Increasing crop heterogeneity enhances multitrophic diversity across agricultural regions

International audienceAgricultural landscape homogenization has detrimental effects on biodiversity and key ecosystem services. Increasing agricultural landscape heterogeneity by increasing seminatural cover can help to mitigate biodiversity loss. However, the amount of seminatural cover is generally low and difficult to increase in many intensively managed agricultural landscapes. We hypothesized that increasing the heterogeneity of the crop mosaic itself (hereafter “crop heterogeneity”) can also have positive effects on biodiversity. In 8 contrasting regions of Europe and North America, we selected 435 landscapes along independent gradients of crop diversity and mean field size. Within each landscape, we selected 3 sampling sites in 1, 2, or 3 crop types. We sampled 7 taxa (plants, bees, butterflies, hoverflies, carabids, spiders, and birds) and calculated a synthetic index of multitrophic diversity at the landscape level. Increasing crop heterogeneity was more beneficial for multitrophic diversity than increasing seminatural cover. For instance, the effect of decreasing mean field size from 5 to 2.8 ha was as strong as the effect of increasing seminatural cover from 0.5 to 11%. Decreasing mean field size benefited multitrophic diversity even in the absence of seminatural vegetation between fields. Increasing the number of crop types sampled had a positive effect on landscape-level multitrophic diversity. However, the effect of increasing crop diversity in the landscape surrounding fields sampled depended on the amount of seminatural cover. Our study provides large-scale, multitrophic, cross-regional evidence that increasing crop heterogeneity can be an effective way to increase biodiversity in agricultural landscapes without taking land out of agricultural production

Probenecid Inhibits the Human Bitter Taste Receptor TAS2R16 and Suppresses Bitter Perception of Salicin

Bitter taste stimuli are detected by a diverse family of G protein-coupled receptors (GPCRs) expressed in gustatory cells. Each bitter taste receptor (TAS2R) responds to an array of compounds, many of which are toxic and can be found in nature. For example, human TAS2R16 (hTAS2R16) responds to β-glucosides such as salicin, and hTAS2R38 responds to thiourea-containing molecules such as glucosinolates and phenylthiocarbamide (PTC). While many substances are known to activate TAS2Rs, only one inhibitor that specifically blocks bitter receptor activation has been described. Here, we describe a new inhibitor of bitter taste receptors, p-(dipropylsulfamoyl)benzoic acid (probenecid), that acts on a subset of TAS2Rs and inhibits through a novel, allosteric mechanism of action. Probenecid is an FDA-approved inhibitor of the Multidrug Resistance Protein 1 (MRP1) transporter and is clinically used to treat gout in humans. Probenecid is also commonly used to enhance cellular signals in GPCR calcium mobilization assays. We show that probenecid specifically inhibits the cellular response mediated by the bitter taste receptor hTAS2R16 and provide molecular and pharmacological evidence for direct interaction with this GPCR using a non-competitive (allosteric) mechanism. Through a comprehensive analysis of hTAS2R16 point mutants, we define amino acid residues involved in the probenecid interaction that result in decreased sensitivity to probenecid while maintaining normal responses to salicin. Probenecid inhibits hTAS2R16, hTAS2R38, and hTAS2R43, but does not inhibit the bitter receptor hTAS2R31 or non-TAS2R GPCRs. Additionally, structurally unrelated MRP1 inhibitors, such as indomethacin, fail to inhibit hTAS2R16 function. Finally, we demonstrate that the inhibitory activity of probenecid in cellular experiments translates to inhibition of bitter taste perception of salicin in humans. This work identifies probenecid as a pharmacological tool for understanding the cell biology of bitter taste and as a lead for the development of broad specificity bitter blockers to improve nutrition and medical compliance

Effect of spatio-temporal landscape heterogeneity on populations distribution and dynamics

L'objectif de cette thèse est de comprendre comment l'hétérogénéité du paysage (i.e. composition, structuration spatiale et dynamique temporelle) affecte les populations, notamment dans les paysages agricoles, fortement structurés par la mosaïque des parcelles et les rotations culturales. Nous abordons cette question à la fois de manière théorique (en simulant des dynamiques de populations dans des paysages aux propriétés spatiales et temporelles contrôlées) mais également empirique (en analysant la sélection d'habitat par la communauté de passereaux des paysages agricoles).Nous avons ainsi montré que la composition, la configuration spatiale et la dynamique temporelle étaient toutes trois importantes pour expliquer les dynamiques de population, et que la nature des réponses à l'hétérogénéité dépendait des traits des espèces (taux de croissance, dispersion, échelle de réponse au paysage). L'analyse sur la communauté de passereaux a montré que la composition en cultures influençait la sélection d'habitat chez certaines espèces, mais nos données ne nous ont pas permis de mettre en avant un effet significatif de la structuration spatiale des cultures sur les passereaux. Une analyse plus fine pour l'Alouette des champs (Alauda arvensis) a montré un effet positif de la diversité des cultures à l'échelle du territoire, expliqué par une complémentarité fonctionnelle entre les cultures, suggérant que des petites parcelles et un mélange des cultures dans le paysage seraient bénéfiques pour cette espèce. L'effet de la structuration spatiale et temporelle des cultures sur les populations mériterait d'être testé de façon plus approfondie à l'échelle adéquate sur de nombreux taxons. Une meilleure connaissance de l'effet des propriétés de la matrice cultivée sur les processus permettrait de prédire l'évolution des populations face à des modifications du paysage à l'aide de modèles mécanistes, et offrirait de nouvelles opportunités pour gérer la biodiversité.The aim of this thesis is to understand how landscape heterogeneity (i.e. composition, configuration and temporal dynamics) affects populations, especially in farmlands, highly structured by the crop mosaic and rotations. We answer this question theoretically (simulating population dynamics in landscapes with controlled spatial and temporal properties) and empirically (analysing habitat selection by the farmland bird community).We found that landscape composition, configuration and temporal dynamics were all important to explain population dynamics and that the response to landscape heterogeneity depended on species traits (growth rate, dispersal, scale of response to the landscape). The analyse of farmland birds data revealed that crop composition influenced habitat selection for some species, but did not reveal a significant effect of crop configuration on birds. A finer analyse on Skylark showed a positive effect of crop diversity at the territory scale explained by a functional complementation among crops. It suggested that small fields and crop well mixed in the landscape would be beneficial for this species. The effect of spatial and temporal crop heterogeneity should be studied in depth at the right scale on many taxa. A good understanding of the effect of the cultivated matrix on processes would allow us to predict the change in populations when modifying the landscape and would offer new opportunities to manage biodiversity

Data from: How to quantify a distance-dependent landscape effect on a biological response

To quantify the effect of the surrounding landscape context on a biological response at a site, most studies measure landscape variables within discs centred on this biological response (threshold-based method). This implicitly assumes that the effect of a unit area of the landscape is consistent up to a threshold distance beyond which it drops to zero. However, it seems more likely that the landscape effect declines with increasing distance from the biological response point. Here we develop a method to quantify landscape context effects by weighting the landscape variables by functions that decrease with distance. We illustrate the method using abundance data on birds and insects, and compare the results to the threshold approach. We defined distance weighting functions by the function family (e.g. negative exponential, Gaussian…) and by the parameters for this function. We developed a method to simultaneously estimate the parameters characterizing the effect of the landscape variables and the parameters of the best weighting functions. For each test dataset, we determined which weighting function (family and parameters) had the most support, by optimizing the model AIC. The distance-weighted method improved model support over the threshold-based method in three of four datasets, with the exponential power function selected as the best weighing function in all three cases. The observed differences between estimations of landscape context effects by the distance-weighted and the threshold methods have significant implications for landscape management. For example, the distance-weighted method suggests that managing a landscape for 90% of its effect on a focal population requires an area over five times larger than the area estimated by the threshold method, a situation that might apply for priority conservation of few remnant populations of a severely endangered species. In contrast, management for 30% of the landscape effect requires only about half the area estimated using the threshold method, a situation that might apply to a management situation with limited resources or low political/societal support. The distance-weighted method is applicable to any species-habitat relationship. More comparisons are needed to determine the situations in which distance-weighted estimation of landscape context effects is warranted over the simpler threshold method

R script

R script of the functions used in the methods of the pape

Breeding habitat selection of Skylarks varies with crop heterogeneity, time and spatial scale, and reveals spatial and temporal crop complementation

International audienceWhile many studies having investigated the effects of landscape complexity or heterogeneity on farmland biodiversity were focus on semi-natural habitats (e.g. forests, hedgerows), few have analyzed the consequences of local crop heterogeneity on species abundance. Here we quantify the effects of crop heterogeneity on the breeding habitat selection of the Skylark Alauda arvensis at spatial scales ranging from micro-habitat to landscape, in a western France farmland. We address the question of finding the processes behind the crop heterogeneity effect, usually never studied whatever the taxa. We first studied how crop composition at continuous spatial scales from within the breeding territory to the landscape (20-2000 m) affected Skylark habitat selection within a breeding season (i.e. the effect of each crop compared to the others), and how this selection changed with time. Second, we examined how the diversity of crops within areas of radius from 20 to 2000 m affected habitat selection by Skylarks. Third, we investigated for the processes behind the crop diversity, examining the detailed pattern of crop selection at the territory scale in presence of only two crops, to identify the synergetic effects of the simultaneous presence of two crops. Using an adequate spatial sampling of 200 m radius circular plots in which Skylarks positions were mapped twice the year, we observed a strong selection for grasslands, an intermediate selection for cereals and spring-sown crops (changing with scale and time), and an avoidance of oilseed rape. Selection for grasslands increased with the season, selection for spring-sown crops and oilseed rape was stable, while selection for cereals decreased but only at fine scale. Skylarks selected high crop diversity at the territory scale. Similarly, the synergetic effect of the presence of two crops was positive in most cases, and Skylarks preferred area with two crops rather than only one for some pairs of crops, indicative of landscape complementation (requirement for complementary resources located in different crop types). Our results suggest that smaller fields and crops well mixed in the landscape may benefit this farmland specialist, favouring the positive effects of the simultaneous presence of several crops. The study demonstrates the importance of considering simultaneously time and spatial scale dependencies, as well as the synergetic effects and the spatial arrangement of habitats in habitat selection studies, particularly in patchy dynamics environments such as farmlands

dataset 4

dataset 4, Pterostichus Melanarius (biological variable) x Corn (landscape variable

dataset 1

dataset 1, Savannah Sparrow (biological variable) x Grassland (landscape variable

ReadMe file

The ReadMe file provides details about the content of the other files

dataset 2

dataset 2, Bobolink (biological variable) x Grassland (landscape variable