Karyotypic Variation in Two Species of Jerboas Jaculus jaculus and Jaculus orientalis (Rodentia, Dipodidae) from Tunisia

Jaculus species are probably associated with chromosomal rearrangements such as pericentric inversions or heterochromatin variation. They appear of lesser magnitude than other changes (especially molecular) that have occurred during the evolution of this genus

High genetic homogeneity of the moon jelly Aurelia aurita (Scyphozoa, Semaeostomeae) along the Mediterranean coast of Tunisia

The moon jelly Aurelia aurita is one of the most common and widespread species of scyphomedusa in the Mediterranean Sea. In all, 18 allozyme loci were studied to investigate the genetic variation and population structure of 11 A. aurita populations from the Tunisian coast. Polymorphism was detected at 14 loci across the sampling localities. Gene frequency differences rather than alternative fixation of alleles characterised the collecting sites. The mean number of alleles per locus ranged from 1.89 to 2.17 (average 2.02), and the mean values of observed (Ho) and expected (He) heterozygosities ranged from 0.20 to 0.36 and from 0.32 to 0.37 respectively. Five out of 14 polymorphic loci were out of Hardy-Weinberg equilibrium (H-WE). Likewise, the multilocus tests showed deviation from H-WE in six populations. These populations apparently showed heterozygote deficiency, whereas the average heterozygosity for the  remaining ones is quite similar to the expected values. Despite extensive sampling across a microgeographical scale and genotyping efforts, the populations of A. aurita under study showed an absence of genetic differentiation under the background of high gene flow (mean FST = 0.01, p < 0.05) and higher value of Nem, suggesting that A. aurita is genetically homogeneous throughout the study area. The absence of population genetic structuring may be associated with environmental conditions and life-history parameters. Keywords: allozyme, Aurelia aurita, gene flow, Mediterranean Sea, TunisiaAfrican Journal of Marine Science 2009, 31(1): 73–8

Significant genetic differentiation among meroplanktonic barrel jellyfish Rhizostoma pulmo (Cnidaria: Scyphozoa) in the Mediterranean Sea

Molecular data have shown that jellyfishes are more geographically restricted and evolutionarily divergent than previously thought. We examined genetic variation and divergence within the meroplanktonic barrel jellyfish Rhizostoma pulmo in the Mediterranean Sea; specific sampling areas were the northern Adriatic, western Mediterranean and Tunisian coast. A total of 19 sampling sites and 68 sequences of the mtDNA cytochrome c oxidase subunit I (COI) gene were used. Of the 68 COI sequences, 45 were newly collected specimens which originated from nine sampling sites along the Tunisian coast. A total of 24 haplotypes were obtained and the specimens sampled were characterised by relatively high levels of haplotype diversity (h = 0.866) and low levels of nucleotide diversity (Ï\u80 = 0.004). Haplotype network analysis showed the presence of three distinct phylogenetic lineages (populations), with separate geographic ranges in the northern Adriatic, western Mediterranean and Tunisian coast. The observed genetic differentiation between these three lineages was supported by the presence of significant genetic differentiation between the 19 populations (FST = 0.757, p < 0.001). The high level of genetic differentiation detected in the barrel jellyfish investigated could be attributed to either intrinsic and/or extrinsic barriers to genetic exchange between different populations that may have adapted to different environmental conditions

Phylogeography of the Greater Egyptian Jerboa (Jaculus orientalis) (Rodentia : Dipodidae) in Mediterranean North Africa

The Mediterranean Basin is an acknowledged hotspot for biodiversity, yet historical processes that shaped this biodiversity in North Africa remain poorly understood. This study aimed to elucidate the phylogeographic pattern of an endemic species of Mediterranean areas of North Africa, the Greater Egyptian Jerboa, Jaculus orientalis. The extent of phylogeographic patterns and molecular genetic diversity (mitochondrial cytochrome b gene) were addressed in a survey of 45 jerboas from 24 localities. Our phylogeographical analyses show a strong genetic subdivision into three areas along a west-east axis, corresponding to (1) Morocco and western Algeria; (2) eastern Algeria, Tunisia and western Libya; (3) eastern Libya and Egypt. Demographic analyses revealed different modalities of population expansion since the last glacial age depending on geographic areas. The dating using relaxed molecular clock analyses revealed that most splits occurred during the Quaternary (<1 million of years ago). Finally, we discussed the relative roles of geological and climatic change in generating this pattern of genetic structure observed for the Greater Egyptian Jerboa and other vegetal and animal species in North Africa

Are there two cryptic species of the lesser jerboa Jaculus jaculus (Rodentia : Dipodidae) in Tunisia ? Evidence from molecular, morphometric, and cytogenetic data

Jerboas belonging to the genus Jaculus are widely distributed rodents inhabiting Palearctic desert and semi-desert areas. Previous studies on the lesser Egyptian jerboa Jaculus jaculus showed the existence of various morphological forms of controversial taxonomic status. They were sometimes related to two different species, J. jaculus and Jaculus deserti, although this has not been recognized in recent taxonomic updates. To clarify the systematic status of J. jaculus in Tunisia, we performed molecular (phylogenetic analyses of cytochrome b sequences), morphological (multivariate analyses of 13 skull measurements) and karyotypic (standard preparations from bone marrow cells) analyses on a number of specimens collected from ten localities. Our analyses revealed two monophyletic, well differentiated clades, with a mean genetic divergence value (K2P = 10.9 +/- 0.01%), which is within the range of distances generally observed between rodent species. Morphometric analyses clearly separated populations of the two genetic clades from each other. However, karyotypes of individuals from both clades appeared similar. Individuals from both molecular clades/morphometric groups were found in sympatry in most of the localities sampled. These results, as obtained from a restricted area of the total distribution, suggest that there are two separate species within the currently accepted J. jaculus in Tunisia. Alternative hypotheses such as the occurrence of a strong, ancient phylogeographic structure, or the presence of pseudogenes, are also considered to account for the results obtained

Use of otolith shape to differentiate two lagoon populations of Pagellus erythrinus (Actinopterygii: Perciformes: Sparidae) in Tunisian waters

Background. The common pandora, Pagellus erythrinus (Linnaeus, 1758), is widely distributed in the Black and the Mediterranean seas. Therefore, P. erythrinus is a valuable component of the commercial fishery in Tunisia and plays an important role in microeconomics of local areas. The goal of this study was to investigate the stock structure and otolith asymmetry for specimens of the common pandora sampled from two lagoons—Ghar El Melh and Bizerte. Materials and methods. We collected a total of 119 specimens of P. erythrinus from the two lagoons, from May through July 2016. The Elliptical Fourier Analysis (EFA) was determined to evaluate the degree of similarity in the otoliths and detect the reciprocal variability. Results. The Discriminant Factor Analysis for the sagitta shape clearly demonstrated an asymmetry when comparing otoliths (left–right) (P < 0.05) within each population and a difference in shape when comparing the same side between the two populations: between the two sides (right–right and left–left). Conclusion. The comparison of the otolith morphology of the two populations showed a clear difference in shape and a left–right asymmetry of otoliths between and within populations. This result is probably related to genetic and local environmental factors. In fact, this investigation improves the knowledge on the stock discrimination for P. erythrinus and provides useful information for analysing fisheries management of this species in Tunisia

Use of otolith shape to differentiate two lagoon populations of Pagellus erythrinus (Actinopterygii: Perciformes: Sparidae) in Tunisian waters

Background. The common pandora, Pagellus erythrinus (Linnaeus, 1758), is widely distributed in the Black and the Mediterranean seas. Therefore, P. erythrinus is a valuable component of the commercial fishery in Tunisia and plays an important role in microeconomics of local areas. The goal of this study was to investigate the stock structure and otolith asymmetry for specimens of the common pandora sampled from two lagoons—Ghar El Melh and Bizerte. Materials and methods. We collected a total of 119 specimens of P. erythrinus from the two lagoons, from May through July 2016. The Elliptical Fourier Analysis (EFA) was determined to evaluate the degree of similarity in the otoliths and detect the reciprocal variability. Results. The Discriminant Factor Analysis for the sagitta shape clearly demonstrated an asymmetry when comparing otoliths (left–right) (P < 0.05) within each population and a difference in shape when comparing the same side between the two populations: between the two sides (right–right and left–left). Conclusion. The comparison of the otolith morphology of the two populations showed a clear difference in shape and a left–right asymmetry of otoliths between and within populations. This result is probably related to genetic and local environmental factors. In fact, this investigation improves the knowledge on the stock discrimination for P. erythrinus and provides useful information for analysing fisheries management of this species in Tunisia

Stock discrimination of two insular populations of Diplodus annularis (Actinopterygii: Perciformes: Sparidae) along the coast of Tunisia by analysis of otolith shape

Background. The annular seabream, Diplodus annularis (Linnaeus, 1758), is the most common sparid fish in the Mediterranean Sea. This species is widespread in Tunisia. Despite their economic importance, due to their excellent white and delicate flesh (demersal fish) and their significant size, few studies have hitherto focused on stock discrimination and on the fisheries management. The goal of this research was to evaluate the stock structure of D. annularis for two Tunisian insular populations  based on the otolith shape, using different statistical approaches. Materials and methods. The specimens of Diplodus annularis were collected during five months ranging from May through September 2014 at two sites: Djerba and Kerkennah. In total, 120 fish were collected from the two study sites: 60 specimens of each population (30 males and 30 females) and were included in different statistical analyses. The Fourier coefficients were determined to evaluate the degree of similarity in the otoliths and detect the reciprocal variability. Results. By comparing the two studied populations, we revealed statistical significant differences, an asymmetry (left–right), of otoliths (P < 0.05). In the same population, symmetry (left–right) was detected for the males, females of Kerkennah, and females of Djerba. However, an asymmetry was detected only for the males of Djerba. Also, sexual dimorphism was observed only for the Djerba population. Conclusion. The comparison of the otolith morphology of the two populations showed a clear difference in shape and a left–right asymmetry of otoliths. This asymmetry indicates that the two populations belong to different stock of fish. The stocks characterization is considered as an important tool for fisheries management. Further studies are necessary to determine the origin of the otolith shape differences and whether they are related only to environmental conditions or a genetic basis may also be responsible

Phylogeography of two cryptic species of African desert jerboas (Dipodidae : Jaculus)

The lesser Egyptian jerboa Jaculus jaculus is a desert dwelling rodent that inhabits a broad ArabianSaharan arid zone. Recently, two distant sympatric lineages were described in North-West Africa, based on morphometric and molecular data, which may correspond to two cryptic species. In the current study, phylogenetic relationships and phylogeographical structure among those lineages and geographical populations from North Africa and the Middle East were investigated. The phylogeographical patterns and genetic diversity of the cytochrome b gene (1110 bp) were addressed on 111 jerboas from 41 localities. We found that the variation in Africa is partitioned into two divergent mitochondrial clades (10.5% divergence relating to 1.654.92 Mya) that corresponds to the two cryptic species: J. jaculus and J. deserti. Diversifications within those cryptic species/clades were dated to 0.231.13 Mya, suggesting that the Middle Pleistocene climatic change and its environmental consequences affected the evolutionary history of African jerboas. The third distant clade detected, found in the Middle East region, most likely represents a distinct evolutionary unit, independent of the two African lineages