The black nectar produced by A combination of analytical biochemistry, transcriptomics, proteomics, and enzyme assays was used to identify the pigment that gives High concentrations of ellagic acid and iron give the nectar its dark black color, which can be recapitulated through synthetic solutions containing only ellagic acid and iron(
- Award ID(s):
- 2025297
- NSF-PAR ID:
- 10342029
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 119
- Issue:
- 5
- ISSN:
- 0027-8424
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Post‐secretory synthesis of a natural analog of iron‐gall ink in the black nectar of Melianthus spp.
Summary Melianthus flowers is thought to serve as a visual attractant to bird pollinators, but the chemical identity and synthesis of the black pigment are unknown.Melianthus nectar its black color and how it is synthesized. Visual modeling of pollinators was also used to infer a potential function of the black coloration.iii ). The nectar also contains a peroxidase that oxidizes gallic acid to form ellagic acid.In vitro reactions containing the nectar peroxidase, gallic acid, hydrogen peroxide, and iron(iii ) fully recreate the black color of the nectar. Visual modeling indicates that the black color is highly conspicuous to avian pollinators within the context of the flower.Melianthus nectar contains a natural analog of iron‐gall ink, which humans have used since at least medieval times. This pigment is derived from an ellagic acid‐Fe complex synthesized in the nectar and is likely involved in the attraction of passerine pollinators endemic to southern Africa. -
Abstract Previous studies have considered floral humidity to be an inadvertent consequence of nectar evaporation, which could be exploited as a cue by nectar-seeking pollinators. By contrast, our interdisciplinary study of a night-blooming flower, Datura wrightii , and its hawkmoth pollinator, Manduca sexta , reveals that floral relative humidity acts as a mutually beneficial signal in this system. The distinction between cue- and signal-based functions is illustrated by three experimental findings. First, floral humidity gradients in Datura are nearly ten-fold greater than those reported for other species, and result from active (stomatal conductance) rather than passive (nectar evaporation) processes. These humidity gradients are sustained in the face of wind and are reconstituted within seconds of moth visitation, implying substantial physiological costs to these desert plants. Second, the water balance costs in Datura are compensated through increased visitation by Manduca moths, with concomitant increases in pollen export. We show that moths are innately attracted to humid flowers, even when floral humidity and nectar rewards are experimentally decoupled. Moreover, moths can track minute changes in humidity via antennal hygrosensory sensilla but fail to do so when these sensilla are experimentally occluded. Third, their preference for humid flowers benefits hawkmoths by reducing the energetic costs of flower handling during nectar foraging. Taken together, these findings suggest that floral humidity may function as a signal mediating the final stages of floral choice by hawkmoths, complementing the attractive functions of visual and olfactory signals beyond the floral threshold in this nocturnal plant-pollinator system.more » « less
-
Climate change is likely to alter both flowering phenology and water availability for plants. Either of these changes alone can affect pollinator visitation and plant reproductive success. The relative impacts of phenology and water, and whether they interact in their impacts on plant reproductive success remain, however, largely unexplored. We manipulated flowering phenology and soil moisture in a factorial experiment with the subalpine perennial Mertensia ciliata (Boraginaceae). We examined responses of floral traits, floral abundance, pollinator visitation, and composition of visits by bumblebees vs. other pollinators. To determine the net effects on plant reproductive success, we also measured seed production and seed mass. Reduced water led to shorter, narrower flowers that produced less nectar. Late flowering plants produced fewer and shorter flowers. Both flowering phenology and water availability influenced pollination and reproductive success. Differences in flowering phenology had greater effects on pollinator visitation than did changes in water availability, but the reverse was true for seed production and mass, which were enhanced by greater water availability. The probability of receiving a flower visit declined over the season, coinciding with a decline in floral abundance in the arrays. Among plants receiving visits, both the visitation rate and percent of non-bumblebee visitors declined after the first week and remained low until the final week. We detected interactions of phenology and water on pollinator visitor composition, in which plants subject to drought were the only group to experience a late-season resurgence in visits by solitary bees and flies. Despite that interaction, net reproductive success measured as seed production responded additively to the two manipulations of water and phenology. Commonly observed declines in flower size and reward due to drought or shifts in phenology may not necessarily result in reduced plant reproductive success, which in M. ciliata responded more directly to water availability. The results highlight the need to go beyond studying single responses to climate changes, such as either phenology of a single species or how it experiences an abiotic factor, in order to understand how climate change may affect plant reproductive success.more » « less
-
Premise Closely related plant species with overlapping ranges often experience competition for pollination services. Such competition can select for divergence in floral traits that attract pollinators or determine pollen placement. While most species in
Centropogon (Campanulaceae: Lobelioideae) have flowers that suggest adaptation to bat or hummingbird pollination, actual pollinators are rarely documented, and a few species have a mix of traits from both pollination syndromes. We studied the pollination biology of a “mixed‐syndrome” species and its co‐occurring congeners to examine the relationship between floral traits and visitation patterns forCentropogon .Methods Fieldwork at two sites in Bolivian cloud forests involved filming floral visitors, quantifying pollen transfer, and measuring floral traits. Stamen exsertion, which determines pollen placement, was measured from herbarium specimens across the geographic range of these species to test for character displacement.
Results Results show a generalization gradient, from primarily bat pollination in white‐flowered
Centropogon incanus , to bat pollination with secondary hummingbird pollination in the cream‐floweredC. brittonianus , to equal reliance on both pollinators in the red‐flowered, mixed‐syndromeC. mandonis . Pollen transfer between these species is further reduced by differences in stamen exsertion that are accentuated in zones of sympatry, a pattern consistent with character displacement.Conclusions Our results demonstrate that key differences in floral color and shape mediate a gradient of specialization in Bolivian
Centropogon . Interspecific pollen transfer is further reduced by potential character displacement of a key trait. Broadly, our results have implications for understanding the hyper‐diversity of Andean cloud forests, in which multiple species of the same genus frequently co‐occur. -
Abstract Floral nectar contains microbes that can influence nectar chemistry and pollinator visitation, and these microbial communities can be affected by pollinators in turn. Some flowers are also visited by nectar robbers, which feed on nectar through holes cut in floral tissue. If nectar robbers alter nectar microbial communities, they might have unexpected impacts on pollinator visitation. We investigated whether robbing could affect nectar microbial communities directly, by introducing microbes, or indirectly, by triggering a plant response to floral damage. We applied four treatments to flowers of
Tecoma × “Orange Jubilee” (Bignoniaceae) in an arboretum setting: flowers were (1) covered to exclude all visitors; (2) available to both pollinators and nectar robbers and robbed naturally by carpenter bees; (3) available to pollinators only but cut at the base to simulate nectar robbing damage; or (4) available to pollinators only. We found that nectar in flowers accessible to any visitors was more likely to contain culturable microbes than flowers from which visitors were excluded. Microbial community composition and beta diversity were similar across treatments. Among flowers containing culturable microbes, flowers available to pollinators and nectar robbers had higher microbial abundance than flowers with simulated robbing, but there were no differences between flowers available to pollinators and robbers and unwounded flowers from which robbers were excluded. Overall, our results suggest that floral damage can affect some features of nectar microbial communities, but specific effects of nectar robbing are limited compared with the influence of visitation in general.