Efecto de la intensidad y el momento de la defoliación sobre el crecimiento de Populus alba y Salix babylonica x Salix alba

Insect defoliations have detrimental impacts on timber production in commercial tree plantations. The effect of intensity and timing of defoliation on the growth of two commercial salicaceae was assessed at plantations located in the Delta of the Paraná River, Argentina. Experimental trees were randomly selected from two 1-year-old plantations of the most common clones planted in forestry production, Populus alba ´Villafranca´ (¨I-58/57¨) and Salix babylonica x Salix alba (¨A-250/33¨). We used a pre-post design to evaluate the effect of five intensities of manual defoliation (i.e. 100 %, 75 %, 50 %, 25 %, and 0 % as control) applied in four different times during the growing season (i.e. October, November, December and January) on tree height and diameter at breast height (DBH). Results indicated that manual defoliation negatively affected the growth of the studied poplar and willow clones in both height and diameter, and that the magnitude of the effect depended on the intensity and timing of defoliation. Willows were only affected by defoliation conducted during the spring (October and November); complete defoliation caused the highest reduction in growth (46 % reduction in height and 62 % in DBH compared to the control). Manual defoliation of poplars had a significant effect on growth at any time during the springsummer; trees subjected to 100 % defoliation showed the highest growth reductions (up to 76 % in height and 88 % in DBH compared to control). This study indicated that commercial poplars were less tolerant to defoliation than willows.Las defoliaciones causadas por insectos tienen impactos perjudiciales sobre la producción de madera en plantaciones comerciales de árboles. El efecto de la intensidad de defoliación sobre el crecimiento en altura y diámetro de dos salicáceas de uso comercial fue evaluado en plantaciones del Delta del Río Paraná, Argentina. Los árboles experimentales fueron elegidos al azar de plantaciones de un año de edad de clones comúnmente utilizados en la producción forestal, Populus alba ´Villafranca´ (¨I-58/57¨) y Salix babylonica x Salix alba (¨A-250/33¨). Mediante un diseño antes-después fue evaluado el efecto de cinco intensidades de defoliación manual (100 %, 75 %, 50 %, 25 %, y 0 % como control) aplicadas en cuatro épocas de la estación de crecimiento (octubre, noviembre, diciembre y enero) sobre la altura y el diámetro a la altura del pecho (DAP) de los árboles. Según los resultados, la defoliación manual afectó negativamente el crecimiento de los clones estudiados, en diámetro y altura; la magnitud del efecto dependió de la intensidad y del momento de la defoliación. Salix sp. solo fue afectado por defoliaciones de primavera (octubre y noviembre); la defoliación completa causó las mayores reducciones en el crecimiento (46 % en altura y 62 % en DAP). La defoliación en Populus sp. afectó el crecimiento en cualquier momento de primavera-verano; los árboles completamente defoliados mostraron las mayores reducciones en el crecimiento (hasta 76 % en altura y 88 % en DAP). Este estudio indica que Populus sp. de uso comercial fue menos tolerante a la defoliación que Salix sp.Fil: Rubio, Alejandra. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Loetti, Verónica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Bellocq, Maria Isabel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

From town to town: Predicting the taxonomic, functional and phylogenetic diversity of birds using NDVI

Biodiversity mapping in urban areas is imperative for their conservation. Remote sensors produce environmental information, such as the Normalized Difference Vegetation Index (NDVI), an indicator of vegetation cover in urban areas. NDVI can be used to predict the taxonomic, functional and phylogenetic bird diversity in urban areas. Moreover, a predictive model constructed in one city can be used to predict the bird diversity in other cities. The objectives of this study were: 1) to construct and evaluate predictive models between NDVI and taxonomic, functional and phylogenetic diversity of birds in Mar del Plata city, Argentina; and 2) to extrapolate these models to two other cities in the region: Balcarce and Miramar. Generalized additive models were applied to relate bird diversity variations to NDVI. In Mar del Plata, the taxonomic and functional diversity increased with increasing NDVI values, and the predictive models explained 64–81% of the taxonomic and functional diversity variation. The models correctly predicted taxonomic and functional diversity values in additional transects not included in the models, although they had a low predictive power of phylogenetic diversity. The models constructed in Mar del Plata adequately predicted the spatial variation of species diversity (Shannon index) in Balcarce and Miramar, the spatial variation of species richness in Balcarce, and the variation of functional diversity in Miramar. Our analysis revealed that a predictive model of bird diversity based on NDVI patterns created in one city can also depict the expected species diversity in other cities, being a time-saving and cost-effective method to create a tool for urban biodiversity conservation.Fil: Leveau, Lucas Matias. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Isla, Federico Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Bellocq, Maria Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentin

Livestock grazing impact differently on the functional diversity of dung beetles depending on the regional context in subtropical forests

The replacement of native forest by cattle pastures reduces functional diversity; however, little is known about whether the changes depend on regional variation. Dung beetles are one of the most diverse and functionally important taxa; through organic matter burial, dung beetles improve soil quality. We collected dung beetles in native forests and cattle ranching areas in subtropical forests with contrasting climatic conditions: the Atlantic Forest, the Humid Chaco, and the Dry Chaco. We measured 11 traits related to the ecology and the physiology of species. Irrespectively of the region, functional richness was higher in forests (native and with cattle) when compared to open pastures. Humid forests (Atlantic Forest and Humid Chaco) showed higher functional richness than Dry Chaco. Functional dispersion in humid forests was similar between native forest and livestock systems, however, functional dispersion in the Dry Chaco was higher in open pastures compared to native forest. According to our results, native forests and forests with cattle maintain functional diversity in all regions. However, in the case of open pastures, the response depends on the regional context; the replacement of native forest by open pastures strongly affected functional diversity in humid forests and showed less impact on dry forest.Fil: Guerra Alonso, Celeste Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Puerto Iguazú | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Puerto Iguazú; ArgentinaFil: Zurita, Gustavo Andres. Universidad Nacional de Misiones. Facultad de Ciencias Forestales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Puerto Iguazú | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Puerto Iguazú; ArgentinaFil: Bellocq, Maria Isabel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentin

Variations in habitat metrics along plantation chronosequences: Contrasting tree plantations in subtropical forest and grassland

The increasing demand for raw materials favours habitat conversion into tree plantations in different biomes over the world. In Argentina, fast-growing plantations occur in physiognomically contrasting biomes, such as the subtropical forest and grassland. Our objectives were to analyze variations in basic habitat metrics and their similarity to the natural habitat along pine plantation cycles, and to compare those patterns between plantations developing in a subtropical forest and a grassland biome. In each biome we selected pine stands of eight ages to represent the environmental gradient of the forest cycle, and natural areas. At each site we estimated the temperature, thermal variability, relative humidity, and percentage coverage of herbaceous plants, shrubs and canopy. We explored environmental similarity between plantations and the natural habitat. In general, patterns of the environmental variables along plantation chronosequences were similar between plantations developing in different biomes. As expected, opposite patterns of similarity in most environmental variables between plantations and the natural habitat were observed along chronosequences developing in contrasting biomes. The time period of high environmental similarity between plantations and the natural environment was longer in the subtropical forest than in the grassland. Our results have implications for land use planning and biodiversity conservation.Fil: Santoandre, Santiago. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Filloy, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; ArgentinaFil: Zurita, Gustavo Andres. Universidad Nacional de Misiones. Facultad de Ciencias Forestales. Instituto de Biología Subtropical - Sede Puerto Iguazú; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Puerto Iguazú | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Puerto Iguazú; ArgentinaFil: Bellocq, Maria Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentin

Dung beetles response to livestock management in three different regional contexts

The response of biological communities to human disturbances depends on factors acting at local and regional scale and on the interaction between them. We compared the response of native forest dung beetle communities to cattle grazing under regional contexts differing on precipitation patterns (Atlantic forest and humid and dry Chaco). Through multivariate and GLMM analyses we contrasted richness and composition across regions and land uses and explored the role of local and regional variables accounting for those changes. We captured a total of 44101 individuals of 109 species. The interaction between local and regional variables influenced the response to livestock management. In the two wet regions (humid Chaco and Atlantic forest) diversity was similar in the native forest regardless of cattle presence but differs strongly in open pastures. In contrast, in the dry Chaco, differences between native forest and land use were not evident. Vegetation structure was a major determinant of species richness, whereas regional climate determined differences in species composition. We concluded that the response of dung beetles to livestock management cannot be generalized for all biomes. In dry ecosystems, dung beetles are probably pre-adapted to environmental conditions imposed by cattle ranching whereas in wet ecosystems the impact of cattle ranching is more significant.Fil: Guerra Alonso, Celeste Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Puerto Iguazú | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Puerto Iguazú; ArgentinaFil: Zurita, Gustavo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Puerto Iguazú | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Puerto Iguazú; ArgentinaFil: Bellocq, Maria Isabel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Different land-use types equally impoverish but differentially preserve grassland species and functional traits of spider assemblages

Land-use change is one of the major drivers of biodiversity loss by introducing environmental modifications, which excludes native species unable to adapt to the novel conditions. Grasslands are among the most threatened biomes; understanding the influence of different land-use types on native species is crucial to achieving sustainable management policies. We hypothesized that land-use types that partially conserve the original vegetation cover would show higher taxonomic and functional diversity and similarity with native assemblages than land-use types that replace the original vegetation cover. We compared the taxonomic and functional alpha and beta diversity of spider assemblages between soybean crops, eucalypt plantations, and cattle fields with seminatural grasslands. Through null models, we assessed the standardized effect sizes to test differences in the strength of environmental filtering among land-use types. Environmental changes introduced by different land-use types resulted in assemblages differentiated in species and trait composition, taxonomically and functionally impoverished with respect to seminatural grasslands. All land-use types drove species replacement and trait loss and replacement of grassland spiders. Each land-use showed a characteristic species and trait composition. Most of the grassland traits were not lost but were under or over-represented according to the land-use type. Only in soybean crops the formation of spider communities would be mainly driven by environmental filtering. Changes in land-use decreased species diversity and modified the composition of spider species and functional traits leading to differentiated spider assemblages. As spider species and traits varied among land-uses, a mitigation measure against grasslands biodiversity loss could be the development of productive landscapes with a mosaic of land-use types, as each of them would provide microhabitats for species with different requirements. Because land-use types mainly led to the rearrangement of grassland functional trait values, most of spider functions might be conserved in mosaics of land-use types.Fil: Pinto, Carolina Melisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Pairo, Pamela Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Bellocq, Maria Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Filloy, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentin

A global consistent positive effect of urban green area size on bird richness

Background: Although the species-urban green area relationship (SARu) has been analyzed worldwide, the global consistency of its parameters, such as the fit and the slope of models, remains unexplored. Moreover, the SARu can be explained by 20 different models. Therefore, our objective was to evaluate which models provide a better explanation of SARus and, focusing on the power model, to evaluate the global heterogeneity in its fit and slope. Methods: We tested the performance of multiple statistical models in accounting for the way in which species richness increases with area, and examined whether variability in model form was associated with various methodological and environmental factors. Focusing on the power model, we analyzed the global heterogeneity in the fit and slope of the models through a meta-analysis. Results: Among 20 analyzed models, the linear model provided the best fit to the most datasets, was the top ranked model according to our efficiency criterion, and was the top overall ranked model. The Kobayashi and power models were the second and third overall ranked models, respectively. The number of green areas and the minimum number of species within a green area were the only significant variables explaining the variation in model form and performance, accounting for less than 10% of the variation. Based on the power model, there was a consistent overall fit (r 2 = 0.50) and positive slope of 0.20 for the species richness increase with area worldwide. Conclusions: The good fit of the linear model to our SARu datasets contrasts with the non-linear SAR frequently found in true and non-urban habitat island systems; however, this finding may be a result of the small sample size of many SARu datasets. The overall power model slope of 0.20 suggests low levels of isolation among urban green patches, or alternatively that habitat specialist and area sensitive species have already been extirpated from urban green areas.Fil: Levau, Lucas M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; ArgentinaFil: Ruggiero, Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Ecotono; ArgentinaFil: Matthews, Thomas J.. Universidade dos Açores; Portugal. University of Birmingham; Reino UnidoFil: Bellocq, Maria Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentin

Simple process-based simulators for generating spatial patterns of habitat loss and fragmentation: a review and introduction to the G-RaFFe model

Landscape simulators are widely applied in landscape ecology for generating landscape patterns. These models can be divided into two categories: pattern-based models that generate spatial patterns irrespective of the processes that shape them, and process-based models that attempt to generate patterns based on the processes that shape them. The latter often tend toward complexity in an attempt to obtain high predictive precision, but are rarely used for generic or theoretical purposes. Here we show that a simple process-based simulator can generate a variety of spatial patterns including realistic ones, typifying landscapes fragmented by anthropogenic activities. The model ‘‘G-RaFFe’’ generates roads and fields to reproduce the processes in which forests are converted into arable lands. For a selected level of habitat cover, three factors dominate its outcomes: the number of roads (accessibility), maximum field size (accounting for land ownership patterns), and maximum field disconnection (which enables field to be detached from roads). We compared the performance of G-RaFFe to three other models: Simmap (neutral model), Qrule (fractal-based) and Dinamica EGO (with 4 model versions differing in complexity). A PCA-based analysis indicated G-RaFFe and Dinamica version 4 (most complex) to perform best in matching realistic spatial patterns, but an alternative analysis which considers model variability identified GRaFFe and Qrule as performing best. We also found model performance to be affected by habitat cover and the actual landuses, the latter reflecting on land ownership patterns. We suggest that simple process-based generators such as G-RaFFe can be used to generate spatial patterns as templates for theoretical analyses, as well as for gaining better understanding of the relation between spatial processes and patterns. We suggest caution in applying neutral or fractal-based approaches, since spatial patterns that typify anthropogenic landscapes are often non-fractal in nature.Fil: Pe’er, Guy. Helmholtz Centre for Environmental Research; AlemaniaFil: Zurita, Gustavo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Universidad Nacional de Misiones. Instituto de Biología Subtropical; ArgentinaFil: Schober, Lucía. Helmholtz Centre for Environmental Research; AlemaniaFil: Bellocq, Maria Isabel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Strer, Maximilian. Helmholtz Centre for Environmental Research; AlemaniaFil: Muller, Michael. Helmholtz Centre for Environmental Research; AlemaniaFil: Putz, Sandro. Helmholtz Centre for Environmental Research; Alemani

Quantifying edge effects: the role of habitat contrast and species specialization

Edge effect is a key process influencing populations and communities, particularly in tropical and subtropical fragmented forests. A general analytical framework has been proposed to quantify the strength of the edge effects (extent and magnitude); however, factors determining the later remain poorly explored. We took advantage of recent advances to explore the response of dung beetle species and assemblages to ecotones which differ in environmental dissimilarity in the Southern Atlantic forest of Argentina. Using baited pitfall traps and automatic sensors, we estimated dung beetle abundance, microclimatic conditions and vegetation structure along five different forest-plantations transects. At the assemblages level, the majority of species showed either edge avoidance or preference; however, the response depended on the environmental dissimilarity between habitats (plantation and native forest) and varied from a neutral response on mature plantations (low contrast ecotone) to edge avoidance on recent ones (high contrast ecotone). At species level, the degree of habitat specialization explains the differential response of species to edge effects; more specialized species showed stronger edge response while generalist species showed softer or neutral responses. Environmental dissimilarity between confronted habitats and species specialization explain the quantitative component of edge effects on species and assemblages. The explanatory and predictive power of theoretical models dealing with edge effects and functional connectivity will gain through the incorporation of the results of this study. This is particularly important on highly fragmented landscapes, such as the Atlantic forest, where edge effect is probably one the most important mechanisms affecting native species and communities.Fil: Peyras, Marina. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Ecologia, Genetica y Evolución; ArgentinaFil: Vespa, Natalia Isabel. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Ecologia, Genetica y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bellocq, Maria Isabel. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Ecologia, Genetica y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Zurita, Gustavo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Puerto Iguazú | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Puerto Iguazú; Argentin

Spatial Variations in the Abundance of Sporophila Seedeaters in the Southern Neotropics: Contrasting the Effects of Agricultural Development and Geographical Position

Human alterations of the habitat may interfere with the natural processes that determine spatial patterns of species abundance. We examine the geographical position hypothesis and the agricultural transformation hypothesis to explain spatial patterns in the abundance of seedeater species (Sporophila spp.) in the southern Neotropics. The geographical position hypothesis predicts decreasing abundance with increasing distance from the center to the edge of a species´ geographical range, and the agricultural transformation hypothesis predicts changing abundance as a response of variations in agricultural intensity. Bird abundance and the proportion of agricultural land were estimated for 16 transects covering 500 km along a gradient of both increasing agricultural intensity and increasing distance from the center of the species´ geographical ranges. We found no evidence of distance effects on seedeater abundance. Responses to agricultural intensity varied among species. Neither the geographical position nor the agricultural transformation seemed to explain the pattern of abundance of Double-collared seedeaters (S. caerulescens). Agricultural intensity accounted for 63% and 99% of the spatial variation in the abundance of Dark-throated (S. ruficollis) and Tawny-bellied (S. hypoxantha) seedeaters, supporting the agricultural transformation hypothesis. The Dark-throated seedeater seem to be more tolerant to agricultural transformation than the Tawny-bellied seedeater, as they were not recorded in areas with more than 60% and 20% of agricultural lands, respectively. Our results indicate that the Dark-throated seedeater and the Tawny-bellied seedeater will most likely face (or may be already facing) a reduction in the southern part of their geographical range due to habitat loss to agriculture.Fil: Filloy, Julieta. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bellocq, Maria Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentin