Nectar Concentration Research Articles

Diptera‐dominated generalist pollination systems in Eurya japonica and Eurya emarginata (Pentaphylacaceae)

AbstractWe investigated the flower visitors and floral traits of two dioecious shrub species Eurya japonica Thunb. (Pentaphylacaceae) and Eurya emarginata (Thunb.) Makino in temperate Kochi and subtropical Okinawa in Japan during the cool seasons. We demonstrated that the two Eurya species could be pollinated by a wide spectrum of flower visitors—mainly Diptera. The main pollinators were probably Chironomidae and Empididae for E. japonica in Kochi and Calliphoridae and Syrphidae for the remaining species–site combinations (i.e., E. emarginata in Kochi, E. japonica in Okinawa, and E. emarginata in Okinawa). We demonstrated that several dominant families of Dipteran visitors have the ability to pollinate the two Eurya species. Interestingly, floral traits (corolla diameter and nectar concentration) could not explain the difference in the assemblages. These results indicate that floral traits are not specifically adapted to their local pollinators. The fruit set rate was significantly lower for naturally pollinated flowers than for hand‐pollinated flowers, indicating pollen limitation in both Eurya species. However, there was no apparent difference in the number of seeds per fruit between naturally pollinated and hand‐pollinated flowers.

Organoleptic Evaluation of Aonla (Emblica officinalis G.) Nectar during Storage

A research experiment was conducted during the year 2019-20 and 2020-21 in the Fruit and Vegetable Processing Unit Laboratory, Department of Horticulture, College of Agriculture, Gwalior with seven different varieties of aonla viz., NA-4, NA-5, NA-6,NA-7, NA-10, Laxmi and Chakaiya. This study was carried out in a completely randomized design with three replications. It was studied about the preparation of various value added products such as aonla nectar. From the finding it was observed that, the increase in the percentage of acidity, moisture, phenols and fiber content of aonla nectar while total soluble solids and total sugar content was decreased. There was gradual increase in moisture content of aonla nectar prepared with different pulp combination of aonla fruits during storage period. However, total soluble solids, ascorbic acid content decreased with advancement of storage period. Observations were recorded up to storage period of six months at ambient conditions. Laxmi and Chakaiya varieties were found superior with respect to colour, appearance, taste and aroma as well as flavour. As per the organoleptic evaluation the overall acceptability of anola nectar was found significant with the storage intervals of 30, 60, 90 and 120 days.

Host-driven phenotypic and phenological differentiation in sympatric races of a parasitic plant

Host specificity is a key factor influencing the ecology and evolutionary diversification of parasitic organisms. Host specialisation and geographic isolation are known to lead to the genetic differentiation of allopatric races in parasitic plants. However, how divergence can co-occur in sympatry remains largely unknown. We investigated phenological and phenotypic differentiation and potential reproductive isolation among three sympatric genetic races of Cytinus hypocistis (Cytinaceae) - an extreme endophytic holoparasite with a high degree of host specialisation. We compared spatio-temporal variations in flowering phenology, flower production, floral longevity, floral rewards, and morphology, and conducted inter-race pollinations among three races parasitising Cistus ladanifer, C. salviifolius, and Halimium halimifolium (Cistaceae) in six co-occurring populations. We found that host-defined genetic races differed significantly across multiple phenotypic and phenological aspects – a phenomenon previously overlooked due to the plants’ cryptic morphology. The race parasitising H. halimifolium showed earlier blooming, higher floral display, longer flowers, and higher pollen production and nectar concentration; the race on C. salviifolius showed later flowering, significantly lower floral display and smaller flowers with lower floral rewards; the race on C. ladanifer had intermediate characteristics. Genetic races were interfertile yet may remain differentiated by restricted gene flow and host-driven selection pressures. Together, our data point to a rare case of sympatric divergent evolution hiding in plain sight: apparently morphologically similar co-occurring parasite races can be genetically, phenotypically, and phenologically distinct. This hitherto unreported example of host-driven sympatric diversification challenges how species concepts are applied to cryptic parasitic plant races.

Nocturnal moth pollination in an alpine orchid, Platanthera tipuloides

AbstractPollination success of alpine plants is often restricted by low and unpredictable pollinator activity because of harsh and unstable weather conditions, where nocturnal pollination is rare. The alpine orchid, Platanthera tipuloides (Orchidaceae), has inconspicuous greenish yellow flowers with a sweet scent and a long spur that contains nectar. These floral traits are expected to be related to nocturnal moth pollination. To elucidate the pollination mode and reproductive characteristics of this species, we measured floral traits (spur length, nectar content in the spur, floral scent), documented flower visitors using camera traps, and quantified self‐compatibility and the degree of pollen limitation through controlled pollinations at two study plots in the Taisetsu Mountains, northern Japan. It was revealed that P. tipuloides is self‐incompatible and pollen limitation was absent at one of the study plots. The flowers emitted more volatile substances during the night, including lilac aldehyde isomers, which are known to attract moths. A nocturnal moth, Entephria amplicosta, was observed foraging nectar from the flowers, while no diurnal visitors were observed. The proboscis of E. amplicosta was shorter than the spur length, but it was long enough to access the accumulated nectar in the spurs. These results suggest that nocturnal pollination by moths is possible and can be efficient even in an alpine ecosystem with harsh environmental conditions.

Influence of Pesticide Application Method, Timing, and Rate on Contamination of Nectar with Systemic and Nonsystemic Pesticides.

Exposure to pesticides is one potential factor contributing to the recent loss of pollinators and pollinator diversity. Few studies have specifically focused on the relationship between pesticide management during ornamental plant production and contamination of nectar. We evaluated contamination of nectar in Salvia 'Indigo Spires' (Salvia longispicata M. Martens & Galeotti × S. farinacea Benth.) associated with applications of the systemic insecticide thiamethoxam, and the nonsystemic fungicides boscalid and pyraclostrobin. Applications were made at the labeled rates for the commercially available products, and we compared the influence of application method (drench vs. spray), timing (relative to flowering), and rate (low vs. high) for each pesticide. Nectar was sampled using 50-µL microcapillary tubes and analyzed by liquid chromatography-tandem mass spectrometry. The results indicate that concentrations from the spray application resulted in the least contamination of nectar with the systemic thiamethoxam, with lower concentrations occurring when thiamethoxam was applied before blooming at the lowest rate. Concentrations of thiamethoxam and its metabolite clothianidin were detected in nectar in all treatments (regardless of the method, timing, or rate of application), and ranged from 3.6 ± 0.5 ng/mL (spray-applied before blooming, low rate) to 1720.0 ± 80.9 ng/mL (drench-applied after blooming, high rate). Residues of clothianidin in nectar ranged from below quantification limits (spray-applied before blooming, low rate) to 81.2 ± 4.6 ng/mL (drench-applied after blooming, high rate). Drench applications resulted in the highest levels of nectar contamination with thiamethoxam, and exceeded published median lethal concentrations (LC50s/median lethal doses for native bees and/or honeybees in all cases). Spray treatments resulted in nectar concentrations exceeding published LC50s for some bee species. In comparison, all nonsystemic treatments resulted in concentrations much lower than the published no-observable-effect doses and sublethal toxicity values, indicating low risks of toxicity. Environ Toxicol Chem 2024;001:1-12. © 2024 SETAC.

Economic foraging in a floral marketplace: asymmetrically dominated decoy effects in bumblebees.

While most models of decision-making assume that individuals assign options absolute values, animals often assess options comparatively, violating principles of economic rationality. Such 'irrational' preferences are especially common when two rewards vary along multiple dimensions of quality and a third, 'decoy' option is available. Bumblebees are models of decision-making, yet whether they are subject to decoy effects is unknown. We addressed this question using bumblebees (Bombus impatiens) choosing between flowers that varied in their nectar concentration and reward rate. We first gave bees a choice between two flower types, one higher in concentration and the other higher in reward rate. Bees were then given a choice between these flowers and either a 'concentration' or 'rate' decoy, designed to be asymmetrically dominated on each axis. The rate decoy increased bees' preference in the expected direction, while the concentration decoy did not. In a second experiment, we manipulated choices along two single reward dimensions to test whether this discrepancy was explained by differences in how concentration versus reward rate were evaluated. We found that low-concentration decoys increased bees' preference for the medium option as predicted, whereas low-rate decoys had no effect. Our results suggest that both low- and high-value flowers can influence pollinator preferences in ways previously unconsidered.

Consumption of pollen contaminated with field-realistic concentrations of fungicide causes sublethal effects in Bombus impatiens (Hymenoptera: Apidae) microcolonies.

Bumble bees are declining across the globe. The causes of this decline have been attributed to a variety of stressors, including pesticides. Fungicides are a type of pesticide that has been understudied in the context of bumble bee health. As a result, fungicides are often applied to flowering plants without consideration of pollinator exposure. Recent work demonstrates that fungicides have sublethal effects in bumble bees, but little is known about how much fungicide it takes to cause these sublethal effects. To address this gap in the literature, we fed microcolonies of the common eastern bumble bee (Bombus impatiens CressonHymenoptera: ApidaeHymenoptera: ApidaeHymenoptera: ApidaeHymenoptera: Apidae) pollen contaminated with a range of fungicide concentrations. We chose these concentrations based on the range of fungicide concentrations in pollen and nectar that were reported in the literature. Results revealed that later-stage pupae and newly emerged males are potentially sensitive to fungicide exposure, showing smaller size and reduced fat reserves at intermediate levels of contamination. Compared to the control, intermediated levels of fungicide-contaminated pollen led to increased pupal mortality and delayed male emergence. Contrary to expectations, higher fungicide levels did not exhibit a linear relationship with negative impacts, suggesting nuanced effects. Because body size and emergence timing are important aspects of bumble bee reproductive behavior, results have implications for mating success, potentially disrupting colony development.

Quantifying Nectar Secretion Capacity of Dombeya torrida (J. F. Gmel.) for Honey Production

The honey production potential of a honey plant is assessed based on the total floral nectar secretion capacity of the plant foraged by honeybees within a specific location. This study aimed to assess the honey production potential of Dombeya torrida plants by examining their nectar secretion dynamics. A group of flowers was enclosed with mesh bags a day before collecting nectar to measure the accumulated volume. Nectar volume, concentration, and ambient temperature were measured at hourly intervals. The data collected were analyzed using statistical methods including one-way ANOVA and linear regression. The average sugar content per flower per season was found to be 14.3 mg, with a range from 2.3 to 47 mg. Based on this, each D. torrida tree was estimated to secrete an average of 0.94 kg of sugar, with a range from 0.15 to 3.1 kg. Nectar volume and concentration varied throughout the day, with temperature significantly influencing nectar concentration. The study estimated that a single D. torrida tree could yield around 1.2 kg of honey per flowering season, with a range from 0.18 to 3.78 kg. Additionally, on a larger scale, D. torrida plants were projected to produce an average of 300 kilograms of honey per hectare, ranging from 45 kg to 945 kg. These findings suggest that D. torrida has considerable potential for honey production. Consequently, planting and conservation of this plant for sustainable honey production practices is recommended.

Reproductive biology as a tool to elucidate taxonomic delimitation: Howdifferent can two highly specialized subspecies of Parodia haselbergii (cactaceae)be?

Reproductive isolation is one of the mechanisms of speciation. The two currently accepted subspecies of Parodia haselbergii (P. haselbergii subsp. haselbergii and P. haselbergii subsp. graessneri) were studied regarding flower traits, phenology, breeding systems and pollination. In addition, a principal component analysis with 18 floral characters and germination tests under controlled conditions were performed for both taxa. Pollination was studied in the field, in two localities of Southern Brazil. Pollinators were recorded through photos and film. Breeding system experiments were performed by applying controlled pollinations to plants excluded from pollinators. Both taxa mostly differ in asynchronous flowering periods, floral traits (including floral part measurements and nectar concentration) and pollinators. The flowers of both subspecies are functionally protogynous and perform remarkably long lifespans (≥ 15 days), both traits being novelties for Cactaceae. Whereas the reddish flowers of P. haselbergii subsp. haselbergii (nectar concentration: ca. 18%) are pollinated by hummingbirds of Thalurania glaucopis, the greenish flowers of P. haselbergii subsp. graessneri (nectar concentration: ca. 29%) are pollinated by Augochlora bees (Halictidae). Both subspecies are self-compatible, yet pollinator-dependent. The principal component analysis evidenced that both subspecies are separated, regarding flower traits. The seeds of both subspecies performed differently in the germination tests, but the best results were recovered at 20°C and germination considerably decreased around 30°C. In conclusion, all these results support that both taxa are in reproductive isolation, and can be treated as different species.

Temporal Variation in Nectar Concentration and pH in Flowering Plants of Ecopark, Kolkata, West Bengal

Temporal Variation in Nectar Concentration and pH in Flowering Plants of Ecopark, Kolkata, West Bengal

Sodium-enriched nectar shapes plant-pollinator interactions in a subalpine meadow.

Many plants have evolved nutrient rewards to attract pollinators to flowers, but most research has focused on the sugar content of floral nectar resources. Concentrations of sodium in floral nectar (a micronutrient in low concentrations in nectar) can vary substantially both among and within co-occurring species. It is hypothesized that sodium concentrations in floral nectar might play an important and underappreciated role in plant-pollinator interactions, especially because many animals, including pollinators, are sodium limited in nature. Yet, the consequences of variation in sodium concentrations in floral nectar remain largely unexplored. Here, we investigate whether enriching floral nectar with sodium influences the composition, diversity, and frequency of plant-pollinator interactions. We experimentally enriched sodium concentrations in four plant species in a subalpine meadow in Colorado, USA. We found that flowers with sodium-enriched nectar received more visits from a greater diversity of pollinators throughout the season. Different pollinator species foraged more frequently on flowers enriched with sodium and showed evidence of other changes to foraging behavior, including greater dietary evenness. These findings are consistent with the "salty nectar hypothesis," providing evidence for the importance of sodium limitation in pollinators and suggesting that even small nectar constituents can shape plant-pollinator interactions.

Synergistic negative effects between a fungicide and high temperatures on homing behaviours in honeybees.

Interactions between environmental stressors may contribute to ongoing pollinator declines, but have not been extensively studied. Here, we examined the interaction between the agricultural fungicide Pristine (active ingredients: 25.2% boscalid, 12.8% pyraclostrobin) and high temperatures on critical honeybee behaviours. We have previously shown that consumption of field-realistic levels of this fungicide shortens worker lifespan in the field and impairs associative learning performance in a laboratory-based assay. We hypothesized that Pristine would also impair homing and foraging behaviours in the field, and that an interaction with hot weather would exacerbate this effect. Both field-relevant Pristine exposure and higher air temperatures reduced the probability of successful return on their own. Together, the two factors synergistically reduced the probability of return and increased the time required for bees to return to the hive. Pristine did not affect the masses of pollen or volumes of nectar or water brought back to the hive by foragers, and it did not affect the ratio of forager types in a colony. However, Pristine-fed bees brought more concentrated nectar back to the hive. As both agrochemical usage and heat waves increase, additive and synergistic negative effects may pose major threats to pollinators and sustainable agriculture.

Natural history of pollination of an Asian bignoniaceous tree: The long-tubed flower and the not-so-long bird bill

Bird pollination is well-established in New World Bignoniaceae, but studies of species with floral traits suggestive of bird pollination in the Old World are lacking. Here we studied the pollination ecology of Mayodendron igneum to test the prediction of pollination by specialist flower-visiting birds. Observations from multiple sites showed that both the Streaked Spiderhunter (Arachnothera magna) and pollen-collecting bees were floral visitors. However, almost no fruit was produced if birds were excluded, suggesting that bees do not play a role in pollination, and that pollination is performed almost exclusively by birds in this self-incompatible tree. Measurements of floral traits revealed a typical bird pollination syndrome, and the nectar concentration and volume were both within the proposed ranges based on other flowers pollinated by specialist birds. However, the rather low level of sucrose (less than 2 %) in nectar sugar contradicts the expectation for nectar of flowers pollinated by specialist nectar-feeding birds. Although the Streaked Spiderhunter is among the longest-billed flower-visiting birds in Asia, its bill is only 2/3 of the corolla tube in length, suggesting that the bird can extend the tongue to access nectar. This study is the first to experimentally confirm bird pollination in the Old World Bignoniaceae. It also indicates aspects that are possibly characteristic of spiderhunter pollination systems, i.e. high degrees of specialization, unusual nectar sugar composition, and floral tubes much longer than bird bills.

Floral traits and their connection with Pollinators and Climate.

Floral characteristics vary significantly among plant species, and multiple underlying factors govern this diversity. Although it is widely known that spatial variation in pollinator groups can exert selection on floral traits, the relative contribution of pollinators and climate to the variation of floral traits across large geographic areas remains a little-studied area. Besides furthering our conceptual understanding of these processes, gaining insight into the topic is also of conservation relevance: understanding how climate may drive floral traits variation can serve to protect plant-pollinator interactions under global change conditions. We used Rhododendron as a model system and collected floral traits (corolla length, nectar volume and concentrations), floral visitors, and climatic data on 21 Rhododendron species across two continents (North America-Appalachians and Asia-Himalaya). Based on this we quantified the influence of climate and pollinators to floral traits using phylogeny-informed analyses. Our results indicate that there is substantial variation in pollinators and morphological traits across Rhododendron species and continents. We came across four pollinator groups: birds, bees, butterflies, and flies. Asian species were commonly visited by birds, bees, and flies, while bees and butterflies were the most common visitors of North American species. The visitor identity explained nectar trait variation, with flowers visited by birds presenting higher volumes of dilute nectar and those visited by insects producing concentrated nectar. Nectar concentration and corolla length exhibited a strong phylogenetic signal across the analysed set of species. We also found that nectar trait variation in the Himalaya could also be explained by climate, which presented significant interactions with pollinator identity. Our results indicate that both pollinators and climate contribute and interact to drive nectar trait variation, suggesting that both can affect pollination interactions and floral (and plant) evolution individually and interacting with each other.

Nectary microstructure and nectar production in two species of Cephalocereus (Cactaceae) and their natural hybrid

Variation in the quantity and quality of reward substances produced by flowers influences reproductive success in angiosperms. In this study, a comparative analysis of nectaries and nectar traits (volume, concentration and sugar composition) was performed on the hybrid Cephalocereus columna-trajani × C. tetetzo and its parental species to identify phenotypic variation that could affect reproductive success. The presence of nectarostomata and two types of nectary cells are significant, as well as the presence of xylem and phloem. Furthermore, possible interspecific differences in the amount of starch and mucilage may be relevant. Interspecific variation in nectar volume and concentration was found, with the hybrid exhibiting the highest concentration. All three taxa presented hexose-dominated nectar. In conclusion, C. columna-trajani × C. tetetzo, like its parental species has a functional and anatomically well-formed nectary. Differences in traits such as the amount of starch and mucilage associated with nectar volume, in combination with differences in nectar concentration could have potential consequences for fitness. Our results confirm previous reports on the development of functional structures in hybrid flowers and serve as the basis for future studies testing whether the differences observed here govern the dynamics of competition in hybridization zones.

Double mutualism involving Melocactus (Cactaceae) and lizards in the Brazilian Caatinga: Another isolated case or is it an established interaction?

AbstractThis work discusses a fascinating ecological relationship, in which the lizard Tropidurus cocorobensis and the cactus Melocactus violaceus engage in a double mutualism. In this interaction, observed in a Caatinga, a dry tropical forest in Northeastern Brazil, T. cocorobensis feed on the nectar and pollen of M. violaceus, transferring the grains to the stigmas of another flower, acting as a potential pollinator. Additionally, the lizards consume fruits of M. violaceus, helping to disperse the seeds. The concentrated nectar of M. violaceus attracts lizards, and the morphological compatibility between the small pink flowers and the size of T. cocorobensis is important to this double mutualism. The findings mentioned here highlight the importance of Tropidurus lizards in the reproductive success of Melocactus species and provide insights into the coevolution of these species in a seasonal and resource‐scarce environment, like the Caatinga.

Nectar-mediated avian pollination in Cattleya (Orchidaceae: Laeliinae).

Orchids are notable for the variety of rewards produced for their pollinators. Nevertheless, many species are rewardless and pollinated by food-deceptive strategies. This is the case for Cattleya, a Neotropical genus of more than 100 species supposedly pollinated by food-deception. Here, I studied a member of the clade Sophronitis (Cattleya cernua) in forest areas of southeastern Brazil. The study included analyses of floral morphology, light microscopy of secretory tissues, histochemistry of flower resources, and measurements of nectar volume and concentration. Data on pollinators and mechanisms of pollination were collected in the field by means of film records, while breeding systems were studied using experimental treatments applied to cultivated specimens. The flower traits of Cattleya cernua show strong adaptation to avian pollination. Flowers produce 1-7 μl of a moderately concentrated nectar (17-50%). A secretory tissue at the distal portion of the cuniculus is responsible for nectar secretion. Secreted nectar is stored in the nectar chamber. Pollinaria deposition on the apex of bird beaks allows both short- and long-billed birds to pollinate the flowers. Plants from the studied population were fully self-compatible but pollinator-dependent. Pollinator frequency was higher than in food-deceptive Cattleya. As far as is known, this is the first record of nectar production in Cattleya. The discovery of a reward-producing species (C. cernua) within a genus entirely pollinated by food-deception strategies (Cattleya) provides clues and new insights into understanding the diversification of Laeliinae across the Neotropics.

Floral biology, pollinators and breeding system of Passiflora chrysophylla (Passifloraceae), a South American passion vine

Context Knowledge of the reproductive biology of plants is fundamental for conservation, especially of the ones with a limited distribution. Aims The sexual reproduction of the small-ranged Passiflora chrysophylla Chod. was studied. Methods Controlled pollinations were performed to assess the breeding system, whereas floral traits and visitors (identity, frequency, activity on the flowers, dimensions and pollen load) were analysed to assess the pollination mechanism. Key results Self-compatibility was partial. Anthesis was matinal. The odour emitted by the corona was sweet, whereas the odour emitted by the persistent sepals and bracts was similar to that of the leaves. Contrasting concentric circular reward guides were present in the visible and UV spectra. Nectar concentration was high, the volume increased throughout anthesis and, if removed, nectar was replenished only once during the flower lifespan. Style movements towards the anthers determined male and hermaphroditic phases in most of the flowers; in a few flowers (smaller, scented and nectarless), styles remained apart from the anthers, thus constituting a functionally andromonecious and deceptive automimicry system. The bees Ptiloglossa sp., Thygater analis and Xylocopa augusti acted as pollinators, whereas ants, butterflies and beetles were nectar or pollen thieves and florivores. Conclusions P. chrysophylla is melittophilous and pollinators increase reproductive success. Implications Pollination biology of P. chrysophylla, reported for the first time, would contribute to conservation management of this species with restricted distribution.

Wild bumblebees use both absolute and relative evaluation when foraging

Abstract Foraging theory assumes that animals assess value based on objective payoffs; however, animals often evaluate rewards comparatively, forming expectations based on recent experience. This form of evaluation may be particularly relevant for nectar foragers such as bumblebees, where individuals can visit thousands of flowers daily that vary in nectar quality. While many animals, including bees, demonstrate reference-based evaluation in experimental contexts, it is unclear whether this occurs in the wild. Here, we asked how daily experience with wildflower nectar influenced wild bumblebees’ reward evaluation. We measured the daily nectar concentration of bee-visited wildflowers (Penstemon spp.), before presenting foragers with conspecific flowers filled with a range of artificial nectar concentrations. We recorded bees’ acceptance of artificial nectar, the probability of subsequent visits to flowers on the same plant, and residence time. While bees had a minimum threshold of nectar acceptability that was unaffected by experience, when there was higher-concentration environmental nectar, they were less likely to accept lower-quality rewards on manipulated plants. Bees also visited more flowers and stayed longer on plants with higher-concentration nectar. This study shows evidence for both absolute and reference-based evaluation in wild bees and points towards differences between bees’ behavior in lab- and wild-foraging contexts.

Effects of experimental warming on floral scent, display, and rewards in two subalpine herbs.

Floral volatiles, visual traits, and rewards mediate attraction and defense in plant-pollinator and plant-herbivore interactions, but these floral traits may be altered by global warming through direct effects of temperature or longer term impacts on plant resources. We examined the effect of warming on floral and leaf volatile emissions, floral morphology, plant height, nectar production, and oviposition by seed predators. We used open-top chambers that warmed plants in the field +2-3 °C on average (+6-11 °C increase in daily maxima) for 2-4 weeks across 1-3 years at 3 sites in Colorado, USA. Volatiles were sampled from two closely related species of subalpine Ipomopsis with different pollinators: I. aggregata ssp. aggregata, visited mainly by hummingbirds, and I. tenuituba ssp. tenuituba, often visited by hawkmoths. While warming had no detected effects on leaf volatiles, the daytime floral volatiles of both I. aggregata and I. tenuituba responded in subtle ways to warming, with impacts that depended on the species, site, and year. In addition to the long-term effect of warming, temperature at the time of sampling independently affected the floral volatile emissions of I. aggregata during the day and I. tenuituba at night. Warming had little effect on floral morphology for either species, and no effect on nectar concentration, maximum inflorescence height, or flower redness in I. aggregata. However, warming increased nectar production in I. aggregata by 41%, a response that would attract more hummingbird visits, and reduced oviposition by fly seed predators by at least 72%. Our results suggest that floral traits can show different levels of plasticity to temperature changes in subalpine environments, with potential effects on animal behaviors that help or hinder plant reproduction. They also illustrate the need for more long-term field warming studies, as shown by responses of floral volatiles in different ways to weeks of warming versus temperature at the time of sampling.