Licenciatura en Diseño de Paisaje

Size-density relationships (SDRs) frequently follow a power-law relationship, with exponents that compensate for the increase in populationlevel metabolic demand-the energetic equivalence rule. However, these exponents present a range of values, and elucidating its methodological and biological determinants has become a main issue. So far, a restricted set of potential relationships, mechanisms, and taxa have been considered. Here, we analyzed SDR in a population of tadpoles inhabiting a network of 16 temporal ponds. Alternative scaling regimes were detected using pacewise regressions and estimating exponents with maximum likelihood (ML). If discontinuities in the SDR are ignored, a scaling close to values reported elsewhere is observed. However, estimated slopes between discontinuities are steeper (threefold to fivefold) than those often reported, but congruent with the performance predicted for ML and the biases reported for other methods. Our estimations largely deviate from an energetic equivalence, suggesting that large individuals use less energy per unit area. The detection of different SDRs in the same database, with a strong decay in abundance with body size, points to a pattern poorly considered in previous studies, widening the range of patterns, mechanisms, and ecological, or evolutionary consequences of the SDRs.

Metacommunity theory, which has gained a central position in ecology, accounts for the role of migration in patterns of diversity among communities at diff erent scales. Community isolation has a main role in this theory, but is diffi cult to estimate empirically, partly due to the taxon-dependent nature of dispersal. Landscapes could be perceived as either fragmented or connected for organisms with contrasting dispersal abilities. Indeed, the dispersal ability of a taxon, and the spatial scale at which eco-evolutionary processes shape local diversity, determine a taxon-dependent metacommunity network. In this paper, we introduce a methodology using graph theory to defi ne this taxon-dependent metacommunity network and then to estimate the isolation of local communities. We analyzed the relative importance of local conditions versus community isolation as determinants of community richness for 25 taxa inhabiting 18 temporary ponds. Although local factors have been the foci of most previous empirical and theoretical considerations, we demonstrate that the metacommunity network is an equally important contributor to local diversity. We also found that the relative eff ect of local conditions and the metacommunity network depend on body size and taxon abundance. Local diversity of larger species was more aff ected by patch isolation, while taxon abundances were associated with positive or negative eff ects of isolation. Our results provide empirical support for the proposed role of metacommunity networks as determinants of community diversity and show the taxon-dependent nature of these networks.

Habitat requirements of migratory birds can be dynamic during the annual cycle, and understanding habitat use during the nonbreeding season is important for conservation planning. In grassland birds, habitat selection is often determined by features of vegetative structure that are associated with predation risk, food resources, or thermal environments. And, these habitats are affected by anthropogenic influences such as agriculture conversion and production of livestock. In our four-year field study, we examined the space use and habitat selection of Upland Sandpipers (Bartramia longicauda) during the nonbreeding season in an area of private grasslands managed for livestock production within the Northern Campos ecoregion of Uruguay. We radio-tracked sandpipers during the nonbreeding season to test the hypothesis that space use, habitat selection, and flock size were determined by vegetative structure in managed grasslands with different grazing and agricultural management regimes. We captured and tagged 62 sandpipers during the nonbreeding season in the austral summer, and recorded a total of 506 locations for our sample of radio-marked birds. Foraging Upland Sandpipers primarily selected two types of native grasslands associated with shallow, rocky soils. The vegetation configuration of disturbed pastures were open landscapes that were good for detection of arthropod prey but offered little cover for avoidance of predators. Sandpipers were usually found in small groups of 2-20 birds, and the largest flocks of 40-50 birds were found in pastures with relatively short grass cover (20 to 40% tall grass cover). Low to moderate stocking densities of domestic livestock created variation in vegetation height and cover in large areas and allowed for coexistence of grassland birds with different habitat requirements. Upland Sandpipers preferred disturbed areas, which may not support the needs of other species of grasslands birds. Our results emphasize the need for habitat heterogeneity and disturbance forces such as grazing in grassland systems. Our research contributes new information on the ecology of migratory grassland birds and provides insights for biodiversity conservation on private lands used for livestock production.

Habitat requirements of migratory birds can be dynamic during the annual cycle, and understanding habitat use during the nonbreeding season is important for conservation planning. In grassland birds, habitat selection is often determined by features of vegetative structure that are associated with predation risk, food resources, or thermal environments. And, these habitats are affected by anthropogenic influences such as agriculture conversion and production of livestock. In our four-year field study, we examined the space use and habitat selection of Upland Sandpipers (Bartramia longicauda) during the nonbreeding season in an area of private grasslands managed for livestock production within the Northern Campos ecoregion of Uruguay. We radio-tracked sandpipers during the nonbreeding season to test the hypothesis that space use, habitat selection, and flock size were determined by vegetative structure in managed grasslands with different grazing and agricultural management regimes. We captured and tagged 62 sandpipers during the nonbreeding season in the austral summer, and recorded a total of 506 locations for our sample of radio-marked birds. Foraging Upland Sandpipers primarily selected two types of native grasslands associated with shallow, rocky soils. The vegetation configuration of disturbed pastures were open landscapes that were good for detection of arthropod prey but offered little cover for avoidance of predators. Sandpipers were usually found in small groups of 2-20 birds, and the largest flocks of 40-50 birds were found in pastures with relatively short grass cover (20 to 40% tall grass cover). Low to moderate stocking densities of domestic livestock created variation in vegetation height and cover in large areas and allowed for coexistence of grassland birds with different habitat requirements. Upland Sandpipers preferred disturbed areas, which may not support the needs of other species of grasslands birds. Our results emphasize the need for habitat heterogeneity and disturbance forces such as grazing in grassland systems. Our research contributes new information on the ecology of migratory grassland birds and provides insights for biodiversity conservation on private lands used for livestock production.

Between 2000–2020, more than ten new populations of the invasive American bullfrog (Lithobates catesbeianus) have been reported in the southern cone of South America. We studied the stomach contents of 126 bullfrogs from a population at an early invasion stage in Uruguay (Aceguá, Cerro Largo Department). We observed a rich diet, with extensive prey volume range (1 mm3 to more than 7 000 mm3); the most frequent items were Hymenoptera (19.6%), Coleoptera (16.4%), Amphipoda (13.3%), Anura (8.9%) and Heteroptera (8.7%). Despite some overlap, differences were observed in volume (χ2 = 54.6, p <0.001, d.f. = 2) and prey quantity (F = 8.1, p <0.001, d.f. = 79) between males, females, and juveniles. Juveniles showed significantly higher consumption of terrestrial prey by count (82% of their total ingestion) than adults (29% for males and 32% for females) (χ2 = 28.5, p <0.001, d.f. = 2). Adults, especially females, showed a high frequency of cannibalism (33% of their total ingestion;...

Frequently new pollutants are released into the environment, demanding the employment of generic methods to detect toxic responses. In vitro bioassays such as the yeast estrogenicity screening (YES) allow detecting estrogenic and citotoxic compounds avoiding the employment of invasive methods. We determined the cytotoxicity and estrogenic activity in sediments of the Santa Lucia River Basin (Uruguay) using YES assay and the association with land uses and parameters of water quality and sediment. Water quality parameters confirm the eutrophication process of the Santa Lucía River, which was mainly reflected by high levels of TP and ammonium. High values of estrogenic activity in sediments (E2-EQ 8.49 ng g-1 of sediment) were found mainly in urbanized and cultivated areas. However, estrogenicity and cytotoxicity also was found in sites associated with other land uses such as rangelands. These data provide evidence that Santa Lucía River basin contains a variety of chemicals (including estrogenic and toxic chemicals of unknown and potentially diverse sources) that should be investigated further. YES assay proved to be a useful tool for characterizing estrogenic responses, and due to the human and ecological health importance, we suggest the employment of these kinds of bioassays as tools for environmental monitoring of EDCs substances.

Habitat requirements of migratory birds can be dynamic during the annual cycle, and understanding habitat use during the nonbreeding season is important for conservation planning. In grassland birds, habitat selection is often determined by features of vegetative structure that are associated with predation risk, food resources, or thermal environments. And, these habitats are affected by anthropogenic influences such as agriculture conversion and production of livestock. In our four-year field study, we examined the space use and habitat selection of Upland Sandpipers (Bartramia longicauda) during the nonbreeding season in an area of private grasslands managed for livestock production within the Northern Campos ecoregion of Uruguay. We radio-tracked sandpipers during the nonbreeding season to test the hypothesis that space use, habitat selection, and flock size were determined by vegetative structure in managed grasslands with different grazing and agricultural management regimes. We captured and tagged 62 sandpipers during the nonbreeding season in the austral summer, and recorded a total of 506 locations for our sample of radio-marked birds. Foraging Upland Sandpipers primarily selected two types of native grasslands associated with shallow, rocky soils. The vegetation configuration of disturbed pastures were open landscapes that were good for detection of arthropod prey but offered little cover for avoidance of predators. Sandpipers were usually found in small groups of 2-20 birds, and the largest flocks of 40-50 birds were found in pastures with relatively short grass cover (20 to 40% tall grass cover). Low to moderate stocking densities of domestic livestock created variation in vegetation height and cover in large areas and allowed for coexistence of grassland birds with different habitat requirements. Upland Sandpipers preferred disturbed areas, which may not support the needs of other species of grasslands birds. Our results emphasize the need for habitat heterogeneity and disturbance forces such as grazing in grassland systems. Our research contributes new information on the ecology of migratory grassland birds and provides insights for biodiversity conservation on private lands used for livestock production.