BackgroundDiversity 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.ResultsWe 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.ConclusionOur 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.
Habitat loss due to land-use change is the greatest threat to biodiversity on a global scale, and agriculture has been the principal driver of change. In Uruguay, the conversion of native grasslands to croplands (e.g., soybean) and exotic forest plantations (Eucalyptus and Pinus) has accelerated during the last two decades. We studied the vulnerability of vertebrate and woody plant diversity to the loss of grassland areas, driven by agricultural and forestry expansion, to identify priority areas for conservation. We assessed the spatial variability of biodiversity vulnerability in function of species richness and number of focal species (i.e., prioritized species) of woody plants and terrestrial vertebrates that use grassland ecosystem as habitat. The top 17% of vulnerable sites (51 of 302 cells) were selected as priority conservation areas for Uruguay, following Aichi Target number 11. Approximately 36 % of the original continental territory of Uruguay, mainly grasslands, was converted to cropland (28%) and exotic forest plantations (8%) in 2015. Approximately 27% of the priority cells for conservation of vertebrates and woody plant diversity have been transformed, especially in three ecoregions in which habitat loss was between 35-45%. We simulated a land-use scenario for 2030, based on national production goals of soybean and exotic forest plantations, projecting that: (1) the overall loss of original habitat (mainly grasslands) would reach 48% of the country's land area, and (2) 45% of the priority cells would be converted to agricultural lands, especially in four ecoregions, with habitat losses greater than 50%. Our results suggest an urgent need to develop strategies to reduce the rate of natural grassland loss in Uruguay, as well as to conserve biodiversity and ecosystem services associated with these systems. Conservation efforts should focus on prioritized cells, especially those with no protection status and a high likelihood of agricultural conversion in 2030, through expanding public and private protected areas and promoting wildlife-friendly agricultural alternatives, such as beef production in natural grasslands.
Potential effects of climate change on the distribution of an endangered species:Melanophryniscus montevidensis (Anura: Bufonidae). Species distributions are linked with climate. Among the effects predicted by the Intergovernmental Panel on Climate Change are changes in precipitation patterns and increases in mean temperatures-factors potentially having a major impact on threatened, rare, and endemic species. Using models to forecast possible changes in the distributions of different species under different climatechange scenarios, we can identify probable impacts on species and build effective conservation strategies. We modeled the effects of two climate-change scenarios on the geographical distribution of the regionally endemic bufonid, Melanophryniscus montevidensis, categorized as vulnerable by the IUCN and as endangered by the Uruguayan Red List of amphibians. Ecological niche models were generated to describe the present and possible future distributions of this species in 2050 and 2080, given severe (A2) and moderate (B2) climatic changes. Legacy data for M. montevidensis were obtained from Uruguayan biocollections and climate data were acquired from the WorldClim database. At present, M. montevidensis could occur along the Atlantic Uruguayan coast and a small section of the southern Brazilian coast. However, changes in climate may lead to a loss of suitable environmental conditions for this toad; thus, this endangered species is vulnerable and in urgent need of protection.Keywords: amphibians, geographical distribution, niche models, threatened species, Uruguay. 98Phyllomedusa -12(2), December 2013 Resumen Efectos potenciales del cambio climático sobre la distribución de una especie amenazada: Melanophryniscus montevidensis (Anura: Bufonidae). La distribución de las especies está relacionada con el clima. Entre los efectos predichos por el Panel Intergubernamental de Cambio Climático, se encuentran los cambios en los patrones de precipitación y los aumentos en la temperatura media global. Estos factores tienen un impacto mayor en especies amenazadas, raras o endémicas. Usando modelos para predecir posibles cambios en la distribución de especies bajo diferentes escenarios de cambios climático, podemos identificar probables impactos sobre las especies y construir estrategias efectivas de conservación. Modelamos los efectos de dos escenarios de cambio climático en la distribución geográfica de un bufónido regionalmente endémico, Melanophryniscus montevidensis, categorizado como Vulnerable por la UICN, y como amenazado según la Lista Roja de Anfibios de Uruguay. Fueron generados modelos de nicho para describir la distribución presente y futura en 2050 y 2080, bajo los escenarios A2 (severo) y B2 (moderado). Los registros fueron obtenidos de las principales colecciones del país y los datos climáticos se tomaron de la base de datos WorldClim. Actualmente, M. montevidensis podría encontrarse en la costa Atlántica de Uruguay, y una pequeña parte de la costa del sureste de Brasil. Sin embargo, los cambi...
ABSTRACT. Amphibians are the most threatened vertebrate group according to the IUCN. Land-use and land cover change (LULCC) and climate change (CC) are two of the main factors related to declining amphibian populations. Given the vulnerability of threatened and rare species, the study of their response to these impacts is a conservation priority. The aim of this work was to analyze the combined impact of LULCC and CC on the regionally endemic species Melanophryniscus sanmartini Klappenbach, 1968. This species is currently categorized as near threatened by the IUCN, and previous studies suggest negative effects of projected changes in climate. Using maximum entropy methods we modeled the effects of CC on the current and mid-century distribution of M. sanmartini under two IPCC scenarios -A2 (severe) and B2 (moderate). The effects of LULCC were studied by superimposing the potential distribution with current land use, while future distribution models were evaluated under the scenario of maximum expansion of soybean and afforestation in Uruguay. The results suggest that M. sanmartini is distributed in eastern Uruguay and the south of Brazil, mainly related to hilly and grasslands systems. Currently more than 10% of this species' distribution is superimposed by agricultural crops and exotic forest plantations. Contrasting with a recent modelling study our models suggest an expansion of the distribution of M. sanmartini by mid-century under both climate scenarios. However, despite the rise in climatically suitable areas for the species in the future, LULCC projections indicate that the proportion of modified habitats will occupy up to 25% of the distribution of M. sanmartini. Future change in climate conditions could represent an opportunity for M. sanmartini, but management measures are needed to mitigate the effects of habitat modification in order to ensure its survival and allow the eventual expansion of its distribution.KEYWORDS. Species distribution modeling, global change, conservation, threatened species. RESUMEN. Efectos de los cambios climáticos y del uso de la tierra en la distribución de un endemismo regional: Melanophryniscus sanmartini (Amphibia, Bufonidae). Los anfibios son el grupo de vertebrados más amenazado en la actualidad según la UICN. El cambio en el uso y cobertura del suelo (CUCS) y el cambio climático (CC) son dos de los principales factores involucrados en el fenómeno de declinación de anfibios. Por lo tanto, investigar sus impactos sobre especies amenazadas o raras es fundamental dado que su vulnerabilidad las convierte en prioridades de conservación. El objetivo de este trabajo fue evaluar conjuntamente el impacto potencial del CUCS y del CC sobre la distribución del endemismo regional Melanophryniscus sanmartini Klappenbach, 1968. Esta especie está categorizada como casi amenazada por UICN y estudios anteriores sugieren efectos negativos del CC en su distribución. Utilizando modelos de máxima entropía modelamos la distribución actual y futura (2050) de M. sanmartini, bajo dos escenarios d...
RESUMEN. El cambio climático (CC) es una de las principales amenazas a la biodiversidad. Se han constatado efectos del CC sobre la distribución de las especies, principalmente corrimientos hacia latitudes altas y zonas elevadas. Las especies amenazadas resultan especialmente vulnerables a dichos cambios. En este marco, las áreas protegidas (AP) podrían ser una herramienta clave para la adaptación al cambio climático. Nuestros objetivos son: estudiar los efectos del CC sobre la distribución y riqueza de anfibios amenazados y casi amenazados de Uruguay, y evaluar la eficacia del Sistema Nacional de Áreas Protegidas (SNAP) en el presente y ante escenarios de CC. Para modelar la distribución de nueve especies se obtuvieron registros de colecciones herpetológicas, publicaciones científicas y del GBIF, datos de clima actual y proyecciones del Modelo de Circulación General HadCM3 bajo los escenarios A2 y B2 del IPCC descargadas del Worldclim. La distribución potencial se obtuvo aplicando modelos de máxima entropía (MAXENT). Para evaluar la eficacia del SNAP se realizó un análisis de vacíos, superponiendo la cobertura de las AP con la distribución de las especies. Los modelos indican que la mayoría de las especies expandirá su distribución a futuro en Uruguay, excepto Pleurodema bibroni y Melanophryniscus montevidensis. La riqueza local de anfibios podría aumentar en el noroeste y este del país. Si bien los anfibios estudiados están incluidos al menos en un área del SNAP, la superficie protegida cubre menos de 2% de la distribución de las especies, tanto en la actualidad como bajo los escenarios de CC. Esto indica la baja eficacia del sistema. Si bien el CC esperado para la región no sería una amenaza para los anfibios estudiados, la escasa protección por parte del SNAP representa un riesgo para la conservación de la herpetofauna nativa frente a otros componentes del cambio global.
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