Browsing by Author "Santos, Carla Sousa"
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- Absence of consistent genetic differentiation among several morphs of Actinia (Actiniaria: Actiniidae) occurring in the portuguese coastPublication . Pereira, Ana Martins; Brito, Cristiana Maria; Sanches, Joana; Santos, Carla Sousa; Robalo, Joana IsabelActinia equina, the beadlet sea anemone, is a very labile species, displaying variable colour patterns, broad habitat choice and diverse modes of reproduction. Historically, studies using genetic markers such as allozymes and differences in habitat choice lead several authors to propose that different colour morphs could represent different species. One of the species defined was A. fragacea. In this paper, the relationships between brown, red and green colour morphs of A. equina and A. fragacea were studied, using two DNA fragments (one mitochondrial and one nuclear). Individuals were sampled from three different areas in Portugal separated by a maximum distance of 500 km. This is the first study applying direct sequencing of selected gene fragments to approach the validity of Actinia morphs as different genetic entities. The results show that, at least in the Portuguese coast, these colour morphs do not correspond to the two valid species recognized in the literature. The existence of cryptic species is discussed.
- Broad-scale sampling of primary freshwater fish populations reveals the role of intrinsic traits, inter-basin connectivity, drainage area and latitude on shaping contemporary patterns of genetic diversityPublication . Santos, Carla Sousa; Robalo, Joana Isabel; Pereira, Ana Martins; Branco, Paulo; Santos, José Maria; Ferreira, Maria Teresa; Sousa, Mónica; Doadrio, IgnacioBackground. Worldwide predictions suggest that up to 75% of the freshwater fish species occurring in rivers with reduced discharge could be extinct by 2070 due to the combined effect of climate change and water abstraction. The Mediterranean region is considered to be a hotspot of freshwater fish diversity but also one of the regions where the effects of climate change will be more severe. Iberian cyprinids are currently highly endangered, with over 68% of the species raising some level of conservation concern. Methods. During the FISHATLAS project, the Portuguese hydrographical network was extensively covered (all the 34 river basins and 47 sub-basins) in order to contribute with valuable data on the genetic diversity distribution patterns of native cyprinid species. A total of 188 populations belonging to 16 cyprinid species of Squalius, Luciobarbus, Achondrostoma, Iberochondrostoma, Anaecypris and Pseudochondrostoma were characterized, for a total of 3,678 cytochrome b gene sequences. Results. When the genetic diversity of these populations was mapped, it highlighted differences among populations from the same species and between species with identical distribution areas. Factors shaping the contemporary patterns of genetic diversity were explored and the results revealed the role of latitude, inter-basin connectivity, migratory behaviour, species maximum size, species range and other species intrinsic traits in determining the genetic diversity of sampled populations. Contrastingly, drainage area and hydrological regime (permanent vs. temporary) seem to have no significant effect on genetic diversity. Species intrinsic traits, maximum size attained, inter-basin connectivity and latitude explained over 30% of the haplotype diversity variance and, generally, the levels of diversity were significantly higher for smaller sized species, from connected and southerly river basins. Discussion. Targeting multiple co-distributed species of primary freshwater fish allowed us to assess the relative role of historical versus contemporary factors affecting genetic diversity. Since different patterns were detected for species with identical distribution areas we postulate that contemporary determinants of genetic diversity (species' intrinsic traits and landscape features) must have played a more significant role than historical factors. Implications for conservation in a context of climate change and highly disturbed habitats are detailed, namely the need to focus management and conservation actions on intraspecific genetic data and to frequently conduct combined genetic and demographic surveys.
- Comparisons of the genetic structure of Squalius populations (Teleostei, Cyprinidae) from rivers with contrasting histories, drainage areas and climatic conditions based on two molecular markersPublication . Almada, Vítor Carvalho; Santos, Carla SousaThe genetic structure of Squalius populations from Portuguese Atlantic- and Mediterranean-type streams (assigned to six distinct morphoclimatic regions) was compared using sequences of the cytb and betaactin genes. The drainage area was significantly correlated to all the genetic diversity indices, pointing to the need to control for this effect in comparing populations with different histories and paleoecologies. A significant correlation was also found between genetic diversity and the morphoclimatic regions to which the rivers were assigned, with the highest diversity in warmer, lower latitude, Mediterranean-type streams. This relationship was not due to idiosyncratic characteristics of the clades compared. When the drainage area and phylogenetic effects were removed, the southern Mediterranean streams harboured significantly more genetic diversity even when compared with much larger northern streams. It is argued that these results are likely caused both by the metapopulation structure of the Mediterranean streams and by the severe reduction or local extinction of populations in the northern rivers during glaciations.
- Conservation challenges imposed by evolutionary history and habitat suitability shifts of endangered freshwater mussels under a global climate change scenarioPublication . Reis, Joaquim; Perea, Silvia; Gama, Mafalda; Mendes, Sofia L.; Sousa, Vitor C.; Lima, Cristina S.; Banha, Filipe; Gil, Maria; Alvarez, Maria Garcia; Anastácio, P.M.; Santos, Carla Sousa; Araujo, RafaelClimate change and associated shifts in temperature and precipitation patterns have become an increasing concern as drivers of ongoing biodiversity loss. The Mediterranean region is particularly vulnerable, being both a biodiversity hotspot and a region very prone to desertification. Freshwater mussels are amongst the most threatened invertebrate taxa worldwide. Unio tumidiformis is an endemic and endangered species restricted to the southern Iberian Peninsula, living in temporary Mediterranean-type streams. Freshwater mussels need a fish host for successful larval transformation, meaning U. tumidiformis must belong to the genus Squalius. The main objective of this study was to evaluate the vulnerability of U. tumidiformis to climate change, by studying its population genetics and evolutionary history, its current and future habitat suitability, and that of its hosts. Genetic population structure and diversity were assessed using Single-Nucleotide Polymorphisms through Genotyping by Sequencing and used to infer species evolutionary history. The species potential distribution was modeled using an ensemble forecasting approach, and future shifts in habitat suitability were assessed with the projected climate data layers from Worldclim. Most populations showed extreme genetic differentiation (Fst up to 0.745), even from close neighboring ones. Upper Guadiana populations were more diverse and less differentiated. We hypothesize that U. tumidiformis originated in Upper Guadiana and followed the same colonization routes as their hosts with numerous founder effects and bottlenecks. Our results also predicted a reduction of 99% of climatically suitable areas for U. tumidiformis in the Iberian Peninsula until 2040. For the fish hosts, a maximum 42% reduction in suitable areas was estimated throughout the century, with remaining adequate habitats in the north. Our results suggest that difficult conservation options are necessary, prioritizing the preservation of populations, translocations to the northern area of its historical range and stream engineering to increase resilience to droughts.
- Development and characterization of novel microsatellite loci for Lusitanian toadfish, Halobatrachus didactylusPublication . Santos, Carla Sousa; Fonseca, Paulo Jorge; Amorim, Maria Clara PessoaThe Lusitanian toadfish Halobatrachus didactylus is an eastern Atlantic polygynous species showing male paternal care. In this paper we describe 5 novel microsatellite loci obtained by 454 GS-FLX Titanium pyrosequencing of a microsatellite-enriched library. The number of alleles per polymorphic locus varied between 2 and 4, and the observed heterozygosity ranged from 0.082 to 0.600. No significant deviation from Hardy–Weinberg equilibrium was found and there was no evidence for linkage disequilibrium. These markers will be of great value for paternity studies and population genetics of this species.
- Evidence of extensive mitochondrial introgression with nearly complete substitution of the typical Squalius pyrenaicus-like mtDNA of the Squalius alburnoides complex (Cyprinidae) in an independent Iberian drainagePublication . Santos, Carla Sousa; Collares-Pereira, Maria João; Almada, Vítor CarvalhoThe first occurrence of massive mitochondrial introgression of Squalius aradensis genes in Squalius alburnoides, a hybridogenetic complex that usually carries mtDNA of its maternal ancestor (Squalius pyrenaicus) is reported. Possible implications of such introgressions for the history of the complex are discussed.
- Evolutionary history and population genetics of a cyprinid fish (Iberochondrostoma olisiponensis) endangered by introgression from a more abundant relativePublication . Santos, Carla Sousa; Gante, Hugo F.; Cunha, Pedro Proença da; Martins, António Antunes; Arruda, Marco; Alves, Maria JuditeThe use of molecular techniques has shown that hybridization and introgression have significant impacts in evolution, by means of transfer of genetic variation and formation of hybrid species. In this paper we use mitochondrial and nuclear sequence data to investigate the evolutionary history, levels of genetic diversity and population differentiation of a rare and endangered fish species. Our results suggest that a hybrid origin scenario of Chondrostoma olisiponensis is a likely explanation for the shared genetic and morphological traits with Iberochondrostoma and Achondrostoma ? Pseudochondrostoma. The basal positioning of C. olisiponensis alleles in all loci analyzed indicates that hybridization events occurred before differentiation within each of these groups, most likely during Middle–Late Miocene. Originally described as C. olisiponensis, we suggest that this species should be placed in the genus Iberochondrostoma to avoid confusion with ‘real’ central European Chondrostoma and to (partially) reflect its evolutionary history. Analyses of levels of genetic diversity and patterns of population subdivision show that populations of the rare Iberochondrostoma olisiponensis are differentiated (high and significant uST and FST) and genetically depauperate (very low S, p, and h). I. olisiponensis is simultaneously imperiled by small population sizes and contemporary bidirectional hybridization with another critically endangered sympatric species (Iberochondrostoma lusitanicum). Urgent ex-situ conservation measures involving supportive breeding of I. olisiponensis are needed to preserve present genetic variation and eventually increase in situ population sizes, along with further studies focused on different life history and behavioral characteristics of this highly endangered species.
- Ex situ reproduction of Portuguese endangered cyprinids in the context of their conservationPublication . Santos, Carla Sousa; Gil, Fátima; Almada, Vítor CarvalhoInexistente
- Feeding ecology and life-history strategy of nesting males in a fish with long parental care, Lusitanian toadfish (Halobatrachus didactylus, Batrachoididae)Publication . Félix, Pedro M.; Amorim, Maria Clara Pessoa; Pereira, Tadeu José; Fonseca, Paulo Jorge; Santos, Carla Sousa; Costa, José LinoThe Lusitanian toadfish, Halobatrachus didactylus, like other batrachoidids, is a benthic fish species with nesting behaviour during the breeding season. During this prolonged period it engages in mating activities and remains in the nest providing parental care. It is not known whether males feed while providing parental care but it is likely that their limited mobility may restrict their diet and influence their fitness. As a consequence, egg cannibalism could occur as a life-history strategy. The aim of the present study is to ascertain the feeding behaviour of nesting males, in comparison to mature non-nesting males, and to identify potential life-history traits related to egg cannibalism. Nest-holders were sampled from artificial nests placed in an intertidal area of the Tagus estuary, only exposed during spring low tides. The diet of nest-holders was compared with that of non-nesting mature males from the same area, captured by otter trawl. The present study demonstrates that despite their constrained mobility nest-holders feed during the breeding season, although in a more opportunistic fashion than non-nesting males. Nest-holders showed a generalist feeding behaviour, with a more heterogeneous diet. Egg cannibalism was not related to male condition, paternity or brood size but showed a higher incidence early in the season when water temperatures were lower. The results suggest a possible seasonal trade-off strategy between care and energy recovery, triggered by environmental factors, where under unfavourable conditions to sustain viable eggs the male may recover energy by eating eggs, thus benefiting future reproductive success, later in the season.
- Fertile triploid males - An uncommon case among hybrid vertebratesPublication . Santos, Carla Sousa; Collares-Pereira, Maria João; Almada, Vítor CarvalhoThe endemic Iberian minnow Squalius alburnoides is a complex of fishes of hybrid origin including both males and females with distinct ploidy levels and varying proportions of the parental genomes. In this paper we demonstrated that in contrast to many vertebrate hybrid lineages the sperm of triploid hybrid males of S. alburnoides is viable and fully functional. Flow cytometry and analysis of sequences of a fragment of the beta-actin nuclear gene applied to progenitors and offspring evidenced that these males produced their sperm clonally, as already described for diploid hybrids. The presence of different types of fertile males (nonhybrid diploids with normal meiosis and both diploid and triploid hybrids) coupled with hybridogenetic meiosis in females endows this vertebrate complex with a high level of independence from other species and contributes to maintain its genetic variability.