Bumblebees (
Bombus spp.) have undergone a documented Europe-wide decline in recent years, mostly attributable to destruction of forage and nest sites caused by agricultural intensification. This ...study was set up to quantify species-specific nest-site preferences of observed UK species for various types of field and forest boundary habitat. In total, 1287 observations were made of seven common bumblebee species; nest-searching behaviour was taken as being indicative of nest site preference. There was interspecific variation in preferred habitat, with some species found to be much more specific in their choice of nest site than others. A strong association was found between those species that are known to prefer subterraneous nesting and those habitats that contained banks (
Bombus terrestris,
B. lapidarius and
B. lucorum); other species were strongly associated with tussock-type vegetation (
B. pascuorum,
B. hortorum and
B. ruderarius). In order to safeguard the continued existence of bumblebee species it is clear that a variety of field and forest boundary types need to be conserved; this has positive implications for the conservation of other species of flora and fauna associated with agroecosystems.
The negative effect of agricultural intensification on bumblebee populations is thought to partly be caused by loss of food plants, for example because of increased field size and concomitant loss of ...non-crop field borders and their nectar and pollen plants. Earlier studies have focused on how loss of foraging resources affects colony growth and thereby abundance of workers and sexual reproduction. By comparing bumblebees in agricultural landscapes of different complexity in Southern Sweden, we here demonstrate that also the adult size of bumblebee foragers is significantly related to the availability of foraging resources. This effect was independent of both species identity and foraging habitat type. This suggests a shortage of flower resources in landscapes of lower complexity, which may also affect the reproductive success of colonies negatively.
Es wird angenommen, dass der negative Einfluss der landwirtschaftlichen Intensivierung auf Hummelpopulationen teilweise durch einen Verlust an Nahrungspflanzen hervorgerufen wird, beispielsweise wegen höherer Feldgrößen und dem damit verbundenen Verlust an Feldrändern und ihren Nektar- und Pollenpflanzen. Frühere Untersuchungen haben sich darauf konzentriert, wie der Verlust von Nahrungspflanzen das Koloniewachstum und damit Arbeiterabundanz und sexuelle Reproduktion beeinflusst. Indem wir Hummeln in südschwedischen Agrarlandschaften von unterschiedlicher Komplexität miteinander verglichen, zeigen wir, dass auch die Körpergröße von Hummelarbeiterinnen signifikant mit der Verfügbarkeit von Ressourcen verbunden ist. Dieser Effekt war unabhängig von der Artzugehörigkeit und dem Typ des Nahrungshabitats. Dies legt nahe, dass in Landschaften von geringer Komplexität ein Mangel an Blütenressourcen herrscht, der auch den reproduktiven Erfolg der Kolonien negativ beeinflussen könnte.
This study, conducted in 2008 and 2012 - 2013, evaluated the flowering pattern (seasonal and diurnal), the abundance of flowering, nectar, and pollen yield, and insect visitor activity for Corydalis ...solida (L.) Clairv. and C. cava Schweig. et Koerte. The populations occur in the ground layer of a deciduous forest (Fagetalia ordo, Querco-Fagetea class) in a natural gorge within the current area of the UMCS Botanical Garden in Lublin, Poland (51° 16â N, 22° 30â E). The phenology of Corydalis species showed distinct year-to-year plasticity (e.g., blooming period in March - April or in April - May; duration 18 - 42 days). The most intensive flower opening was noted in the early morning hours (85 - 90% of daily openings occurred between 6.00 and 10.00 h, GMT +2 h). The average sugar yield was similar at 4.6 kg/ha (C. cava) and 5.2 kg/ha (C. solida), but the average pollen production differed and reached 2.1 kg/ha (C. cava) and 4.1 kg/ha (C. solida). The flower-visitor interaction in Corydalis species involved both biological (early pattern of diurnal flowering, protandry, pollen presentation at the moment of anthesis) and morphological (nectar hidden in deep spur) features. Apis mellifera foragers predominated on both Corydalis species (mean of total visitors, 68.0% to C. solida; 62.5% to C. cava) and foraged mainly for pollen (82% of foragers), while bumblebee queens (mean of total visitors, 32.0% to C. solida; 37.5% to C. cava) collected mainly nectar (68.0% of foragers).
Higher trophic level species such as parasites, parasitoids, and pathogens are frequently ignored in community studies, despite playing key roles in the structure, function, and stability of ...ecological communities. Furthermore, such species are typically among the last in a community to reestablish due to their reliance upon lower trophic level resources and a requirement for persistent, stable ecological conditions. Consequently their presence alone can be indicative of healthy ecosystems. Using replicated, quantitative food webs we studied the impacts of a restoration treatment upon the interactions of a tri-trophic community consisting of plants, their bumble bee pollinators, and the parasites, parasitoids, and pathogens of the bumble bees at heathland sites. We found the lower trophic levels of the community successfully reinstated at restored relative to control sites. However the abundance, load per host, prevalence of parasitism, prevalence of superparasitism, and host range of a key dipteran parasitoid of the family Conopidae were all significantly reduced in restored heathlands. Potential causes for this incomplete reestablishment at restored sites include the lag in floral resources due to differences in floral species composition, and the reduced ability of this parasitoid species in accessing host resources relative to other natural enemy species present in these communities. Moreover the incomplete reinstatement of the natural enemy community was found to significantly reduce levels of network vulnerability (a measure of how vulnerable prey is to being consumed) at restored sites relative to ancient, control networks.
We present two methods for observing bumblebee choice behavior in an enclosed testing space. The first method consists of Radio Frequency Identification (RFID) readers built into artificial flowers ...that display various visual cues, and RFID tags (i.e., passive transponders) glued to the thorax of bumblebee workers. The novelty in our implementation is that RFID readers are built directly into artificial flowers that are capable of displaying several distinct visual properties such as color, pattern type, spatial frequency (i.e., "busyness" of the pattern), and symmetry (spatial frequency and symmetry were not manipulated in this experiment). Additionally, these visual displays in conjunction with the automated systems are capable of recording unrewarded and untrained choice behavior. The second method consists of recording choice behavior at artificial flowers using motion-sensitive high-definition camcorders. Bumblebees have number tags glued to their thoraces for unique identification. The advantage in this implementation over RFID is that in addition to observing landing behavior, alternate measures of preference such as hovering and antennation may also be observed. Both automation methods increase experimental control, and internal validity by allowing larger scale studies that take into account individual differences. External validity is also improved because bees can freely enter and exit the testing environment without constraints such as the availability of a research assistant on-site. Compared to human observation in real time, the automated methods are more cost-effective and possibly less error-prone.
Eusociality and male haploidy of bumblebees (
Bombus spp.
) enhance the deleterious effects of population decline and aggravate the degeneration of population fitness compared to solitary and diploid ...species. The highly dispersive male sex may be the prime driver to connect otherwise isolated populations. We therefore studied the temporal and spatial structure of the male population of
Bombus terrestris
(Linnaeus 1758) and
Bombus lapidarius
(Linnaeus 1758) using microsatellite DNA markers. We found that the majority of the males in a 1000 m² sampling area originated from colonies located outside of the workers foraging range, which was consistent with the genetic distances among colonies. The analyses of temporal population sub-structure based on both colony detection rate over time and the clustering software STRUCTURE consistently suggested one large and temporally unstructured male population. Our results indicate an extended male flight distance for both species. Though the range of queen dispersal remains to be studied, the effective size (
N
e
) of bumblebees is increased by extended male mating flight ranges (
A
m
) exceeding worker foraging distance by factor 1.66 (
A
m
= 69.75 km
2
) and 1.74 (
A
m
= 13.41 km
2
),
B. terrestris
and
B. lapidarius
, respectively. Thus this behaviour may counteract genetic deprivation and its effects. All populations were genetically highly diverse and showed no signs of inbreeding. We discuss the implications of our findings in context of bumblebee population dynamics and conservation. We also highlight the effects and benefits of sampling both workers and males for population genetic studies.
Exotic plant invasions threaten ecological communities world-wide. Some species are limited by a lack of suitable pollinators, but the introduction of exotic pollinators can facilitate rapid spread. ...In Tasmania, where many non-native plants are naturalised, exotic honeybees (Apis mellifera) and bumblebees (Bombus terrestris) have become established. We determined how these species affect the pollination of Lupinus arboreus, an invasive, nitrogen-fixing shrub, which is rarely visited by native pollinators. The proportion of flowers setting seed and the number of ovules fertilised per flower were positively related to the visitation rates of both exotic bee species. There was no effect of bee visitation rates on the proportion of seeds aborted prior to maturity, possibly due to post-fertilisation environmental constraints. We conclude that the spread of B. terrestris may not alter the fecundity of L. arboreus because of the pollination service provided by A. mellifera, and discuss potential interactions between these two bee species.
Flowering phenology, diurnal dynamics of blooming, insect visitation and pollen production in Aconitum lycoctonum L. and Aconitum carmichaelii Debeaux were investigated in 2012–2013 in the Lublin ...area, SE Poland. Flowering of A. lycoctonum occurred in June/July, whereas A. carmichaelii bloomed in September/October. Both Aconitum species differed in terms of the diurnal pattern of flowering. The flowers of A. lycoctonum started opening at 5.00, whereas those of A. carmichaelii started blooming at 8.00 (GMT+2h). The species differed in the number of anthers per flower, the size of anthers, and the mass of pollen produced in anthers. As a result, the flowers of A. lycoctonum produced less pollen (mean = 1.0 mg per 10 flowers) than the flowers of A. carmichaelii (mean = 8.2 mg per 10 flowers). The estimated pollen yield was 0.2 g per m2 for A. lycoctonum and 1.6 g per m2 for A. carmichaelii. The flowers of both Aconitum species were foraged exclusively by bumblebees with the predominance of the long-tongued Bombus hortorum. Nectar was a more attractive floral reward than pollen. The propagation of Aconitum lycoctonum and A. carmichaelii in ornamental gardens may support the conservation of bumblebees whose populations are steadily declining.
A polymerase chain reaction (PCR) based method was developed for the specific and sensitive diagnosis of the microsporidian parasite
Nosema bombi in bumble bees (
Bombus spp.). Four primer pairs, ...amplifying ribosomal RNA (rRNA) gene fragments, were tested on
N. bombi and the related microsporidia
Nosema apis and
Nosema ceranae, both of which infect honey bees. Only primer pair Nbombi-SSU-Jf1/Jr1 could distinguish
N. bombi (323
bp amplicon) from these other bee parasites. Primer pairs Nbombi-SSU-Jf1/Jr1 and ITS-f2/r2 were then tested for their sensitivity with
N. bombi spore concentrations from 10
7 down to 10 spores diluted in 100
μl of either (i) water or (ii) host bumble bee homogenate to simulate natural
N. bombi infection (equivalent to the DNA from 10
6 spores down to 1 spore per PCR). Though the
N. bombi-specific primer pair Nbombi-SSU-Jf1/Jr1 was relatively insensitive, as few as 10 spores per extract (equivalent to 1 spore per PCR) were detectable using the
N. bombi-non-specific primer pair ITS-f2/r2, which amplifies a short fragment of ∼120
bp. Testing 99 bumble bees for
N. bombi infection by light microscopy versus PCR diagnosis with the highly sensitive primer pair ITS-f2/r2 showed the latter to be more accurate. PCR diagnosis of
N. bombi using a combination of two primer pairs (Nbombi-SSU-Jf1/Jr1 and ITS-f2/r2) provides increased specificity, sensitivity, and detection of all developmental stages compared with light microscopy.
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