits and stock ponds 30–60 years old. The different ages of these pools provide different histories of colonization by amphibians and aquatic invertebrates, especially temporary pool specialists such as spadefoot toads and branchiopod crustaceans. Ten pools of five different origins and ages were surveyed in August and/or September 1997 for aquatic organisms; a total of 13 surveys were conducted. Twenty-two taxa were found, with the number of species in a pool during any survey ranging from one to 10. Species composition of the communities changed from one sampling date to the next within individual pools. Community structure is an amalgam of species with different dispersal mechanisms that are influenced by different pool characteristics. Age appears to have little effect overall, but may have influenced branchiopod presence/absence. Distance to permanent water, frequency of disturbance, and current pool size were correlated with presence/absence of some species.     

Comparative Efficiency of the Fenwick Can and Schuiling Centrifuge in Extracting Nematode Cysts from Different Soil Types

The Fenwick can and Schuiling centrifuge are widely used to extract nematode cysts from soil samples. The comparative efficiencies of these two methods during cyst extraction have not been determined for different soil types under different cyst densities. Such information is vital for statutory laboratories that must choose a method for routine, high-throughput soil monitoring. In this study, samples of different soil types seeded with varying densities of potato cyst nematode (Globodera rostochiensis) cysts were processed using both methods. In one experiment, with 200 ml samples, recovery was similar between methods. In a second experiment with 500 ml samples, cyst recovery was higher using the Schuiling centrifuge. For each method and soil type, cyst extraction efficiency was similar across all densities tested. Extraction was efficient from pure sand (Fenwick 72%, Schuiling 84%) and naturally sandy soils (Fenwick 62%, Schuiling 73%), but was significantly less efficient from clay-soil (Fenwick 42%, Schuiling 44%) and peat-soil with high organic matter content (Fenwick 35%, Schuiling 33%). Residual moisture (<10% w/w) in samples prior to analyses reduced extraction efficiency, particularly for sand and sandy soils. For each soil type and method, there were significant linear relationships between the number of cysts extracted and the numbers of cysts in the samples. We discuss the advantages and disadvantages of each extraction method for cyst extraction in statutory soil laboratories.     

Spatial and temporal changes in ecosystem carbon pools following juniper encroachment and removal

Proliferation of woody plants is a predominant global land cover change of the past century, particularly in dryland ecosystems. Woody encroachment and its potential impacts (e.g., livestock forage, wildlife habitat, hydrological cycling) have led to widespread brush management. Although woody plants may have substantial impacts on soils, uncertainty remains regarding woody encroachment and brush management influences on carbon (C) pools. Surface C pools (shallow soils and litter) may be particularly dynamic in response to encroachment and brush management. However, we have limited understanding of spatiotemporal patterns of surface C responses or how surface pools respond relative to aboveground C, litter, roots, and deep soil organic C. Spatial variability and lack of basic ecological data in woody-encroached dryland ecosystems present challenges to filling this data gap. We assessed the impact of western juniper (Juniperus occidentalis) encroachment and removal on C pools in a semi-arid sagebrush ecosystem. We used spatially-intensive sampling to create sub-canopy estimates of surface soil C (0–10 cm depth) and litter C pools that consider variation in tree size/age and sub-canopy location for live juniper and around stumps that were cut 7 years prior to sampling. We coupled the present size distribution of junipers with extensive existing allometric information about juniper in this region to estimate how landscape-level C pools would change through time under future management and land cover scenarios. Juniper encroachment and removal leads to substantial changes in C pools. Best-fit models for surface soil and litter C included positive responses to shrub basal diameter and negative responses to increasing relative distance from the bole to dripline. Juniper removal led to a net loss of surface C as a function of large decreases in litter C and small increases in surface soil C. At the landscape scale, deep soil C was the largest C pool (77 Mg C ha^?1), with an apparent lack of sensitivity to management. Overall, encroachment led to substantial increases in C storage over time as juniper size increased (excluding deep soil C, ecosystem C pools increased from 13.5 to 30.2 Mg C ha^?1 with transition from sagebrush-dominated to present encroachment levels). The largest pool of accumulation was juniper aboveground C, with important other pools including juniper roots, litter, and surface soil C. Woody encroachment and subsequent brush management can have substantive impacts on ecosystem C pools, although our data suggest the spatiotemporal patterns of surface C pools need to be properly accounted for to capture C pool responses. Our approach of coupling spatially-intensive surface C information with shrub distribution and allometric data is an effective method for characterizing ecosystem C pools, offering an opportunity for filling in knowledge gaps regarding woody encroachment and brush management impacts on local-to-regional ecosystem C pools.     

Large Sample Area and Size Are Needed for Forest Soil Seed Bank Studies to Ensure Low Discrepancy with Standing Vegetation

A large number of small-sized samples invariably shows that woody species are absent from forest soil seed banks, leading to a large discrepancy with the seedling bank on the forest floor. We ask: 1) Does this conventional sampling strategy limit the detection of seeds of woody species? 2) Are large sample areas and sample sizes needed for higher recovery of seeds of woody species? We collected 100 samples that were 10 cm (length) ×10 cm (width) ×10 cm (depth), referred to as larger number of small-sized samples (LNSS) in a 1 ha forest plot, and placed them to germinate in a greenhouse, and collected 30 samples that were 1 m×1 m×10 cm, referred to as small number of large-sized samples (SNLS) and placed them (10 each) in a nearby secondary forest, shrub land and grass land. Only 15.7% of woody plant species of the forest stand were detected by the 100 LNSS, contrasting with 22.9%, 37.3% and 20.5% woody plant species being detected by SNLS in the secondary forest, shrub land and grassland, respectively. The increased number of species vs. sampled areas confirmed power-law relationships for forest stand, the LNSS and SNLS at all three recipient sites. Our results, although based on one forest, indicate that conventional LNSS did not yield a high percentage of detection for woody species, but SNLS strategy yielded a higher percentage of detection for woody species in the seed bank if samples were exposed to a better field germination environment. A 4 m² minimum sample area derived from power equations is larger than the sampled area in most studies in the literature. Increased sample size also is needed to obtain an increased sample area if the number of samples is to remain relatively low.     

Towards an optimal sampling strategy for Alexandrium catenella (Dinophyceae) benthic resting cysts

The study proposes methodological developments to optimize sampling strategy of resting cysts of Alexandrium catenella to estimate their abundance with a predefined error. This work also aims to provide information on spatial distribution of resting cysts in sediments. The distribution mode of A. catenella resting cysts related to the abundance variability was studied through sediment cores sampling on four different spatial scales and using Ludox CLX gradient density method. The quantification method underestimates by a factor of 2 the resting cysts abundance in one gram of sediment. Application of Taylor's power law allowed us to define a compromise between sampling effort and abundance estimation error. In the case of A. catenella resting cysts from Thau lagoon, the optimal sampling strategy consists of sampling 10 stations on a surface of 2 km² for a given coefficient of variability (C) of 15%, sampling 3 sediment cores at each station (C = 30%) and counting only one replicate by core (C = 18%). Results related to the application of Taylor's power law are closely dependent on resting cyst density and aggregation in a given sediment. In our area, A. catenella resting cysts are mainly observed in the upper 3 cm of sediment. Horizontally, their heterogeneity is lower on 10 cm² surface and tends to stabilize itself beyond a surface of 10 m². Each author has to carry out this pre-sampling effort for his own resting cysts-forming species, in his own area, in order to increase accuracy of resting cyst mapping.     

Estimation of population allele frequencies from next‐generation sequencing data: pool‐versus individual‐based genotyping

Molecular markers produced by next‐generation sequencing (NGS) technologies are revolutionizing genetic research. However, the costs of analysing large numbers of individual genomes remain prohibitive for most population genetics studies. Here, we present results based on mathematical derivations showing that, under many realistic experimental designs, NGS of DNA pools from diploid individuals allows to estimate the allele frequencies at single nucleotide polymorphisms (SNPs) with at least the same accuracy as individual‐based analyses, for considerably lower library construction and sequencing efforts. These findings remain true when taking into account the possibility of substantially unequal contributions of each individual to the final pool of sequence reads. We propose the intuitive notion of effective pool size to account for unequal pooling and derive a Bayesian hierarchical model to estimate this parameter directly from the data. We provide a user‐friendly application assessing the accuracy of allele frequency estimation from both pool‐ and individual‐based NGS population data under various sampling, sequencing depth and experimental error designs. We illustrate our findings with theoretical examples and real data sets corresponding to SNP loci obtained using restriction site–associated DNA (RAD) sequencing in pool‐ and individual‐based experiments carried out on the same population of the pine processionary moth (Thaumetopoea pityocampa). NGS of DNA pools might not be optimal for all types of studies but provides a cost‐effective approach for estimating allele frequencies for very large numbers of SNPs. It thus allows comparison of genome‐wide patterns of genetic variation for large numbers of individuals in multiple populations.     

ENCYSTMENT OF THE DINOFLAGELLATE GYRODINIUM UNCATENUM: TEMPERATURE AND NUTRIENT EFFECTS1

Sexual reproduction and encystment of the marine dinoflagellate Gyrodinium uncatenum Hulburt were induced in nitrogen and phosphorus-limited batch cultures. Sexuality did not occur under nutrient-replete conditions even when growth rate was reduced by non-optimal temperatures. Growth was optimal over a broader temperature range than encystment and virtually no cysts were produced at some low and high temperatures where growth occurred. Most cells initiated sexuality as intracellular pools of each limiting nutrient reached minimum or subsistence levels as much as four days after extracellular nutrients were exhausted. High nitrogen cell quotas during the phosphorus experiment indicate that sexuality was induced by a shortage of phosphorus and not by an indirect effect on nitrogen uptake. Total cyst yield corresponded to successful encystment of 9–13% of the motile populations, yet 60–85% of the plateau-phase motile cells were planozygotes (swimming zygotes formed from fusing gametes). Batch culture studies monitoring total cyst yield may thus seriously underestimate the extent of sexuality. More importantly, the number of cysts produced in a dinoflagellate population may be significantly reduced by environmental factors acting on the cells after sexual induction and fusion.     

Egg banks in hypersaline lakes of the South-East Europe

The cyst banks of 6 coastal hypersaline lakes of South-East Europe have been investigated. The study concerned the bottom sediments of Khersonesskoe and Koyashskoe lakes in the Crimea (Ukraine), Nartë saltworks (Albania), Vecchia Salina at Torre Colimena (Apulia, Italy), Pantano Grande and Pantano Roveto at Vendicari (Sicily, Italy). A total of 19 cyst types were recognised. The cyst banks of lakes were found to be well separated in the representation derived from a statistical multivariate data analysis. For all the lakes examined a comparison was possible between the resting community in sediments (cyst bank) and the active one in the water. The cyst banks contained more species than those recorded over a multi-year sampling effort in the water column. The study of cyst hatching, performed on 5 cyst types under lab conditions, demonstrated that cysts do not hatch under the same conditions. Furthermore, each cyst type shows a wide range of preferential hatching conditions, which allow us to confirm the ecological generalism of salt lake species.     

Demographic factors shaped diversity in the two gene pools of wild common bean Phaseolus vulgaris L.

Wild common bean (Phaseolus vulgaris L.) is distributed throughout the Americas from Mexico to northern Argentina. Within this range, the species is divided into two gene pools (Andean and Middle American) along a latitudinal gradient. The diversity of 24 wild common bean genotypes from throughout the geographic range of the species was described by using sequence data from 13 loci. An isolation–migration model was evaluated using a coalescent analysis to estimate multiple demographic parameters. Using a Bayesian approach, Andean and Middle American subpopulations with high percentage of parentages were observed. Over all loci, the Middle American gene pool was more diverse than the Andean gene pool (π_sil=0.0089 vs 0.0068). The two subpopulations were strongly genetically differentiated over all loci (F_st=0.29). It is estimated that the two current wild gene pools diverged from a common ancestor ∼111 000 years ago. Subsequently, each gene pool underwent a bottleneck immediately after divergence and lasted ∼40 000 years. The Middle American bottleneck population size was ∼46% of the ancestral population size, whereas the Andean was 26%. Continuous asymmetric gene flow was detected between the two gene pools with a larger number of migrants entering Middle American gene pool from the Andean gene pool. These results suggest that because of the complex population structure associated with the ancestral divergence, subsequent bottlenecks in each gene pool, gene pool-specific domestication and intense selection within each gene pool by breeders; association mapping would best be practised within each common bean gene pool.     

Determination of SNP allele frequencies in pooled DNAs by primer extension genotyping and denaturing high-performance liquid chromatography

By testing DNA pools rather than single samples the number of tests for a case-control association study can be decreased to only two for each marker: one on the patient and one on the control pool. A fundamental requirement is that each pool represents the frequency of the markers in the corresponding population beyond the influence of experimental errors. Consequently the latter must be carefully determined. To this aim, we prepared pools of different size (49-402 individuals) with accurately quantified DNAs, estimated the allelic frequencies in the pools of two SNPs by primer extension genotyping followed by DHPLC analysis and compared them with the real frequencies determined in the single samples. Our data show that (1) the method is highly reproducible: the standard deviation of repeated determinations was +/-0.014; (2) the experimental error (i.e., the discrepancy between the estimated and real frequencies) was +/-0.013 (95% C.I.: 0.0098-0.0165). The magnitude of this error was not correlated to the pool size or to the type of SNP. The effect of the observed experimental error on the power of the association test was evaluated. We conclude that this method constitutes an efficient tool for high-throughput association screenings provided that the experimental error is low. We therefore recommend that before a pool is used for extensive association studies, its quality, i.e., the experimental error, is verified by determining the difference between estimated and real frequencies for at least one marker.     

A Two-Dimensional Pooling Strategy for Rare Variant Detection on Next-Generation Sequencing Platforms

We describe a method for pooling and sequencing DNA from a large number of individual samples while preserving information regarding sample identity. DNA from 576 individuals was arranged into four 12 row by 12 column matrices and then pooled by row and by column resulting in 96 total pools with 12 individuals in each pool. Pooling of DNA was carried out in a two-dimensional fashion, such that DNA from each individual is present in exactly one row pool and exactly one column pool. By considering the variants observed in the rows and columns of a matrix we are able to trace rare variants back to the specific individuals that carry them. The pooled DNA samples were enriched over a 250 kb region previously identified by GWAS to significantly predispose individuals to lung cancer. All 96 pools (12 row and 12 column pools from 4 matrices) were barcoded and sequenced on an Illumina HiSeq 2000 instrument with an average depth of coverage greater than 4,000×. Verification based on Ion PGM sequencing confirmed the presence of 91.4% of confidently classified SNVs assayed. In this way, each individual sample is sequenced in multiple pools providing more accurate variant calling than a single pool or a multiplexed approach. This provides a powerful method for rare variant detection in regions of interest at a reduced cost to the researcher.     

Unexpected collective larval dispersal but little support for sweepstakes reproductive success in the highly dispersive brooding mollusc Crepidula fornicata

In many marine invertebrates, long‐distance dispersal is achieved during an extended pelagic larval phase. Although such dispersal should result in high gene flow over broad spatial scales, fine‐scale genetic structure has often been reported, a pattern attributed to interfamilial variance in reproductive success and limited homogenization during dispersal. To examine this hypothesis, the genetic diversity of dispersing larvae must be compared with the postdispersal stages, that is benthic recruits and adults. Such data remain, however, scarce due to the difficulty to sample and analyse larvae of minute size. Here, we carried out such an investigation using the marine gastropod Crepidula fornicata. Field sampling of three to four larval pools was conducted over the reproductive season and repeated over 3 years. The genetic composition of larval pools, obtained with 16 microsatellite loci, was compared with that of recruits and adults sampled from the same site and years. In contrast to samples of juveniles and adults, large genetic temporal variations between larval pools produced at different times of the same reproductive season were observed. In addition, full‐ and half‐sibs were detected in early larvae and postdispersal juveniles, pointing to correlated dispersal paths between several pairs of individuals. Inbred larvae were also identified. Such collective larval dispersal was unexpected given the long larval duration of the study species. Our results suggest that each larval pool is produced by a small effective number of reproducers but that, over a reproductive season, the whole larval pool is produced by large numbers of reproducers across space and time.