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1.
Previous surveys of population structure in the Atlantic-Mediterranean anchovy Engraulis encrasicolus L. have reported heterogeneity in morphology, allozyme frequencies, and mitochondrial DNA haplotype frequencies at a regional scale. In particular, two stocks of anchovy have been detected in the Adriatic Sea. In this paper, the available data is reviewed with the aim to relate genetic variation to geography at the widest possible geographical scale, for investigating the evolutionary mechanisms underlying stock structure in anchovy. Correspondence analysis of allozyme frequencies (24 samples, three polymorphic loci) compiled from the literature indicates three distinct entities in the Mediterranean Sea. Open-sea or oceanic anchovy populations are genetically different from inshore-water populations within a region (Nei's ^ G ST = 0.035–0.067), while broadscale geographical variation is weak for each of these two habitat-specific forms (^ G ST = 0.005–0.006). Mitochondrial-DNA haplotype frequencies support the distinction between an inshore form and an oceanic form (^ G ST = 0.067–0.107), with virtually no genetic differences among oceanic populations across the Gulf of Biscay, the western Mediterranean and the Ionian Sea (^ G ST = −0.001). If natural selection on marker loci is unimportant, these results indicate the occurrence of two parapatric, genetically distinct, habitat-specific forms that are widely distributed throughout the Mediterranean Sea. Persistent allele and haplotype-frequency differences between these forms indicate reproductive isolation and the presence of an E. encrasicolus species complex in the Mediterranean. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society 75 : 261–269.  相似文献   

2.
Eleven microsatellite loci were developed in the European anchovy, Engraulis encrasicolus, and tested in samples from two geographically distant populations (Atlantic and Mediterranean Sea). Number of alleles ranged from eight to 28 and observed heterozygosity from 0.440 to 0.920. There was no evidence of linkage disequilibrium, although two loci are indeed linked. All loci were in Hardy-Weinberg equilibrium, except for one locus in the Atlantic and two loci in the Mediterranean sample. These three loci plus two more showed evidence for null alleles.  相似文献   

3.
Mitochondrial DNA sequence variation in 655?bpfragments of the cytochrome oxidase c subunit I gene, known as the DNA barcode, of European anchovy (Engraulis encrasicolus) was evaluated by analyzing 1529 individuals representing 16 populations from the Black Sea, through the Marmara Sea and the Aegean Sea to the Mediterranean Sea. A total of 19 (2.9%) variable sites were found among individuals, and these defined 10 genetically diverged populations with an overall mean distance of 1.2%. The highest nucleotide divergence was found between samples of eastern Mediterranean and northern Aegean (2.2%). Evolutionary history analysis among 16 populations clustered the Mediterranean Sea clades in one main branch and the other clades in another branch. Diverging pattern of the European anchovy populations correlated with geographic dispersion supports the genetic structuring through the Black Sea-Marmara Sea-Aegean Sea-Mediterranean Sea quad.  相似文献   

4.
Anchovy semipreserves are elaborated in Mediterranean countries with ripened Engraulis encrasicolus obtained by a traditional process. In order to identify those sensory attributes that are most useful as indicators of the ripening stage of Engraulis encrasicolus we performed sensory analyses of anchovy samples obtained at intervals throughout the ripening process. The resulting 90 × 44 sample-by-attribute matrix was analyzed by principal components analysis, leading to the selection of 11 attributes that are reliable indicators of ripening stage and spoilage. The attributes chosen were gray color of the external side; red color of the external side, internal side and backbone mark; the odors Iberian ham and fish meal; the flavors anchovy and bitter; and the texture attributes firmness and juiciness.  相似文献   

5.
Engraulis encrasicolus is of great economic importance in the Mediterranean. However, little is known about its stock structure. Otolith shape analysis has been successfully used for fish stock identification. In this study, the stock structure of anchovy caught off the open sea and the coastal area of the Gulf of Tunis, lagoon of Bizerte and Lake of Ichkeul were investigated using otolith shape. Otolith shape was determined by Fourier analysis and then compared among specimens sampled from different areas with forward stepwise canonical discriminant analysis. Significant differences in otolith shape between the open sea and inshore anchovy groups were detected. Otolith shape of anchovy collected in the Lake of Ichkeul was distinct from the other groups. This finding suggests a clear discreteness of the open sea and the continental groups. The data highlighted the potential for using otolith shape analysis for anchovy stock identification, as well as the role of oceanographic features in determining stock separation. These findings will have major implications for anchovy fisheries management in Tunisia. By using a precautionary approach and considering the three areas as separate stocks, fisheries management strategies should be adjusted to achieve optimum sustainable production from each stock and to avoid decreases in genetic variety.  相似文献   

6.
Climatic oscillations during the Pleistocene ice ages produced great changes in species' geographical distribution and abundance, which could be expected to have genetic consequences. Living in the temperate upwelling zones of the northwestern Pacific, Japanese anchovy (Engraulis japonicus) might have been affected by these severe climatic oscillations. To investigate the effects of Pleistocene climatic changes on the evolution in Japanese anchovy, fragments of 522 bp at the 5' end of mitochondrial DNA control region were sequenced for 241 individuals from 13 localities and 37 individuals of Australian anchovy. Japanese anchovy and Australian anchovy are reciprocally monophyletic and a late Pleistocene transequatorial divergence between the two species was indicated. High levels of haplotype diversity (>0.99) were found for all samples, indicating a high level of genetic diversity. Analyses of molecular variance and the conventional population statistic F(ST) revealed no significant genetic structure throughout the range of Japanese anchovy. Both mismatch distribution analyses and neutrality tests suggested a late Pleistocene population expansion for both Japanese anchovy (79,000-317,000 years ago) and Australian anchovy (45,000-178,000 years ago).  相似文献   

7.
Analysis of mitochondrial DNA restriction fragment length polymorphism in European anchovy (Engraulis encrasicolus) revealed a large number of mitotypes that form two distinct clusters (phylads). Phylad A consists of one common mitotype and many rare secondary mitotypes that are one mutational step removed from the main type. Nucleotide diversity and number of homoplasious changes are low. Phylad B has a complex pattern of mitotype connectedness, high nucleotide diversity, and a large number of homoplasious changes. It is suggested that the two phylads evolved in isolation from each other and that present coexistence is the result of a secondary contact. Moreover, phylad A has a "star" phylogeny, which suggests that it has evolved in a population that experienced a drastic bottleneck followed by an explosion of size. Phylad A is practically the only phylad present in the Black Sea, with its frequency dropping to 85% in the northern Aegean, and to 40% in the rest of Mediterranean and the Bay of Biscay. The Black Sea is, therefore, the most likely place of origin of phylad A. Molecular data are consistent with a population bottleneck in the Black Sea during the last glaciation event and a subsequent exit of phylad A with the outflow into the Aegean following the ice melting. Phylogenetic analysis of anchovy mtDNA provides a reconstruction of population history in the Mediterranean, which is consistent with the geological information.   相似文献   

8.
Aim Similar regimes of selection in different geographical settings can deterministically produce similar adaptive morphologies. We tested the hypothesis that the evolutionary trajectories of fish in upwelling zones can be altered by biogeographic contingencies in the biological and physical environment. Location Eastern Pacific and western Atlantic oceans. Methods We estimated phylogenetic relationships among eastern Pacific temperate anchovies (genus Engraulis) and tropical anchovies (genus Cetengraulis) with neighbour‐joining and Bayesian tree analysis of a 521‐bp segment of mitochondrial DNA cytochrome b. Available sequences for five additional engraulid taxa were included to establish polarity of the tree. Bayesian estimates (BEAST) of time to most recent common ancestor (TMRCA) for the nodes in the phylogeny were calibrated with divergence between Cetengraulis edentulus and Cetengraulis mysticetus precipitated by the rise of the Panama Isthmus 2.8–3.2 Ma. Results Neighbour‐joining and Bayesian trees indicate that South American Engraulis anchoita (Argentina) and Engraulis ringens (Chile) together are basal sister taxa to the California anchovy (Engraulis mordax) and Old World anchovies (Engraulis japonicas, Engraulis australis, Engraulis capensis and Engraulis encrasicolus). The two tropical species of Cetengraulis are sister‐taxa to Californian E. mordax, even though their phenotypes and ecologies differ markedly. A relaxed molecular clock indicates a TMRCA between Californian E. mordax and Cetengraulis at about 4.2 Ma (3.0–6.3 Ma 95% highest probability density). Main conclusions The TMRCA between the California anchovy, E. mordax, and tropical Cetengraulis coincides with the formation of the Gulf of California, which provided opportunities for allopatric isolation during climate oscillations. Mid‐Pliocene warming (3.1–2.9 Ma) may have trapped ancestors of Cetengraulis in the Gulf of California, where they evolved digestive tract morphologies to exploit inshore tropical habitats with low plankton productivities. While populations of several other temperate fishes have become isolated in the Gulf of California, few of these derived species show strong adaptive shifts from temperate sister taxa or range expansions into the tropical provinces of the western Atlantic and eastern Pacific.  相似文献   

9.
Previous genetic analyses have demonstrated that two phonic types of one of the most common European bats, the Common pipistrelle, belong to distinct species, although they are almost identical morphologically (45 kHz Pipistrellus pipistrellus and 55 kHz Pipistrellus pygmaeus). To reconstruct the history of the species complex and explain the codistribution of both forms in Europe and the Mediterranean, we performed phylogenetic analysis based on a 402-bp portion of the cytochrome b gene. Particular attention was paid to the eastern and southern parts of the range where no data were available. We found further distinctive allopatric haplotypes from Libya and Morocco. The difference of about 6-7% described in the Libyan population suggests the occurrence of a new species in the southern Mediterranean. The species status of Moroccan population is also discussed. The phylogeographic patterns obtained and analysis of fossil records support the hypothesis of expansion of both species into Europe from the Mediterranean region during the Holocene. The allopatric speciation model fits our data best. The paleobiographic scenario envisaged is corroborated also by molecular clock estimations and correlations with Late Neogene environmental changes in the Mediterranean region which ended with the Messinian salinity crisis.  相似文献   

10.
The nostrils of the seabird Calonectris diomedea are endowed with a salt-excreting gland that could produce a suitable environment for the colonization of extreme halophilic prokaryotes. We have studied in this organ the presence of extreme halophiles by means of culturing techniques. We could easily cultivate members of haloarchaea, and all cultures studied were identified as members of one of the two species Halococcus morrhuae and Hcc. dombrowskii. In order to reveal the diversity of these colonizers, we undertook a taxonomic study. Altogether, the results indicated that members of the genus Halococcus may constitute a part of the natural epizootic microbiota of C. diomedea, and that they exhibit such an important degree of taxonomic variability that appeals for a pragmatic species definition. This seabird nests in the west Mediterranean coasts, but its migratory habits, reaching locations as distant from the Mediterranean as the South Atlantic, may help in the dispersal mechanisms of haloarchaea through the Earth’s surface.  相似文献   

11.
Sand-smelts are small fishes inhabiting inshore, brackish and freshwater environments and with a distribution in the eastern Atlantic and Mediterranean Sea, extending south into the Indian Ocean. Here, we present a broad phylogenetic analysis of the genus Atherina using three mitochondrial (control region, 12S and 16S) and two nuclear markers (rhodopsin and 2nd intron of S7). Phylogenetic analyses fully support the monophyly of the genus. Two anti-tropical clades were identified, separating the South African Atherina breviceps from the north-eastern Atlantic and Mediterranean Atherina' species. In European waters, two groups were found. The first clade formed by a well supported species-pair: Atherina presbyter (eastern Atlantic) and Atherina hepsetus (Mediterranean), both living in marine waters; a second clade included Atherina boyeri (brackish and freshwater environments) and two independent lineages of marine punctated and non-punctated fishes, recently proposed as separate species. Sequence divergence values strongly suggest multiple species within the A. boyeri complex.  相似文献   

12.
F. Bonhomme 《Molecular ecology》2016,25(13):3187-3202
Ecophenotypic differentiation among replicate ecotype pairs within a species complex is often attributed to independent outcomes of parallel divergence driven by adaptation to similar environmental contrasts. However, the extent to which parallel phenotypic and genetic divergence patterns have emerged independently is increasingly questioned by population genomic studies. Here, we document the extent of genetic differentiation within and among two geographic replicates of the coastal and marine ecotypes of the European anchovy (Engraulis encrasicolus) gathered from Atlantic and Mediterranean locations. Using a genome‐wide data set of RAD‐derived SNPs, we show that habitat type (marine vs. coastal) is the most important component of genetic differentiation among populations of anchovy. By analysing the joint allele frequency spectrum of each coastal–marine ecotype pair, we show that genomic divergence patterns between ecotypes can be explained by a postglacial secondary contact following a long period of allopatric isolation (c. 300 kyrs). We found strong support for a model including heterogeneous migration among loci, suggesting that secondary gene flow has eroded past differentiation at different rates across the genome. Markers experiencing reduced introgression exhibited strongly correlated differentiation levels among Atlantic and Mediterranean regions. These results support that partial reproductive isolation and parallel genetic differentiation among replicate pairs of anchovy ecotypes are largely due to a common divergence history prior to secondary contact. They moreover provide comprehensive insights into the origin of a surprisingly strong fine‐scale genetic structuring in a high gene flow marine fish, which should improve stock management and conservation actions.  相似文献   

13.
We studied the diet of larval and juvenile Japanese anchovy Engraulis japonicus in the upper Ariake Bay, Japan. Diet was analyzed by examining the digestive tracts; feeding intensity, proportion of empty guts, and prey selectivity were calculated. Anchovy density was negatively influenced by temperature and positively by salinity and prey density. Diet was dominated by Acartia omorii, which was positively selected with two other copepods, Calanus sinicus and Pseudodiaptomus marinus. In contrast, Oithona davisae was highly dominant in the environment but was absent in anchovy guts; thus, this copepod was negatively selected, with two others, Tortanus derjugini and Sinocalanus sinensis. Overall, larger prey were positively selected and smaller ones were negatively selected; value of electivity index correlated negatively with prey size. Larvae [<18 mm of standard length (SL)] showed significantly lower feeding intensities and higher rates of empty guts than juveniles (≥18 mm SL). In juveniles, feeding intensity increased steadily as the fish grew in size, with a corresponding reduction in empty guts. Feeding intensity correlated positively and empty gut correlated negatively with fish size. We suggest that larger prey are important diets for postlarval Japanese anchovy in Ariake Bay.  相似文献   

14.
For a long time, the highly aberrant crinoid Scoliocrinus was known only from the Lower Givetian Eifel area (western Rhenish Massif) as a single oblique calyx with only two out of five radials having an arm facet. Several almost complete crowns of a new species in the Middle Givetian Finnentrop area (eastern Rhenish Massif) have two fan-like arms (in the A and E rays), and a horizontal large anal tube. The probable mode of life of Scoliocrinus is analysed by (a) functional morphology mainly of the arms, (b) criteria of minimised faecal recycling, (c) biostratinomic association with two new species of another aberrant, but four-armed new crinoid genus thus suggesting original syntopy with Scoliocrinus. It is concluded that the construction of Scoliocrinus is probably an adaptation to prevailing unidirectional (tidal?) currents in biostromal reef biotopes. This is supported by rather similar crinoid occurrences in a Lower Givetian biostromal reef-related region in the western Rhenish Massif, with the genotype of Scoliocrinus and a newly assigned third species of Scoliocrinus (arm and probable part of the calyx), as well as four-armed species. The new forms are described as Scoliocrinus ubaghsi nov. sp., Scoliocrinus gerolsteinensis nov. sp., Trapezocrinus scheeri nov. gen., nov. sp., and Trapezocrinus hilperti nov. gen., nov. sp.  相似文献   

15.
Grant WS 《Genetica》2005,125(2-3):293-309
Genetic architectures of marine fishes are generally shallow because of the large potential for gene flow in the sea. European anchovy, however, are unusual among small pelagic fishes in showing large differences among sub-basins and in harbouring two mtDNA phylogroups (‘A’ & ‘B’), representing 1.1–1.85 million years of separation. Here the mtDNA RFLP dataset of Magoulas et al. [1996, Mol. Biol. Evol. 13: 178–190] is re-examined to assess population models accounting for this subdivided population structure and to evaluate the zoogeographical origins of the two major phylogroups. Haplotype and nucleotide diversities are highest in the Ionian Sea and lowest in the Aegean and Black seas. However, this gradient is absent when ‘A’ and ‘B’ haplotypes are examined separately. Neither the self-sustaining nor the basin population models adequately describe anchovy population behaviour. Tests for neutrality, mismatch and nested clade analyses are concordant in depicting recent expansions of both phylogroups. Unimodel mismatch distributions and haplotype coalescences dating to the last (Eemian) interglacial (‘B’) and the Weichselian pleniglacial period (‘A’) indicate separate colonizations of the Mediterranean Basin. Phylogroup ‘A’ is unlikely to have arisen through continuous long-term isolation in the Black Sea because of climate extremes from displaced subpolar weather systems during the ice ages. Ancestors of both groups appear to have colonized the Mediterranean from the Atlantic in the late Pleistocene. Hence, zoogeographic models of anchovy in the Mediterranean must also include the eastern (and possibly southern) Atlantic.  相似文献   

16.
The western woolly lemur is distributed through central western, northwestern and possibly northern Madagascar and is traditionally viewed as a monotypic species (Avahi occidentalis) or as a subspecies of A. laniger. We present new data on body weights of Avahi which, together with previously available body weights, provide additional evidence for recognizing eastern and western woolly lemurs as two distinct species. We then reexamine the distributions of, and chromatic variation within and between, populations of western woolly lemurs. A comparative study of wild subjects and museum skins reveals that several geographically discrete morphs exist in western Avahi, which is clearly polytypic. Marked differences between populations in fur coloration suggest that 3 distinct taxa should be recognized. The populations differ considerably in their habitat structure. In addition, field observations suggest clear differences in population density between 2 of the populations. We describe and name one new species.  相似文献   

17.
Spawning frequency of offshore migrant populations of Japanese anchovy Engraulis japonicus ranged from 0·34 to 0·90, and was higher than that of inshore Japanese anchovy. In addition, spawning frequency of offshore populations varied in response to the sex ratio. They spawned at water temperatures of 5.0, 8.6 and 12.6° C, indicating that the minimum critical water temperature of offshore Japanese anchovy was considerably lower than that of inshore populations. A significant positive relationship was observed between water temperature and relative batch fecundity of offshore Japanese anchovy. Furthermore, water temperature was negatively related to egg size, suggesting a trade-o. between relative batch fecundity and egg size for offshore fish. At the same water temperature, relative batch fecundity of offshore populations was higher than that of inshore ones. The comparison of spawning frequency and relative batch fecundity suggests that offshore Japanese anchovy represent a reproductive ecology by which they spawn more eggs than inshore Japanese anchovy within a certain time period.  相似文献   

18.
A bioenergetics model is implemented for European anchovy (Engraulis encrasicolus) and applied to the north-eastern Aegean Sea (eastern Mediterranean Sea). The model reproduces the growth of anchovy in a one-way linked configuration with a lower trophic level (LTL) ecosystem model. The LTL model provides densities for three zooplankton functional groups (heterotrophic flagellates, microzooplankton and mesozooplankton) which serve as available energy via consumption for the anchovy model. Our model follows the basic structure of NEMURO.FISH type models (North Pacific Ecosystem Model for Understanding Regional Oceanography for Including Saury and Herring). Several model parameters were specific for the Mediterranean or the Black Sea anchovy and some others were adopted from related species and NEMURO.FISH due to lack of biological information on E. encrasicolus. Simulation results showed that the fastest growth rate occurs during spring and the slowest growth rate from August to December. Zooplankton abundance during autumn was low implying that decreased prey density lead to a reduction in anchovy weight, especially for the age-3 class. Feeding parameters were adjusted to adequately fit the model growth estimates to available weight-at-age data. A detailed sensitivity analyses is conducted to evaluate the importance of the biological processes (consumption, respiration, egestion, specific dynamic action, excretion and egg production) and their parameters to fish growth. The most sensitive parameters were the intercept and exponent slope of the weight-dependent consumption and respiration process equations. Fish weight was fairly sensitive to temperature-dependent parameters.  相似文献   

19.
Whilst biological traits of river macroinvertebrates show unimodal responses to geographic changes in habitat conditions in Europe, we still do not know whether spatial turnover of species result in distinct combinations of biological traits for pond macroinvertebrates. Here, we used data on the occurrence of 204 macroinvertebrate taxa in 120 ponds from four biogeographic regions of Europe, to compare their biological traits. The Mediterranean, Atlantic, Alpine, and Continental regions have specific climate, vegetation and geology. Only two taxa were exclusively found in the Alpine and Continental regions, while 28 and 34 taxa were exclusively recorded in the Atlantic and Mediterranean regions, respectively. Invertebrates in the Mediterranean region allocated much energy to reproduction and resistance forms. Most Mediterranean invertebrate species had narrow thermal ranges. In Continental areas, invertebrates allocated lesser energy to reproduction and dispersal, and organisms were short lived with high diversity of feeding groups. These characteristics suggest higher resilience. The main difference between ponds in the Alpine and Atlantic regions was their elevation. Alpine conditions necessitate specific adaptations related to rapid temperature fluctuations, and low nutrient concentrations. Even if our samples did not cover the full range of pond conditions across Europe, our analyses suggest that changes in community composition have important impacts on pond ecosystem functions. Consistent information on a larger set of ponds across Europe would be much needed, but their low accessibility (unpublished data and/or not disclosed by authors) remains problematic. There is still, therefore, a pressing need for the incorporation of high quality data sets into a standardized database so that they can be further analyzed in an integrated European-wide manner.  相似文献   

20.
The distribution of Octopus vulgaris has not yet been completely clarified. For a long time, a cosmopolitan distribution with unknown distribution limits had been assumed. This assumption has recently been questioned and it has been postulated that the distribution is restricted to the Mediterranean and the northeastern Atlantic. However, as our previous studies show, the existence of O. vulgaris can be confirmed for the Mediterranean and the whole eastern Atlantic, and evidence is provided for its occurrence in the western Atlantic. The aim of the present work is to extend our previous data matrix and to clarify whether O. vulgaris exists in the northwestern Pacific. Therefore, the sequence variation in ostensible O. vulgaris from 13 localities in the Mediterranean (France), the Atlantic Ocean [Lanzarote, Senegal, South Africa (Atlantic, Indian Ocean), Tristan da Cunha, north, middle and south Brazil], the Caribbean Sea (Venezuela) and the Pacific Ocean (Taiwan, Japan and Costa Rica) was examined using the mitochondrial genes coding for the 16S rRNA and cytochrome oxidase subunit III (COIII). Sequence divergence was relatively low between populations of O. vulgaris from the Mediterranean, the eastern and western Atlantic (except north Brazil), Venezuela, Taiwan and Japan compared with other species of the genus Octopus . Trees constructed by using maximum likelihood, neighbour joining and maximum parsimony algorithms (PAUP) show the above-mentioned populations from the Mediterranean, the western and eastern Atlantic, Venezuela and the northwestern Pacific (Japan and Taiwan) as a monophyletic cluster. Thus, even if the Octopus vulgaris -like octopus from north Brazil should turn out a cryptic species, the data of this work not only support our hypothesis of the distribution of O. vulgaris in the Mediterranean, the eastern and western Atlantic but also show that O. vulgaris is present in the northwestern Pacific, namely in the waters of Taiwan and Japan.  相似文献   

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