33 research outputs found
Loss of Developmental Diapause as Prerequisite for Social Evolution in Bees
Diapause is a physiological arrest of development ahead of adverse environmental conditions and is a critical phase of the life cycle of many insects. In bees, diapause has been reported in species from all seven taxonomic families. However, they exhibit a variety of diapause strategies. These different strategies are of particular interest since shifts in the phase of the insect life cycle in which diapause occurs have been hypothesized to promote the evolution of sociality. Here we provide a comprehensive evaluation of this hypothesis with phylogenetic analysis and ancestral state reconstruction (ASR) of the ecological and evolutionary factors associated with diapause phase. We find that social lifestyle, latitude and voltinism are significant predictors of the life stage in which diapause occurs. ASR revealed that the most recent common ancestor of all bees likely exhibited developmental diapause and shifts to adult, reproductive, or no diapause have occurred in the ancestors of lineages in which social behaviour has evolved. These results provide fresh insight regarding the role of diapause as a prerequisite for the evolution of sociality in bees
Pervasiveness of Parasites in Pollinators
Many pollinator populations are declining, with large economic and ecological
implications. Parasites are known to be an important factor in the some of the
population declines of honey bees and bumblebees, but little is known about the
parasites afflicting most other pollinators, or the extent of interspecific
transmission or vectoring of parasites. Here we carry out a preliminary
screening of pollinators (honey bees, five species of bumblebee, three species
of wasp, four species of hoverfly and three genera of other bees) in the UK for
parasites. We used molecular methods to screen for six honey bee viruses,
Ascosphaera fungi, Microsporidia, and
Wolbachia intracellular bacteria. We aimed simply to detect
the presence of the parasites, encompassing vectoring as well as actual
infections. Many pollinators of all types were positive for
Ascosphaera fungi, while Microsporidia were rarer, being
most frequently found in bumblebees. We also detected that most pollinators were
positive for Wolbachia, most probably indicating infection with
this intracellular symbiont, and raising the possibility that it may be an
important factor in influencing host sex ratios or fitness in a diversity of
pollinators. Importantly, we found that about a third of bumblebees
(Bombus pascuorum and Bombus terrestris)
and a third of wasps (Vespula vulgaris), as well as all honey
bees, were positive for deformed wing virus, but that this virus was not present
in other pollinators. Deformed wing virus therefore does not appear to be a
general parasite of pollinators, but does interact significantly with at least
three species of bumblebee and wasp. Further work is needed to establish the
identity of some of the parasites, their spatiotemporal variation, and whether
they are infecting the various pollinator species or being vectored. However,
these results provide a first insight into the diversity, and potential
exchange, of parasites in pollinator communities
Towards a sustainable management of bees of the subgenus Osmia (Megachilidae; Osmia) as fruit tree pollinators
International audienceThe limited pollination efficiency of honeybees (Apidae; Apis) for certain crop plants and, more recently, their global decline fostered commercial development of further bee species to complement crop pollination in agricultural systems. In particular, a number of mason bees (Megachilidae; Osmia) are among the most widely used alternative pollinators, and their utilisation has been fine-tuned specifically for pollination in fruit tree orchards. A successful management system should not only aim at optimising pollination efficiency but also consider the relevant biological and ecological requirements to achieve sustainable and healthy bee populations. Here, we review the factors influencing the rate of population increase during the implementation of Osmia bees as orchard pollinators. These factors include nesting material, release methods, and control of antagonists as well as methods optimising management of developmental stages to synchronize bee activity with orchard bloom and to minimize developmental mortality
Combined exposure to sublethal concentrations of an insecticide and a fungicide affect feeding, ovary development and longevity in a solitary bee
Alcohol consumption and non-cirrhotic chronic hepatitis: a case-control study
We carried out a hospital-based case-control study to assess the association of both the daily amount and the duration of alcohol intake with the risk of developing non-cirrhotic chronic liver disease (chronic hepatitis) in 121 chronic hepatitis patients diagnosed by laparoscopy and liver biopsy, and in 242 matched 'controls' randomly selected from inpatients of the same hospital. Alcohol intake was quantified in all subjects using a standardized questionnaire administered by two doctors unaware of the aim of the study. The odds ratio (OR) for chronic hepatitis was estimated by conditional logistic regression and increased exponentially from 1.0 for non-drinkers to 11.4 for daily alcohol intake of 325 g or more. Considering duration of alcohol consumption from up to 10 to up to 30 years, the ORs for chronic hepatitis consistently decreased for the daily alcohol intake categories of 25-50 g (from 74.1 to 0.7 respectively), 75-100 g (from 149.7 to 0.7 respectively) and 125 g or more (from 212.0 to 1.8 respectively). Our results suggest the existence of a dose-dependent individual susceptibility to the damaging effect of alcohol on the liver