Cross-taxon congruence and environmental conditions

<p>Abstract</p> <p>Background</p> <p>Diversity patterns of different taxa typically covary in space, a phenomenon called cross-taxon congruence. This pattern has been explained by the effect of one taxon diversity on taxon diversity, shared biogeographic histories of different taxa, and/or common responses to environmental conditions. A meta-analysis of the association between environment and diversity patterns found that in 83 out of 85 studies, more than 60% of the spatial variability in species richness was related to variables representing energy, water or their interaction. The role of the environment determining taxa diversity patterns leads us to hypothesize that this would explain the observed cross-taxon congruence. However, recent analyses reported the persistence of cross-taxon congruence when environmental effect was statistically removed. Here we evaluate this hypothesis, analyzing the cross-taxon congruence between birds and mammals in the Brazilian Cerrado, and assess the environmental role on the spatial covariation in diversity patterns.</p> <p>Results</p> <p>We found a positive association between avian and mammal richness and a positive latitudinal trend for both groups in the Brazilian Cerrado. Regression analyses indicated an effect of latitude, PET, and mean temperature over both biological groups. In addition, we show that NDVI was only associated with avian diversity; while the annual relative humidity, was only correlated with mammal diversity. We determined the environmental effects on diversity in a path analysis that accounted for 73% and 76% of the spatial variation in avian and mammal richness. However, an association between avian and mammal diversity remains significant. Indeed, the importance of this link between bird and mammal diversity was also supported by a significant association between birds and mammal spatial autoregressive model residuals.</p> <p>Conclusion</p> <p>Our study corroborates the main role of environmental conditions on diversity patterns, but suggests that other important mechanisms, which have not been properly evaluated, are involved in the observed cross-taxon congruence. The approaches introduced here indicate that the prevalence of a significant association among taxa, after considering the environmental determinant, could indicate both the need to incorporate additional processes (e.g. biogeographic and evolutionary history or trophic interactions) and/or the existence of a shared trend in detection biases among taxa and regions.</p

Evaluación de la vulnerabilidad ecológica de los gasterópodos bentónicos marinos del Atlántico Occidental

Assessing the extinction risk in marine invertebrates poses serious challenges to conservation biology, due to the magnitude of marine biodiversity, the inaccessibility of most of the marine realm, and the lack of appropriate data on population dynamics and ecology for most species. However, simple life history traits have a huge potential for preliminary screening criteria for assessing large numbers of species whose status is harsh or impossible to evaluate. Body size and trophic position could be strong predictors of extinction risk providing a general framework for the assessment of species vulnerability. We analyzed the Body Size-Trophic Position (BS-TP) relationship along 1,067 genera representing 4,256 nominal species of western Atlantic benthic gastropods. We found that a carnivore diet characterizes 67% of the genera and that, supporting theoretical predictions, the probability of being carnivores as a function of size showed a unimodal trend. For species with adult body sizes larger than 5 cm, a negative association between trophic position and body size was detected. This result points to an energetic restriction for the viability of large species, implying that organisms placed near the BS-TP boundary are extremely vulnerable to environmental changes. With this result, 109 genera from 42 families of carnivore gastropods and 33 genera from 19 families of herbivore gastropods that may be more vulnerable from the analyzed perspective were identified and ranked. Supporting these results, while the most vulnerable genera are not represented in global IUCN assessments, all our ‘top 10’ vulnerable families are being considered in National or Regional Red Lists. Prior to conducting regional or global conservation assessments for invertebrate taxa, screening methods should be strongly considered.Evaluar el riesgo de extinción de los invertebrados marinos plantea serios desafíos para la biología de la conservación, debido a la magnitud de la biodiversidad marina, la inaccesibilidad de la mayor parte del ámbito marino y la falta de datos apropiados sobre la dinámica de población y la ecología de la mayoría de las especies. Sin embargo, los rasgos simples de la historia de vida tienen un gran potencial como criterios preliminares de selección para evaluar un gran número de especies cuyo estado es difícil o imposible de evaluar. El tamaño del cuerpo y la posición trófica podrían ser fuertes predictores del riesgo de extinción proporcionando un marco general para la evaluación de la vulnerabilidad de las especies. Analizamos la relación Tamaño Corporal-Posición Trófica (BS-TP) a lo largo de 1.067 géneros que representan 4.256 especies nominales de gasterópodos bentónicos del Atlántico Occidental. Encontramos que una dieta carnívora caracteriza al 67% de los géneros y que, apoyando las predicciones teóricas, la probabilidad de ser carnívoros en función del tamaño mostró una tendencia unimodal. Para especies con tamaños corporales adultos mayores de 5 cm, se detectó una asociación negativa entre la posición trófica y el tamaño corporal. Este resultado apunta a una restricción energética para la viabilidad de las especies grandes, lo que implica que los organismos ubicados cerca del límite BS-TP son extremadamente vulnerables a los cambios ambientales. Con este resultado, se identificaron y clasificaron 109 géneros de 42 familias de gasterópodos carnívoros y 33 géneros de 19 familias de gasterópodos herbívoros que pueden ser más vulnerables desde la perspectiva analizada. Respaldando estos resultados, mientras que los géneros más vulnerables no están representados en las evaluaciones globales de la UICN, todas nuestras “10 principales” familias vulnerables están siendo consideradas en las Listas Rojas Nacionales o Regionales. Antes de realizar evaluaciones de conservación regionales o globales para taxones de invertebrados, se deben considerar seriamente los métodos de detección

Distribution of the isopod Excirolana braziliensis on sandy beaches of the Atlantic and Pacific Oceans

We assessed geographic patterns of abundance of the isopodExcirolana braziliensis across its whole distribution range in the context of the abundant centre hypothesis (ACH). We also evaluated auxiliary y potheses to the ACH involving habitat availability and suitability. We compiled species abundance and occurrence information on 139 Pacific and Atlantic sandy beaches of the Americas. Abundance patterns were contrasted against 5 hypothetical distribution models. Habitat availability (sandy beach along the coast), and the role played by grain size on isopod abundance were analysed. Maximum entropy niche modelling based on primary production, salinity, water temperature and tidal range data was used to estimate trends in habitat suitability. E. braziliensis abundance peaked at the 2 edges of its range on the Atlantic coast and towards the centre of its range on the Pacific coast. Congruently, the niche model predicted very low habitat suitability at the centre of the species’ range on the Atlantic coast. Primary production was the main contribution to the model (74.8%). The highest abundances were found in fine sediments (0.20 mm). Support for the ACH forE. braziliensis was found only for the Pacific coast, whereas habitat suitability and availability together with local in-beach morphodynamics accounted for deviations from ACH predictions in the Atlantic. The highest abundances registered in upwelling areas and on beaches with fine sands highlight the primary role played by regional and local conditions over geographic location

Movilidad de ingreso y trampas de pobreza : nueva evidencia para los países del Cono Sur

This paper tests the existence of poverty traps in three Southern Cone countries: Argentina, Brazil and Uruguay. We apply the methodology developed by Antman and McKenzie (2005): based on pseudopanels, we model the income dynamics of households and analyze the existence of heterogeneity in their path and their reactions to recessions. We also focus in income trajectories for different educational levels, and estimate the rate at which households overcome poverty situations or return to their equilibrium income level after a shock. The record of high volatility and strong macroeconomic crisis shared by Argentina, Uruguay and to a lesser extent Brazil, are an opportunity to carry out this type of analysis, which in turn is justified as a contribution to the design of public policies. This papers aims at identifying situations where the future trajectory of households’ income will be systematically below a certain threshold, as a result of past performance. General estimates do not confirm the presence of poverty traps in these three countries during the study period. However, when educational levels are taken into account, poverty traps are found in the cases of Brazil and Uruguay for households whose head belongs to low educational levels.poverty tramps, income mobility, Uruguay, Argentina, Brazil

Ethnobotanical Knowledge Complexity in a Conservation Area of Northern Uruguay: Interlocutors-Medicinal Plant Network and the Structural Patterns of Interaction

With the aim of generating a strategy for biocultural conservation, we explore the structure and robustness of the botanical medical systems in the Biosphere Reserve “Bioma Pampa-Quebradas del Norte,” Uruguay, combining ethnobotanical hypotheses and network theory. We report a heterogeneous distribution of knowledge of medicinal plants with a potential limit to the individual knowledge (truncated–power-law). The robustness analysis in the face of alternative potential scenarios of system degradation indicates that the ethnobotanical system presents a high level of resistance to the loss of agents and medicinal plants species, but also a nonlinear response with a threshold of degradation after which an abrupt collapse in system structure is expected. To counter these threats at the Biosphere Reserve, we propose to promote ethnobotanical knowledge transmission and sustainable development in rural areas, and to encourage the development of strategies for the conservation of medicinal plants.Con el objetivo de generar una estrategia de conservación biocultural, exploramos la estructura y la robustez del sistema botánico médico en la Reserva de Biosfera “Bioma Pampa-Quebradas del Norte,” Uruguay, combinando hipótesis etnobotánicas y teoría de redes. Reportamos una distribución heterogénea del conocimiento sobre las plantas medicinales con un límite potencial del conocimiento individual (ley poder-truncada). El análisis de robustez frente a posibles escenarios alternativos de degradación, indica que el sistema etnobotánico presenta un alto nivel de resistencia a la pérdida de agentes y plantas medicinales. También se observa una respuesta no lineal con un umbral de degradación, después del cual se produce un colapso abrupto de la estructura del sistema. Para contrarrestar estas amenazas en la Reserva de Biosfera, proponemos promover los procesos de transmisión de conocimiento etnobotánico y el desarrollo sostenible en áreas rurales, así como alentar el desarrollo de estrategias para la conservación de plantas medicinales.Laboratorio de Etnobotánica y Botánica Aplicad

Dispersión de la rana toro, Lithobates catesbeianus, y prioridades para su manejo en Aceguá (Cerro Largo)

Presentación de modelos de dispersion de la rana toro, en el marco de un proyecto del Fondo María Viñas.Agencia Nacional de Investigación e Innovació

Heterogeneity in the isolation of patches may be essential for the action of metacommunity mechanisms

The spatial isolation gradient of communities and the gradient in the species dispersal ability are recognized as determinants of biodiversity in metacommunities. In spite of this, mean field models, spatially explicit models, and experiments were mainly focused on idealized spatial arrangements of communities leaving aside the combining role of dispersal and isolation gradients in metacommunity processes. Consequently, we have an incipient understanding of the role of the real spatial arrangement of communities on biodiversity patterns. We focus on six metacommunities for which confident information about the spatial arrangement of water bodies is available. Using coalescent metacommunity models and null models that randomize the location of water bodies, we estimated the potential eect of the landscape on biodiversity and its dependence on species dispersal ability. At extremely lowor high dispersal abilities, the location of ponds does not influence diversity because dierent communities are equally aected by the low or high incoming dispersal. At intermediate dispersal abilities, peripheral communities present a much lower richness and higher beta diversity than central communities.Moreover,metacommunities from real landscapes host more biodiversity than randomized landscapes, a result that is determined by the heterogeneity in the geographic isolation of communities. In a dispersal gradient, mass eects systematically increase the local richness and decrease beta diversity. However, the spatial arrangement of patches only has a large importance in metacommunity processes at intermediate dispersal abilities, which ensures access to central locations but limits dispersal in isolated communities. The ongoing reduction in spatial extent and simplification of the landscape may consequently undermine the metacommunity processes that support biodiversity, something that should be explicitly considered in preserving and restoring strategies

Prey selection along a predators' body size gradient evidences the role of different trait-based mechanisms in food web organization.

An increase in prey richness, prey size and predator trophic position with predator body size has been consistently reported as prime features of food web organization. These trends have been explained by non-exclusive mechanisms. First, the increase in energy demand with body size determines that larger predators must reduce prey selectivity for achieving the required number of resources, being consumption relationships independent of prey traits. Second, when consumption is restricted by gape limitation, small predators are constrained to select among small prey. However, this selection weakens over large predators, which progressively consume more and larger prey. Finally, the optimal foraging mechanism predicts that larger predators optimize their diet by selecting only large prey with high energy reward. Each one of these mechanisms can individually explain the increase in prey richness, prey size and predator trophic position with predator body size but their relative importance or the direct evidence for their combined role was seldom considered. Here we use the community assembly by trait selection (CATS) theory for evaluating the support for each one of these mechanisms based on the prey selection patterns that they predict. We analyzed how prey body size and trophic guild determine prey selection by predators of increasing body size in a killifish guild from a temporary pond system. Results support the combination of the three mechanisms to explain the structural trends in our food web, although their strength is contingent on prey trophic group. Overall, high energy prey are preferred by larger predators, and small predators select small prey of all trophic status. However, large predators prefer large primary producers and avoid large carnivorous prey, probably because of the inherent risk of consuming other carnivorous. Our study provides a mechanistic understanding of how predator traits determine the selection of prey traits affecting food web assembly