Loss Of Nectar Research Articles

The Indirect Threats of Desert Locust Infestation on Honeybees in Ethiopia

This review focuses on the potential effects of a desert locust infestation on Ethiopian honeybees. Data on the country’s infestation, locust activity, honeybee foraging behavior, pesticide kinds, and application rates were collected and analyzed in connection to honeybee life and performance. Desert locust has damaged a considerable number of plants of various kinds, possibly causing pollen and nectar loss. As a result, honeybees are likely to produce less brood, less honey, suffer from poor health, and abscond. Besides, studies suggested that the use of pesticides to control the locust could directly harm honeybees. The pesticide was used for 21 days in a row to cover a huge region infected with locusts, which could have had a severe effect on honeybees. The probability of an influence is also indicated by the overlap of pesticide administration with honeybee foraging seasons and hours. Furthermore, forager bees leave their hive 1 to 13 times per day, spending about 3 hours outside each time, indicating higher chemical exposure. Malathion is one of the pesticides that could harm honeybees, while there is no comprehensive list of the chemicals used on the internet or anywhere else. Finally, the current desert locust invasion and eradication operation in Ethiopia may have caused substantial damage to honeybees as a result of bee forage loss and pesticide hazard, emphasizing the need for future precautions. Because this is speculative work based on evidence, detailed survey research is recommended to determine the actual impact imposed on honeybees.

Unidirectional transitions in nectar gain and loss suggest food deception is a stable evolutionary strategy in Epidendrum (Orchidaceae): insights from anatomical and molecular evidence

BackgroundNectar gain and loss are important flower transitions observed in angiosperms, and are particularly common in orchids. To understand such transitions, the availability of detailed anatomical data and species-level phylogenies are crucial. We investigated the evolution of food deception in Epidendrum, one of the largest orchid genera, using genus phylogeny to map transitions between nectar gain and loss among different clades. Associations between anatomical and histochemical changes and nectar gain and loss were examined using fresh material available from 27 species. The evolution of nectar presence/absence in Epidendrum species was investigated in a phylogenetic framework of 47 species, using one nuclear and five plastid DNA regions available from GenBank and sequenced in this study.ResultsThe presence or absence of nectar was strongly associated with changes in the inner epidermal tissues of nectaries. Nectar-secreting species have unornamented epidermal tissue, in contrast to the unicellular trichomes found on the epidermis of food deceptive species. Bayesian tests confirmed that transitions occurred preferentially from nectar presence to nectar absence across the Epidendrum phylogeny. In addition, independent nectar loss events were found across the phylogeny, suggesting a lack of constraint for these transitions.ConclusionsOrnamented nectaries may play an important role in the deceptive pollination strategy by secreting volatile organic compounds and providing tactile stimuli to pollinators. The recurrent and apparently irreversible pattern of nectar loss in Epidendrum suggests that food deception may constitute an alternative evolutionarily stable strategy, as observed in other orchid groups.

Nectar protection in arid-adapted flowers of Zygophyllaceae-Zygophylloideae

The survival of plants in arid areas depends on efficient adaptation to extreme environments. The protection against nectar loss is an important challenge for flowers in arid environments. Flowers of arid-adapted Zygophyllaceae subfamily Zygophylloideae are characterized by a peculiar structure called staminal scales (SS). The special arrangement of SS around the perigynous disc nectary (DN) suggests their adaptive function for protection against nectar loss. We aim to test the protective function of SS and to understand the synorganised evolution of SS and DN in relation to nectar protection. We, first, manipulate flowers by removal of SS in two representatives of Zygophylloideae. The results indicate a dramatic decrease of nectar volume confirming the protective function of SS. Then, we study the functional synorganisation of SS and DN during development and trace their evolution on a phylogenetic tree. The evolution of SS is closely related to the change in the organization of the DN. Such a synorganised evolution presents an important adaptive advantage promoting the diversification of the subfamily in arid and semiarid areas. Augea represents a unique case in which the protective function of SS is taken over by a hypanthium and the SS have acquired a secondary mechanical role for promotion of autogamy.

Feeding the enemy: loss of nectar and nectaries to herbivores reduces tepal damage and increases pollinator attraction in Iris bulleyana.

Floral nectar usually functions as a pollinator reward, yet it may also attract herbivores. However, the effects of herbivore consumption of nectar or nectaries on pollination have rarely been tested. We investigated Iris bulleyana, an alpine plant that has showy tepals and abundant nectar, in the Hengduan Mountains of SW China. In this region, flowers are visited mainly by pollen-collecting pollinators and nectarivorous herbivores. We tested the hypothesis that, in I. bulleyana, sacrificing nectar and nectaries to herbivores protects tepals and thus enhances pollinator attraction. We compared rates of pollination and herbivory on different floral tissues in plants with flowers protected from nectar and nectary consumption with rates in unprotected control plants. We found that nectar and nectaries suffered more herbivore damage than did tepals in natural conditions. However, the amount of tepal damage was significantly greater in the flowers with protected nectaries than in the controls; this resulted in significant differences in pollinator visitation rates. These results provide the first evidence that floral nectar and nectaries may be 'sacrificed' to herbivores, leading to reduced damage to other floral tissues that are more important for reproduction.

Nutrient enrichment is associated with altered nectar and pollen chemical composition in Succisa pratensis Moench and increased larval mortality of its pollinator Bombus terrestris L.

Pollinators are declining worldwide and possible underlying causes include disease, invasive pest species and large scale land use changes resulting in habitat loss and degradation. One particular cause of habitat degradation is the increased inflow of nutrients due to anthropogenic combustion processes and large scale application of agricultural fertilizers. This nutrient pollution has been shown to affect pollinators through the loss of nectar and pollen-providing plant species. However, it may also affect pollinators through altering the nectar and pollen chemical composition of plant species, hence influencing pollinator food quality. Here, we experimentally investigated the effect of nutrient enrichment on amino acid and sugar composition of nectar and pollen in the grassland plant Sucissa pratensis, and the subsequent colony size and larval mortality of the pollinating bumblebee Bombus terrestris. We found less of the essential amino acids glycine and arginine in the pollen of fertilized plants, and more arginine, ornithine and threonine in the pollen of control plants. Nectar glucose and pollen fructose levels were lower in fertilized plants as compared to control plants. Furthermore, bumblebee colonies visiting fertilized plants showed more dead larvae than colonies visiting control plants. Our results suggest that the fitness of bumblebees can be negatively affected by changes in their food quality following nutrient pollution. If similar patterns hold for other plant and pollinator species, this may have far reaching implications for the maintenance of pollination ecosystem services, as nutrient pollution continues to rise worldwide.

Cover Caption: Nectary Variation vs Pollination Modes

Nectar is an effective reward for pollinators. In this issue, Liu et al. (pp. 178–187) demonstrate that the floral nectary has experienced morphological and functional differentiation among closely related species of Pedicularis, which could have affected nectar production and pollination modes. The results indicate that the gain or loss of nectar, together with variation incorolla form, may have played a key role in driving species diversification in Pedicularis.

The evolution of floral nectaries in Disa (Orchidaceae: Disinae): recapitulation or diversifying innovation?

The Orchidaceae have a history of recurring convergent evolution in floral function as nectar production has evolved repeatedly from an ancestral nectarless state. However, orchids exhibit considerable diversity in nectary type, position and morphology, indicating that this convergence arose from alternative adaptive solutions. Using the genus Disa, this study asks whether repeated evolution of floral nectaries involved recapitulation of the same nectary type or diversifying innovation. Epidermis morphology of closely related nectar-producing and nectarless species is also compared in order to identify histological changes that accompanied the gain or loss of nectar production. The micromorphology of nectaries and positionally equivalent tissues in nectarless species was examined with light and scanning electron microscopy. This information was subjected to phylogenetic analyses to reconstruct nectary evolution and compare characteristics of nectar-producing and nectarless species. Two nectary types evolved in Disa. Nectar exudation by modified stomata in floral spurs evolved twice, whereas exudation by a secretory epidermis evolved six times in different perianth segments. The spur epidermis of nectarless species exhibited considerable micromorphological variation, including strongly textured surfaces and non-secreting stomata in some species. Epidermis morphology of nectar-producing species did not differ consistently from that of rewardless species at the magnifications used in this study, suggesting that transitions from rewardlessness to nectar production are not necessarily accompanied by visible morphological changes but only require sub-cellular modification. Independent nectary evolution in Disa involved both repeated recapitulation of secretory epidermis, which is present in the sister genus Brownleea, and innovation of stomatal nectaries. These contrasting nectary types and positional diversity within types imply weak genetic, developmental or physiological constraints in ancestral, nectarless Disa. Such functional convergence generated by morphologically diverse solutions probably also underlies the extensive diversity of nectary types and positions in the Orchidaceae.

Observations on the effect of nectar-robbery on the reproductive succes of Aeranthes arachnitis (Orchidaceae)

While the presence of nectar is the most common floral reward offered by orchids, approximately one-third of orchid species have evolved mechanisms of deceit whereby the pollinator receives no reward. Lack of reward has been shown to have a significant negative effect on reproductive success in the Orchidaceae, however the phenomenon of nectar-robbery has been poorly studied. Here we investigate the effect of nectar-robbery induced deceit by invasive ants in the nectariferous orchid Aeranthes arachnitis. Fruiting success was found to be below 5% at three sites, including two conservation areas, compared with 48.5% at a site next to plantations. All the populations showed loss of floral nectar, ranging from 64.3% to 100% of flowers observed. Loss of nectar to robbers that do not facilitate pollination not only represents a cost to fruiting success but also a loss of a resource to the orchid through reabsorption of any excess. Using Bell's Theory of nectar concealment it is possible to determine the critical point, below which nectar-robbery negatively affects fruiting success. Based on related angraecoid orchids the proportion of nectar bearing flowers would, theoretically, need to be 70%. The higher levels of reproductive success surrounded by plantations may due to the presence of the non-native Callistemon citrinus acting as nectar source, thus maintaining an increased local abundance of the pollinator. This has important implications for the conservation and management of Aeranthes arachnitis and other species, which rely on nectariferous pollinators, particularly when a nectar bearing species becomes essentially deceptive. The result suggests that management of this nectar-robbery induced deceptive species should involve the manipulation of rewarding species within the surrounding area.

Observations on the effect of nectar-robbery on the reproductive succes of Aeranthes arachnitis (Orchidaceae)

While the presence of nectar is the most common floral reward offered by orchids, approximately one-third of orchid species have evolved mechanisms of deceit whereby the pollinator receives no reward. Lack of reward has been shown to have a significant negative effect on reproductive success in the Orchidaceae, however the phenomenon of nectar-robbery has been poorly studied. Here we investigate the effect of nectar-robbery induced deceit by invasive ants in the nectariferous orchid Aeranthes arachnitis. Fruiting success was found to be below 5% at three sites, including two conservation areas, compared with 48.5% at a site next to plantations. All the populations showed loss of floral nectar, ranging from 64.3% to 100% of flowers observed. Loss of nectar to robbers that do not facilitate pollination not only represents a cost to fruiting success but also a loss of a resource to the orchid through reabsorption of any excess. Using Bell's Theory of nectar concealment it is possible to determine the critical point, below which nectar-robbery negatively affects fruiting success. Based on related angraecoid orchids the proportion of nectar bearing flowers would, theoretically, need to be 70%. The higher levels of reproductive success surrounded by plantations may due to the presence of the non-native Callistemon citrinus acting as nectar source, thus maintaining an increased local abundance of the pollinator. This has important implications for the conservation and management of Aeranthes arachnitis and other species, which rely on nectariferous pollinators, particularly when a nectar bearing species becomes essentially deceptive. The result suggests that management of this nectar-robbery induced deceptive species should involve the manipulation of rewarding species within the surrounding area.

Loss of extrafloral nectary on an oceanic island plant and its consequences for herbivory

Two Hibiscus (Malvaceae) species coexist on the oceanic Bonin (Ogasawara) Islands: Hibiscus glaber (an endemic species) and H. tiliaceus (the ancestral non-endemic species). Hibiscus tiliaceus produces extrafloral nectar from the sepals, while H. glaber does not. To clarify the effects of extrafloral nectar loss on Hibiscus-insect relationships, we examined herbivory and insect communities on flower buds of H. glaber and H. tiliaceus. Larvae of the endemic moth Rehimena variegata (Lepidoptera: Pyralidae) attacked 20% of the flower buds on H. glaber, while less than 0.2% of buds on H. tiliaceus were attacked. Introduced species of ants frequently visited the flower buds of H. tiliaceus to collect extrafloral nectar from the sepal, while they rarely visited those of H. glaber. Therefore, extrafloral nectar on H. tiliaceus sepals may function as a facultative defense against flower bud herbivory. The loss of extrafloral nectaries of H. glaber sepals may be related to the original paucity of native herbivores and ants on the Bonin Islands.

Response of a traplining hummingbird to changes in nectar availability

Theory predicts that nectarivores respond to changes in profitability of patches of flowers or feeders by adjusting visitation rate to increase reward size. We conducted a set of experiments in an outdoor enclosure with seven feeders to determine how Phaethornis longirostris, a traplining hummingbird, adjusts its visitation rates in response to changes in sucrose solution delivery rates. Each experiment tested the response of P. longirostris to the following changes in the timing and volume of sucrose solution delivery: (1) increases in sucrose solution abundance at all feeders (mimicking seasonal increases in numbers of open flowers or nectar output); (2) large changes in sucrose solution availability at one feeder (mimicking increases or decreases of patch profitability); and (3) sudden unexpected decreases in sucrose solution availability at one feeder (mimicking loss of nectar to competitors). We found that P. longirostris (1) decreased visitation rates when the sucrose solution delivery rate was higher at all feeders, (2) increased visitation rates to individual feeders when their profitability increased for whole days but did not significantly decrease visitation rates when feeder output decreased; and (3) responded to sudden food losses at a feeder (due to simulated competition) by increasing use of that feeder for 1 or 2 h after the loss.

Pollinator Specificity in Lantana camara and L. trifolia (Verbenaceae)

Pollinator Specificity in Lantana camara and L. trifolia (Verbenaceae)