Angiosperm flowers have evolved a dazzling palette of colours and a rich bouquet of scents, principally serving to attract pollinators. Despite recent progress in the ecology of pollination, the sensory floral traits that are important for communication with pollinators (for example, colour and scent) have not been assessed in an unbiased, integrative sense within a community context. Nonetheless, floral sensory stimuli are known key factors that mediate flower visitation, thus affecting community dynamics. Here we show that flowers of the phrygana, a natural Mediterranean scrubland, display integrated patterns of scent composition and colour (as perceived by pollinators). Surprisingly, the data reveal predictive relationships between patterns of volatile composition and flower reflectance spectra. The presence of nectar is related to visual cues and the qualitative composition of floral aromas. Our results reveal a coordinated phenotypic integration consistent with the sensory abilities and perceptual biases of bees, suggesting potential facilitative effects for pollination and highlighting the fundamental importance of bees in Mediterranean-type ecosystems. We offer our unbiased approach as a starting point for more extensive, global investigations of the diversity of floral sensory phenotypes and its role in the community ecology of plant-pollinator interactions.

Despite progress in understanding pollination network structure, the functional roles of floral sensory stimuli (visual, olfactory) have never been addressed comprehensively in a community context, even though such traits are known to mediate plant–pollinator interactions. Here, we use a comprehensive dataset of floral traits and a novel dynamic data-pooling methodology to explore the impacts of floral sensory diversity on the structure of a pollination network in a Mediterranean scrubland. Our approach tracks transitions in the network behaviour of each plant species throughout its flowering period and, despite dynamism in visitor composition, reveals significant links to floral scent, and/or colour as perceived by pollinators. Having accounted for floral phenology, abundance and phylogeny, the persistent association between floral sensory traits and visitor guilds supports a deeper role for sensory bias and diffuse coevolution in structuring plant–pollinator networks. This knowledge of floral sensory diversity, by identifying the most influential phenotypes, could help prioritize efforts for plant–pollinator community restoration.

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Chemosensory communication between flowers and pollinators is a fundamentalcomponent of terrestrial biodiversity, given the importance of olfaction to foraging animals. In this respect, exploring chemically mediated interspecific interactions in natural assemblies may provide novel insights into the ecofunctional significance of volatile organic compounds (VOCs) for plant-insect co-evolution.However, multispecies datasets of associations between plant semiochemicals and arthropods are still very rare and tend to lack community context. Here, we present the first insect-floral VOC meta-network using plant-pollinator visitation data and the plants' floral scent blends, collected in a Mediterranean scrubland.2. We assembled the insect-VOC meta-network by substituting each plant species in the plant-pollinator network with the blend of VOCs it emits. Furthermore, we identified the modules of the network that is the most densely connected insect-VOC groups. After describing the role of the species in the network, we focused on the bees of the community, and by building phylogenetically informed GLS models, we found the species traits predicting the degree of chemical specialization.3. Modularity analysis of the meta-network revealed tight associations between several classes of VOCs and pollinator groups. Linkage patterns suggest positive associations between (a) Megachilidae bees and sesquiterpenes, (b) Apidae and Andrenidae bees and benzenoids/phenylpropanoids, and (c) wasps, C6 green-leaf volatiles and specific terpenoids. Benzenoids were found to be the least influential and most specialized chemical class in the community, whereas sesquiterpenes represented the most influential one. Furthermore, the degree of chemical generalization of the bees in the meta-network was significantly associated with their ecological generalization, body mass and phenology, whereas their contribution to the network's structure was related to their level of sociality. Synthesis.Our findings help to disclose the ecofunctional significance of the floral volatile landscape and contribute novel testable hypotheses on the behavioural trends and chemical niches of pollinators in a natural community. The insect-volatilome meta-network is thus shown to be advantageous for detecting and visualizing patterns of chemically mediated interspecific interactions. Given the ubiquity | 2575

Aim: We studied bumblebee diversity and bumblebee pollination networks along the altitudinal gradient of Mt. Olympus, a legendary mountain in Central Greece, also known for its exceptional flora.

is invasive outside its ancestral North America range. • We compared its sexual reproduction in Arizona, USA ("AZ") and Greece ("GR"). • Pollination in GR was by native bees that resemble ancestral AZ pollinators. • GR plants invest more in flowers and ovules but do not produce more seeds. • These results suggest promising avenues for further research.

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The architectural complexity of flower structures (hereafter referred to as floral complexity) may be linked to pollination by specialized pollinators that can increase the probability of successful seed set. As plant—pollinator systems become fragile, a loss of such specialized pollinators could presumably result in an increased likelihood of pollination failure. This is an issue likely to be particularly evident in plants that are currently rare. Using a novel index describing floral complexity we explored whether this aspect of the structure of flowers could be used to predict vulnerability of plant species to extinction. To do this we defined plant vulnerability using the Red Data Book of Rare and Threatened Plants of Greece, a Mediterranean biodiversity hotspot. We also tested whether other intrinsic (e.g. life form, asexual reproduction) or extrinsic (e.g. habitat, altitude, range-restrictedness) factors could affect plant vulnerability. We found that plants with high floral complexity scores were significantly more likely to be vulnerable to extinction. Among all the floral complexity components only floral symmetry was found to have a significant effect, with radial-flower plants appearing to be less vulnerable. Life form was also a predictor of vulnerability, with woody perennial plants having significantly lower risk of extinction. Among the extrinsic factors, both habitat and maximum range were significantly associated with plant vulnerability (coastal plants and narrow-ranged plants are more likely to face higher risk). Although extrinsic and in particular anthropogenic factors determine plant extinction risk, intrinsic traits can indicate a plant’s proneness to vulnerability. This raises the potential threat of declining global pollinator diversity interacting with floral complexity to increase the vulnerability of individual plant species. There is potential scope for using plant—pollinator specializations to identify plant species particularly at risk and so target conservation efforts towards them.