Phylogenetic grouping, curvature and metabolic scaling in terrestrial invertebrates.
ABSTRACT For more than a century, the scaling of animal metabolic rates with individual body masses and environmental temperature has predominantly been described by power-law and exponential relationships respectively. Many theories have been proposed to explain these scaling relationships, but were challenged by empirically documented curvatures on double-logarithmic scales. In the present study, we present a novel data set comprising 3661 terrestrial (mainly soil) invertebrate respiration rates from 192 independent sources across a wide range in body masses, environmental temperatures and phylogenetic groups. Although our analyses documented power-law and exponential scaling with body masses and temperature, respectively, polynomial models identified curved deviations. Interestingly, complex scaling models accounting for phylogenetic groups were able to remove curvatures except for a negative curvature at the highest temperatures (>30 °C) indicating metabolic down regulation. This might indicate that the tremendous differences in invertebrate body architectures, ecology and physiology may cause severely different metabolic scaling processes.
SourceAvailable from: Andrew D. Barnes[Show abstract] [Hide abstract]
ABSTRACT: Our knowledge about land-use impacts on biodiversity and ecosystem functioning is mostly limited to single trophic levels, leaving us uncertain about whole-community biodiversity-ecosystem functioning relationships. We analyse consequences of the globally important land-use transformation from tropical forests to oil palm plantations. Species diversity, density and biomass of invertebrate communities suffer at least 45% decreases from rain-forest to oil palm. Combining metabolic and food-web theory, we calculate annual energy fluxes to model impacts of land-use intensification on multitrophic ecosystem functioning. We demonstrate a 51% reduction in energy fluxes from forest to oil palm communities. Species loss clearly explains variation in energy fluxes; however, this relationship depends on land-use systems and functional feeding guilds, whereby predators are the most heavily affected. Biodiversity decline from forest to oil palm is thus accompanied by even stronger reductions in functionality, threatening to severely limit the functional resilience of communities to cope with future global changes.Nature Communications 10/2014; 5:5351. DOI:10.1038/ncomms6351 · 10.74 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: 1.Human activities may compromise biodiversity if external stressors such as nutrient enrichment endanger overall network stability by inducing unstable dynamics. However, some ecosystems maintain relatively high diversity levels despite experiencing continuing disturbances.2.This indicates that some intrinsic properties prevent unstable dynamics and resulting extinctions. Identifying these “ecosystem buffers” is crucial for our understanding of the stability of ecosystems and an important tool for environmental and conservation biologists. In this vein, weak interactions have been suggested as stabilizing elements of complex systems, but their relevance has rarely been tested experimentally.3.Here, using network and allometric theory we present a novel concept for a-priori identification of species that buffer against externally induced instability of increased population oscillations via weak interactions. We tested our model in a microcosm experiment using a soil food-web motif.4.Our results show that large-bodied species feeding at the food web's base, so called ‘trophic whales’, can buffer ecosystems against unstable dynamics induced by nutrient enrichment. Similar to the functionality of chemical or mechanical buffers, they serve as ‘biotic buffers’ that take up stressor effects and thus protect fragile systems from instability.5.We discuss trophic whales as common functional building blocks across ecosystems. Considering increasing stressor effects under anthropogenic global change, conservation of these network-intrinsic biotic buffers may help maintain the stability and diversity of natural ecosystems.This article is protected by copyright. All rights reserved.Journal of Animal Ecology 11/2014; DOI:10.1111/1365-2656.12324 · 4.73 Impact Factor