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

Kaouèche M., Bahri-Sfar L., Hammami I., Hassine O. K. B.

Oceanologia

2017

No. 59 (2)

129--138

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.

Cluster-based approach for identifying avian life-history groups for use in ecological monitoring

Tworek Stanisław

Polish Journal of Ecology

2007

Vol. 55, nr 1

139-153

Almost 'since ever' ecologists have made attempts at the generalization of various site-specific, species-specific and time-specific situations, including different classifications of species, based on different principles and prepared for different purposes. This paper, presenting a conceptual model for selecting species of similar life-history pattern to other species and providing an example using birds as a model system, represents that current in the ecology. Ali bird species regarded as nesting in a given area of the mosaic landscape in southern Poland were described with respect to nine variables (nest type, nest location, food habits, place and way of foraging, migration status, number of broods, clutch size, incubation and fledging periods), grouped into 43 categories. Cluster analysis was then used to distinguish objectively species displaying similar life history traits and environmental adaptations into unique life-history 'strategies'. The results of an exemplary analysis of variability in the density, domination, number of species and turnover rate in particular strategies, depending on the size of study plots, their structure, degree of isolation and the characteristic features of their surroundings, using regression and canonical correlation techniques, indicate the suitability of this approach to testing detailed hypotheses connected e.g. with studies on the response of species to different habitat conditions. The methods applied allow one to distinguish, in an objective way, the groups of species displaying similarities with respect to life history traits and environmental adaptations, in spite of the fact that the method of describing variables in cluster analysis may determine a different allocation of species to groups. A model, as described, could allow conservation principles to be developed for species of similar distribution, ecological feature or life history; especially for those species which face with population declines and for which no previous patterns have been established.