The influence of environmental variability of a coastal lagoon ecosystem on genetic diversity and structure of white seabream [Diplodus sargus (Linnaeus 1758)] populations

As coastal lagoons serve as nursery areas for some marine and estuarine fish, selective pressures of these brackish or hypersaline lagoons may influence the genetic structure of species and populations. We examined spatial and temporal genetic patterns at eight microsatellite loci in white seabream [Diplodus sargus (Linnaeus 1758)] recruits from the Mar Menor (Southeast Spain) and compared these loci with those in coastal populations from the open sea, observing a high degree of genetic diversity and spatio‐temporal genetic stability. However, the results suggest the presence of subpopulations or genetic substructures in the Mar Menor D. sargus population that could be interpreted as a homogeneous mixture of individuals from three differentiated subpopulations in the Mediterranean and evidence of the Wahlund effect. It also suggests that D. sargus adults return to their original spawning habitat, thus conserving the genetic differences among the respective populations over time. Overall, this study demonstrates the importance of the Mar Menor coastal lagoon as a nursery area for the conservation of genetic diversity of D. sargus populations.     

Temporal partitioning of microhabitat use among four juvenile fish species of the genus Diplodus (Pisces: Perciformes,Sparidae)

Timing, microhabitat selection and behavior from the onset of settlement to recruitment to the adult population of juvenile fishes of the genus Diplodus (Pisces: Sparidae) were investigated along a rocky coastline in the Central Mediterranean Sea. The settlement periods in Diplodus sargus and Diplodus annularis were concentrated in spring, between late May and early June, and the recruits leave the nursery grounds in late September–October. Juvenile fishes of Diplodus puntazzo and Diplodus vulgaris showed a partial time overlapping, sharing the same zones in winter and early spring, from February to May. Multiple correspondence analysis showed that sea breams settle in well‐defined habitats. The smallest juveniles of D. sargus and D. puntazzo settled primarily in the shallowest sheltered pebbly areas, located in sciaphilous crannies covered by red algae. Diplodus vulgaris settlers were observed on a wider range of substrata: rock on sand, gravel and pebbles without algal cover or large boulders, generally in deeper waters. The intermediate‐size juveniles of D. sargus, D. puntazzo and D. vulgaris showed a preference for rocky substrata with substantial algal cover, with arborescent structures (Phaeophyceae). Diplodus annularis juveniles showed high fidelity to seagrass beds (Posidonia oceanica). The home range increased over time in all species, highlighting a loss of substrate specificity: larger juveniles were even observed in deeper and different microhabitats outside nursery grounds. This study suggests that shallow infra‐littoral rocky communities with photophilic algae play a key role in recruitment of sparid fishes, affecting the distribution and abundance of juvenile fishes and therefore determining the renewal of populations and the structure of adult assemblages.     

High gene flow promotes the genetic homogeneity of the fish goby Pomatoschistus marmoratus (Risso, 1810) from Mar Menor coastal lagoon and adjacent marine waters (Spain)

The extreme environmental variability of coastal lagoons suggests that physical and ecological factors could contribute to the genetic divergence among populations occurring in lagoon and open‐coast environments. In this study we analysed the genetic variability of lagoon and marine samples of the sand goby, Pomatoschistus marmoratus (Risso, 1810) (Pisces: Gobiidae), on the SW Spain coast. A fragment of mitochondrial DNA control region (570 bp) was sequenced for 196 individuals collected in five localities: Lo Pagan, Los Urrutias and Playa Honda (Mar Menor coastal lagoon), and Veneziola and Mazarrón (Mediterranean Sea). The total haplotype diversity was h = 0.9424 ± 0.0229, and the total nucleotide diversity was π = 0.0108 ± 0.0058. Among‐sample genetic differentiation was not significant and small‐scale patterns in the distribution of haplotypes were not apparent. Gene flow and dispersal‐related life history traits may account for low genetic structure at a small spatial scale. The high genetic diversity found in P. marmoratus increases its potential to adapt to changing conditions of the Mar Menor coastal lagoon.     

Nassarius corniculus (Olivi, 1792) (Caenogastropoda: Nassariidae): a model of environmental complexity of Italian brackish and marine habitats

Strong environmental selection may give rise to complex species and/or camouflage the presence of sibling species in brackish waters. The prosobranch gastropod Nassarius corniculus (Olivi, 1792) is a common scavenger widely distributed in Mediterranean brackish and marine areas. We examined the morphological and molecular features of N. corniculus populations and related these features to the environmental complexity of brackish habitats. Morphological data revealed differences in radular features between specimens collected from two Mediterranean lagoons (Lake Faro, Messina, Sicily and Lake Fusaro, Gulf of Gaeta). Analysis of with the mitochondrial marker mt 16S rRNA revealed genetic variability within the Lake Faro population but did not show the different geographic structure between the two lagoons indicated by morphological data. We also predicted the gene flow of N. corniculus by comparing populations of two marine areas (Faro Sea and Ischia).     

6种帘蛤科贝类及4个地理种群文蛤线粒体COI基因片段序列分析

对文蛤(Meretrix meretrix L.,1758)、青蛤(Cyclina sinensis G.,1791)、硬壳蛤(Mercenaria mercenaria L.,1758)、江户布目蛤(Protothaca jedoensis L.,1874)、薄片镜蛤(Dosinia corrugata R.,1850)和菲律宾蛤仔(Ruditapes philippinarum A.,1850)6种帘蛤科贝类和4个地理种群文蛤(大连、连云港、湛江、防城港)的细胞色素c氧化酶亚基I(COI)基因片段的核苷酸序列进行了分析,以探讨这一序列在种质鉴定、种群遗传结构和分子系统发生研究中的应用价值.测序结果表明,所有物种扩增片段长度均为709 bp,序列A+T含量(62.2%~67.6%)明显高于GC含量.物种间共有变异位点311个,其中简约信息位点202个;文蛤4个地理种群间共有变异位点46个,其中简约信息位点2个.此区段共编码235个氨基酸,种间共有氨基酸变异位点85个;文蛤种群间只有1个氨基酸变异位点.以COI基因片段序列为标记,用大竹蛏(Solen grandis)作外群,构建了帘蛤科贝类的系统发生树,其拓扑结构显示4个地理种群文蛤首先聚为1个单元,然后与青蛤聚在一起,最后所有帘蛤科物种聚为一枝,与外群相区别,其结果与传统形态分类基本一致,说明COI基因适合作为该科贝类种群遗传结构和系统发生研究的分子标记.     

基于COI序列的翡翠股贻贝Perna viridis线粒体遗传特性分析及其近缘种间的系统关系探讨

应用通用引物 COIL 1490和 COIH 2198对翡翠股贻贝Perna viridis的性腺和体细胞线粒体DNA进行PCR扩增,获得661bp长度的COI基因片段,经过比对性腺与体细胞的COI片段,发现雄性性腺与体细胞COI基因均为一个单倍型,即体内只有一种线粒体DNA类型,没有发现双单性遗传现象,雌、雄性腺的COI基因片段变异率很低（0.31%）。应用PAUP构建了NJ树、MP树以及贝叶斯法构建了贝叶斯树,对股贻贝属3种间的系统关系进行了分析,结果表明,翡翠股贻贝P. viridis与P. canaliculus 和 P. perna 之间的分化与分歧年代的估算是相吻合的。     

Morphological and molecular evidence supports the first occurrence of two fishes,Siganus sutor(Valenciennes, 1835)and Seriolina nigrofasciata(Rüppell, 1829)(Actinopterygii:Perciformes), from marine waters of Odisha coast,Bay of Bengal,India

Marine ecosystems provide a wide variety of diverse habitats that frequently promote migration and ecological adaptation. The extent to which the geographic distribution of marine organism has reshaped by human activities remains underappreciated. The limitations intrinsic to morphology-based identification systems have engendered an urgent need for reliable genetic methods that enable the unequivocal recognition of fish species,particularly those that are prone to overexploitation and/or market substitution. In the present study, however, an attempt has been taken to identify two locally adapted fish species, Siganus sutor(Valenciennes, 1835) and Seriolina nigrofasciata(Rüppell, 1829) of order Perciformes, which happens to be the first record in Odisha coast,Bay of Bengal. The diagnostic characteristics of Siganus sutor are: dorsal fin XIII-10, anal fin VII-9, pectoral fin 15,pelvic fin II-3, while that of Seriolina nigrofasciata dorsal fin VI-I-35, anal fin I-17, pectoral fin 16, pelvic fin 5. All COI barcodes generated in this study were matched with reference sequences of expected species, according to morphological identification. Bayesian and likelihood phylogenetic trees were drawn based on DNA barcodes and all the specimens clustered in agreement with their taxonomic classification at the species level. The phylogeographic studies based on haplotype network and migration rates suggest that both the species were not panmitic and the high-frequency population distribution indicates successful migration. The result of this study provides an important validation of the use of DNA barcode sequences for monitoring species diversity and changes within a complex marine ecosystem.