As global surface temperatures rise, global precipitation rates are predicted to increase. These localised increases in rainfall patterns may significantly affect plant-pollinator interactions in multiple ways. Detrimental effects to plant-pollinator interactions could have significant ecological and economic consequences, and so it is important to understand the effects that rain has on these mutualisms. Increased rainfall has the potential for population-level effects but there also wide scope for individual-level effects, which have received surprisingly little attention. Changes in rainfall patterns could alter the timings of phenological phases while also increasing the likelihood of pollen degradation and nectar dilution, each having detrimental effects to the fitness of the plant, the pollinator or both parties. Pollinators could also be affected through mechanical and energetic constraints, along with disruption of foraging patterns and disruption to sensory signals. In this review, we demonstrate that there are clear gaps in our knowledge of these events, the exploration of which should open new areas of debate surrounding the effects of climate change on biological systems.

Flowers act as multisensory billboards to pollinators by using a range of sensory modalities such as visual patterns and scents. Different floral organs release differing compositions and quantities of the volatiles contributing to floral scent, suggesting that scent may be patterned within flowers. Early experiments suggested that pollinators can distinguish between the scents of differing floral regions, but little is known about how these potential scent patterns might influence pollinators. We show that bumblebees can learn different spatial patterns of the same scent, and that they are better at learning to distinguish between flowers when the scent pattern corresponds to a matching visual pattern. Surprisingly, once bees have learnt the spatial arrangement of a scent pattern, they subsequently prefer to visit novel unscented flowers that have an identical arrangement of visual marks, suggesting that multimodal floral signals may exploit the mechanisms by which learnt information is stored by the bee.

Floral displays are often composed of areas of contrasting stimuli which flower visitors use as guides, increasing both foraging efficiency and the likelihood of pollen transfer. Many aspects of how these displays benefit foraging efficiency are still unexplored, particularly those surrounding multimodal signals and the spatial arrangement of the display components. We compare the nectar discovery times of forager bumblebees (Bombus terrestris) when presented with artificial flowers with unimodal or compound displays of visual and/or olfactory stimuli, positioned in either radiating or non-radiating arrangements. We found that the addition of individual display components from either modality reduces nectar discovery time but there was no time benefit to bimodal displays over unimodal displays or any benefit to radiating stimuli arrangements over non-radiating arrangements. However, preference tests revealed a time advantage to radiating unimodal visual patterns over non-radiating unimodal visual patterns when both types were displayed simultaneously. These results suggest that the benefits of multimodal stimuli arrangements to pollinators are unrelated to benefits in nectar discovery time. Our results also suggest that spatial patterns of scent can be used as nectar guides and can reduce nectar discovery times without the aid of visual stimuli.

The majority of floral displays simultaneously broadcast signals from multiple sensory modalities, but these multimodal displays come at both a metabolic cost and an increased conspicuousness to floral antagonists. Why then do plants invest in these costly multimodal displays? The efficacy backup hypothesis suggests that individual signal components act as a backup for others in the presence of environmental variability. Here, we test the efficacy backup hypothesis by investigating the ability of bumblebees to differentiate between sets of artificial flowers in the presence of either chemical interference or high wind speeds, both of which have the potential to impede the transmission of olfactory signals. We found that both chemical interference and high wind speeds negatively affected forager learning times, but these effects were mitigated in the presence of a visual signal component. Our results suggest that visual signals can act as a backup for olfactory signals in the presence of chemical interference and high wind speeds, and support the efficacy backup hypothesis as an explanation for the evolution of multimodal floral displays.

Bumblebees Bombus terrestris are good at learning to distinguish between patterned flowers. They can differentiate between flowers that differ only in their patterning of scent, surface texture, temperature, or electrostatic charge, in addition to visual patterns. As recently shown, bumblebees trained to discriminate between nonvisual scent patterns can transfer this learning to visually patterned flowers that show similar spatial patterning to the learnt scent patterns. Bumblebees can, therefore, transfer learnt patterns between different sensory modalities, without needing to relearn them. We used differential conditioning techniques to explore whether cross-modal transfer of learnt patterns also occurred between visual and temperature patterns. Bumblebees that successfully learnt to distinguish rewarding and unrewarding temperature patterns did not show any preferences for the corresponding unlearnt visual pattern. Similarly, bumblebees that learnt visual patterns did not transfer these to temperature patterns, suggesting that they are unable to transfer learning of temperature and visual patterns. We discuss how cross-modality pattern learning may be limited to modalities that have potentially strong neurological links, such as the previously demonstrated transfer between scent and visual patterns. Electronic supplementary material The online version of this article (10.1007/s00359-019-01320-w) contains supplementary material, which is available to authorized users.

A protease was purified from Porphyromonas gingivalis 1101, a clinical isolate, by sequential sodium dodecyl sulfate-polyacrylamide gel electrophoresis, substrate diffusion gel electrophoresis, and electroelution. The enzyme cleaved radiolabeled human basement membrane type IV collagen and the synthetic collagen peptide substrate for eukaryotic collagenases. It was inactivated by the thiol protease inhibitor N-ethylmaleimide but not by EDTA or EGTA [ethylene glycol-bis(13-aminoethyl ether)-N,N,N',N'-tetraacetic acid] and activated by reducing agents such as 13-mercaptoethanol. The enzyme exists as an active precursor protein of molecular mass 94 kDa and undergoes proteolytic cleavage to 75-, 56-, and 19-kDa forms. Biotin-labeled collagen bound specifically to the 94-kDa form of the protein and to its cleavage products in ligand blots, suggesting a role for this enzyme not only in collagen degradation but also in adhesion to collagenous substrata.Several studies implicate black-pigmented Porphyromonas (Bacteroides)gingivalis as an important etiological agent associated with the pathogenesis of periodontal disease. In the course of many bacterial infections, proteases are putative virulence factors. Examples include zinc metalloproteases from the insect pathogens Serratia spp. (18) and the fish pathogen Vibrio anguillarum (13) and a protease from Legionella pneumophila (1). Such proteases are essential either for the initial invasive stages of the infection or for protection against the host immune response. In human bacterial infections, inactivation of the host immune response by proteases has been demonstrated with the elastase from Pseudomonas aeruginosa (17) and the immunoglobulin protease from Neisseria gonorrhoeae (14).The proteolytic nature of P. gingivalis strains has been well documented in the literature, where they have been shown capable of hydrolyzing gelatin (25), complement (20), and immunoglobulins A and G (7). Several proteases, including an intracellular, trypsinlike protease (23) and a glycylprolyl protease (5), have been isolated and characterized. Since collagen is the major constituent of the gingival connective tissues, perhaps the most important bacterial enzyme associated with the tissue destruction seen in periodontal disease is the collagenase. Although many workers have identified collagenase activity in various P. gingivalis strains, the biochemical nature of the enzyme has not been established. In this work, we report the purification and characterization of the P. gingivalis collagenase.MATERUILS AND METHODS Culture conditions. P. gingivalis was grown on blood agar plates in a gas mix containing 80% N2, 15% C02, and 5% H2 according to Greiner et al. (4).Collagen labeling. Collagen was radiolabeled for the microplate assay (see below) with lodogen (Pierce Chemical Co.) dissolved in chloroform and coated onto Eppendorf tubes (50 mg per tube) (8). The coated tubes were washed briefly in phosphate-buffered saline (PBS) prior to labeling experiments. Subsequently, 100 p,g of collagen in P...

The evolution of floral guides: using a genetic algorithm to investigate the evolution of floral cue arrangements. Biological Journal of the Linnean Society, 123(4), 739-753. [bly011].

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