Regional Genetic Structure in the Aquatic Macrophyte Ruppia cirrhosa Suggests Dispersal by Waterbirds

The evolutionary history of the genus Ruppia has been shaped by hybridization, polyploidisation and vicariance that have resulted in a problematic taxonomy. Recent studies provided insight into species circumscription, organelle takeover by hybridization, and revealed the importance of verifying species identification to avoid distorting effects of mixing different species, when estimating population connectivity. In the present study, we use microsatellite markers to determine population diversity and connectivity patterns in Ruppia cirrhosa including two spatial scales: (1) from the Atlantic Iberian coastline in Portugal to the Siculo-Tunisian Strait in Sicily and (2) within the Iberian Peninsula comprising the Atlantic-Mediterranean transition. The higher diversity in the Mediterranean Sea suggests that populations have had longer persistence there, suggesting a possible origin and/or refugial area for the species. The high genotypic diversities highlight the importance of sexual reproduction for survival and maintenance of populations. Results revealed a regional population structure matching a continent-island model, with strong genetic isolation and low gene flow between populations. This population structure could be maintained by waterbirds, acting as occasional dispersal vectors. This information elucidates ecological strategies of brackish plant species in coastal lagoons, suggesting mechanisms used by this species to colonize new isolated habitats and dominate brackish aquatic macrophyte systems, yet maintaining strong genetic structure suggestive of very low dispersal.Fundacao para a Cincia e Tecnologia (FCT, Portugal) [PTDC/MAR/119363/2010, BIODIVERSA/0004/2015, UID/Multi/04326/2013]Pew FoundationSENECA FoundationMurcia Government, Spain [11881/PI/09]FCT Investigator Programme-Career Development [IF/00998/2014]Spanish Ministry of Education [AP2008-01209]European Community [00399/2012]info:eu-repo/semantics/publishedVersio

Palaeoclimatic conditions in the Mediterranean explain genetic diversity of Posidonia oceanica seagrass meadows

Past environmental conditions in the Mediterranean Sea have been proposed as main drivers of the current patterns of distribution of genetic structure of the seagrass Posidonia oceanica, the foundation species of one of the most important ecosystems in the Mediterranean Sea. Yet, the location of cold climate refugia (persistence regions) for this species during the Last Glacial Maximum (LGM) is not clear, precluding the understanding of its biogeographical history. We used Ecological Niche Modelling together with existing phylogeographic data to locate Pleistocene refugia in the Mediterranean Sea and to develop a hypothetical past biogeographical distribution able to explain the genetic diversity presently found in P. oceanica meadows. To do that, we used an ensemble approach of six predictive algorithms and two Ocean General Circulation Models. The minimum SST in winter and the maximum SST in summer allowed us to hindcast the species range during the LGM. We found separate glacial refugia in each Mediterranean basin and in the Central region. Altogether, the results suggest that the Central region of the Mediterranean Sea was the most relevant cold climate refugium, supporting the hypothesis that long-term persistence there allowed the region to develop and retain its presently high proportion of the global genetic diversity of P. oceanica.Fundacao para a Ciencia e a Tecnologia (FCT, Portugal) [SFRH/BPD/85040/2012]; FCT [UID/Multi/04326/2013, FCT-BIODIVERSA/004/2015]; Pew foundation (USA)info:eu-repo/semantics/publishedVersio

Drivers of population structure of the bottlenose dolphin (Tursiops truncatus) in the Eastern Mediterranean Sea

The drivers of population differentiation in oceanic high dispersal organisms, have been crucial for research in evolutionary biology. Adaptation to different environments is commonly invoked as a driver of differentiation in the oceans, in alternative to geographic isolation. In this study, we investigate the population structure and phylogeography of the bottlenose dolphin (Tursiops truncatus) in the Mediterranean Sea, using microsatellite loci and the entire mtDNA control region. By further comparing the Mediterranean populations with the well described Atlantic populations, we addressed the following hypotheses: (1) bottlenose dolphins show population structure within the environmentally complex Eastern Mediterranean Sea; (2) population structure was gained locally or otherwise results from chance distribution of preexisting genetic structure; (3) strong demographic variations within the Mediterranean basin have affected genetic variation sufficiently to bias detected patterns of population structure. Our results suggest that bottlenose dolphin exhibits population structures that correspond well to the main Mediterranean oceanographic basins. Furthermore, we found evidence for fine scale population division within the Adriatic and the Levantine seas. We further describe for the first time, a distinction between populations inhabiting pelagic and coastal regions within the Mediterranean. Phylogeographic analysis suggests that current genetic structure, results mostly from stochastic distribution of Atlantic genetic variation, during a recent postglacial expansion. Comparison with Atlantic mtDNA haplotypes, further suggest the existence of a metapopulation across North Atlantic/Mediterranean, with pelagic regions acting as source for coastal environments

Do discrepancies between microsatellite and allozyme variation reveal differential selection between sea and lagoon in the sea bass (Dicentrarchus labrax)?

In the present study the genetic structure of Dicentrarchus labrax (14 samples from the Mediterranean) was analysed at six microsatellite loci, in order to test the hypothesis that some enzymatic loci undergo selection between marine and lagoon habitat. Eight of the 14 samples were analysed at both microsatellite and allozyme markers. The analysis of the genetic variation among the Mediterranean samples showed that (i) (F) over cap(ST) values obtained with the six microsatellite loci were much smaller than those obtained with the 28 allozymes and (ii) microsatellite loci seemed to reflect more the geographical proximity than an ecological one. Thirteen enzymatic loci exhibited moderate to high values compared with microsatellites. This was interpreted as evidence that these allozymes are non-neutral. However, only six loci seemed to be implicated in differentiation between marine and lagoon samples, the causes of selection being unknown for the others. A possible scenario of population dynamics of the sea bass between marine and lagoon habitat is suggested

Ecomorphological variation within and among the two marine species of genus Salaria: Salaria basilisca and Salaria pavo (Perciformes: Blenniidae)

In order to highlight the variation of the form due to the presence of different ecological factors, we investigated in this paper the morphological variation between and within the two marine species Salaria basilisca and S. pavo. This study was based on two approaches, the Truss network and the geometric morphometric and involved specimens of both species divided into marine and lagoon samples. The two approaches yielded complementary results showing clear morphological discrimination of the two species Thus, S. basilisca is distinguished by a higher depth and length as well as a higher head with a compressed snout compared to S. pavo which has a shortened body, a lower head and a slightly stretched snout. At an intraspecific scale, both approaches showed a discrimination of marine and lagoon samples for both species: marine samples tend to have an elongated, shallower body with a small head while lagoon samples are distinguished by a shorter, deeper body and a tall head

Infestation comparée de

Le suivi des paramètres quantitatifs du parasitisme par Ligula intestinalis (Cestoda : Diphyllobothridae) a été réalisé par l’examen de 516 spécimens appartenant à deux espèces introduites de poissons d’eau douce : Rutilus rubilio (350 individus) et Scardinius erythrophthalmus (166 individus). Les échantillonnages ont été réalisés dans deux retenues de barrages, Sidi Salem et Nebhana en Tunisie. L’analyse de la composition spécifique de l’avifaune piscivore dans ces deux retenues a révélé l’existence d’espèces d’oiseaux déjà décrites dans la littérature comme étant des hôtes définitifs de la ligule. Le suivi de l’avifaune dans les deux plans d’eau a montré une abondance relative et une fréquence plus élevées dans la retenue de Sidi Salem que dans celle de Nebhana. L’analyse des prévalences, des intensités moyennes et de l’abondance du parasite a révélé des valeurs plus importantes chez le gardon, Rutilus rubilio qui semble donc le second hôte intermédiaire préférentiel de Ligula intestinalis dans ces milieux. L’analyse comparée de la parasitose, dans les deux retenues prospectées, suggère que la ligule présente deux stratégies différentes d’infestation selon le plan d’eau. À Sidi Salem, grande retenue dont la superficie est plus importante que celle de Nebhana et qui de plus abrite une avifaune piscivore plus importante et beaucoup plus diversifiée, le parasite infeste le maximum d’individus hôtes avec des charges parasitaires faibles. En revanche, à Nebhana, petite retenue, le parasite infeste moins d’individus hôtes qu’à Sidi Salem, mais avec des intensités moyennes beaucoup plus élevées. L’analyse de la prévalence en fonction de la taille et de l’âge au niveau de la retenue de Sidi Salem a révélé des valeurs plus élevées dans les grandes classes de taille chez le gardon

Allozyme and mtDNA variation of white seabream Diplodus sargus populations in a transition area between western and eastern Mediterranean basins (Siculo-Tunisian Strait)

To investigate the possible influence of the Siculo-Tunisian Strait on the genetic structure of white seabream Diplodus sargus, 13 polymorphic allozyme loci and a fragment of the cytochrome b mitochondrial DNA were analysed. Allozyme data indicated a moderate but significant differentiation between some north-eastern (Bizerta, Ghar El Melh Lagoon and Mahdia) and southern (Gabes Gulf and El Biban Lagoon) samples. This heterogeneity was also highlighted after removing PGM* and PGI-1* loci which may be under selection. These results can be explained by the chaotic genetic patchiness hypothesis. In contrast, the mtDNA data indicated genetic homogeneity among localities showing the absence of structure in white seabream populations across the Siculo-Tunisian Strait. Historical demography of this species suggests that it has undergone a recent population expansion as a consequence of a bottleneck event during the Pleistocene glaciations.Keywords: chaotic genetic patchiness, cytochrome b, discrepancy, genetic connectivity, Tunisian coasts, Wahlund effectAfrican Journal of Marine Science 2011, 33(1): 79–9

Infestation comparée de Ligula intestinalis (Cestoda: Diphyllobothridae) chez deux poissons Cyprinidés : Rutilus rubilio et Scardinius erythrophthalmus dans deux retenues de barrages en Tunisie

Le suivi des paramètres quantitatifs du parasitisme par Ligula intestinalis (Cestoda : Diphyllobothridae) a été réalisé par l’examen de 516 spécimens appartenant à deux espèces introduites de poissons d’eau douce : Rutilus rubilio (350 individus) et Scardinius erythrophthalmus (166 individus). Les échantillonnages ont été réalisés dans deux retenues de barrages, Sidi Salem et Nebhana en Tunisie. L’analyse de la composition spécifique de l’avifaune piscivore dans ces deux retenues a révélé l’existence d’espèces d’oiseaux déjà décrites dans la littérature comme étant des hôtes définitifs de la ligule. Le suivi de l’avifaune dans les deux plans d’eau a montré une abondance relative et une fréquence plus élevées dans la retenue de Sidi Salem que dans celle de Nebhana. L’analyse des prévalences, des intensités moyennes et de l’abondance du parasite a révélé des valeurs plus importantes chez le gardon, Rutilus rubilio qui semble donc le second hôte intermédiaire préférentiel de Ligula intestinalis dans ces milieux. L’analyse comparée de la parasitose, dans les deux retenues prospectées, suggère que la ligule présente deux stratégies différentes d’infestation selon le plan d’eau. À Sidi Salem, grande retenue dont la superficie est plus importante que celle de Nebhana et qui de plus abrite une avifaune piscivore plus importante et beaucoup plus diversifiée, le parasite infeste le maximum d’individus hôtes avec des charges parasitaires faibles. En revanche, à Nebhana, petite retenue, le parasite infeste moins d’individus hôtes qu’à Sidi Salem, mais avec des intensités moyennes beaucoup plus élevées. L’analyse de la prévalence en fonction de la taille et de l’âge au niveau de la retenue de Sidi Salem a révélé des valeurs plus élevées dans les grandes classes de taille chez le gardon