Understanding the variation in species interactions along environmental stress gradients is crucial for making robust ecological predictions about community responses to changing environmental conditions. The facilitation-competition framework has provided a strong basis for predictions (e.g. the stress-gradient hypothesis, SGH), yet the mechanisms behind patterns in animal interactions on stress gradients are poorly explored in particular for mobile animals. Here, we proposed a conceptual framework modelling changes in facilitation costs and benefits along stress gradients and experimentally tested this framework by measuring fitness outcomes of benefactor-beneficiary interactions across resource quality levels. Three arthropod consumer models from a broad array of environmental conditions were used including aquatic detritivores, potato moths and rainforest carrion beetles. We detected a shift to more positive interactions at increasing levels of stress thereby supporting the application of the SGH to mobile animals. While most benefactors paid no significant cost of facilitation, an increase in potato moth beneficiary's growth at high resource stress triggered costs for benefactors. This study is the first to experimentally show that both costs and benefits function simultaneously on stress gradients for animals. The proposed conceptual framework could guide future studies examining species interaction outcomes for both animals and plants in an increasingly stressed world.

La produccion del cacao fino de aroma (theobroma cacao l.) debe realizarse de forma sostenible desde un punto de vista economico y ambiental, por lo que las condiciones climaticas deben ser tenidas en una alta consideracion, si se desea hacer un uso racional y sostenible de sus servicios ambientales. La evaluacion del indice potencial productivo (ipp) del cultivo del cacao en la provincia Los Rios brinda la oportunidad de descubrir las fortalezas y debilidades de la region, lo que proporciona poder establecer medidas de manejo o de uso de la tierra de forma efectiva. El ipp del cacao fino de aroma hacia el Sur resulta con valores bajos, con ipps inferiores al 80% que pueden alcanzar solo el 65%. Hacia el norte la provincia se ve favorecida con ipps superiores al 80%, lo que garantiza que en ese mismo porcentaje seran los rendimientos. Se concluye que una reduccion entre un 30 y un 40% del ipp se refleja en los rendimientos en niveles entre 0.308 y 0.264 ton/ha. Considerando que la tonelada de cacao esta en la actualidad a $2090.00 usd, entonces esto significa que por cada hectarea en estas regiones hay perdidas que fluctuan entre $627.00 usd y $836.00 usd. Estos resultados pueden ser mitigados con infraestructura de riego, que de cualquier forma encarece su produccion respecto a las areas localizadas hacia el norte de la provincia.

•Crop pests can access a wide range of favourable microclimate by moving in few cms.•The more solar radiation, the less distance pests must travel to fulfil their thermal needs.•Spatial configuration and composition of crop microclimates influence pest richness.•Diverse and distinctly distributed crop microclimates shelter higher diversity of pests.

Microclimates have long been recognized in controlling the physiology and ecology of species. However, in the context of global warming and increasing climatic variability, a major uncertainty that hampers effective pest management is related to the thermal characteristics of agricultural landscapes, which are known to have profound effects on insect pest dynamics. Here, we addressed the issue of considering microclimates experienced by crop pests in their environments to infer their distribution and develop innovative pest control strategies based on processes of thermal agro-ecology. We assessed the heterogeneity of microclimates experienced by pests and natural enemies in complex agricultural landscapes of Ecuador (from 2800 to 3600 m.a.s.l.), made of various crop types and natural habitats. The assessment of microclimates was performed at the agrosystem, crop field, and plant scales using a combination of UAVs, thermal cameras and temperature micro-loggers. Then, we determined the relationship between microclimates heterogeneity (characterized using spatial metrics) and pest occurrences (measured in the field with pheromone traps and local plant samplings). Results revealed that microclimates heterogeneity must be taken into consideration when estimating ectotherm occurrences. Indeed, at the landscape scale, microclimates of crops and natural habitats substantially affect pest dynamics. At the field scale, the spatial metrics shaping microclimatic conditions are significantly related to pest occurrences. And at the plant scale, we found that pests can access in their close vicinity (<1.2 m) most of the thermal micro-environments recorded at the field level. In complex agro-ecological landscapes, there is likely a wide range of microclimatic conditions resulting in the presence of locallysuitable and unfavourable conditions for ectotherms (crop pests but also natural enemies), the existence of which might not be apparent at a coarser resolution. Consequently, this work stresses the need of a better incorporation of microclimatic data into models of species distribution (and vulnerability to climate change) and evidences that microclimates might provide new leverage for innovative agro-ecological pest management. (Texte integral)

Bridging the gap between the predictions of coarse-scale climate models and the fine-scale climatic reality of species is a key issue of climate change biology research. While it is now well known that most organisms do not experience the climatic conditions recorded at weather stations, there is little information on the discrepancies between microclimates and global interpolated temperatures used in species distribution models, and their consequences for organisms' performance. To address this issue, we examined the fine-scale spatiotemporal heterogeneity in air, crop canopy and soil temperatures of agricultural landscapes in the Ecuadorian Andes and compared them to predictions of global interpolated climatic grids. Temperature time-series were measured in air, canopy and soil for 108 localities at three altitudes and analysed using Fourier transform. Discrepancies between local temperatures vs. global interpolated grids and their implications for pest performance were then mapped and analysed using GIS statistical toolbox. Our results showed that global interpolated predictions over-estimate by 77.5 ± 10% and under-estimate by 82.1 ± 12% local minimum and maximum air temperatures recorded in the studied grid. Additional modifications of local air temperatures were due to the thermal buffering of plant canopies (from -2.7 °K during daytime to 1.3 °K during night-time) and soils (from -4.9 °K during daytime to 6.7 °K during night-time) with a significant effect of crop phenology on the buffer effect. This discrepancies between interpolated and local temperatures strongly affected predictions of the performance of an ectothermic crop pest as interpolated temperatures predicted pest growth rates 2.3-4.3 times lower than those predicted by local temperatures. This study provides quantitative information on the limitation of coarse-scale climate data to capture the reality of the climatic environment experienced by living organisms. In highly heterogeneous region such as tropical mountains, caution should therefore be taken when using global models to infer local-scale biological processes.

Despite its theoretical prominence and sound principles, integrated pest management (IPM) continues to suffer from anemic adoption rates in developing countries. To shed light on the reasons, we surveyed the opinions of a large and diverse pool of IPM professionals and practitioners from 96 countries, using structured concept mapping. The first phase of this method elicited 413 open-ended responses on perceived obstacles to IPM. Analysis of responses revealed 51 unique statements on obstacles, the most frequent of which was " insufficient training and technical support to farmers ". Cluster analyses, based on participant opinions, grouped these unique statements into six themes: research weaknesses, outreach weaknesses, IPM weaknesses, farmer weaknesses, pesticide industry interference, and weak adoption incentives. Subsequently, 163 participants rated the obstacles expressed in the 51 unique statements according to importance and remediation difficulty. Respondents from developing countries and high-income countries rated the obstacles differently. As a group, developing-country respondents rated " IPM requires collective action within a farming community " as their top obstacle to IPM adoption. Respondents from high-income countries prioritized instead the " shortage of well-qualified IPM experts and extensionists ". Differential prioritization was also evident among developing-country regions, and when obstacle statements were grouped into themes. Results highlighted the need to improve the participation of stakeholders from developing countries in the IPM adoption debate, and also to situate the debate within specific regional contexts. Integrated Pest Management │ sustainable agriculture │ developing countries │ technology adoption │ collective action dilemma 3 Significance Statement Integrated pest management, commonly known by its acronym IPM, has been the dominant crop protection paradigm promoted globally since the 1960s. However, its adoption by developing country farmers is surprisingly low. This article reports 51 potential reasons why, identified and prioritized by hundreds of professionals and practitioners around the world. Stakeholders from developing countries prioritized different adoption obstacles than those from high income countries. Surprisingly, a few of the obstacles prioritized in developing countries appear to be overlooked by the literature. We suggest a more vigorous analysis and discussion of the factors discouraging IPM adoption in developing countries may accelerate the progress needed to bring about its full potential. 4 \body Introduction Feeding the 9,000 million people expected to inhabit Earth by 2050 will present a constant and significant challenge in terms of agricultural pest management (1–3). Despite a 15-to 20-fold increase in pesticide use since the 1960s, global crop losses to pests—arthropods, …

Despite its theoretical prominence and sound principles, integrated pest management (IPM) continues to suffer from anemic adoption rates in developing countries. To shed light on the reasons, we surveyed the opinions of a large and diverse pool of IPM professionals and practitioners from 96 countries by using structured concept mapping. The first phase of this method elicited 413 open-ended responses on perceived obstacles to IPM. Analysis of responses revealed 51 unique statements on obstacles, the most frequent of which was "insufficient training and technical support to farmers." Cluster analyses, based on participant opinions, grouped these unique statements into six themes: research weaknesses, outreach weaknesses, IPM weaknesses, farmer weaknesses, pesticide industry interference, and weak adoption incentives. Subsequently, 163 participants rated the obstacles expressed in the 51 unique statements according to importance and remediation difficulty. Respondents from developing countries and high-income countries rated the obstacles differently. As a group, developing-country respondents rated "IPM requires collective action within a farming community" as their top obstacle to IPM adoption. Respondents from high-income countries prioritized instead the "shortage of well-qualified IPM experts and extensionists." Differential prioritization was also evident among developing-country regions, and when obstacle statements were grouped into themes. Results highlighted the need to improve the participation of stakeholders from developing countries in the IPM adoption debate, and also to situate the debate within specific regional contexts.

Understanding how and to what extent the influence of temperature on physiological performance scales up to interspecific interactions and process rate patterns remains a major scientific challenge faced by ecologists. Here, we combined approaches developed by two conceptual frameworks in ecology, the stress‐gradient hypothesis ( SGH ), and the biodiversity–ecosystem functioning relationship (B‐ EF ), to test the hypothesis that interspecific difference in thermal performance modulates multiple species interactions along a thermal stress ( SGH ) and the subsequent richness effects on process rates (B‐ EF ). We designed an experiment using three species of herbivorous agricultural pests with different thermal optima for which we determined how temperature influences the direction and the strength of interaction and subsequent richness effects on crop damage (7 species interaction treatments × 6 temperature treatments × 10 replicates). We showed that both biotic interactions and species richness effects drive variations in crop damages along a thermal stress gradient, and thus have the potential to drive agro‐system responses to climate change. To help explain and generalize underlying mechanisms of richness effects on process rates, we further proposed a conceptual model that views interaction outcomes as shifting between positive and negative along a thermal stress depending on species thermal optima. Overall, our study demonstrates that nonlinear effects of temperature on process rates must be a major concern in terms of prediction and management of the consequences of global warming.

The stress-gradient hypothesis (SGH) postulates an increase in the frequency of positive species interactions at increasing amounts of stress. While the SGH has been extensively tested in plant-plant interactions along abiotic stresses, it remains unclear whether this hypothesis could apply to higher trophic levels, such as herbivores, along biotic stress gradients.To address this issue, we investigated how the interaction between two potato herbivores may change along a stress gradient created by an assortment of potato varieties with different tuber palatability. We used a tuber resistance trait as a measure for biotic stress and one herbivore as the facilitator to gain access to the tuber of the other herbivore.Our experiment revealed a switch from neutral to positive interactions with increasing stress, confirming for the first time the predictions of the SGH for herbivores. Moreover, the intensity of facilitation decreased at high stress levels, suggesting that benefits by the facilitating species were dampened in the most stressful environment.In view of the ubiquitous role played by positive interactions among herbivores, broadening our search image for facilitative effects among other plant enemies will allow a better awareness of the importance of the SGH in structuring plant communities.

Longitudinal bone growth occurs by a process called endochondral ossification that includes chondrocyte proliferation, differentiation, and apoptosis. Recent studies have suggested a regulatory role for intracellular Ca-2 divided by (Ca-i(2 divided by)) in this process. Indirect studies, using Ca2+ channel blockers and measurement of Ca-i(2+), have provided evidence for the existence of Ca2+ channels in growth plate chondrocytes. Furthermore, voltage-gated Ca2+ channels (VGCC), and specifically L-and T-typeVGCCs, have been recently described in murine embryonic growth plates. Our aim was to assess the effect of L-type Ca2+ channel blockers on endochondral ossification in an organ culture. We used cultures of fetal rat metatarsal rudiments at 20 days post gestational age, with the addition of the L-type Ca2+ channel blockers verapamil (10-100 mu M) or diltiazem (10-200 mu M) to the culture medium. Longitudinal bone growth, chondrocyte differentiation (number of hypertrophic chondrocytes), and cell proliferation (incorporation of tritiated thymidine) were measured. Verapamil dose-dependently decreased growth, the number of hypertrophic chondrocytes, and cell proliferation, at concentrations of 10-100 mu M. Growth and the number of hypertrophic chondrocytes decreased significantly with diltiazem at 50-100 mu M and proliferation decreased significantly at concentrations of 10-200 mu M. Additionally, there was no increase in apoptosis over physiological levels with either drug. We confirmed the presence of L-type VGCCs in rat rudiments using immunohistochemistry, and showed that the antagonists did not alter the pattern of VGCC expression. In conclusion, our data suggest that L-type Ca2+ channel activity in growth plate chondrocytes is necessary for normal longitudinal growth, participating in chondrocyte proliferation and differentiation.