Sympatric Subpopulations Research Articles

Variation among bays in spatiotemporal aggregation of Baltic Sea pike highlights management complexity

Understanding the movement ecology of fish communities is necessary to take effective management actions that aim to reverse population declines, especially in fish stocks containing sympatric subpopulations with local adaptations, such as Northern pike (Esox lucius) in the Baltic Sea. We followed the movement and survival of adult pike for one year by tagging 198 individuals in an estuary (an anadromous subpopulation) as well as in two neighbouring bays (individuals of unknown origin) with acoustic transmitters. We found that the estuary was vital in sustaining the local coastal pike stock, that anadromous pike mainly inhabited a coastal area with a radius of 3 km and aggregated in large numbers in the estuary several months prior to spawning. Management should thus prioritise to identify, restore, and protect estuaries from exploitation. The two neighbouring bays demonstrated distinct differences in spatiotemporal aggregations of pike with no aggregations prior to, and during, spawning in the bay without estuaries. The habitat choice during spawning season suggests that 92% of pike sampled in the bay adjacent to the estuary belong to the anadromous subpopulation, while 94% of pike sampled in the neighbouring bay belong to unknown subpopulation(s) of resident brackish spawners. Survival of tagged pike was 84% and suggest low mortality from fisheries and top predators, which have been proposed as threats to pike populations in other areas of the Baltic Sea. Together, these results call for management of high resolution and highlight the importance of detailed movement data.

Environmental stressors induced strong small-scale phenotypic differentiation in a wide-dispersing marine snail

Heterogeneous environments pose a particular challenge for organisms because a single phenotype is unlikely to perform best across the variety of encountered stressors. To understand how species meet this challenge, we investigated the extent to which contrasting environmental pressures induced ecological and phenotypic responses in a natural population of a wide-dispersing marine snail at a small spatial scale. We analyzed several traits ofHeleobia australis(Rissooidea: Cochliopidae) collected from heterogeneous, but highly connected, habitats from the intertidal area of the Bahía Blanca estuary, Argentina. We also conducted molecular analyses by amplifying the COI gene in individuals sampled from each habitat. We found that sympatric subpopulations ofH. australisexhibited a strong phenotypic divergence in shell characters and body weight in response to thermal, saline, and dehydration stress, crab predation risk, and parasitic castrators. We proved that this differentiation occurred even early in life, as most of the characters observed in juveniles mirrored those found in adults. We also found a divergence in penis size in snails collected from each habitat and raised in common garden laboratory conditions. Molecular analyses confirmed that the individuals studied constituted a single species, despite the strong phenotypic differences among subpopulations. The small-scale phenotypic differentiation suggests thatH.australisexperienced a fine-grained environment where conditions imposed by different sources of stress favored the expression of beneficial traits. We discuss the role of plasticity in shaping adaptive phenotypic responses that increase the likelihood of persistence of subpopulations facing environmental stress conditions.

The relative importance of sub-populations to the Gulf of Maine stock of Atlantic cod

AbstractDiscriminating among sympatric sub-populations is critical not only for the investigation of fish population structure, but also for effective fishery management. The Gulf of Maine stock of Atlantic cod contains two genetically distinct sub-populations whose spawning grounds overlap in space, but not season. Lack of a practical tool for discriminating between these spring and winter spawners has thus far prevented addressing metapopulation structure in stock assessments and fishery management plans. To address this issue, we developed a simple approach to discriminate between the sympatric sub-populations that relies on internal otolith structures. Using a logistic regression model fit to training data (n = 577) and evaluated through cross-validation, we correctly classified individuals with 81% accuracy and predicted the overall sub-population mixture within 1%. Applying the model to a broader population dataset (n = 1642) revealed that spring-spawned cod are more concentrated within closed fishing areas and therefore experience a lower mortality rate. However, despite dominating older age classes and comprising a large fraction of the spawning stock, these spring cod contribute little to recruitment. This apparent sub-population difference in the stock–recruitment relationship has important consequences for assessment models and the success of management measures designed to rebuild the stock.

First record of sexual size dimorphism in fossil Strombidae (Mollusca, Gastropoda) from the Miocene of Kutch, western India and its evolutionary implications.

Persististrombus deperditus (Sowerby) from the Lower Miocene of Kutch, Gujarat, western India is represented by two size classes in our collection. Statistical analyses discriminate the size morphs. Large size variations generally result from either (1) sexual differences or (2) ecophenotypic causes. All the living species of the family Strombidae, wherever examined, are characterized by sexual size dimorphism (SSD). Persististrombus deperditus shares all the characters of SSD in these recent species. Size variations due to difference in ecological factors generally occur in allopatric populations. Similar variations are known to characterize sympatric sub-populations of molluscs living only in the intertidal zone, where upper and lower shorefaces differ significantly in physico-chemical and biological properties. Persististrombus deperditus comes from a stable shelf setting that received less siliciclastic input in response to transgression. Hence, its size dimorphism is considered to have sexual origin. This is the first report of SSD in a fossil strombid gastropod. It is argued that fecundity selection was the primary driving force behind the evolution of SSD in this gonochoristic gastropod species. Hence, the larger morph is the female.

Temporal stability and assignment power of adaptively divergent genomic regions between herring (Clupea harengus) seasonal spawning aggregations.

Atlantic herring (Clupea harengus), a vital ecosystem component and target of the largest Northwest Atlantic pelagic fishery, undergo seasonal spawning migrations that result in elusive sympatric population structure. Herring spawn mostly in fall or spring, and genomic differentiation was recently detected between these groups. Here we used a subset of this differentiation, 66 single nucleotide polymorphisms (SNPs) to analyze the temporal dynamics of this local adaptation and the applicability of SNP subsets in stock assessment. We showed remarkable temporal stability of genomic differentiation corresponding to spawning season, between samples taken a decade apart (2005 N = 90 vs. 2014 N = 71) in the Gulf of St. Lawrence, and new evidence of limited interbreeding between spawning components. We also examined an understudied and overexploited herring population in Bras d'Or lake (N = 97); using highly reduced SNP panels (N SNPs > 6), we verified little‐known sympatric spawning populations within this unique inland sea. These results describe consistent local adaptation, arising from asynchronous reproduction in a migratory and dynamic marine species. Our research demonstrates the efficiency and precision of SNP‐based assessments of sympatric subpopulations; and indeed, this temporally stable local adaptation underlines the importance of such fine‐scale management practices.

Visual crypsis as a possible function of polymorphic shell coloration in the infaunal clam Ruditapes philippinarum

The infaunal clam Ruditapes philippinarum exhibits highly polymorphic shell coloration, but the function of the coloration remains uncertain. Here, a hypothesis that such shell coloration functions to enhance visual crypsis (i.e., background color matching) in juveniles (<15 mm in shell length) was tested with a combination of a field survey and laboratory experiments. Shell and background colorations were expressed as mean brightness values. Firstly, the association between shell and background brightness was investigated. For this, a field survey for two sympatric subpopulations with distinct substrates was conducted on an intertidal sandflat in western Kyushu, Japan. Secondly, the visual-crypsis hypothesis was tested experimentally using half-valve clam shells filled with paste of raw clam meat as prey and the pufferfish Takifugu niphobles as a visually hunting predator, in a tank with one to two dark-colored substrates and one light-colored substrate. The field survey showed that shell brightness significantly differed between the two sympatric subpopulations of juvenile clams and was positively associated with background brightness. The laboratory experiments indicated that prey items with comparatively light (dark) coloration on dark- (light-) colored substrate were consumed by predators more immediately and at a higher rate than in the color-matched combinations. Consequently, shell–background color matching could help juvenile clams avoid attack from visually hunting predators. The results provide a new insight into effective management planning for this clam species, creating sand habitats with a more matched coloration.

Genome-wide mosaicism in divergence between zoonotic malaria parasite subpopulations with separate sympatric transmission cycles.

Plasmodium knowlesi is a significant cause of human malaria transmitted as a zoonosis from macaque reservoir hosts in South‐East Asia. Microsatellite genotyping has indicated that human infections in Malaysian Borneo are an admixture of two highly divergent sympatric parasite subpopulations that are, respectively, associated with long‐tailed macaques (Cluster 1) and pig‐tailed macaques (Cluster 2). Whole‐genome sequences of clinical isolates subsequently confirmed the separate clusters, although fewer of the less common Cluster 2 type were sequenced. Here, to analyse population structure and genomic divergence in subpopulation samples of comparable depth, genome sequences were generated from 21 new clinical infections identified as Cluster 2 by microsatellite analysis, yielding a cumulative sample size for this subpopulation similar to that for Cluster 1. Profound heterogeneity in the level of intercluster divergence was distributed across the genome, with long contiguous chromosomal blocks having high or low divergence. Different mitochondrial genome clades were associated with the two major subpopulations, but limited exchange of haplotypes from one to the other was evident, as was also the case for the maternally inherited apicoplast genome. These findings indicate deep divergence of the two sympatric P. knowlesi subpopulations, with introgression likely to have occurred recently. There is no evidence yet of specific adaptation at any introgressed locus, but the recombinant mosaic types offer enhanced diversity on which selection may operate in a currently changing landscape and human environment. Loci responsible for maintaining genetic isolation of the sympatric subpopulations need to be identified in the chromosomal regions showing fixed differences.

Testing for Local Adaptation to Spawning Habitat in Sympatric Subpopulations of Pike by Reciprocal Translocation of Embryos.

We tested for local adaption in early life-history traits by performing a reciprocal translocation experiment with approximately 2,500 embryos of pike (Esox lucius) divided in paired split-family batches. The experiment indicated local adaptation in one of the two subpopulations manifested as enhanced hatching success of eggs in the native habitat, both when compared to siblings transferred to a non-native habitat, and when compared to immigrant genotypes from the other subpopulation. Gene-by-environment effects on viability of eggs and larvae were evident in both subpopulations, showing that there existed genetic variation allowing for evolutionary responses to divergent selection, and indicating a capacity for plastic responses to environmental change. Next, we tested for differences in female life-history traits. Results uncovered that females from one population invested more resources into reproduction and also produced more (but smaller) eggs in relation to their body size compared to females from the other population. We suggest that these females have adjusted their reproductive strategies as a counter-adaptation because a high amount of sedimentation on the eggs in that subpopulations spawning habitat might benefit smaller eggs. Collectively, our findings point to adaptive divergence among sympatric subpopulations that are physically separated only for a short period during reproduction and early development—which is rare. These results illustrate how combinations of translocation experiments and field studies of life-history traits might infer about local adaptation and evolutionary divergence among populations. Local adaptations in subdivided populations are important to consider in management and conservation of biodiversity, because they may otherwise be negatively affected by harvesting, supplementation, and reintroduction efforts targeted at endangered populations.

Anopheles darlingi polytene chromosomes: revised maps including newly described inversions and evidence for population structure in Manaus.

Salivary gland polytene chromosomes of 4th instar Anopheles darlingi Root were examined from multiple locations in the Brazilian Amazon. Minor modifications were made to existing polytene photomaps. These included changes to the breakpoint positions of several previously described paracentric inversions and descriptions of four new paracentric inversions, two on the right arm of chromosome 3 and two on the left arm of chromosome 3 that were found in multiple locations. A total of 18 inversions on the X (n = 1) chromosome, chromosome 2 (n = 7) and 3 (n = 11) were scored for 83 individuals from Manaus, Macapá and Porto Velho municipalities. The frequency of 2Ra inversion karyotypes in Manaus shows significant deficiency of heterozygotes (p < 0.0009). No significant linkage disequilibrium was found between inversions on chromosome 2 and 3. We hypothesize that at least two sympatric subpopulations exist within the An. darlingi population at Manaus based on inversion frequencies.

Causes and consequences of intra-specific variation in vertebral number.

Intraspecific variation in vertebral number is taxonomically widespread. Much scientific attention has been directed towards understanding patterns of variation in vertebral number among individuals and between populations, particularly across large spatial scales and in structured environments. However, the relative role of genes, plasticity, selection, and drift as drivers of individual variation and population differentiation remains unknown for most systems. Here, we report on patterns, causes and consequences of variation in vertebral number among and within sympatric subpopulations of pike (Esox lucius). Vertebral number differed among subpopulations, and common garden experiments indicated that this reflected genetic differences. A QST-FST comparison suggested that population differences represented local adaptations driven by divergent selection. Associations with fitness traits further indicated that vertebral counts were influenced both by stabilizing and directional selection within populations. Overall, our study enhances the understanding of adaptive variation, which is critical for the maintenance of intraspecific diversity and species conservation.

Assessments of Population Structure, Diversity, and Phylogeography of the Swiss Needle Cast Fungus (Phaeocryptopus gaeumannii) in the U.S. Pacific Northwest

Swiss needle cast (SNC) is a foliar disease of Douglas-fir (Pseudotsuga menziesii) caused by Phaeocryptopus gaeumannii (Rohde) Petrak. This fungus is endemic to western North America, where it has historically had little impact in native forests. However, increasing disease severity in western Oregon since the 1990s has prompted renewed interest in P. gaeumannii and SNC. For this study, we analyze multilocus microsatellite genotypes from 482 single-spore isolates from 68 trees across 14 sites in the western Coast Range of Oregon and southwestern Washington. This study assesses genotypic variation and genetic structure at several levels of population hierarchy. Despite the observation that most of the genetic variation occurred within subpopulations, our analyses detected significant differentiation at all hierarchical levels. Clustering among the 482 isolates based on genetic distance clearly supports the existence of two previously described cryptic lineages of P. gaeumannii in the western United States. The two lineages occur in varying proportions along latitudinal and longitudinal gradients in western Oregon and Washington, suggesting a relationship between climate and phylogeography. Sites near Tillamook, Oregon, where SNC is most severe, consist of sympatric subpopulations in which the two lineages comprise roughly equal proportions.

Evolutionary divergence of adult body size and juvenile growth in sympatric subpopulations of a top predator in aquatic ecosystems.

Evolutionary theory predicts that different selective regimes may contribute to divergent evolution of body size and growth rate among populations, but most studies have focused on allopatric populations. Here, we studied five sympatric subpopulations of anadromous northern pike (Esox lucius) in the Baltic Sea subjected to allopatric habitats for a short period of their life cycle due to homing behavior. We report differences in adult body size among subpopulations that were in part due to variation in growth rate. Body size of emigrating juveniles also differed among subpopulations, and differences remained when individuals were reared in a common environment, thus indicating evolutionary divergence among subpopulations. Furthermore, a QST-FST comparison indicated that differences had evolved due to divergent selection rather than genetic drift, possibly in response to differences in selective mortality among spawning habitats during the allopatric life stage. Adult and juvenile size were negatively correlated across subpopulations, and reconstruction of growth trajectories of adult fishes suggested that body size differences developed gradually and became accentuated throughout the first years of life. These results represent rare evidence that sympatric subpopulations can evolve differences in key life-history traits despite being subjected to allopatric habitats during only a very short fraction of their life.

Habitat and resource partitioning among Indo‐Pacific bottlenose dolphins in Moreton Bay, Australia

AbstractInvestigating resource partitioning among mobile marine predators such as cetaceans is challenging. Here we integrate multiple methodologies (analyses of habitat use, stable isotopes and trace elements) to assess ecological niche partitioning amongst two genetically divergent sympatric subpopulations (North and South) of Indo‐Pacific bottlenose dolphins (Tursiops aduncus) in Moreton Bay, Australia. Comparisons of the mean locations (latitude, longitude) and environmental variables (distance from sandbanks, distance from shore and water depth) observed at sightings of biopsy‐sampled individuals indicated that the North subpopulation occurred in the northwestern bay in significantly deeper water than the South subpopulation, which was found in southeastern nearshore waters and closer to sandbanks. Ratios of stable carbon and nitrogen isotopes in skin samples suggested that North dolphins foraged on higher trophic level prey in relatively more pelagic, offshore habitats, while South dolphins foraged on lower trophic prey in more nearshore, demersal and/or benthic habitats. Habitat partitioning was also reflected in higher blubber concentrations of most of the 13 measured trace elements, in particular lead, in the coastal South compared to the more pelagic North dolphins. These findings indicate that genetic subpopulations of bottlenose dolphins in Moreton Bay are adapted to different niches.

Monitoring Dolphins in an Urban Marine System: Total and Effective Population Size Estimates of Indo-Pacific Bottlenose Dolphins in Moreton Bay, Australia

Moreton Bay, Queensland, Australia is an area of high biodiversity and conservation value and home to two sympatric sub-populations of Indo-Pacific bottlenose dolphins (Tursiops aduncus). These dolphins live in close proximity to major urban developments. Successful management requires information regarding their abundance. Here, we estimate total and effective population sizes of bottlenose dolphins in Moreton Bay using photo-identification and genetic data collected during boat-based surveys in 2008–2010. Abundance (N) was estimated using open population mark-recapture models based on sighting histories of distinctive individuals. Effective population size (Ne) was estimated using the linkage disequilibrium method based on nuclear genetic data at 20 microsatellite markers in skin samples, and corrected for bias caused by overlapping generations (Nec). A total of 174 sightings of dolphin groups were recorded and 365 different individuals identified. Over the whole of Moreton Bay, a population size N of 554±22.2 (SE) (95% CI: 510–598) was estimated. The southern bay sub-population was small at an estimated N = 193±6.4 (SE) (95% CI: 181–207), while the North sub-population was more numerous, with 446±56 (SE) (95% CI: 336–556) individuals. The small estimated effective population size of the southern sub-population (Nec = 56, 95% CI: 33–128) raises conservation concerns. A power analysis suggested that to reliably detect small (5%) declines in size of this population would require substantial survey effort (>4 years of annual mark-recapture surveys) at the precision levels achieved here. To ensure that ecological as well as genetic diversity within this population of bottlenose dolphins is preserved, we consider that North and South sub-populations should be treated as separate management units. Systematic surveys over smaller areas holding locally-adapted sub-populations are suggested as an alternative method for increasing ability to detect abundance trends.

Population divergence in East African coelacanths

The coelacanth, Latimeria chalumnae, occurs at the Eastern coast of Africa from South Africa up to Kenya. It is often referred to as a living fossil mainly because of its nearly unchanged morphology since the Middle Devonian. As it is a close relative to the last common ancestor of fish and tetrapods, molecular studies mostly focussed on their phylogenetic relationships. We now present a population genetic study based on 71 adults from the whole known range of the species. Despite an overall low genetic diversity, there is evidence for divergence of local populations. We assume that originally the coelacanths at the East African Coast derived from the Comoros population, but have since then diversified into additional independent populations: one in South Africa and another in Tanzania. Unexpectedly, we find a split of the Comoran coelacanths into two sympatric subpopulations. Despite its undeniably slow evolutionary rate, the coelacanth still diversifies and is therefore able to adapt to new environmental conditions.

SUBPOPULATION DIFFERENTIATION ASSOCIATED WITH NONRIBOSOMAL PEPTIDE SYNTHETASE GENE CLUSTER DYNAMICS IN THE CYANOBACTERIUM PLANKTOTHRIX SPP.1

The Plankthotrix Anagn. et Komárek population in the mesotrophic Lake Steinsfjorden has been intensively studied over several decades. This Planktothrix population produces a number of different classes of oligopetides. However, over the study period, only four main oligopeptide profiles (chemotypes) have been associated with the strains isolated from the lake. The chemotypes show distinct interactions with the environment, demonstrated by shifts in abundance along time series and vertical profiles. Here, we present genetic analysis of nonribosomal peptide synthetase (NRPS) gene regions in strains representing the four Planktothrix chemotypes in Lake Steinsfjorden. On the basis of phylogenetic analyses, we show that the NRPS genes for microcystin (mcy) and cyanopeptolin (oci) display the same clustering as do the chemotypes. Nucleotide diversity in mcy and oci was significantly higher between strains of different chemotypes than between strains of the same chemotype. Ka/Ks (nonsynonymous vs. synonymous mutations) values indicated positive selection in several polymorphic regions of the mcy and oci genes. Notably, incongruence between the phylogenetic trees for different gene segments and split decomposition analyses for segments of oci suggested horizontal gene transfer (HGT) events between strains showing different oligopeptide profiles. The oci HGT region encodes a module responsible for incorporating a variable amino acid in cyanopeptolin and is one of the regions suggested to be under positive selection. Taken together, our data suggest that there are four genetically distinct sympatric subpopulations—displayed as distinct chemotypes—in Lake Steinsfjorden. The diversification process of the chemotypes, and consequently the subpopulations, is driven by HGT and reinforced by positive selection of the corresponding NRPS gene regions.

SYMPATRIC SUBPOPULATIONS OF BOTRYTIS CINEREA ON STRAWBERRIES BASED ON THE CONTENT OF TRANSPOSABLE ELEMENTS AND THEIR CONNECTION WITH RESISTANCE TO BOTRYTICIDES

Botryotinia fuckeliana (anamorph Botrytis cinerea) is the cause of grey mould on strawberries, wich is one of the most widely occuring diseases wherever the strawberry crop is grown. The fungus manifests extraordinary genotype and phenotype variability and adaptability. One of the causes of variability is atributed to transposable elements (TE) from transposone and retrotransposone group. In connection with this fungus, two TE have been discovered so far: retrotransposons (Boty) and transposons (Flipper), based on wich the fungus Botrytis cinerea has been divided into two sympatric subpopulations: Botrytis transposa, which contains both (Boty+Flipper+), and Botrytis vacuma, which contains none (Boty-Flipper-). In order to determine to connection between these subpopulations and resistance to botryticides, we identified 184 isolates from strawberry fields that had been treated with botryticides, from groups consisting of dicarboximides, benzimidazoles, phenylsulfamides, anilinopyrimidines and hydroxianilidines. Based on this research, we determined four subpopulations of the fungus with the following content of TE: Boty+Flipper+, Boty-Flipper-, Boty+Flipper-, Boty-Flipper+. The representation of the subpopulation Botrytis transposa was 41 %, subpopulation Botrytis vacuma 23 %. The remaining two subpopulations with one of each of these elements were represented by 26 % (Boty-Flipper+) and 9 % (Boty+Flipper-). Most of the isolates proved to be resistant to at least one of the mentioned botryticides, with most of them being resistant to phenylsulfamides and benzimidazoles. The ratio of the subpopulations to botryticide resistance was different

Culture and conservation of non-humans with reference to whales and dolphins: review and new directions

There is increasing evidence that culture is an important determinant of behavior in some non-human species including great apes and cetaceans (whales and dolphins). In some cases, there may be repercussions for population biology and conservation. Rapidly evolving “horizontal” cultures, transmitted largely within generations, may help animals deal with anthropogenic change and even allow them to exploit it, sometimes with negative consequences for both the animals and humans. In contrast, stable “vertical” or “oblique” cultures, transmitted principally between generations, may impede adaptation to environmental change, and confound range recovery, reintroductions and translocations. Conformist stable cultures can lead to maladaptive behavior, which may be mistaken for the results of anthropogenic threats. They can also structure populations into sympatric sub-populations with distinctive cultural variants. Such structuring is common among cetaceans, among which sympatric sub-populations may face different anthropogenic threats or respond to the same threat in different ways. We suggest that non-human culture should be integrated into conservation biology when considering populations with such attributes, and also more generally by refining definitions of evolutionarily significant units and considering how cultural attributes may change our perspectives of non-humans.

SEXUAL CONFLICT AND PROTEIN POLYMORPHISM

Sexual conflict, where male and female reproductive interests differ, is probably widespread and often mediated by male or sperm proteins and female or egg proteins that bind to each other during mating or fertilization. One potential consequence is maintenance of polymorphism in these proteins, which might result in reproductive isolation between sympatric subpopulations. I investigate the conditions for polymorphism maintenance in a series of mathematical models of sexual conflict over mating or fertilization frequency. The models represent a male or sperm ligand and a female or egg receptor, and they differ in whether expression of either protein is haploid or diploid. For diploid expression, the conditions imply that patterns of dominance, which involve neither overdominance nor underdominance, can determine whether polymorphism is maintained. For example, suppose ligand expression is diploid, and consider ligand alleles L1 and L2 in interactions with a given receptor genotype; if L1/L1 males are fitter than L2/L2 males in these interactions, then polymorphism is more likely to be maintained when L1/L2 males more closely resemble L1/L1 males in these interactions. Such fitter-allele dominance might be typical of a ligand or its receptor due to their biochemistry, in which case polymorphism might be typical of the pair.

Genetically different Atlantic herring Clupea harengus spawning waves

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 247:303-309 (2003) - doi:10.3354/meps247303 Genetically different Atlantic herring Clupea harengus spawning waves Arran A. McPherson1,3,*, Robert L. Stephenson2, Christopher T. Taggart1 1Department of Oceanography, Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada 2St. Andrews Biological Station, Department of Fisheries and Oceans, 531 Brandy Cove Road, St. Andrews, New Brunswick E5B 2L9, Canada 3Present address: Bedford Institute of Oceanography, Department of Fisheries and Oceans, 1 Challenger Drive, Dartmouth, Nova Scotia B2Y 4A2, Canada *Email: mcphersona@mar.dfo-mpo.gc.ca ABSTRACT: Putative spawning waves of Atlantic herring Clupea harengus were collected from 4 locations and genetically compared using 9 microsatellite loci. Shelf-scale (100s km) spatial differences were measured (max FST = 0.01, p < 0.001) and 1 sub-annual temporal difference (FST = 0.0058, p = 0.001) was revealed between spawning fish (predominantly comprising the same year-class) collected, 6 d apart, from the same location (Devastation Shoal, coastal Nova Scotia). Herring in the second spawning collection at Devastation Shoal had a greater average length-at-age within the year-class (t-test, p < 0.001). The genetic and morphometric differences between the Devastation Shoal collections are assumed to reflect a replacement period of spawning fish of approximately 6 d or less (at least at this location). We offer 3 explanations to account for the observations: (1) genetically distinct sympatric subpopulations or spawning waves; (2) sub-annual (d) genetic patchiness; and (3) transient use of spawning grounds which may indicate that the assumption of philopatry (natal spawning-site fidelity) in herring is invalid. KEY WORDS: Spawning wave · Atlantic herring · Sympatric populations · Genetic Full text in pdf format PreviousExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 247. Online publication date: February 04, 2003 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2003 Inter-Research.