Relative role of life-history traits and historical factors in shaping genetic population structure of sardines (Sardina pilchardus) (original) (raw)
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Canadian Journal of Fisheries and Aquatic Sciences, 2012
The Adriatic stock of European sardine ( Sardina pilchardus ) has experienced large interannual demographic fluctuations over the last 30 years, with a severe decline beginning in 1991 and continuing until 1997. In the present study, six microsatellite loci were used on a time series collection of otoliths and scales from sampling locations of northern (Chioggia) and southern (Vieste) Adriatic Sea, with the aim to investigate the genetic effects of these stock biomass fluctuations. The northern samples showed significant reduction in observed heterozygosity (HO) and mean number of alleles (Na) that explain the genetic diversity variation, while the same parameters turned out to be more stable in the southern samples. In addition, we detected the presence of a genetic bottleneck and low effective population size (Ne) values in several northern samples. Even if the northern and southern Adriatic sardine samples belong to the same genetic stock, the more pronounced decrease in genetic ...
Signature of an early genetic bottleneck in a population of Moroccan sardines (Sardina pilchardus)
Molecular Phylogenetics and Evolution, 2006
Fishery assessment models meant to determine sustainability of commercial marine Wsh failed to predict recent stock collapses due to overexploitation. One Xaw of assessment models is that they strongly rely on catch and age-composition statistics, but largely ignore the genetic background of the studied populations. We examined population genetic structure of sardine (Sardina pilchardus) in the centraleastern and northeastern Atlantic Ocean and Mediterranean Sea to aid Wshery management of this heavily Wshed small pelagic species. We found that sardine has a striking mitochondrial control region, and sequenced a fragment of 387 bp of its 5Ј-end in 261 individuals collected oV the coasts of Morocco (Dakhla, Tantan, SaW, Larache, and Nador), Portugal (Quarteira), Spain (Pasajes, Barcelona), and Greece (Kavala). High levels of haplotypic diversity rendered a rather unresolved NJ phylogeny. The recovered tree had no phylogeographic structuring except for the clustering of 13 individuals of SaW. In contrast, individuals grouped together according to the presence or absence of a 13-bp insertion in the sequence. ST pairwise comparisons and molecular variance analyses supported genetic diVerentiation between the population of Pasajes (Bay of Biscay), and those of the Mediterranean Sea and Moroccan coast, with a contact zone around the Strait of Gibraltar. This result conWrms the existence of two subspecies, S. pilchardus pilchardus and S. pilchardus sardina that were previously identiWed based on meristics and morphometry. Mismatch distribution analysis showed that sardine populations are expanding since the Pleistocene. Surprisingly, the population of SaW showed strong and statistically signiWcant levels of genetic diVerentiation that could be related with isolation and genetic drift. Comparative analysis of the SaW population versus the rest including mismatch distributions, and a Bayesian skyline plot suggest that the SaW population likely underwent an early genetic bottleneck. The genetic singularity of the SaW population could have been responsible for the historical collapse of this sardine stock in the 1970s.
2006
Fishery assessment models meant to determine sustainability of commercial marine fish failed to predict recent stock collapses due to overexploitation. One flaw of assessment models is that they strongly rely on catch and age-composition statistics, but largely ignore the genetic background of studied populations. We examined population genetic structure of sardine (Sardina pilchardus) in the centraleastern and northeastern Atlantic Ocean and Mediterranean Sea in order to aid fishery management of this heavily fished small pelagic species. We found that sardine has a striking mitochondrial control region, and sequenced a fragment of 387 bp of its 5'-end in 261 individuals collected off the coasts of Morocco (Dakhla, Tantan, Safi, Larache, Nador), Portugal (Quarteira), Spain (Pasajes, Barcelona), and Greece (Kavala). High levels of haplotypic diversity rendered a rather unresolved NJ phylogeny. The recovered tree had no phylogeographic structuring except for the clustering of 13 individuals of Safi. In contrast, individuals grouped together according to the presence or absence of a 13-bp insertion in the sequence. Φ st pairwise comparisons and molecular variance analyses supported genetic differentiation between the population of Pasajes (Bay of Biscay), and those of the Mediterranean Sea and Moroccan coast, with a contact zone around the Strait of Gibraltar. This result confirms the existence of two subspecies, S. pilchardus pilchardus and S. pilchardus sardina that were previously identified based on meristics and morphometry. Mismatch distribution analysis showed that sardine populations are expanding since the Pleistocene. Surprisingly, the population of Safi showed strong and statistically significant levels of genetic differentiation that could be related with isolation and genetic drift. Comparative analysis of the Safi population versus the rest including mismatch distributions, and a Bayesian skyline plot suggest that the Safi population likely underwent an early genetic bottleneck. The genetic singularity of the Safi population could have been responsible for the historical collapse of this sardine stock in 1970s.
Marine Biotechnology, 2002
A genetic stock structure analysis of 11 sardine samples from the Adriatic Sea and Ionian neighboring area was carried out through sequence variation analysis of a 307-bp cytochrome b gene fragment in order to identify self-recruiting units in the Adriatic Sardina pilchardus stock. The overall lack of genetic subdivision among samples detected by analysis of molecular variance, pairwise ⌽ st values, and the exact test of population differentiation indicates this sardine stock is part of a larger self-recruiting population whose boundaries are larger than the investigated area. This conclusion is in agreement with preliminary allozymic and mitochondrial DNA restriction fragment length polymorphism data, but contradicts the previous identification of 2 subpopulations of sardines in the Adriatic Sea argued on morphologic differences, which could be rather attributed to different hydrographic or ecologic conditions occurring in different areas of the Adriatic Sea. The reduced gene flow observed between Adriatic-Ionian and Spanish sardine geographic samples (P < 0.001) suggests that reproductively isolated populations of sardines may occur in the Mediterranean Sea.
Scientia Marina, 2011
The genetic structure of the European sardine (Sardina pilchardus) was assessed throughout its geographic range using five microsatellite loci. One of the loci seemed to be under hitchhiking selection and exhibited a latitudinal cline along the eastern Atlantic, with abrupt change in allele frequencies from the Alboran Sea to the western Mediterranean and from the east Atlantic coast to the Azores and Madeira. This pattern was very similar to that previously described for the allozymic locus SOD* and these 2 loci could be linked. A Bayesian analysis of environmental factors with the genetic data indicated temperature as a potential selection factor. Selection pressure may be stronger at the southern limit of sardine distribution, because heterozygosity of the non-neutral locus was much lower there. The abrupt change in allele frequencies of the non-neutral locus in certain regions seem to be related more to strong barriers to gene flow, which were not evident for neutral loci, than to abrupt changes in selection pressure. These areas of discontinuity provide a guideline to define and delineate genetic stocks and are generally consistent with areas of phenotypic change in sardine, but they are not in concordance with the currently recognized morphological subspecies.
Most surveys of mitochondrial DNA (mtDNA) in marine fishes reveal low levels of sequence divergence between haplotypes relative to the differentiation observed between sister taxa. It is unclear whether this pattern is due to rapid lineage sorting accelerated by sweepstakes recruitment, historical bottlenecks in population size, founder events, or natural selection, any of which could retard the accumulation of deep mtDNA lineages. Recent advances in paleoclimate research prompt a reexamination of oceanographic processes as a fundamental influence on genetic diversity; evidence from ice cores and anaerobic marine sediments document strong regime shifts in the world's oceans in concert with periodic climatic changes. These changes in sea surface temperatures, current pathways, upwelling intensities, and retention eddies are likely harbingers of severe fluctuations in population size or regional extinctions. Sardines (Sardina, Sardinops) and anchovies (Engraulis) are used to assess the consequences of such oceanographic processes on marine fish intrageneric gene genealogies. Representatives of these two groups occur in temperate boundary currents on a global scale, and these regional populations are known to fluctuate markedly. Biogeographic and genetic data indicate that Sardinops has persisted for at least 20 million years, yet the mtDNA genealogy for this group coalesces in less than half a million years and points to a recent founding of populations around the rim of the Indian-Pacific Ocean. Phylogeographic analysis of Old World anchovies reveals a Pleistocene dispersal from the Pacific to the Atlantic, almost certainly via southern Africa, followed by a very recent recolonization from Europe to southern Africa. These results demonstrate that regional populations of sardines and anchovies are subject to periodic extinctions and recolonizations. Such climate-associated dynamics may explain the low levels of nucleotide diversity and the shallow coalescence of mtDNA genealogies. If these findings apply generally to marine fishes, management strategies should incorporate the idea that even extremely abundant populations may be relatively fragile on ecological and evolutionary time scales.
Imsiridou, A; Karnezi, S; Minos, G; Exadactylos, A;, 2021
The identification of fish stocks is the first step in management and conservation processes. The European Commission has established among others the Protected Geographical Indication (PGI) protection label in order to identify an agricultural product, raw or processed, for which quality, reputation or other characteristics are linked to its geographical origin. In the present study, the Greek Sardina pilchardus haplotypes found with three mitochondrial segments (COI, cytb, D-loop), were compared with the ones previously submitted in the databases, to test the uniqueness of the discovered Greek haplotypes for a future PGI definition. For all the three mtDNA markers, the discovered Greek haplotypes were found to be common with species' haplotypes all over the world. These results reinforce the aspect that a single sardine individual cannot be classified as coming from a certain population (Mediterranean or Atlantic), as most of the data (present and former) support a single evolutionary unit for sardines.
Molecular phylogeny of Philippine freshwater sardines based on mitochondrial DNA analysis
Journal of Heredity, 2000
The commercially important Sardinella species (family Clupeidae or herrings) usually thrive in marine environments. An exception is Sardinella tawilis of Taal Lake, Batangas, Philippines, the only known freshwater sardine. This species is believed to have immigrated from Balayan Bay to the lake when it was formed in the course of volcanic eruptions some 240 years ago. To determine the relationship of S. tawilis to the marine species S. albella, S. fimbriata, and S. longiceps from the Balayan Bay we sequenced 358 bp of the cytochrome b gene and the mitochondrial control region. The cytochrome b gene was highly conserved and contained little phylogenetic information. The control region sequences, however, demonstrated two highly diversified main haplotypes grouping S. tawilis with S. albella, as shown by maximum parsimony and neighbor-joining analysis. The haplotypes are characterized by the presence of an 81 bp indel and up to eight 35 bp tandem repeat elements. The repeat copy number varied within individuals of S. tawilis and S. albella, thus showing heteroplasmy in these two species only. The analysis of two subpopulations of S. tawilis revealed restricted substitutions that may indicate the beginning of genetic differentiation of the two subpopulations.
Marine Biology, 1996
Temperate sardines fall into two related monotypic genera, Sardina and Sardinops. Sardina exists as a cluster of subpopulations in the northeastern Atlantic and Mediterranean, and Sardinops encompasses five geographically-isolated regional populations: (1) South Africa-Namibia, (2) Australia-New Zealand, (3) Chile-Peru, (4) Mexico-California and (5) Japan-Russia. We surveyed electrophoretic variability in the products of 34 protein encoding loci in Sardina (N = 26) and the five Indian-Pacific populations of Sardinops (N = 222), collected from 1983 to 1991. Nei's unbiased genetic distances (D) between samples of Sardina and Sardinops averaged 1.04 and are typical of distances between species of related genera./)s between the regional forms of Sardinops were < 0.011, indicating that Sardinops consists of a single species with widely-scattered subpopulations. Assuming a molecular clock calibrated by the rise of the Panama Isthmus and the opening of the Bering Strait, these genetic distances correspond to times since divergence of < 200 000 yr. Although Sardinops populations showed a significant degree of allele-frequency heterogeneity (Fsr, a measure of population differentiation, averaged 0.085 over 8 polymorphic loci), the distribution of genetic distances and tests of allele-frequency heterogeneity could not distinguished between hypotheses of north-south antitropical or east west oceanic dispersal. Low levels of gene diversity in Sardinops and muta-Communicated by M. F. Strathmann, Friday Harbor
Heredity, 1997
were studied using electrophoretic methods in order to characterize stocks of sardines from the western Mediterranean Sea. The results showed differentiated groups distributed throughout the area studied. They did not form a panmictic population, but they existed as semi-independent, although not completely isolated, breeding units with an estimation of migration of Nem = 3.1 (number of migrants per generation). In the LDH-1 system a north-south dine was detected. We have also detected a discontinuity between the Alboran and the rest of the Mediterranean populations sampled at the enzymatic level. This result confirms the action of the Almeria-Oran front as a barrier that produces discontinuities as detected in other marine species.