Browsing by Author "Stefanni, Sergio"
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- Establishment of a coastal fish in the Azores : Recent colonisation or sudden expansion of an ancient relict population?Publication . Stefanni, Sergio; Castilho, Rita; Sala-Bozano, Maria; Robalo, Joana Isabel; Francisco, Sara Martins; Santos, Ricardo Serrão; Marques, N.; Brito, Alberto; Almada, Vítor Carvalho; Mariani, StefanoThe processes and timescales associated with ocean-wide changes in the distribution of marine species have intrigued biologists since Darwin's earliest insights into biogeography. The Azores, a mid-Atlantic volcanic archipelago located >1000 km off the European continental shelf, offers ideal opportunities to investigate phylogeographic colonisation scenarios. The benthopelagic sparid fish known as the common two-banded seabream (Diplodus vulgaris) is now relatively common along the coastline of the Azores archipelago, but was virtually absent before the 1990s. We employed a multiple genetic marker approach to test whether the successful establishment of the Azorean population derives from a recent colonisation from western continental/island populations or from the demographic explosion of an ancient relict population. Results from nuclear and mtDNA sequences show that all Atlantic and Mediterranean populations belong to the same phylogroup, though microsatellite data indicate significant genetic divergence between the Azorean sample and all other locations, as well as among Macaronesian, western Iberian and Mediterranean regions. The results from Approximate Bayesian Computation indicate that D. vulgaris has likely inhabited the Azores for ∼40 (95% confidence interval (CI): 5.5-83.6) to 52 (95% CI: 6.32-89.0) generations, corresponding to roughly 80-150 years, suggesting near-contemporary colonisation, followed by a more recent demographic expansion that could have been facilitated by changing climate conditions. Moreover, the lack of previous records of this species over the past century, together with the absence of lineage separation and the presence of relatively few private alleles, do not exclude the possibility of an even more recent colonisation event.
- Gaidropsarus (Gadidae, Teleostei) of the North Atlantic Ocean: A brief phylogenetic reviewPublication . Francisco, Sara Martins; Robalo, Joana Isabel; Stefanni, Sergio; Levy, André; Almada, Vítor CarvalhoThe phylogenetic relationships among theNorth Atlantic Gaidropsarus and between the three Gaidropsarinae genera Gaidropsarus, Ciliata and Enchelyopus are reviewed with the hitherto most comprehensive taxonomic sampling of this group. Phylogenetic results (maximum parsimony, maximum likelihood and Bayesian inference) based on nuclear (rhodopsin) and concatenated mitochondrial (12s, 16s and cytb)markers clearly support this subfamily. For the north-eastern Atlantic species of Gaidropsarus, two previously unreported clades were strongly supported, clarifying the relationships within the genus, and revealing fewer distinct taxa in the north Atlantic Gaidropsarus than previously stipulated. The data challenge the specific status of Gaidropsarus mediterraneus and Gaidropsarus guttatus and raise doubts concerning the distinctiveness of other species. A taxonomic revision of the genus is suggested.
- Genetic divergence in the Atlantic-Mediterranean Montagu's blenny Coryphoblennius galerita revealed by molecular and morphological charactersPublication . Domingues, Vera dos Santos; Faria, Cláudia Barreiros Macedo de; Stefanni, Sergio; Santos, Ricardo Serrão; Brito, Alberto; Almada, Vítor CarvalhoCoryphoblennius galerita is a small intertidal fish with a wide distribution and limited dispersal ability, occurring in the northeastern Atlantic and Mediterranean. In this study, we examined Atlantic and Mediterranean populations of C. galerita to assess levels of genetic divergence across populations and to elucidate historical and contemporary factors underlying the distribution of the genetic variability. We analyse three mitochondrial and one nuclear marker and 18 morphological measurements. The combined dataset clearly supports the existence of two groups of C. galerita : one in the Mediterranean and another in the northeastern Atlantic. The latter group is subdivided in two subgroups: Azores and the remaining northeastern Atlantic locations. Divergence between the Atlantic and the Mediterranean can be the result of historical isolation between the populations of the two basins during the Pleistocene glaciations. Present-day barriers such as the Gibraltar Strait or the ‘Almeria-Oran jet’ are also suggested as responsible for this isolation. Our results show no signs of local extinctions during the Pleistocene glaciations, namely at the Azores, and contrast with the biogeographical pattern that has been observed for Atlantic– Mediterranean warm-water species, in which two groups of populations exist, one including the Mediterranean and the Atlantic coast of western Europe, and another encompassing the western tropical coast of Africa and the Atlantic islands of the Azores, Madeira and Canaries. Species like C. galerita that tolerate cooler waters, may have persisted during the Pleistocene glaciations in moderately affected locations, thus being able to accumulate genetic differences in the more isolated locations such as the Azores and the Mediterranean. This study is one of the first to combine morphological and molecular markers (mitochondrial and nuclear) with variable rates of molecular evolution to the study of the relationships of the Atlantic and Mediterranean populations of a cool-water species.
- Phylogenetic relationships of the North-eastern Atlantic and Mediterranean forms of Atherina (Pisces, Atherinidae)Publication . Francisco, Sara Martins; Congiu, Leonardo; Stefanni, Sergio; Castilho, Rita; Brito, Alberto; Ivanova, P. P.; Levy, André; Cabral, Henrique; Kilias, Georgio; Doadrio, Ignacio; Almada, Vítor CarvalhoInexistente
- Phylogeny of the shanny, Lipophrys pholis, from the NE Atlantic using mitochondrial DNA markersPublication . Stefanni, Sergio; Domingues, Vera dos Santos; Bouton, Niels; Santos, Ricardo Serrão; Almada, Frederico José Oliveira de; Almada, Vítor CarvalhoInexistente
- Phylogeography and demography of the Blenniid Parablennius parvicornis and its sister species P. sanguinolentus from the northeastern Atlantic Ocean and the western Mediterranean SeaPublication . Domingues, Vera dos Santos; Stefanni, Sergio; Brito, Alberto; Santos, Ricardo Serrão; Almada, Vítor CarvalhoInexistente