Browsing by Author "Francisco, Sara Martins"
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- Are local extinctions and recolonizations continuing at the colder limits of marine fish distributions? Halobatrachus didactylus (Bloch & Schneider, 1801), a possible candidatePublication . Robalo, Joana Isabel; Crespo, Ana Maria Azambuja Farinha da Conceição Pereira; Castilho, Rita; Francisco, Sara Martins; Amorim, Maria Clara Pessoa; Almada, Vítor CarvalhoIn this paper, we compare the populations of the Lusitanian toadfish Halobatrachus didactylus along the Portuguese shore, using a putative fragment of the mitochondrial control region and the first intron of the S7 ribosomal protein gene. This demersal species ranges from the tropical West African coast to the Iberian Peninsula and the Mediterranean, having its northern limit in the Tagus River. For the putative control region, a single haplotype occurs in all fish from Tagus and Sado (the location immediately to the south) with a clear increase in diversity to the South, peaking at Algarve (south Portugal). The data seem to point to a very recent Holocenic colonization of Tagus and Sado from the South (possibly Algarve). We suggest that even small oscillations in sea surface temperature (SST) may cause local extinctions and subsequent recolonizations in populations of thermophilic fish that are at the cold limit of their distributions.
- Contrasts in genetic structure and historical demography of marine and riverine populations of Atherina at similar geographical scalesPublication . Francisco, Sara Martins; Cabral, Henrique; Vieira, Maria Natividade; Almada, Vítor CarvalhoIn this paper, we compare the genetic structure and the historical demography of two populations of the sand smelt Atherina boyeri from the rivers Tagus and Mondego (Portugal) with two groups of samples of the closely related marine Atherina presbyter collected on the shore at comparable latitudes. A. presbyter is a pelagic marine inshore fish, while A. boyeri is typically found in coastal lagoons, estuaries and freshwaters bodies. Analysis of mtDNA control region sequences showed that the marine A. presbyter did not display signs of genetic differentiation between sites some hundreds of kilometers apart. On the contrary, A. boyeri showed clear differences between populations. The populations of A. boyeri showed a much lower genetic diversity and younger coalescence times when compared with A. presbyter. We suggest that these differences reflect the interplay between differences in ecology between the two species and the historical impact of the glaciations. While A. presbyter likely moved to the south evading the cold periods, A. boyeri probably went extinct and its populations in Western Europe are recent recolonizations from western Mediterranean refugia.
- 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 structure and historical demography of the shanny Lipophrys pholis in the Portuguese coast based on mitochondrial DNA analysisPublication . Francisco, Sara Martins; Vieira, Maria Natividade; Almada, Vítor CarvalhoInexistente
- Historical gene flow constraints in a northeastern atlantic fish: Phylogeography of the ballan wrasse labrus bergylta across its distribution rangePublication . Almada, Frederico José Oliveira de; Francisco, Sara Martins; Lima, Cristina Silva; Fitzgerald, Richard; Mirimin, Luca; Villegas-Ríos, David; Saborido-Rey, Fran; Afonso, Pedro; Morato, Telmo; Bexiga, Sérgio; Robalo, Joana IsabelThe distribution and demographic patterns of marine organisms in the north Atlantic were largely shaped by climatic changes during the Pleistocene, when recurrent glacial maxima forced them to move south or to survive in northern peri-glacial refugia. These patterns were also influenced by biological and ecological factors intrinsic to each species, namely their dispersion ability. The ballan wrasse (Labrus bergylta), the largest labrid fish along Europe's continental margins, is a target for fisheries and aquaculture industry. The phylogeographic pattern, population structure, potential glacial refugia and recolonization routes for this species were assessed across its full distribution range, using mitochondrial and nuclear markers. The existence of a marked population structure can reflect both recolonization from three distinct glacial refugia and current and past oceanographic circulation patterns. Although isolated in present times, shared haplotypes between continental and Azores populations and historical exchange of migrants in both directions point to a common origin of L. bergylta. This situation is likely to be maintained and/or accentuated by current circulation patterns in the north Atlantic, and may lead to incipient speciation in the already distinct Azorean population. Future monitoring of this species is crucial to evaluate how this species is coping with current environmental changes.
- Identification of adult and juvenile Atherina presbyter Cuvier, 1829 in a marine coastal area adjacent to Tagus estuary (NE Atlantic): A molecular tool for an ecological questionPublication . Almada, Frederico José Oliveira de; Carpi, Piera; Carlos, Fábio Ferreira; Francisco, Sara Martins; Faria, Ana Margarida; Lungu, Ruxanda; Coelho, Pedro Duarte; Neto, José; Gonçalves, Emanuel João; Robalo, Joana IsabelA simple PCR-RFLP consisting in the digestion of a fragment of the 12S ribosomal RNA (12SrRNA) with species-specific restriction enzymes (MboII and HinfI) was developed to distinguish northeastern Atlantic species in the genus Atherina. Unambiguous identification of morphologically similar sympatric species is frequently difficult, especially when younger specimens are included in the analysis. Genetic and morphological analysis of a total of 123 atherinids collected near the mouth of the Tagus estuary (west Portugal) confirmed that only Atherina presbyter (sand smelt) adults and juveniles are recurrently using these marine rocky habitats as spawning and nursery grounds, respectively. The importance of applying non-destructive methods is emphasized. In the future, the conditions involved in the transition from marine A. presbyter to estuarine/ riverine A. boyeri should be further evaluated along with the ability of larvae and juveniles to cope with river flow and tidal currents drift.
- Longitudinal distribution and lateral pattern of megalopal settlement and juvenile recruitment of Carcinus maenas (L.) (Brachyura, Portunidae) in the Mira River Estuary, PortugalPublication . Silva, Inês C.; Dinis, Ana M.; Francisco, Sara Martins; Flores, Augusto A. V.; Paula, José R.Settlement is a critical process in the life history of crabs, and thus affecting the abundance, distribution and structure of estuarine communities. The spatial pattern of settlement of megalopae of the shore crab Carcinus maenas along a longitudinal estuarine gradient (Mira River Estuary, Portugal) was examined, as well as its effects on the juvenile population. To measure megalopal settlement, four replicate collectors were deployed in six equally spaced stations along the estuarine axis. Juveniles were collected on the same locations with a quadrat randomly deployed on the substrate. To assess fine-scale megalopal settlement within a curved region of the estuary, replicate collectors were deployed on both margins along Moinho da Asneira curve. Megalopae settled differently along the six longitudinal points, with a tendency to attenuate their settlement upstream. Within the curved region, megalopae preferentially settled on the left margin collectors, probably due to the weaker velocity speeds felt on this margin. Concerning the overall juvenile density, there were significant differences among the stations distributed along the estuary, but they did no reflect a longitudinal dispersion attenuation pattern. Size-frequency distribution of the juvenile population showed that the average size is higher on the left margin. Recruits (carapace length between 1.0 mm and 3.4 mm) were more abundant on the upstream stations. Density of early juveniles (3.4 mme6.5 mm) and juveniles (6.5 mme10 mm) was more stable throughout the estuary axis than that of recruits. This distribution pattern may result from tidal excursion processes or mechanisms to avoid biotic interactions, such as predation and competition.
- Metapopulations in temporary streams - The role of drought-flood cycles in promoting high genetic diversity in a critically endangered freshwater fish and its consequences for the futurePublication . Santos, Carla Sousa; Robalo, Joana Isabel; Francisco, Sara Martins; Carrapato, Carlos; Cardoso, Ana Cristina; Doadrio, IgnacioGenetic factors have direct and indirect impacts in the viability of endangered species. Assessing their genetic diversity levels and population structure is thus fundamental for conservation and management. In this paper we use mitochondria] and nuclear markers to address phylogeographic and demographic data on the critically endangered Anaecypris hispanica, using a broad sampling set which covered its known distribution area in the Iberian Peninsula. Our results showed that the populations of A. hispanica are strongly differentiated (high and significant Phi(ST) and F-ST values, corroborated by the results from AMOVA and SAMOVA) and genetically diversified. We suggest that the restricted gene flow between populations may have been potentiated by ecological, hydrological and anthropogenic causes. Bayesian skyline plots revealed a signal for expansion for all populations (t(MRCA) between 68 kya and 1.33 Mya) and a genetic diversity latitudinal gradient was detected between the populations from the Upper (more diversified) and the Lower (less diversified) Guadiana river basin. We postulate a Pleistocenic westwards colonization route for A. hispanica in the Guadiana river basin, which is in agreement with the tempo and mode of paleoevolution of this drainage. The colonization of River Guadalquivir around 60 kya with migrants from the Upper Guadiana, most likely by stream capture, is also suggested. This study highlights the view that critically endangered species facing range retreats (about 47% of its known populations have disappeared in the last 15 years) are not necessarily small and genetically depleted. However, the extinction risk is not negligible since A. hispanica faces the combined effect of several deterministic and stochastic negative factors and, moreover, recolonization events after localized extinctions are very unlikely to occur due to the strong isolation of populations and to the patchily ecologically-conditioned distribution of fish. The inferred species distribution models highlight the significant contribution of temperature seasonality and isothermality to A. hispanica occurrence in Guadiana environments and emphasize the importance of stable climatic conditions for the preservation of this species. Given the strong population structure, high percentage of private haplotypes and virtual absence of inter-basin gene flow we suggest that each A. hispanica population should be considered as an independent Operational Conservation Unit and that ex-situ and in-situ actions should be conducted in parallel to allow for the long-term survival of the species and the preservation of the genetic integrity of its populations. (C) 2014 Elsevier Inc. All rights reserved.
- Multilocus phylogenetic analysis of the genus Atherina (Pisces: Atherinidae)Publication . Francisco, Sara Martins; Congiu, Leonardo; von der Heyden, Sophie; Almada, Vítor CarvalhoSand-smelts are small fishes inhabiting inshore, brackish and freshwater environments and with a distribution in the eastern Atlantic and Mediterranean Sea, extending south into the Indian Ocean. Here, we present a broad phylogenetic analysis of the genus Atherina using three mitochondrial (control region, 12S and 16S) and two nuclear markers (rhodopsin and 2nd intron of S7). Phylogenetic analyses fully support the monophyly of the genus. Two anti-tropical clades were identified, separating the South African Atherina breviceps from the north-eastern Atlantic and Mediterranean Atherina’ species. In European waters, two groups were found. The first clade formed by a well supported species-pair: Atherina presbyter (eastern Atlantic) and Atherina hepsetus (Mediterranean), both living in marine waters; a second clade included Atherina boyeri (brackish and freshwater environments) and two independent lineages of marine punctated and non-punctated fishes, recently proposed as separate species. Sequence divergence values strongly suggest multiple species within the A. boyeri complex.