Our understanding of how floral visitors integrate visual and olfactory cues when seeking food, and how background complexity affects flower detection is limited. Here, we aimed to understand the use of visual and olfactory information for bumblebees (Bombus terrestris terrestris L.) when seeking flowers in a visually complex background. To explore this issue, we first evaluated the effect of flower colour (red and blue), size (8, 16 and 32 mm), scent (presence or absence) and the amount of training on the foraging strategy of bumblebees (accuracy, search time and flight behaviour), considering the visual complexity of our background, to later explore whether experienced bumblebees, previously trained in the presence of scent, can recall and make use of odour information when foraging in the presence of novel visual stimuli carrying a familiar scent. Of all the variables analysed, flower colour had the strongest effect on the foraging strategy. Bumblebees searching for blue flowers were more accurate, flew faster, followed more direct paths between flowers and needed less time to find them, than bumblebees searching for red flowers. In turn, training and the presence of odour helped bees to find inconspicuous (red) flowers. When bees foraged on red flowers, search time increased with flower size; but search time was independent of flower size when bees foraged on blue flowers. Previous experience with floral scent enhances the capacity of detection of a novel colour carrying a familiar scent, probably by elemental association influencing attention.

Crops worldwide are simultaneously affected by weeds, which reduce yield, and by climate change, which can negatively or positively affect both crop and weed species. While the individual effects of environmental change and of weeds on crop yield have been assessed, the combined effects have not been broadly characterized. To explore the simultaneous impacts of weeds with changes in climate-related environmental conditions on future food production, we conducted a meta-analysis of 171 observations measuring the individual and combined effects of weeds and elevated CO2, drought or warming on 23 crop species. The combined effect of weeds and environmental change tended to be additive. On average, weeds reduced crop yield by 28%, a value that was not significantly different from the simultaneous effect of weeds and environmental change (27%), due to increased variability when acting together. The negative effect of weeds on crop yield was mitigated by elevated CO2 and warming, but added to the negative effect of drought. The impact of weeds with environmental change was also dependent on the photosynthetic pathway of the weed/crop pair and on crop identity. Native and non-native weeds had similarly negative effects on yield, with or without environmental change. Weed impact with environmental change was also independent of whether the crop was infested with a single or multiple weed species. Since weed impacts remain negative under environmental change, our results highlight the need to evaluate the efficacy of different weed management practices under climate change. Understanding that the effects of environmental change and weeds are, on average, additive brings us closer to developing useful forecasts of future crop performance.

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Seventy five percent of fruit production of the major global crops benefit from insect pollination. Hence, there has been increased interest in how global change drivers impact this critical ecosystem service. Because standardized data on crop pollination are rarely available, we are limited in our capacity to understand the variation in pollination benefits to crop yield, as well as to anticipate changes in this service, develop predictions, and inform management actions. Here, we present CropPol, a dynamic, open and global database on crop pollination. It contains measurements recorded from 189 crop studies, covering 3,216 field observations, 2,421 yield measurements (i.e. berry weight, number of fruits and kg per hectare, among others), and 46,262 insect records from 49 commercial crops distributed around the globe. CropPol comprises 32 of the 87 leading global crops and commodities that are pollinator dependent. Malus domestica is the most represented crop (25 studies), followed by Brassica napus (22 studies), Vaccinium corymbosum (13 studies), and Citrullus lanatus (12 studies). The most abundant pollinator guilds recorded are honey bees (33.12% counts), bumblebees (18.65%), flies other than Syrphidae and Bombyliidae (13.76%), other wild bees (13.51%), beetles (11.47%), Syrphidae (4.86%), and Bombyliidae (0.06%). Locations comprise 32 countries distributed among European (70 studies), Northern America (59), Latin America and the Caribbean (27), Asia (22), Oceania (10), and Africa (7). Sampling spans three decades and is concentrated on 2001-05 (21 studies), 2006-10 (38), 2011-15 (87), 2016-20 (40). This is the most comprehensive open global data set on measurements of crop flower visitors, crop pollinators and pollination to date and we encourage researchers to add more datasets to this database in the future. No copyright restrictions are associated with the use of this dataset. Please cite this data paper when the data are used in publications and cite individual studies when appropriate.