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Circadian rhythmicity of nectar secretion in Hoya carnosa

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Abstract

Matile Ph. 2006. Circadian rhythmicity of nectar secretion in Hoya carnosa. Bot. Helv. 116: 1–7. A simple device for continuous sampling of nectar secreted in single flowers of Hoya carnosa R. Br. (Asclepiadaceae) is described. Sampling at 3hrs intervals over several days revealed an oscillating secretion with maxima around midnight. Plants were transferred from a 12:12hrs photoperiod to continuous illumination in order to distinguish between diurnal and circadian regulation. Under conditions of continuous illumination oscillations prevailed for two cycles and the free running period was about 29hrs. Upon transfer to an inverted photoperiod, oscillations were immediately resumed and the maxima were entrained as to fall into the dark period. It is concluded that the rhythmicity of nectar secretion in H. carnosa is a manifestation of the biological clock.

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... Several plant reproductive events happen at specific times of the day, which may be the most propitious moment for pollination to occur. Examples of such events include opening and closing times of flowers and anthers, stigma receptivity, production and concentration of nectar and odor (Van Doorn & Van Meeteren, 2003;Terada et al., 2005;Matile, 2006;Silva et al., 2010;Edge et al., 2012;Van Doorn & Kamdee, 2014). ...
Article
Pollination is an ecological process that relies on the matching traits of flower visitors and flowers. Morphology, behavior, and temporal patterns play essential roles in mediating the interactions between plants and floral visitors. This study analyzed the temporal aspects of visitors and flowers interaction and the possible adjustment between both organisms. We used Ipomoea bahiensis and its flower visitors as a model system. We evaluated the visitor frequency on the flowers throughout the day, flower opening and closing times, pollen availability and stigma receptivity. We also evaluated the highest fruit production time during the flower longevity was analyzed, and the time of highest pollinator activity, related to climatic factors. Among the floral visitors, bees, especially Melitoma spp., Apis mellifera, and Pseudaugochlora pandora were the most frequent visitors, presenting regular visits synchronized with the flower opening and closing times, which were also regular. This system was influenced mainly by light intensity. Besides, these bees were very active during the times of the highest fruit production. These data indicate the presence of temporal patterns for both the bees and the visited plants, and synchronization between them, being the light intensity as a modulator of the rhythms of bees and plant, confirming the importance of the temporal adjustments for pollination efficiency.
... The main food sources for bees are nectar and pollen, which are often available to them during restricted temporal windows (van Doorn & van Meeteren, 2003;Matile, 2006;Edge et al., 2012). Therefore, the presence of a temporal memory constitutes an evolutionary advantage in this group, as bees can save energy, programming their flight activity to coincide with the peaks of daily rhythms of nectar secretion in flowers (Corbet & Delfosse, 1984;Edge et al., 2012) or with the times of higher sugar concentration in the nectar (Edge et al., 2012). ...
Article
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Bees feed on nectar and pollen, however these resources are often available to floral visitors during restricted temporal windows. The presence of temporal memory is an advantage, as foragers can save energy by scheduling their flight activity to coincide with peaks of nectar secretion in the flowers or at times of higher sugar concentration in the nectar. Thus, the objectives of this study were (i) to investigate whether Melipona subnitida has temporal memory, and evaluate whether it becomes more accurate over the days, and (ii) to determine whether the behavior of anticipating the offered resource presents intra-individual consistency in the behavior of foragers. The visitation of the bees was high before and during the opening interval of the food resource, but rare after the closing, suggesting that M. subnitida has the ability to memorize the time of availability of the resource, increasing the accuracy over the days, with bees anticipating their visits in relation to the time they discovered the resource, and the opening time of the resource. There was individual consistency in the behavior of food-anticipatory activity, with the presence of bees that consistently anticipated in relation to the opening time of the resource (inspectors) and bees that consistently did not anticipate (reactivated forager) . By anticipating the search for a resource, foragers allow the group to exploit it effectively, as they exploit it in the first hours of its opening, and foragers that never anticipate avoid unnecessary risks of predation and energy expenditure.
... Hoya species produce white flowers, strong nocturnal fragrance, and abundant nectar, which is strongly suggestive of moth pollination (Faegri and van der Pijl, 1979;Altenburger and Matile, 1988;Matile, 2006). Floral scents have been well studied in some asclepiad genera such as Pachycarpus (Shuttleworth and Johnson, 2012), Xysmalobium (Shuttleworth and Johnson, 2009), Orbea (Shuttleworth et al., 2017) and Ceropegia (Heiduk et al., 2016). ...
Article
Hoya floral characters are highly elaborate and associated with a complex and specialised pollination mechanism. The pollination of two Hoya species has been studied previously, but little is known about the specific nature and interactions between flower morphology, pollinators, and their environment. Here we investigate the pollination of Hoya pottsii, where pollinaria are transferred onto several insects’ legs and arolia including moths in the Erebidae family, ants, and a praying mantis. Hypopyra vespertilio (Erebidae, Erebinae) was the most effective at both carrying and depositing the pollinaria, Colobopsis leonardii (Formicidae) was shown to successfully insert only one pollinium whereas Hymenopus coronatus (Hymenopodidae) could only attach the pollinaria between its two euplantulae. Several Hoya species were used to compare the effectiveness of pollinaria removal and insertion, pollinator size which was correlated to strength, floral scent, and morphology of the guide rail. The floral scent was dominated by Linalool, Methyl benzoate and Benzaldehyde which are known to attract moth, other species displayed similar scents but also showed many different compounds. The effectiveness of a medium-sized moth in pollinating H. pottsii could be explained by the morphology of the guide rail which comprises a landing platform for the arolium. In Hoya carnosa the guide rail lacks a landing platform which could explain why stronger and larger moths were more effective in this species. The importance of the interaction between insect arolia and guide rails in the pollination of Hoya is illustrated and we suggest that their morphology corresponds with pollinator strength and how smoothly and precisely the pollinia can be inserted.
... However, very few studies have addressed the question of whether the secretion is also under circadian control. One such study used wax plant flowers [42] and showed that nectar production oscillated under continuous light conditions with a maximum during the subjective night which corresponded with the pattern of floral scent emission and the presence of nocturnal pollinators [31]. Diel regulation of pollen production has been observed, especially in anemophilous (wind pollinated) plants, such as varieties of grasses (Poaceae), Roman wormwood (Ambrosia artemesiifolia) and maize (Zea mays) [43 -45]. ...
Article
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The interactions between flowering plants and insect pollinators shape ecological communities and provide one of the best examples of coevolution. Although these interactions have received much attention in both ecology and evolution, their temporal aspects are little explored. Here we review studies on the circadian organization of pollination-related traits in bees and flowers. Research, mostly with the honeybee, Apis mellifera , has implicated the circadian clock in key aspects of their foraging for flower rewards. These include anticipation, timing of visits to flowers at specified locations and time-compensated sun-compass orientation. Floral rhythms in traits such as petal opening, scent release and reward availability also show robust daily rhythms. However, in only few studies was it possible to adequately determine whether these oscillations are driven by external time givers such as light and temperature cycles, or endogenous circadian clocks. The interplay between the timing of flower and pollinator rhythms may be ecologically significant. Circadian regulation of pollination-related traits in only few species may influence the entire pollination network and thus affect community structure and local biodiversity. We speculate that these intricate chronobiological interactions may be vulnerable to anthropogenic effects such as the introduction of alien invasive species, pesticides or environmental pollutants. This article is part of the themed issue ‘Wild clocks: integrating chronobiology and ecology to understand timekeeping in free-living animals’.
... Th e plant fl owers continuously from May to October, with a downward, spherical infl orescence formed by aggregated, salver-shaped, white-colored, hairy fl owers ( Fig. 1A, B ). Th e white color of the corolla provides a good contrast against the pinkish red staminal corona ( Fig. 1B ). Th e pollination biology of H. carnosa is unknown, but the nocturnal fragrance emission and nectar production ( Altenburger and Matile, 1988 ;Matile, 2006 ) and the whitish fl ower color are suggestive of moth pollination ( Faegri and van der Pijl, 1979 ;Willmer, 2011 ). However, the fl owers lack the nectar spurs or corolla tubes typical of some moth-pollinated plants. ...
Article
Premise of the study: The genus Hoya (Apocynaceae; Asclepiadoideae) is characterized by a set of complex floral characters unique among the asclepiads, but their role in pollination is poorly understood. Here, we report a new mechanism of asclepiad pollination in the wax plant Hoya carnosa: the pollinaria are transferred on the legs of medium or large settling moths. Methods: Floral visitors and their behavior were observed on Amami-Oshima Island during 2013-2015, and the efficacy of different pollinators was determined by counting the pollinarium loads on different flower visitors. The floral characters were studied to establish the process of pollination in relation to pollinator behavior on the flower. Key results: Hoya carnosa was visited by various settling moths at night, but pollinia attachment was confirmed predominantly on the legs of the large moth Erebus ephesperis (Noctuidae) and less frequently on the legs of the medium-sized moths Bastilla arcuata (Crambidae) and Cleora injectaria (Geometridae). The moths walked around and searched for nectar on the inflorescence, and the corpusculum became clipped to the arolia (adhesive pads on moth tarsi) as they stepped on the pollinaria between the staminal corona. The downward spherical inflorescence of aggregated flowers with flat, velvety petals and a slippery corona provides restricted footholds for the visitors, which efficiently leads pollinator legs to the pollinaria. Conclusions: Although the pollination system of Hoya is largely unknown, pollination by insect legs may be a major pollination system in this genus because these basic floral characters are shared among many species.
... These masses were not found in significant amounts in the whole flower measurements. This may be due to the low presence of nectar content in measured flowers, since the flowers could have been already visited and since nectar production is also very variable, depending on factors such as plant water balance and nutrient status (Pacini et al., 2003), time of day (Matile, 2006), or/and plant's genotype (Witt et al., 1999), among others. ...
... Like scent signals, both nectar quantity and quality vary within plant populations (Herrera, Perez & Alonso 2006) and between plant species (Petanidou 2005). Some of the factors affecting nectar production are a plant's water balance and nutrient status (Pacini, Nepi & Vesprini 2003), time of day (Matile 2006), the plant's genotype (Witt et al. 1999) and damage caused by herbivores (Kessler & Halischke 2009). We expect pollinators to be sensitive to differences in floral rewards; indeed, both nectar quality and quantity influence pollinator behaviour (Cnaani, Thomson & Papaj 2006). ...
Article
1. The evolution of flowering plants has undoubtedly been influenced by a pollinator’s ability to learn to associate floral signals with food. Here, we address the question of ‘why’ flowers produce scent by examining the ways in which olfactory learning by insect pollinators could influence how floral scent emission evolves in plant populations. 2. Being provided with a floral scent signal allows pollinators to learn to be specific in their foraging habits, which could, in turn, produce a selective advantage for plants if sexual reproduction is limited by the income of compatible gametes. Learning studies with honeybees predict that pollinator-mediated selection for floral scent production should favour signals which are distinctive and exhibit low variation within species because these signals are learned faster. Social bees quickly learn to associate scent with the presence of nectar, and their ability to do this is generally faster and more reliable than their ability to learn visual cues. 3. Pollinators rely on floral scent as a means of distinguishing honestly signalling flowers from deceptive ones. Furthermore, a pollinator’s sensitivity to differences in nectar rewards can bias the way that it responds to floral scent. This mechanism may select for flowers that provide olfactory signals as an honest indicator of the presence of nectar or which select against the production of a detectable scent signal when no nectar is present. 4. We expect that an important yet commonly overlooked function of floral scent is an improvement in short-term pollinator specificity which provides an advantage to both pollinator and plant over the use of a visual signal alone. This, in turn, impacts the evolution of plant mating systems via its influence on the species-specific patterns of floral visitation by pollinators.
... Honey bees (Apis mellifera) have the remarkable ability to form and use spatiotemporal memories in order to direct their foraging behavior. This is adaptive because different species of flowering plants bloom at different times of day (Linnaeus, 1751), and nectar and pollen are available for pollinators only during discrete, but consistent, windows of time (Gimenes et al., 1993; Doorn and Meeteren, 2003; Matile, 2006). Honey bees can learn not only where to fly to collect food, but also when to do so (Beling, 1929; Wahl, 1932). ...
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Honey bees can form distinct spatiotemporal memories that allow them to return repeatedly to different food sources at different times of day. Although it is becoming increasingly clear that different behavioral states are associated with different profiles of brain gene expression, it is not known whether this relationship extends to states that are as dynamic and specific as those associated with foraging-related spatiotemporal memories. We tested this hypothesis by training different groups of foragers from the same colony to collect sucrose solution from one of two artificial feeders; each feeder was in a different location and had sucrose available at a different time, either in the morning or afternoon. Bees from both training groups were collected at both the morning and afternoon training times to result in one set of bees that was undergoing stereotypical food anticipatory behavior and another that was inactive for each time of day. Between the two groups with the different spatiotemporal memories, microarray analysis revealed that 1329 genes were differentially expressed in the brains of honey bees. Many of these genes also varied with time of day, time of training or state of food anticipation. Some of these genes are known to be involved in a variety of biological processes, including metabolism and behavior. These results indicate that distinct spatiotemporal foraging memories in honey bees are associated with distinct neurogenomic signatures, and the decomposition of these signatures into sets of genes that are also influenced by time or activity state hints at the modular composition of this complex neurogenomic phenotype.
... As part of their long and intricate coevolution with flowering plants, bees have evolved many behaviors that increase their foraging efficiency. Because different species of flowering plants bloom at different times of day (Linnaeus, 1751), nectar and pollen are available for pollinators only during discrete yet consistent windows of time ( Gimenes et al., 1993;Doorn and Meeteren, 2003;Matile, 2006). Honey bees, accordingly, have evolved the ability to alter their foraging behavior in a circadian manner based on experience of when food has been available on previous days (Beling, 1929;Wahl, 1932). ...
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Bromelia antiacantha flowered from December to February and during this period the central leaves and bracts displayed a bright red colour. The inflorescence bears 150-350 flowers, with 10-35 flowers opening per day over 4-5 days. The flowers are dark magenta coloured with white margins, tubular-shaped with a wide opening, and their stigma is situated below the anthers. Anthesis began around 4:00 h and flowers lasted approximately 15 h. The highest nectar volume and sugar concentration occurred between 4:00-6:00 h; after this period, both decreased throughout the day. B. antiacantha is partially self-incompatible, non-autogamous, and therefore, pollinator dependent. The hummingbirds Thalurania glaucopis, Amazilia fimbriata, and Ramphodon naevius were its most frequent pollinators (55% of the visits), visiting flowers mainly in the afternoon. The scattered distribution of B. antiacantha promoted trap-lining behaviour of the hummingbirds, which favoured fruit set through xenogamy. Corolla colour, wide flower opening, sweet odour and concentrated nectar early in the day favoured bee visitation. Of the 38 % of bee visits, 96% were made by Bombus morio, mainly in the morning and their behaviour promoted self-pollination. The bee Trigona spinipes frequently acted as a pollen and nectar thief early in the morning, excluding most of the hummingbirds. Bromelia antiacantha has ornithophilous and melittophilous features, and despite being pollinated by two kinds of agents, its reproductive success depends on a given set of circumstances.
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