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PubMed2004

Evolution of a complex coevolved trait: active pollination in a genus of fig wasps.

Only three insect lineages have evolved complex active pollination behaviour and only fig wasps (Agaonidae) have also reverted from active to passive pollination. Previously, it was assumed that there was a single origin of active pollination in fig wasps, followed by one independent loss in each of five genera. We show here that there have been three to six changes in pollination behaviour within just one genus (Pleistodontes). The results suggest multiple gains of active pollination in fig wasps, but are sensitive to assumptions about the relative costs of gaining and losing this complex behaviour. In addition, previous comparative studies at higher taxonomic levels have reported correlated evolution between active pollination in wasps and low anther/ovule ratios in figs. We report that changes in pollination behaviour between congeneric species correlate perfectly with changes in anther/ovule ratios in the host figs, showing no phylogenetic inertia in coadaptation at the species level.

Animals↗
PubMed2006

Relative effects of nocturnal vs diurnal pollinators and distance on gene flow in small Silene alba populations.

Silene alba exists in natural metapopulations throughout its range and is visited by a suite of both diurnal and nocturnal pollinators. Pollen-mediated gene flow may help reduce genetic isolation of subpopulations. Here, we compared the relative effects of nocturnal vs diurnal pollinators on pollen-mediated gene flow in subpopulations separated by two distance treatments. We established populations consisting of genetically marked individuals in an old field in Tennessee (USA). Electrophoretic examination of seedlings produced by plants exposed to nocturnal, diurnal and control pollinator treatments and separated by either 20 or 80 m allowed us to directly measure pollen-mediated gene flow. Gene flow was more common between populations separated by only 20 m. Nocturnal pollinators were responsible for most gene flow between populations, regardless of distance. Diurnal pollinators played only a small role in pollen-mediated gene flow. The results suggest that nocturnal pollinators are better than diurnal pollinators at moving pollen between small S. alba subpopulations. However, their effectiveness declines as the distance between subpopulations increases, making them relatively ineffective at moving genes between isolated subpopulations.

Animals↗
PubMed2006

Increased tomato yield through pollination by native Australian Amegilla chlorocyanea (Hymenoptera: Anthophoridae).

Amegilla spp. (Hymenoptera: Anthophoridae) have been suggested as potential native Australian alternative to overseas used bumblebees (Bombus spp.) for pollination of tomato in greenhouses. In this study, we investigate the effectiveness of Amegilla chlorocyanea Cockerell as a greenhouse pollinator of tomato, Lycopersicon esculentum Mill. We show that (1) a single buzz by a female increases tomato weight by 11% compared with pollination by using an industrial pollination wand, (2) multiple buzzes increase tomato weight compared with a single buzz, and (3) unlimited flower visits lead to an increase in fruit weight of 21% compared with wand pollination. These results are comparable with those achieved by bumblebee pollination and demonstrate that A. chlorocyanea is a valid alternative to bumblebees for greenhouse tomato pollination in Australia.

Animals↗
PubMed2000

Artocarpus (Moraceae)-gall midge pollination mutualism mediated by a male-flower parasitic fungus.

A previously undescribed pollination system involving a monoecious tree species, Artocarpus integer (Moraceae), pollinator gall midges, and fungi is reported from a mixed dipterocarp forest in Sarawak, Borneo. The fungus Choanephora sp. (Choanephoraceae, Mucorales, Zygomycetes) infects male inflorescences of A. integer, and gall midges (Contarinia spp., Cecidomyiinae, Diptera) feed on the fungal mycelia and oviposit on the inflorescence. Their larvae also feed on the mycelia and pupate in the inflorescence. The gall midges are also attracted by female inflorescences lacking mycelia, probably due to a floral fragrance similar to that of male inflorescences. Because of the sticky pollen, dominance of Contarinia spp. in flower visitors, and pollen load observed on Contarinia spp. collected on both male and female inflorescences, Artocarpus integer is thought to be pollinated by the gall midges. Although several pathogenic fungi have been reported to have interactions with pollinators, this is the first report on a pollination mutualism in which a fungus plays an indispensable role. The pollination system described here suggests that we should be more aware of the roles fungi can play in pollinations.

Journal Article↗
PubMedDate not supplied

[Structure of coadaptive complex of forest entomophylous plants with broad spectrum of pollinators].

Pollinators of common forest entomophylous plants were studied at 1982-1985 near Zvenigorod biological station (Moscow region) and at 1989-1993 near Torma (Jogeva maakond, Estonia). The comparative analysis of spectra of pollinators has allowed to distinguish five groups (subcomplexes) of plants characterized by dominance of different groups of pollinators: myiophylous (flies from superfamily Muscoidea dominate), syrphidophylous (flies from family Syrphidae dominate), nonspecialized melittophylous (Apoidea, mainly bumblebees, dominate), psychophylous (butterflies dominate), and cantharophylous (beetles dominate). The belonging of plants to concrete subcomplex is determined by the morphology of flowers and influorescences, but in some cases habitat and time of blooming are also important. From year to year the composition of pollinators of the same plant species varies because of change in abundance of different groups of pollinators. However for long term these fluctuations are leveled off. External reproductive isolation of plants of myiophylous subcomplex is achieved mainly by spatial (ecological) and time (different time of flowering) isolations. However when two species of the same subcomplex grow together and their flowering time strongly overlap, there are some distinction in their pollinators reducing competition for pollinators.

Animals↗
PubMed2005

Symptoms of the olive pollen allergy: do they really occur only in the pollination season?

BACKGROUND: Olive (Olea europaea; O.e.) pollen is a major cause of seasonal respiratory allergy. The O.e. pollination season lasts two months from the beginning of May till the end of June. It was expected that patients with allergic disease from O.e. sensitization were symptomatic only during this period. However, during the last few years, we have observed that the clinical symptoms appear not only during the O.e. pollination season but also during the rest of the year. OBJECTIVE: The aim of this study was to observe and document symptoms of respiratory allergic diseases in the O.e. sensitized patients during the O.e. pollination season and after it. METHODS: One hundred and twenty-seven patients with respiratory allergic disease were enrolled in the study. Allergenic sensitizations were shown by SPT. Finally, patients were split into two groups as monosensitized with O.e. (n=19) and polysensitized (n=108). Patients were assessed by using scores of respiratory allergic disease symptoms and percentage of peak expiratory flow rate values (PEFR %) (only for asthmatic patients) during the O.e. pollination season and after it. RESULTS: Of the patients with O.e. monosensitization, 13 had allergic rhinitis (AR) only while six had allergic asthma (AA) additionally. AR alone and accompanied by AA was present in 84 and 24 polysensitized patients respectively. Eleven patients with O.e. sensitization (57.9 %) and 86 patients with polysensitization (79.6 %) had AR symptoms throughout the year irrespective of the O.e. pollination season. Similarly, three of the O.e. monosensitized and ten of the polysensitized patients with AA had asthmatic symptoms during the O.e. pollination season and also after it. CONCLUSIONS: In the patient group sensitive to O.e. along with other pollen extracts, it was possible to observe symptoms outside the pollination season. However, patients with O.e. monosensitization also had symptoms to a great extent outside the season.

Adolescent↗
PubMed2006

Impact of insect pollinator group and floral display size on outcrossing rate.

Despite the strong influence of pollination ecology on the evolution of selfing, we have little information on how distinct groups of insect pollinators influence outcrossing rate. However, differences in behavior between pollinator groups could easily influence how each group affects outcrossing rate. We examined the influence of distinct insect pollinator groups on outcrossing rate in the rocky mountain columbine, Aquilegia coerulea. The impact of population size, plant density, size of floral display, and herkogamy (spatial separation between anthers and stigmas) on outcrossing rate was also considered as these variables were previously found to affect outcrossing rate in some plant species. We quantified correlations between all independent variables and used simple and two-factor regressions to determine direct and indirect impact of each independent variable on outcrossing rate. Outcrossing rate increased significantly with hawkmoth abundance but not with the abundance of any of the other groups of floral visitors, which included bumblebees, solitary bees, syrphid flies, and muscidae. Outcrossing rate was also significantly affected by floral display size and together, hawkmoth abundance and floral display size explained 87% of the variation in outcrossing rate. None of the other independent variables directly affected the outcrossing rate. This is the first report of a significant impact of pollinator type on outcrossing rate. Hawkmoths did not visit fewer flowers per plant relative to other pollinator groups but preferred visiting female-phase flowers first on a plant. Both the behavior of pollinators and floral display size affected outcrossing rate via their impact on the level of geitonogamous (among flower) selfing. Given that geitonogamous selfing is never advantageous, the variation in outcrossing rate and maintenance of mixed mating systems in populations of A. coerulea may not require an adaptive explanation.

Animals↗
PubMed2005

The safety of thiamethoxam to pollinating bumble bees (Bombus terrestris L.) when applied to tomato plants through drip irrigation.

Thiamethoxam, mainly sold under the trademark of Actara, is a neonicotinoid widely used in covered vegetables for the control of aphids and whiteflies. In these crops, and particularly in covered tomatoes, bumble-bees are used for cross-pollination as an alternative to labour intensive manual techniques. In this study, made on tomatoes grown in separated greenhouse plots in Murcia, Southern Spain, thiamethoxam was applied through drip irrigation at a rate of 200 g ai/ha, and as a split application of the same rate, to evaluate the effects on pollinating bumble bees compared to a foliar application of a toxic standard. The results showed that the toxic foliar standard had a clear effect on the pollination of tomato flowers, declining to zero pollination two weeks after application, whereas both the single and split drip irrigation applications of Actara had no effect on pollination when compared to the control plots. The count of dead adults and larvae did not show any differences between the treatments, whereas the measurement of sugar water consumption was shown to correlate well with pollination. The consumption of sugar water declined in the toxic standard plots by 69% with respect to the control, whilst the decline in lower dose drip irrigation application was only 3%. In regard to hive weight, and number of adults and brood after destructive sampling; there were no statistical differences between the treatments but a negative effect of the foliar treatment was observed. Based on these results we can conclude that a split application of Actara applied in drip irrigation to the soil/substrate has no effect on the bumble-bees used in tomatoes for pollination.

Agriculture↗
PubMed2005

[The dynamics of calcium distribution in stigma and style of lettuce (Lactuca sativa L.) before and after pollination].

Potassium antimonite was used to deposit calcium in the stigma and style of lettuce (Lactuca sativa L.) before and after pollination. The stigma of lettuce is two splits. Abundant calcium granules are displayed in the wall of papillae on the receptive surface of stigma before and after pollination, which may facilitate pollen germination. However, a few calcium granules in the wall of epidermis cell on no-receptive surface. Calcium distribution in style presents a gradient in transmitting tissue and parenchyma cells from the top to the base of the style before pollination. After pollination, calcium in transmitting tissue distinctly increased and its gradient distribution became more evident. Pollen tubes grow in the intercellular gaps of transmitting tissue. When pollen tubes grew into transmitting tissue, calcium granules in parenchyma around transmitting tissue decreased, suggesting a calcium movement was controlled by pollen tubes. The calcium gradient distribution also appeared in the trachea of vascular bundle of style. In general, calcium in style displays a feature of time-special distribution: transmitting tissue doesn't need much more calcium that is only stored in the parenchyma before pollination. However, calcium in parenchyma cells may be transported to transmitting tissue and make the latter contain more calcium to form an evident calcium gradient and meet the requirement of pollen tubes directionally growing after pollination. This is the second sample of calcium gradient existing in style, which was found by using potassium antimonite method.

Calcium↗
PubMed1998

Population dynamics of resource limited plants and their pollinators.

In this paper we build upon and generalize an earlier model of the interactions between a plant and its pollinator (Ingvarsson and Lundberg, 1995). In this model we assume that the performance of the pollinator population is directly linked to the size of the plant population. To avoid the problem of both populations growing exponentially we have, without loss of generality, assumed the plant population to be resource limited. Analysis of the system shows that there exists either two or no internal equilibrium points. The case with no equilibrium points corresponds to the trivial case where the system cannot persist, resulting in the extinction of both the plant and pollinator population. When the two internal equilibrium points do exist, one of them will always be unstable. This unstable equilibrium can be viewed as an equivalent of the threshold criteria derived in Ingvarsson and Lundberg (1995) in the sense that whenever the system is initiated above the unstable equilibrium point, persistence of the system is assured, while both species will go extinct whenever the system is initiated below the unstable equilibrium point. The analytical results were verified by numerical simulations of the system. We conclude that the existence of a threshold criteria, below which the system cannot persist is a general feature of plant-pollinator systems. We discuss how the existence of the threshold criteria will affect the persistence of plant-pollinator systems in light of, for instance, habitat fragmentation or stochastic reductions in the densities of either the plant or pollinator population. We further highlight some recent empirical studies that indicate the existence of a threshold in natural populations below which extinction is inevitable.

Animals↗
PubMed2002

Cycads: their evolution, toxins, herbivores and insect pollinators.

Palaeobiological evidence indicates that gymnosperms were wind-pollinated and that insect pollination began in angiosperms in the Lower Cretaceous (ca. 135 mya) leading to close associations between higher plants and their pollinators. Cycads, which were widespread and pervasive throughout the Mesozoic (250-65 mya) are among the most primitive living seed-plants found today. Because pollination by beetles and by thrips has now been detected in several modern cycads, it is attractive to speculate that some insects and cycads had already developed similar mutualistic interactions in the Triassic (250-205 mya), long before the advent of angiosperms. We also draw attention to another key factor in this insect-plant relationship, namely secondary, defensive plant substances which must always have controlled interspecific interactions. Cycads mainly produce toxic azoglucosides and neurotoxic non-protein amino acids (e.g. BMAA), which apparently are crucial elements in the development and maintenance of mutualism (pollination) and parasitism (herbivory) by cycad-linked herbivores. We now add new results on the uptake and storage of the main toxin, cycasin, of the Mexican cycad Zamia furfuracea by its pollinator, the weevil Rhopalotria mollis, and by a specialist herbivore of Zamia integrifolia, the aposematic Atala butterfly Eumaeus atala.

Animals↗
PubMed2004

Pollination between maize and teosinte: an important determinant of gene flow in Mexico.

Gene flow between maize [Zea mays (L.)] and its wild relatives does occur, but at very low frequencies. Experiments were undertaken in Tapachula, Nayarit, Mexico to investigate gene flow between a hybrid maize, landraces of maize and teosinte (Z. mays ssp. mexicana, races Chalco and Central Plateau). Hybridization, flowering synchrony, pollen size and longevity, silk elongation rates, silk and trichome lengths and tassel diameter and morphology were measured. Hybrid and open-pollinated maize ears produced a mean of 8 and 11 seeds per ear, respectively, when hand-pollinated with teosinte pollen, which is approximately 1-2% of the ovules normally produced on a hybrid maize ear. Teosinte ears produced a mean of 0.2-0.3 seeds per ear when pollinated with maize pollen, which is more than one-fold fewer seeds than produced on a maize ear pollinated with teosinte pollen. The pollination rate on a per plant basis was similar in the context of a maize plant with 400-500 seeds and a teosinte plant with 30-40 inflorescences and 9-12 fruitcases per inflorescence. A number of other factors also influenced gene-flow direction: (1) between 90% and 95% of the fruitcases produced on teosinte that was fertilized by maize pollen were sterile; (2) teosinte collections were made in an area where incompatibility systems that limit fertilization are present; (3) silk longevity was much shorter for teosinte than for maize (approx. 4 days vs. approx. 11 days); (4) teosinte produced more pollen on a per plant basis than the landraces and commercial hybrid maize; (5) teosinte frequently produced lateral branches with silks close to a terminal tassel producing pollen. Collectively these factors tend to favor crossing in the direction of teosinte to maize. Our results support the hypothesis that gene flow and the subsequent introgression of maize genes into teosinte populations most probably results from crosses where teosinte first pollinates maize. The resultant hybrids then backcross with teosinte to introgress the maize genes into the teosinte genome. This approach would slow introgression and may help explain why teosinte continues to co-exist as a separate entity even though it normally grows in the vicinity of much larger populations of maize.

Breeding↗
PubMed2003

Does pollination limit tolerance to browsing in Ipomopsis aggregata?

Ungulate browsing of flowering stalks of the semelparous herb Ipomopsis aggregata leads to regrowth of lateral inflorescences, a response that has been reported to yield overcompensation in some cases (browsed plants with higher reproductive success than unbrowsed), but undercompensation in others. Little is known about the mechanisms that cause such variable tolerance to herbivory. We explored one possible mechanism--variation in effects of browsing on pollination--by clipping I. aggregata inflorescences to mimic browsing, observing subsequent visits by pollinators and nectar-robbers, and adding pollen by hand to flowers of some clipped and unclipped plants. Clipping reduced floral display size and increased inflorescence branching, but neither hummingbirds, the primary pollinators, nor nectar-robbing bumblebees showed any preference for unclipped versus clipped plants. Clipping delayed flowering; this shift in phenology caused clipped plants to miss the peak of hummingbird activity and to have lower per-flower visitation rates than unclipped controls in one year, but to have greater overlap with birds and higher visitation rates in the subsequent year. In three sites and 2 years, clipped plants exposed to natural pollination suffered extreme undercompensation, producing on average only 16% as many seeds as unclipped controls. This was not directly attributable to clipping effects on pollination, however, because clipped plants were unable to increase fecundity when provided with supplemental pollen by hand. Taken altogether, our results suggest that compensation was constrained less by indirect effects of browsing on pollination than by its direct impacts on resource availability and hence on the ability of plants to regrow lost inflorescence tissue and to fill seeds. Exploring the physiological and developmental processes involved in regrowth of inflorescences and provisioning of seeds is a promising future direction for research designed to understand variation in browsing tolerance.

Adaptation, Physiological↗
PubMed2002

Pollination failure in plants: why it happens and when it matters.

Pollination is the primary step in seed formation. Pollination biologists have shown that pollination failure can occur at all steps in the dispersal process and at several different levels. Increased risk of pollination failure is associated with pollen if it is delivered to a stigma too little, too much, too late, too mixed in composition or too poor in quality. It is associated with pollinators when they are too few or too inconstant, and with plants when they are too specialized or too selective. It is associated with populations when they are too sparse, too small in number or too uniform genetically, and with communities when they are too fragmented, genetically impoverished or under rapid modification. Understanding the causes of pollination failure in plants can aid the successful conservation and recovery of rare plants, maintenance of crop yields, and sustainable use of wild plant resources such as forest timber.

Agriculture↗
PubMed1997

Effect of pollination on accumulation of ACC synthase and ACC oxidase transcripts, ethylene production and flower petal abscission in geranium (Pelargonium x hortorum L.H. Bailey).

Self-pollination of diploid zonal geranium (Pelargonium x hortorum L.H. Bailey) florets leads to a dramatic rise in ethylene production, followed by abscission within 4 h. Neither wounding of the stigma, pollination with tetraploid pollen, nor heat-killed self pollen could elicit as much ethylene production and petal abscission as self-pollination. A cDNA sharing sequence identity with ACC synthase (GACS2) and three different cDNAs sharing sequence identity with ACC oxidase (GACO1, GACO2, GACO3) were isolated from geranium pistils. Transcripts hybridizing with these probes increased slightly in response to self-pollination, but the degree of accumulation in response to various treatments did not correlate with ethylene production. When calculated on a per-plant-part basis, transcripts hybridizing with GACS2 were equally distributed among the stigma+style, sterile ovary, and ovary tissues, but transcripts hybridizing with the three ACC oxidase clones were differentially distributed. All transcripts were differentially expressed among the other tissues of the plant, with GACO1 being the most widely distributed. Ethylene production in geranium pistils was not autocatalytic. Propylene failed to induce ethylene production and ethylene did not induce the accumulation of ACC synthase or ACC oxidase transcripts. ACC accumulated in the stigma and style, and to a smaller extent in the sterile ovary, after pollination. These data support a model of pollination-induced ethylene production by post-transcriptional regulation of ethylene biosynthetic gene expression.

Amino Acid Oxidoreductases↗
PubMed2004

Pollination effectiveness and pollen dispersal in a Rhododendron ferrugineum (Ericaceae) population.

Many alpine plants are predominantly outcrossing, thus plant reproductive success is highly dependent on effectiveness of pollinators. How pollinators transfer pollen from one flower to another is of great interest in understanding the genetic structure in plant populations. We studied (1) the role and effectiveness of insect visitors for pollination, and (2) their contribution as pollen vectors for gene dispersal in a Rhododendron ferrugineum population. Various insect visitors were recorded, including Hymenoptera, Diptera, Coleoptera, and Lepidoptera. The most frequent and effective insects were honey bees and bumblebees. Muscid flies were considered as important pollinators, particularly due to their relatively high visitation rate. Syrphid flies, Formicidae, and Coleoptera were ineffective in transporting pollen, while the effectiveness of Lepidoptera and Empididae was negligible. A fluorescence labelling experiment revealed that pollen dispersal was restricted (0 - 2 m) in a dense R. ferrugineum stand and decreased in a leptokurtic fashion. This might lead to geitonogamous self-pollination that could explain the close relationship between individuals found in genetic studies of R. ferrugineum. However, some pollen grains may travel 40 - 45 m, which implies the occurrence of cross-pollination through the foraging activities of bumblebees and honey bees.

Animals↗
PubMed2002

Crop pollination from native bees at risk from agricultural intensification.

Ecosystem services are critical to human survival; in selected cases, maintaining these services provides a powerful argument for conserving biodiversity. Yet, the ecological and economic underpinnings of most services are poorly understood, impeding their conservation and management. For centuries, farmers have imported colonies of European honey bees (Apis mellifera) to fields and orchards for pollination services. These colonies are becoming increasingly scarce, however, because of diseases, pesticides, and other impacts. Native bee communities also provide pollination services, but the amount they provide and how this varies with land management practices are unknown. Here, we document the individual species and aggregate community contributions of native bees to crop pollination, on farms that varied both in their proximity to natural habitat and management type (organic versus conventional). On organic farms near natural habitat, we found that native bee communities could provide full pollination services even for a crop with heavy pollination requirements (e.g., watermelon, Citrullus lanatus), without the intervention of managed honey bees. All other farms, however, experienced greatly reduced diversity and abundance of native bees, resulting in insufficient pollination services from native bees alone. We found that diversity was essential for sustaining the service, because of year-to-year variation in community composition. Continued degradation of the agro-natural landscape will destroy this "free" service, but conservation and restoration of bee habitat are potentially viable economic alternatives for reducing dependence on managed honey bees.

Animals↗
PubMed2005

The role of local species abundance in the evolution of pollinator attraction in flowering plants.

We present a population genetic model that incorporates aspects of pollinator efficiency and abundance to examine the effect of the local plant community on the evolution of floral trait specialization. Our model predicts that plant species evolve to be pollinator specialists on the most effective and common pollinators when their abundance is low relative to other plant species in the community (i.e., conspecific pollen is relatively rare) and evolve to be pollinator generalists when they are numerically dominant (i.e., conspecific pollen is abundant). Strong flower constancy also favors generalist floral traits. Furthermore, generalist species are predicted to differentiate when there is a concave trade-off in attracting pollinator species with different floral trait preferences. This result implies that populations that evolve toward a generalist strategy may be more prone to speciation. Ours is the first theoretical model to include local species abundance explicitly, despite the fact that it has been previously identified as an important factor in the evolution of plant specialization. Our results add a layer of ecological complexity to previous models of floral evolution and therefore have the potential to improve our power to predict circumstances under which specialized and generalized plant-pollinator interactions should evolve.

Diploidy↗