National University of Comahue

About: National University of Comahue is a education organization based out in Neuquén, Argentina. It is known for research contribution in the topics: Population & Species richness. The organization has 2242 authors who have published 4498 publications receiving 87157 citations. The organization is also known as: UNCOMA & UNCo.

Low growth resilience to drought is related to future mortality risk in trees

Abstract: Severe droughts have the potential to reduce forest productivity and trigger tree mortality. Most trees face several drought events during their life and therefore resilience to dry conditions may be crucial to long-term survival. We assessed how growth resilience to severe droughts, including its components resistance and recovery, is related to the ability to survive future droughts by using a tree-ring database of surviving and now-dead trees from 118 sites (22 species, >3,500 trees). We found that, across the variety of regions and species sampled, trees that died during water shortages were less resilient to previous non-lethal droughts, relative to coexisting surviving trees of the same species. In angiosperms, drought-related mortality risk is associated with lower resistance (low capacity to reduce impact of the initial drought), while it is related to reduced recovery (low capacity to attain pre-drought growth rates) in gymnosperms. The different resilience strategies in these two taxonomic groups open new avenues to improve our understanding and prediction of drought-induced mortality.

The PREDICTS database: a global database of how local terrestrial biodiversity responds to human impacts

Abstract: Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species Existing global databases of species’ threat status or population time series are dominated by charismatic species The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary to enable better understanding of historical declines and to project – and avert – future declines We describe and assess a new database of more than 16 million samples from 78 countries representing over 28,000 species, collated from existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world The database contains measurements taken in 208 (of 814) ecoregions, 13 (of 14) biomes, 25 (of 35) biodiversity hotspots and 16 (of 17) megadiverse countries The database contains more than 1% of the total number of all species described, and more than 1% of the described species within many taxonomic groups – including flowering plants, gymnosperms, birds, mammals, reptiles, amphibians, beetles, lepidopterans and hymenopterans The dataset, which is still being added to, is therefore already considerably larger and more representative than those used by previous quantitative models of biodiversity trends and responses The database is being assembled as part of the PREDICTS project (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems – wwwpredictsorguk) We make site-level summary data available alongside this article The full database will be publicly available in 2015

Worldwide occurrence records suggest a global decline in bee species richness

Abstract: Summary Wild and managed bees are key pollinators, ensuring or enhancing the reproduction of a large fraction of the world's wild flowering plants and the yield of ∼85% of all cultivated crops. Recent reports of wild bee decline and its potential consequences are thus worrisome. However, evidence is mostly based on local or regional studies; the global status of bee decline has not been assessed yet. To fill this gap, we analyzed publicly available worldwide occurrence records from the Global Biodiversity Information Facility spanning over a century. We found that after the 1990s, the number of collected bee species declines steeply such that approximately 25% fewer species were reported between 2006 and 2015 than before the 1990s. Although these trends must be interpreted cautiously given the heterogeneous nature of the dataset and potential biases in data collection and reporting, results suggest the need for swift actions to avoid further pollinator decline.

Inequalities in fruit-removal and seed dispersal: consequences of bird behaviour, neighbourhood density and landscape aggregation

Abstract: Summary 1. Frugivores disperse the seeds of the majority of woody plant species world-wide. Thus, insights on how frugivores influence the dispersal of plants and the variability of this process are crucial for understanding plant population dynamics in a rapidly changing world. 2. We used a spatially explicit, stochastic, individual-based model that simulates fruit-removal and seed dispersal by birds to assess bird density, landscape and neighbourhood effects on the inequalities of within-population fruit-removal rates and seed dispersal. We also compared model predictions with spatially-explicit field data. 3. In our simulations, bird density had a strong effect on the distribution of fruit-removal rates creating large inequalities among plants. Also, for equal bird densities, inequalities increased with the landscape level aggregation of plants. 4. Fruit removal increased with increasing plant neighbourhood density although there was a tendency to decline at the highest densities. Neighbourhood density also changed average dispersal distances, but with shorter distances at higher densities. Plants with few neighbours not only had longer distance dispersal but also a larger variance in seed rain across distances than plants with ten or more neighbours. These relationships between neighbourhood density and fruit removal and dispersal distance were scale-dependent with a peak in correlations at 150-m radius. 5. Similar to model predictions, field data shows an inverse relationship between dispersal distances (inferred from bird movements) and fruiting neighbourhood density. Also, fruit-removal rates observed in the field show large numbers of plants receiving little or zero fruit-removal. Fruitremoval rate distributions were statistically indistinguishable between the simulation and field data. But, distributions were strikingly different from two alternative models that lacked spatial effects. 6. Synthesis . Our model and field data show that as fruiting plants become aggregated, inequalities in fruit-removal rates increase and seed dispersal distance decreases. Both of these processes could help create and maintain plant aggregation and affect genetic structuring. The model also predicts that small-scale neighbourhood effects can be controlled by large-scale processes such as overall frugivore abundance and landscape-level plant aggregation. Most importantly, both simulations and field data shows an interaction between plant spatial pattern and bird foraging, which results in neighbourhood-specific dispersal and rates of fruit removal.