Morphometric variations in white seabream Diplodus sargus (Linneus, 1758) populations along the Tunisian coast

Morphometric characters of the white seabream Diplodus sargus (Linnaeus 1758) were compared among samples collected from six marine and lagoon sites along the Tunisian coast to elucidate the impact of the geographical barrier of the Siculo-Tunisian Strait and/or the lagoon environment in the morphological variation among the Tunisian white seabream population. Two morphometric descriptors (twenty-five Truss elements and six traditional measurements) were used to study the pattern of this morphological variation. Univariate analysis of variance revealed significant differences (P < 0.001) for both traditional and Truss variables. Multivariate analysis using the two morphometric descriptors detected a clear variation in the body shape between D. sargus populations along the Tunisian coast. All these analyses showed the distinctness of the sample from El Biban lagoon compared to the remaining ones. This discrimination was due to the head and the peduncle of the studied fish. Varying degrees of differences were also observed between northern and southern samples, and between the lagoon and the marine samples. The morphological variations of the head explain also the discrimination between the different lagoons samples. Observed morphological heterogeneity seems to be related to the impact of ecological factors

Morphological and genetic characterization of the sharpsnout seabream populations (<i>Diplodus puntazzo</i>, Sparidae) along a boundary area between the two Mediterranean basins

<p>In order to test the potential ecological role of the Siculo-Tunisian Strait as a geographic barrier, the morphological and genetic variation of eight Tunisian samples of the sharpsnout seabream, <i>Diplodus puntazzo</i>, were studied, based on 23 truss network elements and 13 polymorphic allozyme loci. Significant morphological differences were observed between studied samples, especially between lagoon ones. Although genetic data did not support the detected morphometric variation, <i>F</i>-statistics indices (<i>F</i>_IS and <i>F</i>_ST) revealed a significant departure from panmixia with heterozygote deficiencies and slight genetic differentiation between samples. Genetic results suggested the existence of moderate and local genetic heterogeneity that can be explained by the chaotic genetic patchiness hypothesis. Morphological and genetic results showed that the Siculo-Tunisian Strait does not seem to act as a barrier limiting the connectivity between the natural populations of <i>D. puntazzo</i>, at least at the scale of the Tunisian coast. Thus, the phenotypic variation identified in this study appears to be environmentally induced through the exploitation of different ecological niches and hydrodynamic constraints.</p