Spatial versus spatio-temporal approaches for studying metacommunities: a multi-taxon analysis in Mediterranean and tropical temporary ponds.

Prior research on metacommunities has largely focused on snapshot surveys, often overlooking temporal dynamics. In this study, our aim was to compare the insights obtained from metacommunity analyses based on a spatial approach repeated over time, with a spatio-temporal approach that consolidates all data into a single model. We empirically assessed the influence of temporal variation in the environment and spatial connectivity on the structure of metacommunities in tropical and Mediterranean temporary ponds. Employing a standardized methodology across both regions, we surveyed multiple freshwater taxa in three time periods within the same hydrological year from multiple temporary ponds in each region. To evaluate how environmental, spatial and temporal influences vary between the two approaches, we used nonlinear variation partitioning analyses based on generalized additive models. Overall, this study underscores the importance of adopting spatio-temporal analytics to better understand the processes shaping metacommunities. While the spatial approach suggested that environmental factors had a greater influence, our spatio-temporal analysis revealed that spatial connectivity was the primary driver influencing metacommunity structure in both regions. Temporal effects were equally important as environmental effects, suggesting a significant role of ecological succession in metacommunity structure.

Inconsistent response of taxonomic groups to space and environment in mediterranean and tropical pond metacommunities.

The metacommunity concept provides a theoretical framework that aims at explaining organism distributions by a combination of environmental filtering, dispersal, and drift. However, few works have attempted a multitaxon approach and even fewer have compared two distant biogeographical regions using the same methodology. We tested the expectation that temperate (mediterranean-climate) pond metacommunities would be more influenced by environmental and spatial processes than tropical ones, because of stronger environmental gradients and a greater isolation of waterbodies. However, the pattern should be different among groups of organisms depending on their dispersal abilities. We surveyed 30 tropical and 32 mediterranean temporary ponds from Costa Rica and Spain, respectively, and obtained data on 49 environmental variables. We characterized the biological communities of bacteria and archaea (from the water column and the sediments), phytoplankton, zooplankton, benthic invertebrates, amphibians and birds, and estimated the relative role of space and environment on metacommunity organization for each group and region, by means of variation partitioning using generalized additive models. Purely environmental effects were important in both tropical and mediterranean ponds, but stronger in the latter, probably due to their larger limnological heterogeneity. Spatially correlated environment and pure spatial effects were greater in the tropics, related to higher climatic heterogeneity and dispersal processes (e.g., restriction, surplus) acting at different scales. The variability between taxonomic groups in the contribution of spatial and environmental factors to metacommunity variation was very wide, but higher in active, compared with passive, dispersers. Higher environmental effects were observed in mediterranean passive dispersers, and higher spatial effects in tropical passive dispersers. The unexplained variation was larger in the tropical setting, suggesting a higher role for stochastic processes, unmeasured environmental factors, or biotic interactions in the tropics, although this difference affected some actively dispersing groups (insects and birds) more than passive dispersers. These results, despite our limitations in comparing only two regions, provide support, for a wide variety of aquatic organisms, for the classic view of stronger abiotic niche constraints in temperate areas compared with the tropics. The heterogeneous response of taxonomic groups between regions also points to a stronger influence of regional context than organism adaptations on metacommunity organization.

The antagonistic effect of UV radiation on warming or nitrate enrichment depends on ecotypes of freshwater macroalgae (Charophytes).

Increases in ultraviolet radiation (UVR), a negative global change factor, affect aquatic primary producers. This effect is expected to be modulated by other global change factors, and to be different for populations adapted to different environments. A common garden experimental approach using freshwater green macroalgae, the cosmopolitan charophyte species Chara hispida and C. vulgaris, allowed us to test whether the beneficial increases in water temperature (T) and nitrate concentration (N) mitigate negative UVR effects. Also, whether these interactions would be not only species-specific but also according to the origin of the population; therefore, two populations of each species were used: one from a coastal wetland and the other from a mountain lake. Two factorial-design experiments were performed: (i) the presence and absence of UVR × lower and higher T × four populations, and (ii) the presence and absence of UVR × lower and higher N × four populations. Response variables were: growth, morphometry, UVR-protective compounds, photosynthetic pigments, and stoichiometric composition. There were consistent response patterns in the key variables that represent different organization levels. Our main results showed that both warming and, to a lesser extent, the increase in nutrients ameliorated the negative effects of UVR on the molecular processes involved in acclimation to UVR, and that such a mitigating effect depended on the different phenotypic plasticity of each species and each ecotype. The coastal populations, being from a more variable environment, were more resilient than the mountain populations, mainly because of changes in growth and morphology.

Propuesta de procedimientos para elaborar tareas integradoras en asignaturas de la carrera Medicina / Proposal of procedures to develop integrative tasks in subjects from Medicine career

RESUMEN Fundamento: La educación médica en el siglo XXI exige de un estudiante capaz de captar las conexiones entre las diferentes asignaturas para dar solución a determinada problemática y puedan integrar aquello que se les enseñó aisladamente en las asignaturas. Objetivo: Describir procedimientos generales de las asignaturas de Anatomía Patológica, Microbiología y Genética para elaborar tareas integradoras que contribuyan al desarrollo de la independencia cognoscitiva de los estudiantes de la carrera Medicina. Desarrollo: Se exponen las características de las tareas docentes integradoras y los procedimientos para su elaboración a partir de la determinación de los nodos interdisciplinarios entre las asignaturas de Anatomía Patológica, Microbiología y Genética. Conclusiones: Los procedimientos que se presentan para la elaboración de las tareas docentes integradoras, orientan metodológicamente la actividad del profesor para desarrollar la independencia cognoscitiva de los estudiantes de la carrera Medicina.

ABSTRACT Background: In the 21st century, medical education requires a student capable of understanding the relations among the different subjects in order to solve a certain problem and integrate everything taught in isolation in all of them. Objective: To describe general procedures in the Pathological Anatomy, Microbiology and Genetics subjects to elaborate integrative tasks that contribute to the development of the cognitive independence in Medicine students. Development: The characteristics of the integrating teaching tasks and the procedures for their elaboration from the determination of the interdisciplinary nodes among the Pathological Anatomy, Microbiology and Genetics subjects are exposed. Conclusions: The procedures presented for the elaboration of the integrating teaching tasks, methodologically guide the teacher´s activity to develop the cognitive independence in Medicine students.

Hydrology Affects Environmental and Spatial Structuring of Microalgal Metacommunities in Tropical Pacific Coast Wetlands.

The alternating climate between wet and dry periods has important effects on the hydrology and therefore on niche-based processes of water bodies in tropical areas. Additionally, assemblages of microorganism can show spatial patterns, in the form of a distance decay relationship due to their size or life form. We aimed to test spatial and environmental effects, modulated by a seasonal flooding climatic pattern, on the distribution of microalgae in 30 wetlands of a tropical dry forest region: the Pacific coast of Costa Rica and Nicaragua. Three surveys were conducted corresponding to the beginning, the highest peak, and the end of the hydrological year during the wet season, and species abundance and composition of planktonic and benthic microalgae was determined. Variation partitioning analysis (as explained by spatial distance or environmental factors) was applied to each seasonal dataset by means of partial redundancy analysis. Our results show that microalgal assemblages were structured by spatial and environmental factors depending on the hydrological period of the year. At the onset of hydroperiod and during flooding, neutral effects dominated community dynamics, but niche-based local effects resulted in more structured algal communities at the final periods of desiccating water bodies. Results suggest that climate-mediated effects on hydrology can influence the relative role of spatial and environmental factors on metacommunities of microalgae. Such variability needs to be accounted in order to describe accurately community dynamics in tropical coastal wetlands.

Inferring the relative resilience of alternative states.

Ecological systems may occur in alternative states that differ in ecological structures, functions and processes. Resilience is the measure of disturbance an ecological system can absorb before changing states. However, how the intrinsic structures and processes of systems that characterize their states affects their resilience remains unclear. We analyzed time series of phytoplankton communities at three sites in a floodplain in central Spain to assess the dominant frequencies or "temporal scales" in community dynamics and compared the patterns between a wet and a dry alternative state. The identified frequencies and cross-scale structures are expected to arise from positive feedbacks that are thought to reinforce processes in alternative states of ecological systems and regulate emergent phenomena such as resilience. Our analyses show a higher species richness and diversity but lower evenness in the dry state. Time series modeling revealed a decrease in the importance of short-term variability in the communities, suggesting that community dynamics slowed down in the dry relative to the wet state. The number of temporal scales at which community dynamics manifested, and the explanatory power of time series models, was lower in the dry state. The higher diversity, reduced number of temporal scales and the lower explanatory power of time series models suggest that species dynamics tended to be more stochastic in the dry state. From a resilience perspective our results highlight a paradox: increasing species richness may not necessarily enhance resilience. The loss of cross-scale structure (i.e. the lower number of temporal scales) in community dynamics across sites suggests that resilience erodes during drought. Phytoplankton communities in the dry state are therefore likely less resilient than in the wet state. Our case study demonstrates the potential of time series modeling to assess attributes that mediate resilience. The approach is useful for assessing resilience of alternative states across ecological and other complex systems.

Allelopathic effects of microcystin-LR on the germination, growth and metabolism of five charophyte species and a submerged angiosperm.

Microcystins (MCs) are produced by cyanobacteria in aquatic environments and adversely affect macrophytes at very high concentrations. However, the effects of MC on macrophytes at concentrations of environmental relevance are largely unknown. The main objective of this study was to analyze the allelopathic effects of MC-LR at natural concentrations (1, 8 and 16 µg MC-LR/L) on five charophyte species (Chara aspera, C. baltica, C. hispida, C. vulgaris and Nitella hyalina) and the angiosperm Myriophyllum spicatum. Macrophyte specimens were obtained from a restored area located in Albufera de València Natural Park, a protected coastal Mediterranean wetland. Two different experiments were conducted involving (i) the addition of MC-LR to natural sediment to evaluate its effects on seed germination and (ii) the addition of MC-LR to water cultures of macrophytes to evaluate its effects on growth and metabolic functions. In water, the MC-LR concentration decreased by 84% in two weeks; the loss was not significant in sediment. The first seedlings (all C. hispida) emerged from the wetland sediment following a delay of a few days in the presence of MC-LR. The germination rates in 8 and 16 µg MC-LR/L treatments were 44% and 11% of that occurring in the absence of MC, but these differences disappeared over time. The final density was 6-7 germlings/dm(3). Final germling length was unaffected by MC-LR. Rotifers (Lecane spp.) emerging from the natural sediment during the experiment were favored by MC-LR; the opposite pattern was observed in the cladoceran Daphnia magna. The growth rates of C. vulgaris, C. baltica and N. hyalina were unaffected by MC exposure, whereas those of C. hispida and C. aspera were reduced in the MC treatments relative to the control treatment. The concentration of chlorophyll-a and the in vivo net photosynthetic rate were lower in the presence of MC-LR, even at the lowest concentration, for all of the characeans tested. M. spicatum was sensitive to the presence of MC-LR in the culture medium; the growth and chlorophyll-a concentrations were reduced. Therefore, environmentally relevant concentrations of MC might induce important changes in macrophyte meadows and the structure of the associated plankton community. Synchrony or delay in the processes evaluated here in response to environmentally relevant concentrations of cyanobacteria MC exudates can enhance understanding of the turning point to alternative states and the point of no return in eutrophicated shallow lakes.

Unusual early recurrence of granular dystrophy after deep anterior lamellar keratoplasty: case report.

We report an atypical case of granular corneal dystrophy recurrence after deep anterior lamellar keratoplasty. We describe clinical features, histopathological analysis of the lamellar graft specimen and DNA analysis results. The slit-lamp examination and histopathological findings from the graft specimen indicated the confinement of the typical deposits of granular corneal dystrophy deep in the graft interface area. This localization is atypical, since in most cases recurrences in grafts tend to be initially superficial and situated in the epithelial or subepithelial corneal layers. Molecular genetic analysis revealed an already described mutation and a new intronic variant. The unusual localization and timing of this recurrence of granular corneal dystrophy after deep anterior lamellar keratoplasty suggests that corneal stromal keratocytes may play a role in the formation of granular deposits.

Unusual early recurrence of granular dystrophy after deep anterior lamellar keratoplasty: case report / Recorrência atípica e precoce de distrofia granular após transplante lamelar profundo: relato de caso

We report an atypical case of granular corneal dystrophy recurrence after deep anterior lamellar keratoplasty. We describe clinical features, histopathological analysis of the lamellar graft specimen and DNA analysis results. The slit-lamp examination and histopathological findings from the graft specimen indicated the confinement of the typical deposits of granular corneal dystrophy deep in the graft interface area. This localization is atypical, since in most cases recurrences in grafts tend to be initially superficial and situated in the epithelial or subepithelial corneal layers. Molecular genetic analysis revealed an already described mutation and a new intronic variant. The unusual localization and timing of this recurrence of granular corneal dystrophy after deep anterior lamellar keratoplasty suggests that corneal stromal keratocytes may play a role in the formation of granular deposits.

É relatado um caso atípico de recorrência de distrofia corneana granular após transplante lamelar anterior profundo. São descritas as características clínicas, a análise histopatológica do espécime do enxerto lamelar e os resultados de análises de DNA. O exame com lâmpada de fenda e a análise histopatológica do espécime do enxerto demonstram o confinamento dos depósitos típicos da distrofia corneana granular profundamente, na área de interface do enxerto. Esta localização é atípica, uma vez que, na maioria dos casos de recidivas em enxertos, estes tendem a ser no início localizados superficialmente, nas camadas epiteliais ou subepitelial da córnea. A análise genética molecular revelou uma mutação já descrita e uma nova variante intrónica. A localização incomum e o tempo de aparecimento da presente recorrência da distrofia corneana granular após transplante lamelar anterior profundo sugere que ceratócitos do estroma corneano possam desempenhar algum papel na formação dos depósitos granulares.

Does seston size structure reflect fish-mediated effects on water quality in a degraded semiarid wetland?

This study evaluates whether the size structure of seston (the sum of living and nonliving particles in the water column) reflects the effects of fish on wetland water quality. Using enclosures, we measured water quality and zooplankton community structure in the presence and absence of two fish species with distinct foraging strategies [benthivorous carp (Cyprinus carpio) and planktivorous mosquitofish (Gambusia holbrooki)]. Seston collected from the enclosures was counted and sized automatically with a Coulter counter, and the size structure in the range of 1-60 microm was modelled using the underlying Pareto distribution of particles. Only Cyprinus contributed to a loss of water quality (increased nutrient levels, algal and non-algal turbidity, hypoxia), while both fish species changed zooplankton community composition compared to fishless controls. However, these changes were not reflected in parameters [goodness of fit (r (2)) and parameter c (slopes)] of Pareto models. Multivariate statistics suggest that seston size structure responded more to environmental gradients related to water depth but the relationships were also weak. Our overall result contrasts with the regulation of size spectra constructed from living organisms. Although seston integrates many structural and functional features of the water column, the lack of strong relationships between Pareto model parameters and water quality suggests that a size-based approach to characterise seston structure has a limited potential for assessing biota-mediated effects in wetlands in a straightforward manner.

Perirenal fat diameter measured by echography could be an early predictor of lipodystrophy in HIV type 1-infected patients receiving highly active antiretroviral therapy.

Echographically measured thicknesses of perirenal and subcutaneous fat, as well as serum metabolic and anthropometric parameters, were evaluated in 74 human immunodeficiency virus-infected patients receiving highly active antiretroviral therapy (HAART), 22 of whom were HAART-naive at baseline, who were followed-up for 27 months to detect predictive factors of lipodystrophy. Perirenal fat diameter (PRFD) at baseline differed in HAART-naive and HAART-experienced patients (P<.001), and it was the best predictor of lipodystrophy changes after 12 months of follow-up in the HAART-naive patients (hazard ratio, 7.34; 95% confidence interval, 1.18-45.49; P=.032). In addition, HAART-experienced patients in whom lipodystrophy improved had thinner baseline perirenal fat than those in whom lipodystrophy did not improve (P=.04). A PRFD of >2.6 mm at baseline or >4.9 mm during receipt of HAART suggested lipodystrophy predisposition. PRFD correlated significantly with other metabolic and anthropometric parameters. Echographically measured PRFD is associated with lipodystrophy and could be used as an early predictor of this syndrome in treatment-naive patients starting HAART.

Influence of aquatic microbiota on the survival in water of the human and eel pathogen Vibrio vulnificus serovar E.

The eel and human pathogen Vibrio vulnificus serovar E (biotype 2) is seldom isolated from natural waters, although it can survive in sterilized artificial seawater microcosms for years. The main objective of the present study was to investigate whether aquatic microbiota can limit its survival and recovery from water samples. A set of preliminary experiments of survival in microcosms containing natural seawater and water from eel farms showed that the persistence of this pathogen was mainly controlled by grazing, and secondarily by bacterial competition. The bacterial competition was further analysed in artificial seawater microcosms co-inoculated with selected virulent serovar E (VSE) strains and potential competitors. Competitors included V. vulnificus biotype 1 isolates and strains of selected species that can grow on the selective media designed for V. vulnificus isolation from water samples. Evidences of bacterial competition that was detrimental for VSE recovery were recorded. Thus, some species produced a deleterious effect on VSE strains under starvation, and others were able to use the resources more efficiently under nutrient input. These results suggest that an overgrowth of more efficient competitor bacteria in conventional media used for isolation of V. vulnificus could mask the recovery of VSE strains and explain the scarcity of reports on the isolation of this human and eel pathogen from natural waters.