Browsing by Author "Chefaoui, Rosa"
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- Abandonment of traditional saltworks facilitates degradation of halophytic plant communities and Carpobrotus edulis invasionPublication . Chefaoui, Rosa; Chozas, SergioAims In Mediterranean countries, traditional salt exploitation has been practiced over centuries. However, there is a progressive reduction of active saltworks, causing changes in the adjacent halophytic communities and, ultimately, the invasion by opportunistic plant species. Assessing the impact of land use change is key to understanding and protecting these fragile wetland ecosystems. Here, we explore how the abandonment of saltworks is impacting plant communities. We assess if the reduction in saltworks activity alters the composition of protected halophytic communities and favours the invasion by Carpobrotus edulis, an invasive species in many coastal regions throughout the world. Location The Natural Park of Ria Formosa (Algarve, Portugal). Methods We studied variations in the structure of halophytic communities affected to different degrees by C. edulis over three saltworks land use regimes in the Ria Formosa. Plant cover and soil salinity were estimated in a total of 60 transects pertaining to two saltworks complexes harbouring different land use and hydrologic regimes. We performed a non-metric multidimensional scaling ordination of saltworks based on plant cover and identified the indicator species of each saltworks class. Results We found that plant communities significantly varied among types of saltworks according to the pattern of soil salinity and hydrologic regime. We identified C. edulis as the main indicator species of the abandoned saltworks' communities, characterized by less saline soils and being desiccated in summer. Conclusions Land-use change caused by the abandonment of salinas facilitated the transition of halophytic into psammophytic communities and the invasiveness of C. edulis. The maintenance of traditional saltworks activities is vital for the preservation of this fragile wetland ecosystem.
- Accounting for uncertainty in predictions of a marine species: Integrating population genetics to verify past distributionsPublication . Chefaoui, Rosa; Serrao, EsterWe develop a new perspective on the uncertainties affecting the predictions of coastal species distributions using patterns of genetic diversity to assess the congruence of hindcasted distribution models. We model the niche of the subtidal seagrass Cymodocea nodosa, for which previous phylogeographic findings are used to contrast hypotheses for the Last Glacial Maximum (LGM) in the Mediterranean and adjacent Atlantic coastal regions. We focus on amelioration of sampling bias, and explore the influence of other sources of uncertainty such as the number of variables, Ocean General Circulation Models (OGCMs), and thresholds used. To do that, we test geographical and environmental filtering of presences, and a species-specific weighted filter related to political boundaries for background data. Contrary to our initial hypothesis that reducing sampling bias by means of geographical, environmental or background filtering would enhance predictive power and reliability of the models, none of these approaches consistently improved performance. These counter-intuitive results might be explained by the higher relative occurrence area (ROA) inherent to linear coastal study areas in relation to terrestrial regions, which may cause worse predictions and, thus, higher variability among models. We found that the Ocean General Circulation Models (OGCMs), the threshold and, to a smaller extent, the number of variables used, conditioned greatly the variability of the predictions in both accuracy and geographic range. Despite these uncertainties, all models achieved the goal of identifying long-term persistence regions (glacial refugia) where the highest genetic diversity for Cymodocea nodosa is found nowadays. However, only the CCSM corroborated the hypothesis, raised in previous studies, of a vicariant process in shaping the species' genetic structure. (C) 2017 Elsevier B.V. All rights reserved.
- Assessing the conservation status of an Iberian moth using pseudo-absencesPublication . Chefaoui, Rosa; Lobo, J. M.Knowing the distribution of endangered species is of substantial importance for conservation. We considered a useful approach for modeling species distribution when managing information from atlases and museums but when absence data is not available. By modeling the distribution for Graellsia isabelae, a threatened moth species, we assessed its current conservation status and identified its most relevant distribution explanatory variables using Geographic Information System and Generalized Linear Models. The distribution model was built from 136 occurrence records and 25 digitized explanatory variables at a 10310 km resolution. Model predictions from logistic-regressed pseudo-absences, obtained from a presence-only method (Ecological-Niche Factor Analysis), explained 96.23% of the total deviance. We found that the best predictor variables were summer precipitation, aridity, and mean elevation. With respect to host plants, the presence of G. isabelae associated mainly with Scots pine (Pinus sylvestris) and Austrian pine (P. nigra). The finding of 8 areas, exclusively in the eastern Iberian territory, and a larger unoccupied habitat in the western Iberian Peninsula indicates that this species is probably not in equilibrium with its environment by historical factors. Sites of Community Importance under protection do not seem sufficient to maintain current populations, necessitating the protection of suitable neighboring habitats. Our methodology is useful to manage the conservation status of species for which reliable absence data is not available. It is possible to determine those variables that most affect the distribution of species as well as the potential suitable areas with the purpose of evaluating protected areas, connectivity among populations, and possible reintroductions.
- Assessing the effects of pseudo-absences on predictive distribution model performancePublication . Chefaoui, Rosa; Lobo, J. M.Modelling species distributions with presence data from atlases, museum collections and databases is challenging. In this paper, we compare seven procedures to generate pseudoabsence data, which in turn are used to generate GLM-logistic regressed models when reliable absence data are not available. We use pseudo-absences selected randomly or by means of presence-only methods (ENFA and MDE) to model the distribution of a threatened endemic Iberian moth species (Graellsia isabelae). The results show that the pseudo-absence selection method greatly influences the percentage of explained variability, the scores of the accuracy measures and, most importantly, the degree of constraint in the distribution estimated. As we extract pseudo-absences from environmental regions further from the optimum established by presence data, the models generated obtain better accuracy scores, and over-prediction increases. When variables other than environmental ones influence the distribution of the species (i.e., non-equilibrium state) and precise information on absences is non-existent, the random selection of pseudo-absences or their selection from environmental localities similar to those of species presence data generates the most constrained predictive distribution maps, because pseudo-absences can be located within environmentally suitable areas. This study showsthat ifwe do not have reliable absence data, the method of pseudo-absence selection strongly conditions the obtained model, generating different model predictions in the gradient between potential and realized distributions.
- Effects of species' traits and data characteristics on distribution models of threatened invertebratesPublication . Chefaoui, Rosa; Lobo, J. M.; Hortal, JoaquínEffects of species’ traits and data characteristics on distribution models of threatened invertebrates.— The lack of information about the distribution of threatened species inhibits the development of strategies for their conservation. This is a particularly important problem when considering invertebrates. Here we evaluate the effects of species’ traits and data characteristics on the accuracy of species distribution models (SDM) of 20 threatened Iberian invertebrates. We found that the accuracy of the predictions was mostly affected by the characteristics of the data. Species whose distributions were most accurately modelled were those with a greater sample size or smaller relative occurrence area (ROA). Species in habitats that were difficult to detect using GIS data, such as riparian species, tended to be more difficult to predict.
- Environmental drivers of distribution and reef development of the Mediterranean coral Cladocora caespitosaPublication . Chefaoui, Rosa; Casado-Amezua, Pilar; Templado, JoseCladocora caespitosa is the only Mediterranean scleractinian similar to tropical reef-building corals. While this species is part of the recent fossil history of the Mediterranean Sea, it is currently considered endangered due to its decline during the last decades. Environmental factors affecting the distribution and persistence of extensive bank reefs of this endemic species across its whole geographic range are poorly understood. In this study, we examined the environmental response of C. caespitosa and its main types of assemblages using ecological niche modeling and ordination analysis. We also predicted other suitable areas for the occurrence of the species and assessed the conservation effectiveness of Mediterranean marine protected areas (MPAs) for this coral. We found that phosphate concentration and wave height were factors affecting both the occurrence of this versatile species and the distribution of its extensive bioconstructions in the Mediterranean Sea. A set of factors (diffuse attenuation coefficient, calcite and nitrate concentrations, mean wave height, sea surface temperature, and shape of the coast) likely act as environmental barriers preventing the species from expansion to the Atlantic Ocean and the Black Sea. Uncertainties in our large-scale statistical results and departures from previous physiological and ecological studies are also discussed under an integrative perspective. This study reveals that Mediterranean MPAs encompass eight of the ten banks and 16 of the 21 beds of C. caespitosa. Preservation of water clarity by avoiding phosphate discharges may improve the protection of this emblematic species.
- Environmental niche divergence among three dune shrub sister species with parapatric distributionsPublication . Chozas, Sergio; Chefaoui, Rosa; Correia, Otilia; Bonal, Raul; Hortal, JoaquínBackground and Aims The geographical distributions of species are constrained by their ecological requirements. The aim of this work was to analyse the effects of environmental conditions, historical events and biogeographical constraints on the diversification of the three species of the western Mediterranean shrub genus Stauracanthus, which have a parapatric distribution in the Iberian Peninsula. Methods Ecological niche factor analysis and generalized linear models were used to measure the response of all Stauracanthus species to the environmental gradients and map their potential distributions in the Iberian Peninsula. The bioclimatic niche overlap between the three species was determined by using Schoener's index. The genetic differentiation of the Iberian and northern African populations of Stauracanthus species was characterized with GenalEx. The effects on genetic distances of the most important environmental drivers were assessed through Mantel tests and non-metric multidimensional scaling. Key Results The three Stauracanthus species show remarkably similar responses to climatic conditions. This supports the idea that all members of this recently diversified clade retain common adaptations to climate and consequently high levels of climatic niche overlap. This contrasts with the diverse edaphic requirements of Stauracanthus species. The populations of the S. genistoides-spectabilis clade grow on Miocene and Pliocene fine-textured sedimentary soils, whereas S. boivinii, the more genetically distant species, occurs on older and more coarse-textured sedimentary substrates. These patterns of diversification are largely consistent with a stochastic process of geographical range expansion and fragmentation coupled with niche evolution in the context of spatially complex environmental fluctuations. Conclusions: The combined analysis of the distribution, realized environmental niche and phylogeographical relationships of parapatric species proposed in this work allows integration of the biogeographical, ecological and evolutionary processes driving the evolution of species adaptations and how they determine their current geographical ranges.
- Evidence for rangewide panmixia despite multiple barriers to dispersal in a marine musselPublication . Lourenço, Carla R.; Nicastro, Katy; McQuaid, Christopher D.; Chefaoui, Rosa; Assis, J.; Taleb, Mohammed Z.; Zardi, Gerardo I.Oceanographic features shape the distributional and genetic patterns of marine species by interrupting or promoting connections among populations. Although general patterns commonly arise, distributional ranges and genetic structure are species-specific and do not always comply with the expected trends. By applying a multimarker genetic approach combined with Lagrangian particle simulations (LPS) we tested the hypothesis that oceanographic features along northeastern Atlantic and Mediterranean shores influence dispersal potential and genetic structure of the intertidal mussel Perna perna. Additionally, by performing environmental niche modelling we assessed the potential and realized niche of P. perna along its entire native distributional range and the environmental factors that best explain its realized distribution. Perna perna showed evidence of panmixia across > 4,000 km despite several oceanographic breaking points detected by LPS. This is probably the result of a combination of life history traits, continuous habitat availability and stepping-stone dynamics. Moreover, the niche modelling framework depicted minimum sea surface temperatures (SST) as the major factor shaping P. perna distributional range limits along its native areas. Forthcoming warming SST is expected to further change these limits and allow the species to expand its range polewards though this may be accompanied by retreat from warmer areas.
- Integrating reproductive phenology in ecological niche models changed the predicted future ranges of a marine invaderPublication . Chefaoui, Rosa; Serebryakova, Alexandra; Engelen, Aschwin; Viard, Frédérique; Serrao, EsterAim Phenology of a wide diversity of organisms has a dependency on climate, usually with reproductive periods beginning earlier in the year and lasting longer at lower latitudes. Temperature and day length are known environmental drivers of the reproductive timing of many species. Hence, reproductive phenology is sensitive to warming and is important to be considered for reliable predictions of species distributions. This is particularly relevant for rapidly spreading non-indigenous species (NIS). In this study, we forecast the future ranges of a NIS, the seaweed Sargassum muticum, including its reproductive phenology. Location Coastal areas of the Northern Hemisphere (Pacific and Atlantic oceans). Methods We used ecological niche modelling to predict the distribution of S. muticum under two scenarios forecasting limited (RCP 2.6) and severe (RCP 8.5) future climate changes. We then refined our predictions with a hybrid model using sea surface temperature constraints on reproductive phenology. Results Under the most severe climate change scenario, we predicted northward expansions which may have significant ecological consequences for subarctic coastal ecosystems. However, in lower latitudes, habitats currently occupied by S. muticum will no longer be suitable, creating opportunities for substantial community changes. The temperature constraints imposed by the reproductive window were shown to restrict the modelled future species expansion strongly. Under the RCP 8.5 scenario, the total range area was expected to increase by 61.75% by 2100, but only by 1.63% when the reproductive temperature window was considered. Main conclusions Altogether these results exemplify the need to integrate phenology better to improve the prediction of future distributional shifts at local and regional scales.
- Landscape metrics as indicators of coastal morphology: A multi-scale approachPublication . Chefaoui, RosaIn this study, the aim was to assess how commonly used landscape metrics perform as predictors ofcoastal shape. I examined nine metrics computed in FRAGSTATS to model the distribution of three coastalfeatures of the Iberian Peninsula: beaches, capes and gulfs. A multi-scale approach was used combiningthree extents, three resolutions and five moving-window sizes to implement generalized linear models(GLMs). This study has found that three landscape metrics (edge density, mean perimeter-area ratioand percentage of landscape) were good indicators for the three coastal features, while mean shapeindex was only for beaches and gulfs. Differences in performance were found among the coastal featuresand scales studied. GLMs revealed that the smallest extent (Levante coast) and resolutions (250 m2and1 km2) achieved better validation results, suggesting a higher suitability of these scales for detectingchanges in vectorial shorelines. Differences in sensitivity and specificity were also found among modelsestimated from different moving-window sizes. The present study confirms previous findings on the highmulticollinearity of landscape metrics, and the convenience of testing correlations in advance. Raster-based metrics computed from vectorial coastlines were effectively incorporated in spatial modeling. Thisresearch provides new insight into the use of coastal shape to predict species distributions and othercoastal processes, serving as a base for future studies.