The present investigation aims at unveiling the main causes of the recorded disparate phylogeographic patterning among the two highly dispersive coastal crab species Carcinus aestuarii and Pachygrapsus marmoratus in t...The present investigation aims at unveiling the main causes of the recorded disparate phylogeographic patterning among the two highly dispersive coastal crab species Carcinus aestuarii and Pachygrapsus marmoratus in the Mediterranean Sea.For this purpose,available mitochondrial and nuclear data for both species were re-analyzed and investigated for genetic polymorphism and differentiation patterns across three defined geographic scales in their distribution ranges,but also across the same locations in the Mediterranean Sea.The temporal frame of genetic diversification was also determined for both species in order to check whether observed differences in phylogeographic patterns among these coastal decapods could be attributed to different evolutionary histories.The obtained results revealed a more variable and diversified gene pool in the green crab C.aestuarii than the one recorded in the marbled crab P.marmoratus.Lack of significant correlation between pairwise genetic dissimilarities observed among C.aestuarii populations and those detected for P.marmoratus was notably discerned across the same defined Mediterranean locations.This finding indicates that the pattern of pairwise genetic differentiation does not vary in the same way in both examined crab species.Significant outputs of population genetic differentiation,retrieved within both species,were shown to be differently associated with the potential effects of various kinds of isolation processes(related to geography,environment and biogeographic boundary).Evolutionary history reconstruction showed older genetic diversification event in C.aestuarii than the one recorded in P.marmoratus.These recorded temporal frames suggest different modes of genetic diversification in both crab species(glacial vicariance for C.aestuarii and interglacial dispersal for P.marmoratus).They may also provide an explanation for the recorded differences in variation of patterns of population genetic diversity and structure,when integrated with species ecological requirements and life-history traits.展开更多
The present study reports on population structure analysis of the marbled crab Pachygrapsus marmoratus （Fabricius, 1787） from the Tunisian coast, an appropriate location to study biogeographical processes because of...The present study reports on population structure analysis of the marbled crab Pachygrapsus marmoratus （Fabricius, 1787） from the Tunisian coast, an appropriate location to study biogeographical processes because of the presence of a well-known discontinuous biogeographic area （the Siculo-Tunisian Strait）. Patterns of morphological and genetic variation of this highly dispersive and continuously distributed decapod species were assessed among its geographically close populations which cover almost the entire Tunisian coastline. A total of 386 specimens from nine sites were collected and examined for morphometric variability at 14 morphometric traits. The results of multivariate analyses of linear morphometric traits showed the existence of sexual dimorphism in this species by PERMANOVA （Permutational multivariate analysis of variance）. In addition, both CDA （Canonical discriminant analysis） and NPMANOVA （Non parametric MANOVA test） analyses revealed statistically significant differences among the studied locations for both sexes. Overall, the outcome of CDA analysis showed that over 87% of individuals could be assigned correctly to three regional groups in both sexes （North, Center and South）. Specifically, SIMPER （Similarity Percentages） analysis showed that carapace length, carapace width and merus length were major contributors to the morphometric separation between populations. The pattern of phenotypic variation suggested by morphometric analyses was found to be highly discordant with that suggested by the analysis of a mitochondrial marker （cytochrome oxidase I, COI）. Indeed, the results inferred from restriction fragment analysis of the COI in 180 crabs, suggested high genetic homogeneity. Very low levels of haplotype diversity （h） were found in almost all the studied populations, associated with non significant genetic distances for nearly all population comparisons. Explanations to these morphometric and mtDNA patterns as well as the discrepancy between them are discussed.展开更多
The present investigation focuses on population structure analysis of the purple sea urchin Paracentrotus lividus across the African Mediterranean coast, with the main aim of assessing the influence of the Siculo-Tuni...The present investigation focuses on population structure analysis of the purple sea urchin Paracentrotus lividus across the African Mediterranean coast, with the main aim of assessing the influence of the Siculo-Tunisian Strait on gene flow disruption in this highly dispersive echinoid species. For this purpose, patterns of morphological and genetic variation were assessed among its populations from the western and eastern Mediterranean coasts. A total of 302 specimens from seven Tunisian sites were collected and examined for morphometric variability at twelve morphometric traits. Concordant results, inferred from CDA（canonical discriminant analyses）, pairwise NPMANOVA（non parametric multivariate analysis of variance） comparisons and MDS（multidimensional scaling） plot, unveiled significant inter-population differences in the measured traits among the studied populations. Furthermore, the combined use of the one way ANOSIM（analysis of similarities） and the Discriminant/Hotelling analysis allowed unravelling two morphologically differentiated groups assigned to both western and eastern Mediterranean basins. The SIMPER（similarity percentages） routine analysis showed that total dry weight, test diameter and spine length were major contributors to the morphometric separation between locations and between groups. Pattern of phenotypic divergence discerned in P. lividus across the Siculo-Tunisian Strait is interestingly in congruence with that inferred from the genetic investigation of the purple sea urchin populations from the same region based on the analysis of the mt DNA COI（cytochrome oxidase I） gene in 314 specimens from nineteen locations covering a wider geographic transect, streching westward to the Algerian coast and eastward to the Libyan littoral. The specific haplotypic composition characterizing each Mediterranean basin,as inferred from the minimum spanning network, confirmed the geographic partioning of genetic variation, as revealed by F-statistics and AMOVA（analysis of molecular variance） analyses, yielding significant genetic differentiation between eastern and western Mediterranean populations. The newly detected phylogeographic patterns, observed for the first time in P. lividus throughout the explored distribution range, suggest the involvement of different biotic and abiotic processes in shaping such variation, and provide evidence that a large and geographically exhaustive dataset is necessary to unveil phylogeographic structure within widespread marine species, previously cathegorized as panmictic in part of their distribution range.展开更多
The lesser Egyptian jerboa Jaculus jaculus, is a member of the subfamily Dipodinae, known to have a number of subspecies. Previous studies of J. jaculus from North Africa found various morphological forms of unknown t...The lesser Egyptian jerboa Jaculus jaculus, is a member of the subfamily Dipodinae, known to have a number of subspecies. Previous studies of J. jaculus from North Africa found various morphological forms of unknown taxonomic status, which are frequently grouped into two taxa： J. jaculus and J. deserti. We assessed the taxonomic status of this taxon in Tunisia using allozymic （phylogenetic analysis of 23 genetic loci encoding 16 enzymatic proteins） and morphological （multivariate analysis of 13 craniodental characters） analyses of 136 J. jaculus specimens collected from seven localities within its distribution range. Allozymic analysis clearly indicated the existence of two distinct groups of J. jaculus, with a mean genetic distance （D） value of 0.99 and FΩ=0.52. Individuals within the two groups did not show any obvious geographical structuration, even within the Matmata locality which represents the meeting point for the two groups where they were found in sympatry. Additionally, morphometric analysis of 13 craniodental characters was clearly separated the two groups. These results were obtained over a very restricted area of the total distribution of J. jaculus and strongly suggest the occurrence of two separate and often sympatric species within the currently accepted J.jaculus in Tunisia： J.jaculus and J. deserti展开更多
Morphometric variation ofPelophylax saharicus was analysed using univariate and multivariate statistics, with both traditional and geometric morphometrics, based on 148 specimens from four different geographical local...Morphometric variation ofPelophylax saharicus was analysed using univariate and multivariate statistics, with both traditional and geometric morphometrics, based on 148 specimens from four different geographical localities in Tunisia and Algeria. The results show the existence of three morphotypes in Tunisia and one in Algeria, and indicate a significant degree of variation in morphometric characters between regions. Specimens from the southernmost region have the smallest body size and the greatest morphometrie divergence from other populations. This pattern of morphometric variation probably results from phenotypic plasticity in response to local environmental factors. The results of our chromosomal study （C-, Ag-NOR-, endonuclease digestion, DAPI, CMA3 and Q-banding） reveal this species to exhibit the plesiomorphic Pelophylax karyotype of 2n=26 biarmed chromosomes and NORs on the eleventh pair. Similarities and differences of the North African green frog are discussed in relation to the different forms of data collected （chromosomal, morphometric, ecological） [Current Zoology 56 （6）： 678~586, 2010].展开更多
Genetic variability and divergence among natural populations of Jaculus jaculus and J. orientalis in Tunisia were examined by electrophoretic analysis of 16 enzymatic proteins encoded by 23 genetic loci. Low levels of...Genetic variability and divergence among natural populations of Jaculus jaculus and J. orientalis in Tunisia were examined by electrophoretic analysis of 16 enzymatic proteins encoded by 23 genetic loci. Low levels of genetic variability were found among populations of both species in comparison to those of other rodent and mammal species of which data are available. In J. jaculus populations, the mean level of observed heterozygosity （Hobs） ranged from 0.08 to 0.19, while the mean percentage of polymorphic loci （P） ranged from 26.2% to 45.2% and the mean number of alleles per locus （A） ranged from 1.1 to 1.4. Nevertheless, the mean values were 0.10 to 0.15, 29.3% to 44.1% and 1.1 to 1.7, respectively, for J. orientalis. In addition, populations of the two species have revealed a lower degree of genetic differentiation （Fst=0.0017 for J. jaculus and 0.0019 for J. orientalis）. Moreover, Fst was 0.607, P〈0.05 between populations of the two species, indicating that they were highly genetically diverged from each other. The present data assures the previous results on the validity of the present taxonomic situation of the two species and emphasis on the effect of geographic factors （environments type and bioclimatic stages） on the genetic structure of both species.展开更多
The present study deals with double-diffusive convection within a two-dimensional inclined cavity filled with an air-CO_(2) binary gas mixture.The left and the right vertical walls are differentially heated and subjec...The present study deals with double-diffusive convection within a two-dimensional inclined cavity filled with an air-CO_(2) binary gas mixture.The left and the right vertical walls are differentially heated and subjected to different locations of(CO_(2))contaminants to allow for the variation of the buoyancy strength(N).However,the horizontal walls are assumed adiabatic.The simulations are conducted using the finite volume method to solve the conservation equations of continuity,momentum,energy,and species transport.Good agreement with other numerical results in the literature is obtained.The effect of multiple parameters,namely,buoyancy ratio(N),thermal Rayleigh number(Ra),and inclination angle(α)on entropy generation rate is analyzed and discussed in the postprocessing stage,while considering both laminar and turbulent flow regimes.The computations reveal that these parameters considerably affect both the heat and mass transfer performances of the system.展开更多
文摘The present investigation aims at unveiling the main causes of the recorded disparate phylogeographic patterning among the two highly dispersive coastal crab species Carcinus aestuarii and Pachygrapsus marmoratus in the Mediterranean Sea.For this purpose,available mitochondrial and nuclear data for both species were re-analyzed and investigated for genetic polymorphism and differentiation patterns across three defined geographic scales in their distribution ranges,but also across the same locations in the Mediterranean Sea.The temporal frame of genetic diversification was also determined for both species in order to check whether observed differences in phylogeographic patterns among these coastal decapods could be attributed to different evolutionary histories.The obtained results revealed a more variable and diversified gene pool in the green crab C.aestuarii than the one recorded in the marbled crab P.marmoratus.Lack of significant correlation between pairwise genetic dissimilarities observed among C.aestuarii populations and those detected for P.marmoratus was notably discerned across the same defined Mediterranean locations.This finding indicates that the pattern of pairwise genetic differentiation does not vary in the same way in both examined crab species.Significant outputs of population genetic differentiation,retrieved within both species,were shown to be differently associated with the potential effects of various kinds of isolation processes(related to geography,environment and biogeographic boundary).Evolutionary history reconstruction showed older genetic diversification event in C.aestuarii than the one recorded in P.marmoratus.These recorded temporal frames suggest different modes of genetic diversification in both crab species(glacial vicariance for C.aestuarii and interglacial dispersal for P.marmoratus).They may also provide an explanation for the recorded differences in variation of patterns of population genetic diversity and structure,when integrated with species ecological requirements and life-history traits.
文摘The present study reports on population structure analysis of the marbled crab Pachygrapsus marmoratus （Fabricius, 1787） from the Tunisian coast, an appropriate location to study biogeographical processes because of the presence of a well-known discontinuous biogeographic area （the Siculo-Tunisian Strait）. Patterns of morphological and genetic variation of this highly dispersive and continuously distributed decapod species were assessed among its geographically close populations which cover almost the entire Tunisian coastline. A total of 386 specimens from nine sites were collected and examined for morphometric variability at 14 morphometric traits. The results of multivariate analyses of linear morphometric traits showed the existence of sexual dimorphism in this species by PERMANOVA （Permutational multivariate analysis of variance）. In addition, both CDA （Canonical discriminant analysis） and NPMANOVA （Non parametric MANOVA test） analyses revealed statistically significant differences among the studied locations for both sexes. Overall, the outcome of CDA analysis showed that over 87% of individuals could be assigned correctly to three regional groups in both sexes （North, Center and South）. Specifically, SIMPER （Similarity Percentages） analysis showed that carapace length, carapace width and merus length were major contributors to the morphometric separation between populations. The pattern of phenotypic variation suggested by morphometric analyses was found to be highly discordant with that suggested by the analysis of a mitochondrial marker （cytochrome oxidase I, COI）. Indeed, the results inferred from restriction fragment analysis of the COI in 180 crabs, suggested high genetic homogeneity. Very low levels of haplotype diversity （h） were found in almost all the studied populations, associated with non significant genetic distances for nearly all population comparisons. Explanations to these morphometric and mtDNA patterns as well as the discrepancy between them are discussed.
文摘The present investigation focuses on population structure analysis of the purple sea urchin Paracentrotus lividus across the African Mediterranean coast, with the main aim of assessing the influence of the Siculo-Tunisian Strait on gene flow disruption in this highly dispersive echinoid species. For this purpose, patterns of morphological and genetic variation were assessed among its populations from the western and eastern Mediterranean coasts. A total of 302 specimens from seven Tunisian sites were collected and examined for morphometric variability at twelve morphometric traits. Concordant results, inferred from CDA（canonical discriminant analyses）, pairwise NPMANOVA（non parametric multivariate analysis of variance） comparisons and MDS（multidimensional scaling） plot, unveiled significant inter-population differences in the measured traits among the studied populations. Furthermore, the combined use of the one way ANOSIM（analysis of similarities） and the Discriminant/Hotelling analysis allowed unravelling two morphologically differentiated groups assigned to both western and eastern Mediterranean basins. The SIMPER（similarity percentages） routine analysis showed that total dry weight, test diameter and spine length were major contributors to the morphometric separation between locations and between groups. Pattern of phenotypic divergence discerned in P. lividus across the Siculo-Tunisian Strait is interestingly in congruence with that inferred from the genetic investigation of the purple sea urchin populations from the same region based on the analysis of the mt DNA COI（cytochrome oxidase I） gene in 314 specimens from nineteen locations covering a wider geographic transect, streching westward to the Algerian coast and eastward to the Libyan littoral. The specific haplotypic composition characterizing each Mediterranean basin,as inferred from the minimum spanning network, confirmed the geographic partioning of genetic variation, as revealed by F-statistics and AMOVA（analysis of molecular variance） analyses, yielding significant genetic differentiation between eastern and western Mediterranean populations. The newly detected phylogeographic patterns, observed for the first time in P. lividus throughout the explored distribution range, suggest the involvement of different biotic and abiotic processes in shaping such variation, and provide evidence that a large and geographically exhaustive dataset is necessary to unveil phylogeographic structure within widespread marine species, previously cathegorized as panmictic in part of their distribution range.
文摘The lesser Egyptian jerboa Jaculus jaculus, is a member of the subfamily Dipodinae, known to have a number of subspecies. Previous studies of J. jaculus from North Africa found various morphological forms of unknown taxonomic status, which are frequently grouped into two taxa： J. jaculus and J. deserti. We assessed the taxonomic status of this taxon in Tunisia using allozymic （phylogenetic analysis of 23 genetic loci encoding 16 enzymatic proteins） and morphological （multivariate analysis of 13 craniodental characters） analyses of 136 J. jaculus specimens collected from seven localities within its distribution range. Allozymic analysis clearly indicated the existence of two distinct groups of J. jaculus, with a mean genetic distance （D） value of 0.99 and FΩ=0.52. Individuals within the two groups did not show any obvious geographical structuration, even within the Matmata locality which represents the meeting point for the two groups where they were found in sympatry. Additionally, morphometric analysis of 13 craniodental characters was clearly separated the two groups. These results were obtained over a very restricted area of the total distribution of J. jaculus and strongly suggest the occurrence of two separate and often sympatric species within the currently accepted J.jaculus in Tunisia： J.jaculus and J. deserti
文摘Morphometric variation ofPelophylax saharicus was analysed using univariate and multivariate statistics, with both traditional and geometric morphometrics, based on 148 specimens from four different geographical localities in Tunisia and Algeria. The results show the existence of three morphotypes in Tunisia and one in Algeria, and indicate a significant degree of variation in morphometric characters between regions. Specimens from the southernmost region have the smallest body size and the greatest morphometrie divergence from other populations. This pattern of morphometric variation probably results from phenotypic plasticity in response to local environmental factors. The results of our chromosomal study （C-, Ag-NOR-, endonuclease digestion, DAPI, CMA3 and Q-banding） reveal this species to exhibit the plesiomorphic Pelophylax karyotype of 2n=26 biarmed chromosomes and NORs on the eleventh pair. Similarities and differences of the North African green frog are discussed in relation to the different forms of data collected （chromosomal, morphometric, ecological） [Current Zoology 56 （6）： 678~586, 2010].
文摘Genetic variability and divergence among natural populations of Jaculus jaculus and J. orientalis in Tunisia were examined by electrophoretic analysis of 16 enzymatic proteins encoded by 23 genetic loci. Low levels of genetic variability were found among populations of both species in comparison to those of other rodent and mammal species of which data are available. In J. jaculus populations, the mean level of observed heterozygosity （Hobs） ranged from 0.08 to 0.19, while the mean percentage of polymorphic loci （P） ranged from 26.2% to 45.2% and the mean number of alleles per locus （A） ranged from 1.1 to 1.4. Nevertheless, the mean values were 0.10 to 0.15, 29.3% to 44.1% and 1.1 to 1.7, respectively, for J. orientalis. In addition, populations of the two species have revealed a lower degree of genetic differentiation （Fst=0.0017 for J. jaculus and 0.0019 for J. orientalis）. Moreover, Fst was 0.607, P〈0.05 between populations of the two species, indicating that they were highly genetically diverged from each other. The present data assures the previous results on the validity of the present taxonomic situation of the two species and emphasis on the effect of geographic factors （environments type and bioclimatic stages） on the genetic structure of both species.
文摘The present study deals with double-diffusive convection within a two-dimensional inclined cavity filled with an air-CO_(2) binary gas mixture.The left and the right vertical walls are differentially heated and subjected to different locations of(CO_(2))contaminants to allow for the variation of the buoyancy strength(N).However,the horizontal walls are assumed adiabatic.The simulations are conducted using the finite volume method to solve the conservation equations of continuity,momentum,energy,and species transport.Good agreement with other numerical results in the literature is obtained.The effect of multiple parameters,namely,buoyancy ratio(N),thermal Rayleigh number(Ra),and inclination angle(α)on entropy generation rate is analyzed and discussed in the postprocessing stage,while considering both laminar and turbulent flow regimes.The computations reveal that these parameters considerably affect both the heat and mass transfer performances of the system.
