Honeybee colonies compensate for pesticide-induced effects on royal jelly composition and brood survival with increased brood production.

Sublethal doses of pesticides affect individual honeybees, but colony-level effects are less well understood and it is unclear how the two levels integrate. We studied the effect of the neonicotinoid pesticide clothianidin at field realistic concentrations on small colonies. We found that exposure to clothianidin affected worker jelly production of individual workers and created a strong dose-dependent increase in mortality of individual larvae, but strikingly the population size of capped brood remained stable.

Time-dependent effects on bumble bees of dietary exposures to farmland insecticides (imidacloprid, thiamethoxam and fipronil).

Background: Farmland bees encounter insecticides in their diet when visiting the flowers of pesticide-treated crops with residues in nectar and pollen. A sustained exposure to even trace residues could be severely harmful if the ingested substance has a long biological half-life and its toxicity therefore intensifies over time, which is termed time-reinforced toxicity (TRT). Bumble bees are important farmland pollinators, but their susceptibility to TRT from insecticides has not been established previously.

Apomixis and Hybridization Drives Reticulate Evolution and Phyletic Differentiation in L.: Implications for Conservation.

Hybridization and polyploidy are major forces in the evolution of plant diversity and the study of these processes is of particular interest to understand how novel taxa are formed and how they maintain genetic integrity. is an example of a genus where active diversification and speciation are ongoing and, as such, represents an ideal model to investigate the roles of hybridization, polyploidy and apomixis in a reticulate evolutionary process. To elucidate breeding systems and evolutionary origins of a complex of closely related taxa, we assessed genotypic diversity and population structure within and among taxa, combining data from nuclear DNA microsatellite markers and flow cytometry.

Fipronil pesticide as a suspect in historical mass mortalities of honey bees.

Mass mortalities of honey bees occurred in France in the 1990s coincident with the introduction of two agricultural insecticides, imidacloprid and fipronil. Imidacloprid, a neonicotinoid, was widely blamed, but the differential potency of imidacloprid and fipronil has been unclear because of uncertainty over their capacity to bioaccumulate during sustained exposure to trace dietary residues and, thereby, cause time-reinforced toxicity (TRT). We experimentally quantified the toxicity of fipronil and imidacloprid to honey bees and incorporated the observed mortality rates into a demographic simulation of a honey bee colony in an environmentally realistic scenario.

Dominance of cropland reduces the pollen deposition from bumble bees.

Intensive agricultural landscapes can be hostile for bees due to a lack of floral and nesting resources, and due to management-related stress such as pesticide use and soil tillage. This threatens the pollination services that bees deliver to insect-pollinated crops. We studied the effects of farming intensity (organic vs.

The effect of dietary neonicotinoid pesticides on non-flight thermogenesis in worker bumble bees (Bombus terrestris).

For bumble bees (genus Bombus), the capacity for non-flight thermogenesis is essential for two fundamental processes undertaken by adult workers, namely recovery from torpor after chilling and brood incubation. Farmland bees can be widely exposed to dietary residues of neurotoxic neonicotinoid insecticides that appear in the nectar and pollen of treated bee-attractive crops, which may harm them. An earlier study shows that dietary neonicotinoids cause complex alterations to thermoregulation in honey bees, but their effect on the thermogenic capabilities of individual bumble bees has been untested previously.

Synergistic interactions between a variety of insecticides and an ergosterol biosynthesis inhibitor fungicide in dietary exposures of bumble bees (Bombus terrestris L.).

Background: In recent years, concern has been raised over honey bee colony losses, and also among wild bees there is evidence for extinctions and range contractions in Europe and North America. Pesticides have been proposed as a potential cause of this decline. Bees are exposed simultaneously to a variety of agrochemicals, which may cause synergistically detrimental impacts, which are incompletely understood.

Sensitivity of commercial pumpkin yield to potential decline among different groups of pollinating bees.

The yield of animal-pollinated crops is threatened by bee declines, but its precise sensitivity is poorly known. We therefore determined the yield dependence of Hokkaido pumpkin in Germany on insect pollination by quantifying: (i) the relationship between pollen receipt and fruit set and (ii) the cumulative pollen deposition of each pollinator group. We found that approximately 2500 pollen grains per flower were needed to maximize fruit set.

Breeding system and spatial isolation from congeners strongly constrain seed set in an insect-pollinated apomictic tree: Sorbus subcuneata (Rosaceae).

In plants, apomixis results in the production of clonal offspring via seed and can provide reproductive assurance for isolated individuals. However, many apomicts require pollination to develop functional endosperm for successful seed set (pseudogamy) and therefore risk pollination-limitation, particularly in self-incompatible species that require heterospecific pollen. We used microsatellite paternity analysis and hand pollinations to investigate pollen-limitation in Sorbus subcuneata, a threatened endemic tree that co-occurs with its congener, S.

Effects of the neonicotinoid pesticide thiamethoxam at field-realistic levels on microcolonies of Bombus terrestris worker bumble bees.

Neonicotinoid pesticides are currently implicated in the decline of wild bee populations. Bumble bees, Bombus spp., are important wild pollinators that are detrimentally affected by ingestion of neonicotinoid residues.

Repression and recuperation of brood production in Bombus terrestris bumble bees exposed to a pulse of the neonicotinoid pesticide imidacloprid.

Currently, there is concern about declining bee populations and some blame the residues of neonicotinoid pesticides in the nectar and pollen of treated crops. Bumble bees are important wild pollinators that are widely exposed to dietary neonicotinoids by foraging in agricultural environments. In the laboratory, we tested the effect of a pulsed exposure (14 days 'on dose' followed by 14 days 'off dose') to a common neonicotinoid, imidacloprid, on the amount of brood (number of eggs and larvae) produced by Bombus terrestris L.

Clearance of ingested neonicotinoid pesticide (imidacloprid) in honey bees (Apis mellifera) and bumblebees (Bombus terrestris).

Background: Bees in agricultural landscapes are exposed to dietary pesticides such as imidacloprid when they feed from treated mass-flowering crops. Concern about the consequent impact on bees makes it important to understand their resilience. In the laboratory, the authors therefore fed adult worker bees on dosed syrup (125 μg L(-1) of imidacloprid, or 98 μg kg(-1)) either continuously or as a pulsed exposure and measured their behaviour (feeding and locomotory activity) and whole-body residues.

Differential sensitivity of honey bees and bumble bees to a dietary insecticide (imidacloprid).

Currently, there is concern about declining bee populations and the sustainability of pollination services. One potential threat to bees is the unintended impact of systemic insecticides, which are ingested by bees in the nectar and pollen from flowers of treated crops. To establish whether imidacloprid, a systemic neonicotinoid and insect neurotoxin, harms individual bees when ingested at environmentally realistic levels, we exposed adult worker bumble bees, Bombus terrestris L.

Comment on "A common pesticide decreases foraging success and survival in honey bees".

Henry et al. (Reports, 20 April, p. 348) used a model to predict that colony collapse in honey bees could be precipitated by pesticide-induced intoxication that disrupts navigation.

Effects of imidacloprid, a neonicotinoid pesticide, on reproduction in worker bumble bees (Bombus terrestris).

Bumble bees are important pollinators whose populations have declined over recent years, raising widespread concern. One conspicuous threat to bumble bees is their unintended exposure to trace residues of systemic neonicotinoid pesticides, such as imidacloprid, which are ingested when bees forage on the nectar and pollen of treated crops. However, the demographic consequences for bumble bees of exposure to dietary neonicotinoids have yet to be fully established.

Dietary traces of neonicotinoid pesticides as a cause of population declines in honey bees: an evaluation by Hill's epidemiological criteria.

Background: Honey bees are important pollinators of both crops and wild plants. Pesticide regimes that threaten their sustainability should therefore be assessed. As an example, evidence that the agricultural use of neonicotinoid pesticides is a cause of the recently observed declines in honey bees is examined.

A meta-analysis of experiments testing the effects of a neonicotinoid insecticide (imidacloprid) on honey bees.

Honey bees provide important pollination services to crops and wild plants. The agricultural use of systemic insecticides, such as neonicotinoids, may harm bees through their presence in pollen and nectar, which bees consume. Many studies have tested the effects on honey bees of imidacloprid, a neonicotinoid, but a clear picture of the risk it poses to bees has not previously emerged, because investigations are methodologically varied and inconsistent in outcome.

Conifer ovulate cones accumulate pollen principally by simple impaction.

In many pine species (Family Pinaceae), ovulate cones structurally resemble a turbine, which has been widely interpreted as an adaptation for improving pollination by producing complex aerodynamic effects. We tested the turbine interpretation by quantifying patterns of pollen accumulation on ovulate cones in a wind tunnel and by using simulation models based on computational fluid dynamics. We used computer-aided design and computed tomography to create computational fluid dynamics model cones.

Effect of pollinator abundance on self-fertilization and gene flow: application to GM Canola.

Cross-pollination from fields of transgenic crops is of great public concern. Although cross-pollination in commercial canola (Brassica napus) fields has been empirically measured, field trials are expensive and do not identify the causes of cross-pollination. Therefore, theoretical models can be valuable because they can provide estimates of cross-pollination at any given site and time.

The effect of wind direction on cross-pollination in wind-pollinated GM crops.

In Europe, regulatory thresholds restrict adventitious GM (genetically modified) presence in conventional crops. Minimum distances for the spatial separation of fields are often recommended to reduce field-to-field cross-pollination to an acceptable level. Field trials are typically the basis for setting separation distances.

A search theory model of patch-to-patch forager movement with application to pollinator-mediated gene flow.

We present a spatially implicit analytical model of forager movement, designed to address a simple scenario common in nature. We assume minimal depression of patch resources, and discrete foraging bouts, during which foragers fill to capacity. The model is particularly suitable for foragers that search systematically, foragers that deplete resources in a patch only incrementally, and for sit-and-wait foragers, where harvesting does not affect the rate of arrival of forage.

The potential for adaptive evolution of pollen grain size in Mimulus guttatus.

We tested whether pollen grain size (PGS) shows heritable variation in three independent populations of Mimulus guttatus by imposing artificial selection for this character. In addition, we looked for correlated responses to selection in a range of 15 other floral characters. Heritable variation in PGS was found in all three populations, with heritabilities of between 19 and 40% (average 30%).

The influence of genotypic variation on metabolite diversity in populations of two endophytic fungal species.

The relationship between metabolite production and genotypic diversity in two endophytic fungi was investigated. We selected populations of Cylindrocarpon destructans and Heliscus lugdunensis from the roots of a single tree. A total of 49 isolates of both species were selected and classified by simple genotypic tests (random amplified polymorphic DNA analysis and rDNA-ITS sequencing).

Towards the theory of pollinator-mediated gene flow.

I present a new exposition of a model of gene flow by animal-mediated pollination between a source population and a sink population. The model's parameters describe two elements: (i) the expected portion of the source's paternity that extends to the sink population; and (ii) the dilution of this portion by within-sink pollinations. The model is termed the portion-dilution model (PDM).

Morphological correlates of necromass accumulation in the traps of an Eastern tropical pitcher plant, Nepenthes ampullaria Jack, and observations on the pitcher infauna and its reconstitution following experimental removal.

I studied the trap morphology, necromass accumulation rates and pitcher infauna of an eastern tropical pitcher plant, Nepenthes ampullaria, that grew in `kerangas' heath forest in the Sungei Ingei Conservation Area, Brunei. I surveyed 164 pitchers distributed among 35 plants and extracted the necromass and larval infauna from the pitchers and then resampled the pitcher contents after 14 days. Plants varied significantly in the morphology of their pitchers, in their rate of necromass accumulation per pitcher and in the abundance and composition of the pitcher infaunas.