Search

Nα-acylated β2,3-3-azapeptides, or α-hydrazidopeptides, of different lengths were synthesized starting from a conformationally restricted imidazolidinone-tethered monomer. The preferential conformations of the oligomers were investigated by NMR and CD spectroscopy, supported by computational analysis. The experimental data clearly confirmed the tendency of these α-hydrazidopeptides to fold into a zig-zag (Z8) 8-helix conformation, whose stability is length-dependent, stabilized by the C=O(i)···H–N(i + 2) and N(i)···H–N(i + 1) intramolecular H-bonding pattern, as well as by non-standard C=O···H-C hydrogen bonds.

The PPR Panel was asked to deliver a scientific opinion on the science behind the development of a risk assessment of plant protection products on bees (Apis mellifera, Bombus spp. and solitary bees). Specific protection goals options were suggested based on the ecosystem services approach. The different routes of exposure were analysed in detail for different categories of bees. The existing test guidelines were evaluated and suggestions for improvement and further research needs were listed. A simple prioritisation tool to assess cumulative effects of single pesticides using mortality data is suggested. Effects from repeated and simultanous exposure and synergism are discussed. Proposals for separate risk assessment schemes, one for honey bees and one for bumble bees and solitary bees, were developed.

Several biotic and abiotic factors affect the seasonal and daily activities of flower-visiting insects, which, ultimately, influence the composition and abundance of a pollinator community and the extent of their pollination service. The aim of this four-year study was to assess the effect of some abiotic and biotic factors on the abundance and activity pattern of flower-visiting insects throughout the blooming of a locally rare plant species, Dictamnus albus L. (Rutaceae). We found a large inter-annual variation in the abundance and activity of flower visitors, with up to a six-fold variation in the total number of individual insects observed. Moreover, a similar fluctuation among years was also highlighted by biodiversity indices and by the changes in the relative frequency of each flower-visiting taxon. Annual, seasonal and daily variations were explained by a certain level of “response diversity” between flower-visiting taxa in relation to different environmental conditions during D. albus blooming. The foraging activity was related to ambient temperature in the tribe of Halictini and to relative humidity in four flower-visiting taxa (positive relation in the tribe Anthophorini; negative relation in the taxa Megachilini, Halictini and Syrphidae). The climate conditions during the winter might have also affected the phenology and the abundance of flower-visiting taxa with a large number of insects observed in warmer years. Among the biotic factors, flower availability did not affect the abundance of insects observed in the patch. Moreover, we did not find any significant negative associations (e.g. possible competition) in the co-occurrence of different flower visiting taxa, instead we found six significant positive associations probably related to similar preferences towards specific environmental conditions. In conclusion, our results show that the flower visitor community of D. albus is quite variable among years, seasons and daily hours, but the relative high visitor diversity and the different patterns of activity related to different environmental responses might guarantee a stable pollination service of this plant species in years with extreme environmental conditions.

The aim of this study was to assess the dynamic activity of the mandible by means of a computerised kinesiograph in Class II patients treated with orthodontic therapy and to compare the results of this group with those of a sample of untreated Class II patients.Twenty young adolescents who had undergone orthodontic treatment for correction of Class II malocclusion and twenty age and sex-matched adolescents exhibiting Class II malocclusion, whose parents refused the orthodontic treatment, were enrolled. Maximum vertical opening (MVO), maximum anterior-posterior movement (MAPM), maximum right deviation (MRD), maximum left deviation (MLD), MVO/ MAPM ratio, maximum velocity in opening (MVIO), maximum velocity in closure (MVIC), verticality (ID-V), anterior-posteriority (ID-AP) and laterality (ID-L) were recorded during the kinesiographic evaluations. Differences in the kinesiographic data were analysed using the Wilcoxon sum rank test; data are expressed as means and standard deviations (SD). Differences between groups in age were analysed using unpaired t-test, while differences in gender distribution were assessed using the Fisher's exact test. The level of significance was set at p0.05.No differences were detected in the distribution of sex and age between the two groups. Significant differences between the two groups were observed for MVO, MAPM, that were higher in the control group, and MLD, which was higher in the case group; no other significant differences were detected for MRD, MVO/ MAPM, MVIO, MVIC, ID-V, ID-AP, ID-L.Orthodontic treatment of young patients with Class II malocclusion may reduce the maximum vertical opening as well as the maximum anterior-posterior movement and enhance the lateral displacement; however, further studies are needed to assess the relationship between impaired mandible kinetics of orthodontic treatment in patients with Class II malocclusion and craniomandibular disorders.

The purpose of this study was to investigate the prevalence of astigmatism among a paediatric population.A total of 322 consecutive patients of the department of Orthodontics and Gnathology, Dental Clinic, University of L'Aquila, were enlisted for the study and 176 were selected according to the exclusion criteria. Pre- treatment diagnostic data, which included radiographic cephalometric and dental cast evaluation, were recorded and presence of astigmatism was assessed through an ophthalmological examination. Differences in the prevalence of astigmatism by sex and malocclusion were analysed by using the chi-square (Pearson's chi-square test) and Fisher's exact tests.According to the sagittal malocclusion, patients were classified as Class I (N=122), Class II Division 1 (N=26), Class II Division 2 (N=9), or Class III (N=19); according to the transverse malocclusion patients were classified into cross-bite (N=39) and no cross-bite (N=137) groups; after ophthalmological examination astigmatism was detected in 32 patients (18.18%). Statistically significant correlations were found between astigmatism and cross-bite (p0.0001), while no associations were found with other malocclusions. No gender influence was found for astigmatism or malocclusion.Few study investigated a possible relationship between the ocular and stomatognathic system, and no data are available in the scientific literature. A higher prevalence of astigmatism was found in patients with cross-bite: as expected no other significant association was found. The relationship between astigmatism and cross-bite could be either related to a specific skeletal pattern, which could induce visual alterations, or to the effect of abnormal visual input on the postural system, which could induce stomatognathic alterations.The findings of the present study suggest a possible association between astigmatism and cross-bite, but future studies are needed to confirm and explain this observation.

The recent global decline in insect populations is of particular concern for pollinators. Wild and managed bees (Hymenoptera, Apoidea) are of primary environmental and economic importance because of their role in pollinating cultivated and wild plants, and synthetic pesticides are among the major factors contributing to their decline. Botanical biopesticides may be a viable alternative to synthetic pesticides in plant defence due to their high selectivity and short environmental persistence. In recent years, scientific progress has been made to improve the development and effectiveness of these products. However, knowledge regarding their adverse effects on the environment and non-target species is still scarce, especially when compared to that of synthetic products. Here, we summarize the studies concerning the toxicity of botanical biopesticides on the different groups of social and solitary bees. We highlight the lethal and sublethal effects of these products on bees, the lack of a uniform protocol to assess the risks of biopesticides on pollinators, and the scarcity of studies on specific groups of bees, such as the large and diverse group of solitary bees. Results show that botanical biopesticides cause lethal effects and a large number of sublethal effects on bees. However, the toxicity is limited when comparing the effects of these compounds with those of synthetic compounds.

The recent EU ban of the three most widely used neonicotinoids (imidacloprid, thiamethoxam and clothianidin) to all outdoors applications has stimulated the introduction of new insecticides into the market. Sulfoxaflor is a new systemic insecticide that, like neonicotinoids, acts as a modulator of nicotinic acetylcholine receptors. In agro-environments, bees can be exposed to this compound via contaminated pollen and nectar for long periods of time. Therefore, it is important to assess the potential effects of chronic exposure to sulfoxaflor, alone and in combination with fungicides, on pollinators. In this study, we tested the effects of chronic exposure to two field concentrations of sulfoxaflor (20 and 100 ppb) alone and in combination with four concentrations of the fungicide fluxapyroxad (7500, 15,000, 30,000 and 60,000 ppb) on syrup consumption and longevity in females of the solitary bee Osmia bicornis L. Exposure to 20 ppb of sulfoxaflor, alone and in combination with the fungicide, stimulated syrup consumption, but did not affect longevity. In contrast, syrup consumption decreased in bees exposed to 100 ppb, all of which died after 2–6 days of exposure. We found no evidence of synergism between the two compounds at any of the two sulfoxaflor concentrations tested. Comparison of our findings with the literature, confirms that O. bicornis is more sensitive to sulfoxaflor than honey bees. Our results highlight the need to include different bee species in risk assessment schemes., This study was supported by a grant from the University of Bologna to FS (Grant RFO2019_SGOLASTRA), the Spanish Ministry of Science, Innovation and Universities (Grant R+D RTI2018-098399-B-I00) and the postdoctoral fellowship from the French Association POLLINIS (www.pollinis.org) to CA.

Bees and other pollinators play vital roles in biodiversity and food security, and they are a source of income and inspiration. Yet, bees’ biodiversity and abundance are decreasing every day. Their decline, driven by pesticides (1–3), poses serious threats to the environment, ecosystems, and human health. The European pesticide authorization framework states that a pesticide can only be put on the market if it has no harmful effects on human health or animal health and no unacceptable effects on the environment (4). EU ministries met in June to decide what constitutes an “acceptable” effect of a pesticide on bees (5). Despite scientific evidence indicating that the current level of protection is barely adequate, they tentatively agreed to provide even less protection moving forward (5). We call on EU governments to apply the maximum level of protection of pollinators from pesticides (6).

Current pesticide risk assessment for bees relies on a single (social) species, the western honey bee, Apis mellifera L. (Hymenoptera: Apidae). However, most of the >20,000 bee species worldwide are solitary. Differences in life history traits between solitary bees (SB) and honey bees (HB) are likely to determine differences in routes and levels of pesticide exposure. The objectives of this review are to: 1) compare SB and HB life history traits relevant for risk assessment; 2) summarize current knowledge about levels of pesticide exposure for SB and HB; 3) identify knowledge gaps and research needs; 4) evaluate whether current HB risk assessment schemes cover routes and levels of exposure of SB; and 5) identify potential SB model species for risk assessment. Most SB exposure routes seem well covered by current HB risk assessment schemes. Exceptions to this are exposure routes related to nesting substrates and nesting materials used by SB. Exposure via soil is of particular concern because most SB species nest underground. Six SB species (Hymenoptera: Megachilidae - Osmia bicornis L., O. cornifrons Radoszkowski, O. cornuta Latreille, O. lignaria Say, Megachile rotundata F., and Halictidae - Nomia melanderi Cockerell) are commercially available and could be used in risk assessment. Of these, only N. melanderi nests underground, and the rest are cavity-nesters. However, the three Osmia species collect soil to build their nests. Life history traits of cavity-nesting species make them particularly suitable for semifield and, to a lesser extent, field tests. Future studies should address basic biology, rearing methods and levels of exposure of ground-nesting SB species.

In many countries, the Western honey bee is used as surrogate in pesticide risk assessments for bees. However, uncertainty remains in the estimation of pesticide risk to non-Apis bees because their potential routes of exposure to pesticides, life histories, and ecologies differ from honey bees. We applied the vulnerability concept in pesticide risk assessment to 10 bee species including the honey bee, two bumble bee species, and seven solitary bee species with different nesting strategies. The trait-based vulnerability considers the evaluation of a species both at the level of the organism (exposure and effect) and the population (recovery) that goes beyond the sensitivity of individuals to a toxicant assessed in standard laboratory toxicity studies by including effects on populations in the field. Based on expert judgement, each trait was classified by its relationship to the vulnerability to pesticide exposure, effects (intrinsic sensitivity), and population recovery. The results suggested that the non-Apis bees included in our approach are potentially more vulnerable to pesticides than the honey bee due to traits governing exposure and population recovery potential. Our analysis highlights many uncertainties related to the interaction between bee ecology and the potential exposures and population-level effects of pesticides, emphasizing the need for more research to identify suitable surrogate species for higher-tier bee risk assessments. This article is protected by copyright. All rights reserved.

The sulfoximine insecticide sulfoxaflor is regarded as a potential substitute for neonicotinoids that were recently banned in the EU due to their side effects on bees. Like neonicotinoids, sulfoxaflor acts as a competitive modulator of nicotinic acetylcholine receptors. In agricultural environments, bees are commonly exposed to combinations of pesticides, and neonicotinoids are known to interact synergistically with fungicides. The objective of our study is to assess the acute oral toxicity of sulfoxaflor alone and in combination with a single dose of fluxapyroxad, a succinate dehydrogenase inhibitor (SDHI) fungicide, in three bee species:Apis mellifera,Bombus terrestrisandOsmia bicornis. Because synergism may be dose-dependent, we tested a range of sulfoxaflor doses. Synergistic effects were assessed using three different approaches: Bliss criterion of drugs independence, ratio test comparing LD50s and model deviation ratio.Osmia bicorniswas the most sensitive species to sulfoxaflor and bothO. bicornisandA. melliferashowed significant synergism between the insecticide and the fungicide. For the most part, these synergistic effects were weak and only occurred at early assessment times and intermediate sulfoxaflor doses. The potential ecological relevance of these effects should be confirmed in field and/or cage studies. Overall, our laboratory results demonstrate that sulfoxaflor is somewhat less toxic than the recently banned neonicotinoids imidacloprid, thiamethoxam and clothianidin, but much more toxic than other neonicotinoids (acetamiprid, thiacloprid) still in use in the EU at the time this study was conducted.

CONTEXT There is growing evidence that agroecology can reconcile the environmental, economic, and social pillars of agricultural sustainability. However, teaching and learning agroecology is challenging, especially since most agricultural graduate programs in Europe are not adapted to teach the diversity of its related practices. OBJECTIVE To improve agroecology learning, we built the online simulation game SEGAE. This article illustrates the game's relevance for learning agroecology. METHODS The game is based on a modeling framework that gamifies the implementation of agroecological practices in an integrated crop-livestock farm and assesses their impacts on sustainability. To do so, SEGAE is based on an output-oriented approach that represents impacts of practices on various indicators. These impacts are included in a matrix, which is associated with a dynamic graphical interface accessible to players. Two examples of game sessions were developed to illustrate the game's potential. RESULTS AND CONCLUSIONS In the first example, players can gain knowledge about agroecological practices by implementing practices that improve soil quality and assessing their impacts on sustainability. Results of this example place the farm's improved overall sustainability into perspective with its reduced food production potential. In the second example, players can improve their skills in transition management and acquire a systems approach by converting the farm to organic farming within five years. Results of this example prompt discussion of the steps needed to obtain organic certification and the coherence between crop and animal production needed to foster sustainability. SIGNIFICANCE SEGAE was designed to strengthen European training in agroecology, and active contributions from users would help to improve this tool, extend it to new farming systems and forge connections within the community of teachers working on agroecology.

Agroecology represents a pertinent option to improve the sustainability of agriculture. To promote its application, agroecological concepts should be taught to students and professionals in the agricultural sector. However, most agricultural courses are not adapted to teach these concepts due to little interactivity or interdisciplinarity, and a lack of a systems approach to farm management. Serious games help to fill these gaps by simulating complex models in which players can learn by doing. We thus developed a serious computer game, called SEGAE (SErious Game for AgroEcology learning), which represents a mixed crop&ndash, livestock farm and assesses impacts of farming practices on indicators related to environmental, economic, and social sustainability. Its pedagogical interest was evaluated through two types of surveys given to university students who played the game during a one-week workshop: A knowledge survey on agroecology, and a feedback survey based on flow theory. Results showed that students increased their knowledge of agroecology significantly, particularly those who had had little knowledge of crop production. More than 86% of the students enjoyed the game, appreciating its interaction and feedback. Thus, SEGAE is an interesting tool to help students acquire knowledge of agroecology in a fun way by facilitating interdisciplinary and collaborative learning.

Neonicotinoid insecticides have been signaled as an important driver of widespread declines in bee diversity and abundance. Neonicotinoids were registered in the 1990s and by 2010 accounted for one third of the global insecticide market. Following a moratorium in 2013, their use on open-field crops was completely banned in the EU in 2018. Pesticide regulation should be based on solid and updated scientific evidence, whereby products showing unacceptable effects on the environment are not approved. Clearly, pesticide regulation failed to detect the ecological threats posed by neonicotinoids. We argue that at the time neonicotinoids were authorized, risk assessment (RA) protocols were inadequate to detect some of the risks associated with neonicotinoid properties, including high efficacy, long persistence, high systemicity, high mobility, and application versatility. We advocate for the adoption of a more holistic RA approach that should account for: a) temporal and spatial dimensions of pesticide exposure; b) co-exposure to multiple compounds; c) differences among bee species with different life histories in levels of exposure and sensitivity; and d) sublethal effects (mostly ignored in current RA procedures). We also argue that regulatory studies conducted to support pesticide registration should be publicly available, and that pesticide regulation should not be discontinued once a product has been authorized. We should use the knowledge acquired through the neonicotinoid experience as an opportunity to profoundly revise bee RA schemes. These efforts should be initiated promptly; the neonicotinoid story has also taught us that the regulatory system is reluctant to react.

Besides the wind, insects are the main pollinating agents and many of them are hymenopterans. However, among the 20,000 species of bees (Superfamily Apoidea), only a very restricted group has been domesticated for commercial crop pollination, including social and solitary species. The honey bee Apis mellifera L. has been the first domesticated pollinator species, anyway, many cultivated crops benefit largely from the activity of other pollinators, especially when honey bees cannot provide a sufficient pollination service. This occurrence is particularly frequent in crops blooming in early spring or in crops with flowers not enough attractive to honey bees, i.e. because of low nectar and pollen production or for particular flower shapes. In addition to these ecological aspects, which are the result of a long history of coevolution between insects and flowers, modern agriculture and the well-known difficulties that honey bees are suffering of, create new concern that a general decline in the native pollinator populations will have unavoidable consequences on crop production due to insufficient pollination service. The most striking contradiction of the “industrial” extensive monocultures is that on one side they put in forth the need of enormous number of pollinators to satisfy the vast number of flowers contemporarily ready to be pollinated; on the other side, they cancel from the agroecosystem uncultivated meadows, edges and forests, which serve as refuge and conservation areas. The immediate repercussion on pollinating insects is the lack of continuity in blooms: on large areas, flowers are extremely abundant during the short blooming period of the main crops and nearly almost absent in the remaining part of their reproductive season (what is called “green desert”). In addition, very often a dramatic reduction of adequate nesting sites and materials may strongly limit the reproductive success, while, up today, the knowledge about the acute and chronic effects of pesticides on native bees is still insufficient.

Solitary bees are frequently exposed to pesticides, which are considered as one of the main stress factors that may lead to population declines. A strong immune defence is vital for the fitness of bees. However, the immune system can be weakened by environmental factors that may render bees more vulnerable to parasites and pathogens. Here we demonstrate for the first time that field-realistic concentrations of the commonly used neonicotinoid insecticide thiacloprid can severely affect the immunocompetence of Osmia bicornis. In detail, males exposed to thiacloprid solutions of 200 and 555 µg/kg showed a reduction in hemocyte density. Moreover, functional aspects of the immune defence - the antimicrobial activity of the hemolymph - were impaired in males. In females, however, only a concentration of 555 µg/kg elicited similar immunosuppressive effects. Although males are smaller than females, they consumed more food solution. This leads to a 2.77 times higher exposure in males, probably explaining the different concentration thresholds observed between the sexes. In contrast to honeybees, dietary exposure to thiacloprid did not affect melanisation or wound healing in O. bicornis. Our results demonstrate that neonicotinoid insecticides can negatively affect the immunocompetence of O. bicornis, possibly leading to an impaired disease resistance capacity.

International audience; This article presents data designed by European researchers who performed a literature review and interpreted the results to determine impact factors of many agroecological practices on a wide variety of sustainability indicators. The impact factors are represented in a matrix that connects practices to indicators. The indicators are related to environmental, economic and social sustainability of a typical European integrated crop-livestock farm. The data are included in the serious game SEGAE to learn agroecology, as described in “SEGAE: a serious game to learn agroecology” [1]. The data can be modified to adapt the game to other agricultural systems. Finally, the data can be re-used in research projects as a basis to assess impacts of agroecological practices.

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. Although bees consumed larger amounts of syrup than pollen, pesticide intake via syrup and pollen were similar. 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.

Simple Summary Methods to rear Osmia bees to pollinate fruit trees have been developed in various parts of the world. These bees are excellent pollinators but evidence that their populations can be sustained in orchards and their use results in increased fruit production is scarce. We released an Osmia cornuta population at one end of an almond orchard. Then, we surveyed the pollinators visiting the almond flowers and measured fruit set in trees located at increasing distances from the nesting stations. We found that fruit production was higher in the trees that received more Osmia visits. Importantly, this result was obtained against a strong background of honeybees, which were 10 times more abundant than Osmia. The Osmia population obtained at the end of the flowering period was 1.28 larger than the population initially released. Our study demonstrates that Osmia populations can be sustained in orchard environments and that even a small population of a highly effective pollinator may have a significant impact on fruit set. Our results are encouraging for the use of Osmia populations and for the implementation of measures to promote wild pollinators in agricultural environments. Abstract Osmia spp. are excellent orchard pollinators but evidence that their populations can be sustained in orchard environments and their use results in increased fruit production is scarce. We released an Osmia cornuta population in an almond orchard and measured its population dynamics, as well as visitation rates and fruit set at increasing distances from the nesting stations. Honeybees were 10 times more abundant than O. cornuta. However, the best models relating fruit set and bee visitation included only O. cornuta visitation, which explained 41% and 40% of the initial and final fruit set. Distance from the nesting stations explained 27.7% and 22.1% of the variability in initial and final fruit set. Of the 198 females released, 99 (54.4%) established and produced an average of 9.15 cells. Female population growth was 1.28. By comparing our results with those of previous O. cornuta studies we identify two important populational bottlenecks (female establishment and male-biased progeny sex ratios). Our study demonstrates that even a small population of a highly effective pollinator may have a significant impact on fruit set. Our results are encouraging for the use of Osmia managed populations and for the implementation of measures to promote wild pollinators in agricultural environments.

Most insects from temperate areas enter diapause ahead of winter. Species diapausing in a feeding stage and accumulating metabolic reserves during permissive pre-wintering conditions are expected to enter diapause shortly before the onset of winter. In contrast, species diapausing in a non-feeding stage are expected to lower their metabolism as soon as possible to avoid excessive consumption of metabolic reserves. The solitary bee Osmia lignaria winters as a non-feeding adult within its cocoon, but previous studies show important weight losses and increased winter mortality in populations pre-wintered for extended periods. We measured respiration rates to assess diapause initiation and maintenance during pre-wintering, and tested whether timing of adult eclosion affected fitness by measuring fat body depletion, winter mortality and post-winter longevity. We worked with different cohorts of a population reared under natural conditions, and manipulated pre-wintering duration in a population reared under artificial conditions. In agreement with our expectation, O. lignaria lower their metabolic rates within a few days of adult eclosion, but nonetheless suffer strong weight loss during pre-wintering. Early developing individuals suffer greater weight loss and fat body depletion, and have short post-winter longevity. Although, we found no differences in winter mortality among treatments, our results indicate that increased mortality may occur in years with late winter arrivals. We discuss fundamental ecophysiological differences between adult and prepupal diapause within the Megachilidae, and hypothesize that species wintering as adults will be more negatively affected by a situation of extended summers under a scenario of global warming.

The interplay between insect and plant traits outlines the patterns of pollen transfer and the subsequent plant reproductive fitness. We studied the factors that affect the pollination efficiency of a pollinator community of Dictamnus albus L. by evaluating insect behaviour and morphological characteristics in relation to flowering phenology. In order to extrapolate the pollinator importance of single taxa and of the whole pollinator guild, we calculated an index distinguishing between potential (PPI) and realized (RPI) pollinator importance. Although the pollinator species spectrum appeared rather constant, we found high intra- and inter-annual variability of pollinator frequency and importance within the insect community. Flower visitation rate strictly depended on insect abundance and on the overlap between their flying period and flower blooming. All the pollinators visited flowers from the bottom to the top of the racemes, excluding intra-plant geitonogamous pollination, and most of them showed high pollen fidelity. Only medium large-sized bees could contact the upward bending stiles while feeding on nectar, highlighting a specialisation of the plant towards bigger pollinators. Moreover, we found evidence of functional specialisation, since all pollinators were restricted to a single taxonomic group (order: Hymenoptera; superfamily: Apoidea). Both the PPI and RPI indices indicate Habropoda tarsata as the most important pollinator of D. albus. Following hand cross-pollination experiments we revealed the presence of pollination limitation in 1 of the 3 years of field study. We discuss this result in relation to flowering abundance and to possible mismatches of phenological periods between plants and insects.

he impact of climate change on insect populations depends on specific life cycle traits and physiological adaptations. The solitary bee Osmia lignaria winters as a pre-emergent adult, and requires a period of cold temperature for winter diapause completion. It is a univoltine species, and diapause induction does not depend on photoperiod. To understand the potential effects of longer summers on O. lignaria populations, we exposed individuals to three treatments simulating early, mid and late winter arrivals, and measured respiration rates, metabolic expenditure, weight loss, fat body depletion, lipid levels and winter mortality. The early-winter treatment disrupted diapause development, but had no apparent negative effects on fitness. In contrast, late-winter bees had a greater energetic expenditure (1.5-fold), weight (1.4-fold) and lipid (2-fold) loss, greater fat body depletion, and a 19% increase in mortality compared to mid-winter bees. We also monitored adult eclosion and arrival of winter temperatures under natural conditions in four years. We found a positive correlation between mean degree-day accumulation during pre-wintering (a measure of asynchrony between adult eclosion and winter arrival) and yearly winter mortality. Individually, bees experiencing greater degree-day accumulations exhibited reduced post-winter longevity. Timing of adult eclosion in O. lignaria is dependent on the duration of the prepupal period, which occurs in mid-summer, is also diapause-mediated, and is longer in populations from southerly latitudes. In a global warming scenario, we expect long summer diapause phenotypes to replace short summer diapause phenotypes, effectively maintaining short pre-wintering periods in spite of delayed winter arrivals.