Showing papers by "Vincent Bretagnolle published in 2020"

Meta-analysis of multidecadal biodiversity trends in Europe

Abstract: Local biodiversity trends over time are likely to be decoupled from global trends, as local processes may compensate or counteract global change. We analyze 161 long-term biological time series (15–91 years) collected across Europe, using a comprehensive dataset comprising ~6,200 marine, freshwater and terrestrial taxa. We test whether (i) local long-term biodiversity trends are consistent among biogeoregions, realms and taxonomic groups, and (ii) changes in biodiversity correlate with regional climate and local conditions. Our results reveal that local trends of abundance, richness and diversity differ among biogeoregions, realms and taxonomic groups, demonstrating that biodiversity changes at local scale are often complex and cannot be easily generalized. However, we find increases in richness and abundance with increasing temperature and naturalness as well as a clear spatial pattern in changes in community composition (i.e. temporal taxonomic turnover) in most biogeoregions of Northern and Eastern Europe.

Land-use history impacts functional diversity across multiple trophic groups.

Abstract: Land-use change is a major driver of biodiversity loss worldwide. Although biodiversity often shows a delayed response to land-use change, previous studies have typically focused on a narrow range of current landscape factors and have largely ignored the role of land-use history in shaping plant and animal communities and their functional characteristics. Here, we used a unique database of 220,000 land-use records to investigate how 20-y of land-use changes have affected functional diversity across multiple trophic groups (primary producers, mutualists, herbivores, invertebrate predators, and vertebrate predators) in 75 grassland fields with a broad range of land-use histories. The effects of land-use history on multitrophic trait diversity were as strong as other drivers known to impact biodiversity, e.g., grassland management and current landscape composition. The diversity of animal mobility and resource-acquisition traits was lower in landscapes where much of the land had been historically converted from grassland to crop. In contrast, functional biodiversity was higher in landscapes containing old permanent grasslands, most likely because they offer a stable and high-quality habitat refuge for species with low mobility and specialized feeding niches. Our study shows that grassland-to-crop conversion has long-lasting impacts on the functional biodiversity of agricultural ecosystems. Accordingly, land-use legacy effects must be considered in conservation programs aiming to protect agricultural biodiversity. In particular, the retention of permanent grassland sanctuaries within intensive landscapes may offset ecological debts.

Configurational crop heterogeneity increases within-field plant diversity

Abstract: Increasing landscape heterogeneity by restoring semi-natural elements to reverse farmland biodiversity declines is not always economically feasible or acceptable to farmers due to competition for land. We hypothesized that increasing the heterogeneity of the crop mosaic itself, hereafter referred to as crop heterogeneity, can have beneficial effects on within-field plant diversity. Using a unique multi-country dataset from a cross-continent collaborative project covering 1,451 agricultural fields within 432 landscapes in Europe and Canada, we assessed the relative effects of compositional and configurational crop heterogeneity on within-field plant diversity components. We also examined how these relationships were modulated by the position within the field. We found strong positive effects of configurational crop heterogeneity on within-field plant alpha and gamma diversity in field interiors. These effects were as high as the effect of semi-natural cover. In field borders, effects of crop heterogeneity were limited to alpha diversity. We suggest that a heterogeneous crop mosaic may overcome the high negative impact of management practices on plant diversity in field interiors, whereas in field borders, where plant diversity is already high, landscape effects are more limited. Synthesis and applications. Our study shows that increasing configurational crop heterogeneity is beneficial to within-field plant diversity. It opens up a new effective and complementary way to promote farmland biodiversity without taking land out of agricultural production. We therefore recommend adopting manipulation of crop heterogeneity as a specific, effective management option in future policy measures, perhaps adding to agri-environment schemes, to contribute to the conservation of farmland plant diversity.

Agriculture intensification reduces plant taxonomic and functional diversity across European arable systems

Abstract: Agricultural intensification is one of the main drivers of species loss worldwide, but there is still a lack of information about its effect on functional diversity of arable weed communities. Using a large-scale pan European study including 786 fields within 261 farms from eight countries, we analysed differences in the taxonomic and functional diversity of arable weeds assemblages across different levels of agricultural intensification. We estimated weed species frequency in each field, and collected species' traits (vegetative height, SLA and seed mass) from the TRY plant trait database. With this information, we estimated taxonomic (species richness), functional composition (community weighted means) and functional diversity (functional richness, evenness, divergence and redundancy). We used indicators of agricultural management intensity at the individual field scale (e.g. yield, inputs of nitrogen fertilizer and herbicides, frequency of mechanical weed control practices) and at the landscape scale surrounding the field (i.e. number of crop types, mean field size and proportion of arable land cover within a radius of 500 m from the sampling points). The effects of agricultural intensification on species and functional richness at the field scale were stronger than those of intensification at the landscape scale, and we did not observe evidence of interacting effects between the two scales. Overall, assemblages in more intensified areas had fewer species, a higher prevalence of species with ruderal strategies (low stature, high leaf area, light seeds), and lower functional redundancy. Maintaining the diversity of Europe's arable weed communities requires some simple management interventions, for example, reducing the high intensity of field-level agricultural management across Europe, which could be complemented by interventions that increase landscape complexity. A free Plain Language Summary can be found within the Supporting Information of this article.

Weeds Enhance Multifunctionality in Arable Lands in South-West of France

Abstract: The current challenge in agriculture is to move from intensively managed to multifunctional agricultural landscapes that can simultaneously provide multiple ecological functions (multifunctionality), thus ensuring the delivery of ecosystem services important for human well-being. There is evidence that biodiversity is the main driver of multiple ecosystem functions. However, how biodiversity, and which components of biodiversity are the sources of multifunctionality, remain elusive. In the present study, we explore the role of weed richness and weed abundance as possible sources of ecosystem multifunctionality of an intensive agricultural landscape. Weeds are a key component of the arable field ecosystem trophic network by supporting various ecological functions while being a possible threat for production. We combine empirical data on ten ecosystem functions related to pollination, pest control and soil fertility, and measured across 184 fields cultivated with winter cereal, oilseed rape or hays in the Long Term Socio-Ecological Research site Zone Atelier Plaine & Val de Sevre. We found that weed diversity was a strong contributor to multifunctionality in all crop types, especially when using the threshold-based approach. The effects of weed diversity were less pronounced for individual ecological functions except for weed seed predation and urease activity. As weeds may have dual effects on yields, we also explored the relationship between ecosystem multifunctionality and yield considering weed abundance. We however found a neutral relationship between yield and ecosystem multifunctionality. These results suggest that field management that maintains high levels of weed diversity can enhance multifunctionality and most ecological functions. Understanding how to maintain weed diversity in agricultural landscapes can therefore help to design sustainable management favoring the delivery of multiple services while maintaining food production. The next challenge will therefore be to assess the relative contribution of management practices, landscape features and weed diversity on ecosystem multifunctionality and yield.

Social–ecological experiments to foster agroecological transition

Abstract: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2020 The Authors. People and Nature published by John Wiley & Sons Ltd on behalf of British Ecological Society 1USC 1339, Centre d'Etudes Biologiques de Chizé, INRAE, Villiers-en-Bois, France 2Centre d'Etudes Biologiques de Chizé, UMR 7372, CNRS & Université de La Rochelle, Villiers-en-Bois, France 3LTSER “Zone Atelier Plaine & Val de Sèvre”, CNRS, Villiers-en-Bois, France

Honeybee lifespan: the critical role of pre-foraging stage

Abstract: Assessing the various anthropogenic pressures imposed on honeybees requires characterizing the patterns and drivers of natural mortality. Using automated lifelong individual monitoring devices, we monitored worker bees in different geographical, seasonal and colony contexts creating a broad range of hive conditions. We measured their life-history traits and notably assessed whether lifespan is influenced by pre-foraging flight experience. Our results show that the age at the first flight and onset of foraging are critical factors that determine, to a large extent, lifespan. Most importantly, our results indicate that a large proportion (40%) of the bees die during pre-foraging stage, and for those surviving, the elapsed time and flight experience between the first flight and the onset of foraging is of paramount importance to maximize the number of days spent foraging. Once in the foraging stage, individuals experience a constant mortality risk of 9% and 36% per hour of foraging and per foraging day, respectively. In conclusion, the pre-foraging stage during which bees perform orientation flights is a critical driver of bee lifespan. We believe these data on the natural mortality risks in honeybee workers will help assess the impact of anthropogenic pressures on bees.

Weed diversity is driven by complex interplay between multi-scale dispersal and local filtering.

Abstract: Arable weeds are key organisms for biodiversity maintenance and ecosystem service provision in agroecosystems. Disentangling the drivers of weed diversity is critical to counteract the global decline of farmland biodiversity. Even if distinct scale-dependent processes were alternatively proposed, no general framework unifying the multi-scale drivers of weed dynamics has yet emerged. Here, we investigate the joint effects of field- and landscape-scale processes on weed assemblages in 444 arable fields. First, field margins sheltered greater weed diversity than field core, evidencing their role as biodiversity refugia. Second, community similarity between field core and margin decreased with the distance to margin, highlighting a major role of local dispersal. Third, weed diversity at field margins increased with organic field cover in the landscape, pointing out massive regional dispersal. Fourth, while both local and landscape dispersal explained up to 41% of field core weed diversity, crop type strongly modulated their strength, depicting an intense filtering effect by agricultural management. This study sheds new light on the complex multi-scale interactions shaping weed diversity, field margins playing a key role by strengthening regional dispersal and sustaining local dispersal. Land-sharing strategies improving habitat heterogeneity both locally and regionally should largely promote agroecosystem multifunctionality and sustainability.

A complex scenario of glacial survival in Mediterranean and continental refugia of a temperate continental vole species (Microtus arvalis) in Europe

Abstract: This work was supported by I + D National Plan Projects of the Spanish Ministry of Economy, Industry and Competitiveness (CGL2011‐30274, CGL2015‐71255‐P, CGL2013‐42451‐P), and the Fundacion BBVA Research Project TOPIGEPLA (2014 call).

Ecological Specialization and Rarity of Arable Weeds: Insights from a Comprehensive Survey in France

Abstract: The definition of “arable weeds” remains contentious. Although much attention has been devoted to specialized, segetal weeds, many taxa found in arable fields also commonly occur in other habitats. The extent to which adjacent habitats are favorable to the weed flora and act as potential sources of colonizers in arable fields remains unclear. In addition, weeds form assemblages with large spatiotemporal variability, so that many taxa in weed flora are rarely observed in plot-based surveys. We thus addressed the following questions: How often do weeds occur in other habitats than arable fields? How does including field edges extend the taxonomic and ecological diversity of weeds? How does the weed flora vary across surveys at different spatial and temporal scales? We built a comprehensive dataset of weed taxa in France by compiling weed flora, lists of specialized segetal weeds, and plot-based surveys in agricultural fields, with different spatial and temporal coverages. We informed life forms, biogeographical origins and conservation status of these weeds. We also defined a broader dataset of plants occupying open habitats in France and assessed habitat specialization of weeds and of other plant species absent from arable fields. Our results show that many arable weeds are frequently recorded in both arable fields and non-cultivated open habitats and are, on average, more generalist than species absent from arable fields. Surveys encompassing field edges included species also occurring in mesic grasslands and nitrophilous fringes, suggesting spill-over from surrounding habitats. A total of 71.5% of the French weed flora was not captured in plot-based surveys at regional and national scales, and many rare and declining taxa were of Mediterranean origin. This result underlines the importance of implementing conservation measures for specialist plant species that are particularly reliant on arable fields as a habitat, while also pointing out biotic homogenization of agricultural landscapes as a factor in the declining plant diversity of farmed landscapes. Our dataset provides a reference species pool for France, with associated ecological and biogeographical information.

Measuring ontogenetic shifts in central-place foragers: A case study with honeybees

Abstract: Measuring time-activity budgets over the complete individual life span is now possible for many animals with the recent advances of life-long individual monitoring devices. Although analyses of changes in the patterns of time-activity budgets have revealed ontogenetic shifts in birds or mammals, no such technique has been applied to date on insects. We tested an automated breakpoint-based procedure to detect, assess and quantify shifts in the temporal pattern of the flight activities in honeybees. We assumed that the learning and foraging stages of honeybees will differ in several respects, to detect the age at onset of foraging (AOF). Using an extensive dataset covering the life-long monitoring of 1,167 individuals, we compared the AOF outputs with the more conventional approaches based on arbitrary thresholds. We further evaluated the robustness of the different methods comparing the foraging time-activity budget allocations between the presumed foragers and confirmed foragers. We revealed a clear-cut learning-foraging ontogenetic shift that differs in duration, frequency and time of occurrence of flights. Although AOF appeared to be highly plastic among bees, the breakpoint-based procedure seems better capable to detect it than arbitrary threshold-based methods that are unable to deal with inter-individual variation. We developed the aof r-package including a broad range of examples with both simulated and empirical datasets to illustrate the simplicity of use of the procedure. This simple procedure is generic enough to be derived from any individual life-long monitoring devices recording the time-activity budgets, and could propose new ecological applications of bio-logging to detect ontogenetic shifts in the behaviour of central-place foragers.

Measuring ontogenetic shifts in central-place foraging insects: a case study with honey bees

Abstract: Measuring time-activity budgets over the complete individual lifespan is now possible for many animals with the recent advances of life-long individual monitoring devices. Although analyses of changes in the patterns of time-activity budgets have revealed ontogenetic shifts in birds or mammals, no such technique has been applied to date on insects. We tested an automated breakpoint-based procedure to detect, assess and quantify shifts in the temporal pattern of the flight activities in honey bees. We assumed that the learning and foraging stages of honey bees will differ in several respects, to detect the age at onset of foraging (AOF). Using an extensive dataset covering the life-long monitoring of 2,100 individuals, we compared the AOF outputs with the more conventional approaches based on arbitrary thresholds. We further evaluated the robustness of the different methods comparing the foraging time-activity budget allocations between the presumed foragers and confirmed foragers. We revealed a clear-cut learning-foraging ontogenetic shift that differs in duration, frequency, and time of occurrence of flights. Although AOF appeared to be highly plastic among bees, the breakpoint-based procedure seems better able to detect it than arbitrary threshold-based methods that are unable to deal with inter-individual variation. We developed the aof R-package including a broad range of examples with both simulated and empirical dataset to illustrate the simplicity of use of the procedure. This simple procedure is generic enough to be derived from any individual life-long monitoring devices recording the time-activity budgets of honey bees, and could propose new ecological applications of bio-logging to detect ontogenetic shifts in the behaviour of central-place foraging insects.

Towards a standardized experimental protocol to investigate interactions between weed seeds and ground beetles (Carabidae, Coleoptera)

Abstract: Seed bank control is the mainspring of agricultural management practices. Using weeds seeds natural predators as a weed control strategy can be a valuable alternative to herbicide use. Among natural predators, ground beetles (Coleoptera, family Carabidae) have been claimed to be one of the most important invertebrate seeds predators in agroecosystems. However, information on the trophic relationship among these two large communities is fragmentary. Laboratory experiments have been conducted using a wide variety of protocols on a few ground beetle and weed seed species. To better characterize trophic relationship among these communities, a standardized and simple protocol is required. We propose a protocol to quantitatively assess weed seed consumption by ground beetles. Importantly, we explore parameters that should be optimized and fixed since they are not targeted, such as fasting time, test duration and substrate type. We also investigate whether, and under which conditions, tests may be replicated with the same individuals. Tests were carried out on five ground beetle species and eight weed seed species, though in the majority of tests Viola arvensis was used. Using climatic chambers, parameters such as temperature, humidity and photoperiod were fixed at 25 °C, 70% and 17-h/7-h day/night, respectively. Fasting time prior testing and test duration were fixed to 3 days and 24 h, respectively, to avoid mortality of ground beetle species that do not rely on seeds as their main food. Also, a recovery period of 24 h between successive tests is required when multiple tests are conducted on the same individuals. Among the substrate tested, we recommend to use sand as it appeared the most convenient substrate to conduct a large amount of replicated experiments.

Sex-Specific Contributions to Reproduction in Whiskered Tern Chlidonias hybrida Colonies of Varying Breeding Density

Abstract: Addressing the question of the parental effort allocation when breeding remains central to life-history theory. This is particularly the case for monogamous species with obligate bi-parental care, where each parent should evaluate its contribution throughout the breeding season taking into account both the effort of its mate and environmental constraints. In colonial species, social environments may influence the activities of breeders. Here we compared patterns of mate effort in the Whiskered Tern Chlidonias hybrida, throughout breeding in two regions that differed greatly in colony nest density. This species builds large floating nesting platforms on aquatic plant beds. Accordingly, we explored whether nest building was sex-specific and influenced the activities of breeders throughout the season. In both regions, parental effort was indeed differentiated by sex; males invested strongly in nest-material delivery and mate provisioning during the nest-building stage, and females displayed increased investment during chick rearing. Contrary to expectations, courtship feeding and social interactions were less frequent in the region with high nest density. Our findings demonstrate that each parent clearly adjusted its reproductive effort throughout the season, whereas the contrast in social conditions between the two study regions weakly affected the activities of breeders.—Chambon, R., Latraube, F., Bretagnolle, V. & Paillisson, J.-M. (2019). Sex-specific contributions to reproduction in Whiskered Tern Chlidonias hybrida colonies of varying breeding density. Ardeola, 67: 113-125.

Designing Multifunctional and Resilient Agricultural Landscapes: Lessons from Long-Term Monitoring of Biodiversity and Land Use

Abstract: In this chapter, we illustrate how the current challenges of agriculture - i.e. maintaining food security while preserving biodiversity, landscapes and ecosystem functions - have been addressed in a long-term social-ecological research site, the Zone Atelier Plaine & Val de Sevre, operated since 1994. After a presentation of the study area and its research program, we present landscape changes over the past 25 years. Then, we review the most relevant studies conducted in this area that examined the effect of landscape on farmland biodiversity. We focus on biodiversity because it is a central tenet of sustainable agriculture, which delivers ecosystem services that benefit human well-being and ensure ecosystem stability and resilience. Finally, we show that approaches that sustain biodiversity can also support food production, the delivery of multiple ecosystem services and the economy of local stakeholders. One major result from studies in the LTSER ZA-PVS is that biodiversity decline is a severe threat to food security in itself: improving biodiversity can improve yields, gross margins, or both. Biodiversity in arable habitats is, therefore, required to maintain food security, especially through pollination, natural pest regulation and soil services. Long-term monitoring of biodiversity, ecosystem functioning and agricultural practices as well as land use revealed that the interplay between local and landscape factors can provide solutions to reach these goals of multifunctionality (biodiversity, food production and farmers’ profitability) in agricultural landscapes. The next step is to engage stakeholders, in collaboration with scientists, and increase awareness of their mutual interdependencies with nature to foster the transition to more agroecological farming.