Extent, intensity and drivers of mammal defaunation:a continental-scale analysis across the Neotropics

Neotropical mammal diversity is currently threatened by several chronic human-induced pressures. We compiled 1,029 contemporary mammal assemblages surveyed across the Neotropics to quantify the continental-scale extent and intensity of defaunation and understand their determinants based on environmental covariates. We calculated a local defaunation index for all assemblages—adjusted by a false-absence ratio—which was examined using structural equation models. We propose a hunting index based on socioenvironmental co-variables that either intensify or inhibit hunting, which we used as an additional predictor of defaunation. Mammal defaunation intensity across the Neotropics on average erased 56.5% of the local source fauna, with ungulates comprising the most ubiquitous losses. The extent of defaunation is widespread, but more incipient in hitherto relatively intact major biomes that are rapidly succumbing to encroaching deforestation frontiers. Assemblage-wide mammal body mass distribution was greatly reduced from a historical 95th-percentile of ~ 14 kg to only ~ 4 kg in modern assemblages. Defaunation and depletion of large-bodied species were primarily driven by hunting pressure and remaining habitat area. Our findings can inform guidelines to design transnational conservation policies to safeguard native vertebrates, and ensure that the “empty ecosystem” syndrome will be deterred from reaching much of the New World tropics

Integrative modelling reveals mechanisms linking productivity and plant species richness

How ecosystem productivity and species richness are interrelated is one of the most debated subjects in the history of ecology1. Decades of intensive study have yet to discern the actual mechanisms behind observed global patterns2, 3. Here, by integrating the predictions from multiple theories into a single model and using data from 1,126 grassland plots spanning five continents, we detect the clear signals of numerous underlying mechanisms linking productivity and richness. We find that an integrative model has substantially higher explanatory power than traditional bivariate analyses. In addition, the specific results unveil several surprising findings that conflict with classical models4, 5, 6, 7. These include the isolation of a strong and consistent enhancement of productivity by richness, an effect in striking contrast with superficial data patterns. Also revealed is a consistent importance of competition across the full range of productivity values, in direct conflict with some (but not all) proposed models. The promotion of local richness by macroecological gradients in climatic favourability, generally seen as a competing hypothesis8, is also found to be important in our analysis. The results demonstrate that an integrative modelling approach leads to a major advance in our ability to discern the underlying processes operating in ecological systems

Freshwater phytoplankton diversity: models, drivers and implications for ecosystem properties

Our understanding on phytoplankton diversity has largely been progressing since the publication of Hutchinson on the paradox of the plankton. In this paper, we summarise some major steps in phytoplankton ecology in the context of mechanisms underlying phytoplankton diversity. Here, we provide a framework for phytoplankton community assembly and an overview of measures on taxonomic and functional diversity. We show how ecological theories on species competition together with modelling approaches and laboratory experiments helped understand species coexistence and maintenance of diversity in phytoplankton. The non-equilibrium nature of phytoplankton and the role of disturbances in shaping diversity are also discussed. Furthermore, we discuss the role of water body size, productivity of habitats and temperature on phytoplankton species richness, and how diversity may affect the functioning of lake ecosystems. At last, we give an insight into molecular tools that have emerged in the last decades and argue how it has broadened our perspective on microbial diversity. Besides historical backgrounds, some critical comments have also been mad

Plant species richness is not consistently associated with productivity in experimental subalpine meadow plant communities

© 2015, Institute of Botany, Academy of Sciences of the Czech Republic. The relationship between species richness and productivity has been a central issue in community ecology, and this issue has resulted in much debate in the ecological literature. To evaluate whether species richness is consistently associated with productivity and the underlying mechanisms, a potted experiment with various combinations of three perennial plant species (Elymus nutans, Roegneria nutans and Festuca sinensis) was conducted under three fertilization levels over three years with interannual variation in rainfall in a subalpine meadow on the Tibetan plateau, China. The additive partitioning method was used for measuring net, selection and complementarity effects. The results suggest that species richness, composition and density had significant effects on aboveground biomass, but their effects were much less than abiotic factors (fertility and year). Relative yield total (RYT), net, selection and complementarity effects were not consistently positive or negative across years in the mixed communities. Both the interaction of year and species richness and the interaction of year and composition had significant effects on aboveground biomass, selection and complementarity effects. Fertilization and density had no significant effects on net, selection and complementarity effects. Our results indicate that plant richness is not consistently associated with productivity in these experimental plant communities, considering that selection and complementarity effects can vary with complex environmental conditions, and that these factors influence plant productivity. We suggest that different forms of relationships between species richness and productivity may be exhibited based on biotic or abiotic factors in plant communities