Pesticide use is one of the main causes of pollinator declines in agricultural ecosystems. Traditionally, most laboratory studies on bee ecotoxicology test acute exposure to single compounds. ...However, under field conditions, bees are often chronically exposed to a variety of chemicals, with potential synergistic effects. We studied the effects of field-realistic concentrations of three pesticides measured in pollen and nectar of commercial melon fields on the solitary bee Osmia bicornis L. We orally exposed females of this species throughout their life span to 8 treatments combining two neonicotinoid insecticides (acetamiprid, imidacloprid) and a triazole fungicide (myclobutanil) via pollen and sugar syrup. We measured pollen and syrup consumption, longevity, ovary maturation and thermogenesis. Pesticide intake was three orders of magnitude higher via syrup than pollen. At the tested concentrations, no synergistic effects emerged, and we found no effects on longevity and ovary maturation. However, all treatments containing imidacloprid resulted in suppressed syrup consumption and drastic decreases in thoracic temperature and bee activity. Our results have important implications for pesticide regulation. If we had measured only lethal effects we would have wrongly concluded that the pesticide combinations containing imidacloprid were safe to O. bicornis. The incorporation of tests specifically intended to detect sublethal effects in bee risk assessment schemes should be an urgent priority. In this way, the effects of pesticide exposure on the dynamics of bee populations in agroecosystems will be better assessed.
Cultivation of pollinator-dependent crops has expanded globally, increasing our reliance on insect pollination. This essential ecosystem service is provided by a wide range of managed and wild ...pollinators whose abundance and diversity are thought to be in decline, threatening sustainable food production. The Western honey bee (Apis mellifera) is amongst the best-monitored insects but the state of other managed pollinators is less well known. Here, we review the status and trends of all managed pollinators based on publicly accessible databases and the published literature. We found that, on a global scale, the number of managed A. mellifera colonies has increased by 85% since 1961, driven mainly by Asia. This contrasts with high reported colony overwinter mortality, especially in North America (average 26% since 2007) and Europe (average 16% since 2007). Increasing agricultural dependency on pollinators as well as threats associated with managing non-native pollinators have likely spurred interest in the management of alternative species for pollination, including bumble bees, stingless bees, solitary bees, and flies that have higher efficiency in pollinating specific crops. We identify 66 insect species that have been, or are considered to have the potential to be, managed for crop pollination, including seven bumble bee species and subspecies currently commercially produced mainly for the pollination of greenhouse-grown tomatoes and two species that are trap-nested in New Zealand. Other managed pollinators currently in use include eight solitary bee species (mainly for pollination services in orchards or alfalfa fields) and three fly species (mainly used in enclosures and for seed production). Additional species in each taxonomic category are under consideration for pollinator management. Examples include 15 stingless bee species that are able to buzz-pollinate, will fly in enclosures, and some of which have a history of management for honey production; their use for pollination is not yet established. To ensure sustainable, integrated pollination management in agricultural landscapes, the risks, as well as the benefits of novel managed pollinator species must be considered. We, therefore, urge the prioritization of biodiversity-friendly measures maintaining native pollinator species diversity to provide ecosystem resilience to future environmental changes.
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•Diversity of managed pollinators has increased over time, totalling 66 species.•Native species and their traits might drive the trend in diversification.•Globally, the number of managed honey bee colonies has risen by 85% since 1961.•High colony mortality of Apis mellifera is reported, especially in North America.•Managed pollinators may negatively affect native, non-managed pollinators.
Agricultural intensification is one of the main causes for the current biodiversity crisis. While reversing habitat loss on agricultural land is challenging, increasing the farmland configurational ...heterogeneity (higher field border density) and farmland compositional heterogeneity (higher crop diversity) has been proposed to counteract some habitat loss. Here, we tested whether increased farmland configurational and compositional heterogeneity promote wild pollinators and plant reproduction in 229 landscapes located in four major western European agricultural regions. High-field border density consistently increased wild bee abundance and seed set of radish (Raphanus sativus), probably through enhanced connectivity. In particular, we demonstrate the importance of crop–crop borders for pollinator movement as an additional experiment showed higher transfer of a pollen analogue along crop–crop borders than across fields or along semi-natural crop borders. By contrast, high crop diversity reduced bee abundance, probably due to an increase of crop types with particularly intensive management. This highlights the importance of crop identity when higher crop diversity is promoted. Our results show that small-scale agricultural systems can boost pollinators and plant reproduction. Agri-environmental policies should therefore aim to halt and reverse the current trend of increasing field sizes and to reduce the amount of crop types with particularly intensive management.
Understanding how ecological networks are assembled is important because network structure reflects ecosystem functioning and stability. Quantitative network analysis incorporates measures of ...interaction strength as an estimate of the magnitude of the effect of interaction partners on one another. Most plant-pollinator network studies use frequency of interaction between individual pollinators and individual plants (encounter) as a surrogate of interaction strength. However, the number of flowers visited per encounter may strongly vary among pollinator and plant species, and therefore not all encounters are quantitatively equivalent. We sampled plant-pollinator interactions in a Mediterranean scrubland and tested whether using a measure of interaction strength based on the number of flowers visited resulted in changes in species (species strength, interaction species asymmetry, specialization) and network descriptors (nestedness, H2', interaction evenness, plant generality, pollinator generality) compared to the encounter-based measure. Several species (including some of the most abundant ones) showed important changes in species descriptors, notably in specialization. These changes were especially important in plant species with large floral displays, which became less specialized with the visit-based measure of interaction strength. At the network level we found significant changes in all properties analysed. With the encounter-based approach plant generality was much higher than pollinator generality (high specialization asymmetry between trophic levels). However, with the visit-based approach plant generality was greatly reduced so that plants and pollinators had similar levels of generalization. Interaction evenness also decreased strongly with the visit-based approach. We conclude that accounting for the number of flowers visited per encounter provides a more ecologically relevant measure of interaction strength. Our results have important implications for the stability of pollination networks and the evolution of plant-pollinator interactions. The use of a visit-based approach is especially important in studies relating interaction network structure and ecosystem function (pollination and/or exploitation of floral resources).
As predicted by Conditional Sex Allocation Theory, females of the solitary bee
Osmia cornuta exposed to scarce floral resources biased their progeny sex ratio towards males, the least costly sex, and ...produced smaller-than-average females. Surprisingly, nesting females also produced a number of ‘tiny’ offspring, which contrasted with regular-sized offspring within the same nest. Developmental and wintering mortality are strongly size dependent in
O. cornuta, and a high proportion of tiny offspring did not survive. This result is in disagreement with Optimal Allocation Theory, according to which resources should be allocated in portions that maximize fitness returns. I ask why did
O. cornuta females build tiny provisions and why did they lay female eggs (with lower survival probability than male eggs) on these provisions. I argue that egg maturation rates and selective pressure to avoid kleptoparasitism and provision desiccation in cells left unsealed for long periods may impose a limit to the time available for cell provisioning. Under low food availability, this limit will be reached before provision sizes resulting in maximum fitness returns are attained. I also argue that the decision to fertilize an egg (and thus produce a female) is made at the beginning of the cell-provisioning process, so that females cannot adjust offspring sex to provision size. At the same time, altering the female–male cell sequence within a nest would result in fratricide because of protandric emergence. I provide evidence supporting these ecological and physiological constraints on resource allocation decisions in
O. cornuta.
Objective
In children born small for gestational age (SGA), the relationship between growth hormone (GH) treatment and insulin resistance (IR) has only been investigated for a short period, ...necessitating a longer observation period. This study aimed to evaluate the long‐term (10 years) effect of GH to SGA‐children on IR and safety during treatment.
Design
This was a multicenter observational study.
Patients: SGA‐children who received GH treatment in Spain (stratified by Tanner‐stage and age at GH onset two groups: ≤6 years old or >6 years old).
Measurements: The analysed variables (yearly measures) included auxologic, metabolic (insulin‐like growth factor‐1 (IGF‐1), height velocity HV, weight and homeostatic model assessment‐IR HOMA‐IR) and safety data. Data were collected prospectively (since the study approval: 2007) and retrospectively (since the initiation of GH treatment: 2005–2007).
Results
A total of 389 SGA children (369 Tanner‐I) were recruited from 27 centres. The mean age (standard deviation) of the children at GH treatment onset was 7.2 (2.8) years old. IGF‐1 (standard deviation score SDS) and HOMA‐IR values tended to increase until the sixth year of GH‐treatment, with significant differences being observed only during the first year, while these remained stable in the later years (within normal ranges). Height (SDS) increased significantly (basal: −3.0; tenth year: −1.13), and the maximum HV (SDS) occurred during the first year (2.75 ± 2.39).
Conclusions
HOMA‐IR values increased significantly in SGA‐children during the first year of GH‐treatment, remained stable and were within normal ranges in all cases. Our 10‐year data suggests that long‐term GH treatment does not promote IR and is well‐tolerated, safe and effective.
Health related quality of life (HRQoL) is a relevant result when assessing the course of different pathologies and the efficacy of their treatments. HRQoL has been studied previously on adults born ...small for gestational age (SGA), both in the general population and in patients who had received recombinant human growth hormone (rhGH) treatment, with disparate results. Our study included 50 adults who had received rhGH treatment for the SGA indication in 4 Spanish hospitals. Data have been gathered retrospectively from their clinical records, current weight and height were measured, and patients have been asked to fill out SF-36 and QoLAGHDA quality of life forms, and the Graffar test to evaluate their socio-economical status. Patient's adult height was - 1.2 ± 0.9 SD, lower than their target height of 1 ± 0.8 SD, but gaining 1.7 ± 1 SD from the beginning of the treatment. SF-36 test results showed lower scoring on Mental Health domains than on those related to Physical Health. No correlation was found between HRQoL results and final height, rhGH treatment duration or puberty. Correlation was indeed found between QoLAGHDA and several domains of SF-36, but QoLAGHDA detected fewer patients with low HRQoL than SF-36. Thus, it is concluded that SGA patient's follow-up should include a HRQoL, neuro-cognitive and psychiatric assessment in their transition to adult age. Adult SGA patients without catch up growth have impaired HRQoL, especially in mental health domains.
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