Blog - bumblebee
Bumblebee pollen collecting
Bumblebees (and bees) collect nectar and pollen. Pollen is a vital food, used in the various stages of a bumblebee’s life. In Spring, newly emerged queens feed on pollen, then it is used to feed its their sister workers. The workers, in turn, take over the feeding of the colony (the larvae and future queens). If not enough pollen is collected, then the colony will not thrive, which can have significant long term effects. Bumblebees are already facing many threats (from habitat fragmentation, agrochemicals and disease). The collection of pollen is a demanding process, and bumblebees will forage over a wide area. They start their pollen collecting activities earlier than many insects as they can warm themselves up by ‘shivering’, that is, rapid muscle contractions which generate heat, warming the insects up ready for flight. Bumblebees can fly in colder conditions and at higher elevations than many other insects. However, research at North Carolina State University has shown that the North American bumblebee (Bombus impatiens) can overheat when exposed to high temperatures (circa 42oC plus). So, if a bee is carrying a significant load of pollen and it is a hot day, its muscles have to work harder and the bee is at risk of overheating. A bumblebee loaded with pollen may be 2oC hotter than an unladen bee; it may be reaching its ‘thermal limit’ - a temperature at which its organs are damaged. Climate change means that many parts of the world are now experiencing extreme weather events, when temperatures can reach into the forties. [caption id="attachment_39978" align="aligncenter" width="675"] Bumblee leaving foxglove[/caption] Increasing temperatures could affect the foraging activities of bumblebees in a significant way - affecting how much pollen is collected and how much pollination takes place. If pollen collection is reduced then colony development is affected and so population numbers will be affected. Bumblebees are key pollinators in natural and agricultural systems, and if their numbers decline there will be ecological and agricultural consequences.
Flowering plants and pollinators
Plants have existed for hundreds of millions of year - as algae, mosses, liverworts, ferns but flowering plants only appeared about 140 million years ago. The exact timing of their appearance is a matter of some debate (see article) They have been a massive evolutionary success, there are perhaps 300,000 to 400,000 species world wide. They reproduce using pollen. This is used to fertilise the ovules and produce viable seeds. Most plants rely on insects to transfer this pollen to the ovules, indeed over 80% of flowering plants have relied on insects for this service. To this end, flowering plants (Angiosperms) have evolved a number of inducements to attract insects : colour, scent and nectar. When we think of pollinators, we generally tend to think of bees, bumblebees, hover flies. But when flowering plants first evolved, fossil evidence suggests that many of these flowers were quite small so it is probably that the first pollinators were also quite small, and hence able to access these small flowers. The first pollinators were probably small flies, midges or beetles (more than 77,000 beetle species are estimated to visit flowers). Quite when bees (and their pollen collecting activities) evolved is not known. A recent analysis of the "family tree" of the families of flowering plants indicates when different plant families evolved and when various forms of pollination emerged. Insect pollination is / was clearly the most common method of pollination, and was probably the first means of pollination. This analysis also indicated that other means of pollination (involving small mammals, birds, bats) have evolved several times, as has wind pollination. Wind pollination seems to have evolved more often in open habitats and at higher altitudes , whereas animal pollination is associated with closed canopy tropical forests. The pollen of insect pollinated flowers is significantly different to that of wind pollinated species. Flowers that are insect pollinated tend to produce pollen that is heavy, 'sticky' and protein-rich. Pollen is an important constituent of the diet of many insects. Wind pollinated species by contrast produce large quantities of pollen, the grains being light and small.
Professor Goulson on allotments, gardens and bees.
I recently attended the National Allotment Society AGM, where the keynote speaker was Professor David Goulson. His main academic studies focus on the threats to bees, bumblebees and other insects. He is based at Sussex University. Back in 2006, he founded the Bumblebee Conservation Trust; a charity which has grown to some 12,000 members. In his talk at the meeting, he made the following points : He loves allotments because they capture carbon and are rich in biodiversity. They produce a lot of food. Typically producing some 10 tonnes / hectare whereas farming productivity is about 3 tonnes per hectare. The record on a 1m2 in an allotment is 10 kg, which is the equivalent of 100 tonnes / hectare. Allotments not only produce good food for healthy eating, but people get good exercise through their gardening activities. A study shows the ‘over-60s’ with allotments have longer life expectancies [controlling for other variables]. [caption id="attachment_40124" align="aligncenter" width="675"] A bee at risk of extinction.[/caption] There are over 300,000 allotment plots in the UK and some 90,000 people on waiting lists. More allotments could help counter poor health and cut NHS costs. We should turn our cities, towns and villages into a network of nature reserves - essentially a form of urban rewilding. Gardens are a vital part of this, as there are some 400,000 hectares of them in Britain. Prof Goulson is really keen on less mowing, more ponds and no pesticides. Interestingly, France banned pesticide use in public and urban areas, such as parks, back in 2014 - it is an example that we should follow. Even pet flea treatment is damaging to insect life. The strength of the doses used means that the chemicals can pass into the environment - to grass, rivers, canals and pools. Sadly, now 8% of gardens have some plastic lawns, and plastic hedges (and Wisteria !). Plastic makes him despair.Plant diversity in pavements should be celebrated. Wild flowers / weeds are sources of pollen & nectar for pollinators. Verges should be nature reserves. A Scottish "On the Verge" group stopped councils mowing 8x a year and planted a seed mix to transform verges in their area. Councils should mow less. Some people may object, so people should strengthen their Council’s hands by writing to them and praising them for no-mow-May-type efforts. The Buzz Club - has been set up, this is a citizen science project to see what works best for insects. There are lots of short films on his youtube channel . Bees and other pollinators need help. He suggested lots of ways to help them, for example, drilling holes in logs for bug hotels. You can follow Prof Goulson on Twitter or Facebook. [caption id="attachment_40132" align="aligncenter" width="675"] Bumblebees 'enjoing' a small clump of poppies[/caption] [caption id="attachment_40129" align="aligncenter" width="428"] urban herbicide use[/caption]
woodlands web updates : 25
Earlier flowering times. A survey has shown that plants are flowering earlier in the year. Cambridge University researchers compared the dates of flowering of some four hundred plus species before and after 1986. They found that plants are now flowering roughly one month earlier. More recent decades have been associated with rising air temperatures. This change in flowering time may have profound consequences for the plants. The vast majority of plants are dependent on pollinating insects (bees, bumblebees, hoverflies) to set seed and complete their life cycles. By flowering early their cycle, plants may not match up with the activities of their pollinators. They may flower but their pollinators bee ‘missing’. Their pollinators need to emerge from their overwintering stage earlier. Earlier flowering may not matter for those plants that are visited by several pollinators but for those that are dependent on one or two specific visitors - it may critical. For example, Sainfoin. Sainfoin is host to a particular (solitary) bee Melitta dimidiata (remote image here). It is a monolectic bee; i.e., a bee that collects food (nectar and pollen) from only one species of flower - the sainfoin. If the sainfoin flowers earlier in the year and the bee does not match the shift in flowering, then the bee has a problem. Work on the effects of climate change on pollinators has been somewhat limited to date, but studies in Japan suggest that bees / bumblebees are somewhat behind plants in their response to environmental changes. Bee and bumblebee news. Recent research data provide evidence that (buff tailed) bumblebees are not able to detect or avoid concentrations of pesticides [imidacloprid, thiamethoxam, clothianidin, or sulfoxaflor], as used ‘on the farm’ - from signals sent by their mouthparts. The mouthparts are covered with tiny hairs and these hairs have ‘pores’ in them. Chemicals pass through these ‘pores’ to sensory cells; this is how the bee tastes and smells. It seems likely that the bumblebees are at considerable risk of consuming pesticides in their search for nectar when visiting pesticide-treated crops. [caption id="attachment_19675" align="alignleft" width="300"] Bumbles foraging in artichoke[/caption] Another agrochemical, Roundup, has been found to affect the learning and memory of bumblebees. Roundup, which contains glyphosate, affects their ability to learn and memorise connections between colour and taste. Impaired colour vision is likely to affect the foraging and nesting success of the bees. The research was conducted in Finland by researchers at the University of Turku. In yet another concerning study, researchers at the University of Maryland have found that the life span of laboratory-raised honey bees has reduced considerably. Five decades ago, the lifespan for a worker honeybee (Apis mellifera) under controlled laboratory conditions was about 34 days. Now it is some 17/ 18 days - according the report in Nature. The study also reviewed the scientific literature [from the 1970s to now] and noted a trend in the life span of bees. Shortened worker bee lifespan has implications for colony health and survivorship. The work at the University of Maryland is ongoing. Methane release. Ghost forests are found in coastal areas. As a consequence of climate change, sea water has ‘invaded’ low laying areas and trees have died. The dead trees are sometimes referred to as ‘snags. A number of woodland / forest communities along the eastern coast of the United States have been affected. Recent work by North Carolina State University has shown that these ghost forests release methane. The methane is generated by bacteria in the soil but then ‘escapes’ by means of the ‘snags’. As it passes through the wood of the ‘snags’, microbes may consume and alter the methane. As methane is a potent greenhouse gas, understanding the nature and extent of these methane emissions from ‘ghost forests’ is important. Tree rings The study of tree rings has been invaluable in dating many historic objects ./ archaeological sites. Now, it seems that they could play a role in estimating the amount of carbon that trees are actually absorbing (carbon sequestration), if woodland / forest inventories are coupled with core samples of the trees. The measurement of the annual rings from such cores could create a record of ‘tree growth across space and time’, yielding a more accurate estimate of the amount of carbon being taken up by woodland and forests. Forests, soils and oceans are major ‘carbon sinks’.
Woodlands web updates 21
Ancient Trees A recent report has emphasised the importance of protecting and preserving ancient trees. Ancient (veteran) oaks can live in excess of a thousand years, as can Yews. The Bristlecones of California and Nevada may live for some five thousand years ! Such trees represent a massive carbon store; the carbon dioxide from the atmosphere being locked away for a millennium or five! Not only are such trees a significant carbon store but they also offer a home or food for many other species - fungi, epiphytes such lichens & mosses, plus larval and adult stages of insects, birds and mammals. As such they localised centres of diversity that contribute to ecosystem stability. Not only are these trees ‘hotspots’ for species diversity but they are also centres of mycorrhizal activity and connectivity. Mycorrhizae represent the symbiosis between fungi and plant. Plants ‘register’ wounding. When we are hurt, our nerves register the pain through the movement of sodium and potassium ions along the nerves. When a plant is wounded, calcium ions are known to move in response, travelling from cell to cell, and leaf to leaf. However, it is now known (through research at the John Innes Centre in Norwich) that this is not the first response of the plant to physical injury. When cells are wounded they release glutamate, a form of glutamic acid. This travels along the cell was and activates channels in the cell membranes that allow the movement of the calcium ions. A bumblebee pathogen. One of parasites of bumblebees is Crithidia bombi. It is a protozoan (single celled animal) that reproduces in the gut of the bumble bee. When infected with this parasite the foraging behaviour of the bee is impaired, as is its ability to learn. A colony will suffer from increased worker mortality. Now research has shown that floral structure may influence the transmission of this parasite from bee to bee. The length and shape of the petals seems to be a critical factor. If the bees ‘crawls’ in a ‘tube’ of petals, then it may leave behind some faeces. If the bee is infected with the parasite, then it will be present in the faeces. If the flower is then listed by another bee then it runs the risk of coming in contact with and being infected with the parasite. Plants that have flowers with shorter petals / corollas are less likely to have faeces deposited within them, and therefore less likely to pass on the parasite to the visiting bumblebees.
Problems for bees and bumblebees.
The decline in many insect populations across the globe is worrying, threatening economies and ecosystems. A German study in 2017 indicated that the mass of flying insects (in various natural areas) had fallen by some 70%+. The decline in insect populations has been associated with habitat fragmentation, the spread of agriculture and the use of pesticides, with the neonicotinoids being particularly associated with damage to bee and bumblebee populations. Recent work at the University of Konstanz suggests that when bumblebee colonies are exposed to limited resources of nectar and exposure to the herbicide - glyphosate, then their colonies may fail. Bumblebee colonies need a good supply of nectar as a ‘fuel’ in order to maintain a constant brood temperature (of approximately 32oC). Only at this sort of temperature does the eggs & larvae develop quickly from egg to adult, and the colony grow from a single queen to several hundred bees. If the temperature is not maintained, then the brood develops slowly or not at all. The loss of wild flowers (and their nectar) plus the use of the herbicide (in agricultural areas) looks to be a problem for the bumblebees. Just as bumblebees are facing problems, so are honey bees. The bees have faced infections with a variety of viruses, such as the deformed wing virus. This virus affects wing development so that the wings are 'stubby' and useless, plus they may be deformities of the abdomen and leg paralysis; the insect cannot function and dies. The virus is transmitted by the Varroa mite - a parasite (that also feeds on the bees’ tissues). The virus was originally identified in Japan in 1980’s and is referred to as DWV-A. However, a new form of the virus (DWV-B) was identified in the Netherlands in 2001 and it is spreading across Europe, and to other continents. Sadly, this variant of the virus kills bees faster and is more easily transmitted (according to research at the Martin Luther University).
If bumblebees are exposed to heat stress during their development (they go through four stages : egg / larva / pupa / adult or imago) their bodies develop asymmetries. The wings in particular are affected, so the left and right wing are shaped differently. This asymmetry can be measured and has been used by a team from the Natural History Museum and Imperial College to investigate how changing climate over time has affected bees. They investigated four species of bumblebee [Bombus hortorum, B. lapidarius, B. pascuorum and B. muscorum] in museum collections that dated back to 1900 CE. The bees were ‘held’ in collections at various museums [Natural History Museum (London), National Museums Scotland (Edinburgh), Oxford University Museum of Natural History, Tullie House Museum and Art Gallery Trust (Carlisle) and World Museum (Liverpool)]. [caption id="attachment_38920" align="alignleft" width="300"] Landing[/caption] Using digital images of many bees collected at different times over the last 130 years, they measured the asymmetry of their wings. The data from these measurements were then correlated with information about annual rainfall and mean annual temperature in the year the bee was collected. It became clear that wing asymmetry was associated with hotter and wetter years; and that each of the bee species displayed greater asymmetry, hence stress, in the second half of the twentieth century. As hotter and wetter conditions are predicted to become more frequent with climate change, it is probable that bumblebees will experience greater stress, indeed they may be in for a ‘rough time’ as this century progresses. Apart from investigating wing asymmetry, the team used a leg from some of the historical specimens to analyse the DNA / genetic make-up of the bumblebees (B. lapidarius). With the DNA data from these bees (dating aback over a century), the Natural History Museum and the Earlham Institute were able to construct a ‘reference genome’ - a standard against which they can see how bee genomes change over time. This may ultimately reveal how bees are adapting (or not) to a changing climate / environment.
Mini-meadows of wild flowers
The decline in insects numbers, especially pollinators is a cause for concern. Insect numbers have fallen as natural ecosystems have been lost or disrupted by the expansion of farming and urbanisation, plus the increased use of pesticides and herbicides. The loss of insects not only affects the pollination of many commercially important plants, but also affects the animals and birds that feed upon insects. So, there are knock on effects throughout food chains and ecosystems. Plantlife has launched a number of initiatives, such as No Mow May, Transforming Road Verges Saving Meadows to help offset the decline in insect numbers. Now work done in Professor Goulson’s laboratory at Sussex Univeristy by Janine Griffiths-Lee (a PhD student) suggests another approach to increasing insect / pollinator levels in urban settings. Her research has demonstrated that creating a small patch of wild flowers in gardens can go some way to address this fall in insects numbers. She and colleagues managed to enlist the help of some 150 volunteers distributed across the UK (many were members of the Buzz Club*). Each volunteer set aside a wild flower area - a mini-meadow (two metres by 2 metres). Some of the volunteers then sowed the mini-meadow area with a commercial seed mix of wild flowers, others sowed a seed mix designed / thought to be ‘beneficial to pollinators’. A third group did not receive wild flowers seeds but were asked to set insect traps and record insects in their gardens in the same way as the two ‘wild flower seed groups’. The results were interesting and revealing. The mini-meadows proved to be resource-rich habitats, with an increased numbers of wild bees, more bumblebees, solitary bees and also wasps (when compared to the control group with no wild flower seed sowing). There were differences in the insect populations for the two groups of seed. The commercial mix attracted more solitary bees and bumblebees, whereas the ‘designer mix’ of seeds attracted more solitary wasps. There was no difference in the number of hoverflies that visited the two types of wild flower rich mini-meadows. Solitary wasps, whilst not pollinators, are important in that they prey on a number of insect pests of fruit and vegetables. Clearly, the planting of small areas in gardens with wild flowers could do much to encourage the numbers and variety of insects / pollinators visiting (or possibly help control the damage done by insects pests). * The Buzz club is a citizen science initiative. The UK has a tradition of using the enthusiasm of volunteers to collect data for ecology research. The Buzz Club projects are focused on gardens - see here. Membership of the Club is free and the research projects are generally involve no cost. You might be asked to supply simple equipment or to cover the cost of sending samples back to the club based at Sussex University. Should you sign up then you will receive : A ‘thank you’ email from the team! Information direct to your inbox of new projects being planned. A newsletter about what your data is telling us. Professor Goulson has previously written a blog about bumblebees for woodlands.co.uk