Blog - bees
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]
Ragwort is a common wild flower. Its common names include, common ragwort, stinking willie and tansy ragwort (though its resemblance to true tansy is rather superficial). It is not particularly a woodland plant, it is found in dry, open places - on waste land, waysides and (grazing) pastures. It is not a plant favoured by land owners because it has toxic effects on cattle and horses. It is generally considered to be a biennial, but can persist for some years. The stems are erect, straight, basically hairless. The actual plant may grow to a height of two metres. The leaves are lobed in a ‘pinnate’ fashion and have a distinctive smell that has lead to some of its common names - such as stinking willie. The ragwort is a member of the daisy family (Compositae, now the Asteraceae), and its flowers are massed together into dense, flat topped clusters. Each ‘flower’ is made up of many small, individual florets. In the centre are the disc florets whilst around the edge are the ray florets. The latter have a large lip or flap, which serves to increase the visibility of the plant to pollinators. During the flowering season, a plant may produce many thousands of seeds. The seeds have hairs attached to them, which help in dispersal. Ragwort is a plant that is much loved by pollinators - bees, flies, moths and butterflies. It is generous in its nectar production, and has been placed in the top ten of nectar producers by one survey. The plant also provides home and / or a food source for many invertebrate species, some of which feed on ragwort exclusively*, including some species on the IUCN RED LIST. One species that is reliant of this plant is the cinnabar moth, whose status is described as ‘common and widespread, but rapidly declining”. Interestingly, the cinnabar moth feeds on the plant absorbing the alkaloids and these make it distasteful to its predators . However, important as the plant is in ecological terms, it is toxic as it contains a number of alkaloids. These are poisonous to various animals, such as horses and cattle. The bitter taste is a ‘disincentive’ to much of the plant being eaten. However, because of the alkaloids, it is one of the five plants (in the UK) named as ‘an injurious weed’ [as defined by the Weeds Act of 1959]. Some people may suffer an allergic reaction after handling the plant, experiencing a form of dermatitis. [caption id="attachment_38929" align="aligncenter" width="675"] Cinnabar moth, image courtesy of mcbeaner on Pixabay.[/caption] [caption id="attachment_38599" align="alignleft" width="300"] Cinnabar caterpillar[/caption] [caption id="attachment_38566" align="alignright" width="300"] Leaves of Ragwort[/caption]
woodlands web updates 16
LASI is the Laboratory of Apiculture and Social Insects at the University of Sussex. It is particularly noted for its research work on bees. Recently, Dr Balfour and Professor Ratnieks have published a study on the rôle of certain 'injurious weeds'. Five of our native wildflowers fall into this category : Ragwort (Jacobaea vulgaris), Creeping or Field Thistle (Cirsium arvense), Spear or Common Thistle (Cirsium vulgar), Curly Dock (Rumex crispus), and Broadleaved or Common Dock (Rumex obtusifolius). They compared the ragwort and the thistles with plants like red clover and wild marjoram (often encouraged / sown on field edges etc).. They found that the 'injurious weeds' were particularly 'effective' at attracting pollinators, not only did they they attract greater numbers of pollinators than clover etc, but also a greater range of pollinator species. This was ascribed to the open nature of their flowers and their generous nectar production. This brings into question the control of species like the ragwort, as it is clearly important to pollinators (as are some 'botanical thugs' - like brambles). Ragwort contains chemicals that are toxic to livestock, causing liver damage; it has been blamed for the deaths of horses and other animals. At the Smithsonian, Kress and Krupnick have analysed the features of some 80,000+ species of plants to see how they might fare in the Earth's changing climate (the Anthropocene). This may seem like a large number of different plants, but represents approximately only 30% of the known species of vascular plants. There is not enough information of the remaining species to make a reasonable guess as to how they might react to climate change; a reflection on how little we actually known about our 'botanical resources'. Sadly, they conclude that more plants will lose out than win. Particularly at risk of extinction are the Cypress family (which includes the redwoods and junipers) and the Cycads, whereas black cherry might be a winner. As was reported previously in the woodlands blog, there is a difference between the leaves of the redwoods found at the top of the tree and those lower down. Those at the top are small, thick, and fused to the vertical stem axis; this fusion of leaf and stem creates a relatively large volume of tissue and intercellular space that can store water. The leaves in the lower part of the crown by comparison are large, flat and horizontal to the stem axis. Now scientists as the University of California (Davis) have further investigated the role of these leaves. They now believe that the different leaf forms help explain how the exceptionally tall trees are able to survive in both wet and dry parts of their range in California. In the rainy and wet North Coast, the water absorbing leaves are found on the lower branches of the trees. In the Southern part of the redwoods range, the water collecting leaves are found at a higher level to take advantage of the fog (and rain, which occurs less often).
It would seem that pollinators have ‘favourite plants’. Research centred on the National Botanic Garden of Wales has looked in some detail at the foraging habits of bees, bumblebees, hover flies and solitary bees - our most important pollinators. Dr Abigail Lowe identified the plants that the insects were visiting by analysing the DNA from pollen grains on their bodies (a process known as DNA barcoding). It is clear that the ‘preferences’ of the insects change with the seasons and indeed the availability of particular flowers. In Spring, nearly all the pollinators frequent buttercups, lesser celandines and dandelions (all brightly coloured yellow flowers). Come the summer, honey bees and bumblebees tend to favour thistles, knapweeds and brambles, whilst hover flies may be seen on hogweeds and angelica plus thistles and knapweeds. In autumn, the bumblebees can be see visiting asters (Daisy family flowers) and brambles. Full details of her work can be found here : https://botanicgarden.wales/press/plants-for-pollinators-new-dna-research-reveals-fascinating-insights-into-the-plants-used-by-bees-and-hoverflies/ There are also suggestions on how to help pollinators in your garden, such as encourage buttercups and dandelions by reducing mowing (in the Spring) plant late flowering daisy type flowers encourage some bramble (you might get some blackberries, in return) reduce the use of chemicals (especially pesticides and herbicides) hoverflies can be encouraged by damp, wet areas and rotting wood and these suggestions would also work in a woodland. [caption id="attachment_38320" align="aligncenter" width="700"] Marmalade hover fly[/caption]
Drought and pollinators
Climate change is affecting all parts of the world, from the melting of the ice caps in Antarctica, to droughts in Australia and California. On a more local level, we may see changes in our rainfall pattern. Certainly for many parts of the UK, it has been a very dry start to the Spring, coupled with some very cold nights. Cold and dry weather affects plant growth in significant ways. Warmth is needed for a plant’s enzymes (catalysts) to work, speeding up reactions and allowing growth. Similarly, if water is in short supply, growth is stunted; plants do not realise their full ‘potential’. They are smaller overall as is the number and size of flowers that they produce. Flowers attract visitors by colour, size and scent; or combinations thereof. Smaller and fewer flowers, in turn, have ‘knock-on effects’ for their pollinators - bees, bumble bees, hoverflies etc. The effects of drought on pollination has been recently investigated by researchers at Ulm University in Germany. They studied the effect of drought on field mustard (aka Charlock) : Sinapsis arvensis. This is an annual plant that is to be found in fields, waysides and field margins across Europe. It has bright yellow flowers, with four petals. It is visited by many different pollinators (it cannot self-pollinate). The researchers compared the number of visits by bumblebees (Bombus terrestris) to drought-stressed plants to well-watered ones. The data showed that as the number and size of the flowers decreased so did the number of pollinator visits. [caption id="attachment_21589" align="aligncenter" width="600"] Bumblebees also favour the teasels[/caption] The ‘attractiveness’ of the plants / flowers to pollinators was reduced, and it is possible that the smaller flowers were more difficult for relatively large pollinators (like the bumblebees) to ‘deal with’. If pollen movement is reduced, then fewer fruits / seeds will be set and (insect pollinated) plant populations could decline. The effects of reduced rainfall and water stress need to be considered alongside the declining number of pollinators. The reduction in pollen movement has lead some to speculate that it might lead to a selective pressure for self-pollination / self-fertilisation, with plants dispensing with the need for visiting insects. Other Woodlands blogs have reported on the falling numbers of insects / pollinators. Featured image : garlic mustard.
woodlands web updates 10.
Bees and solar parks As the country tries to move towards carbon zero, so we see more and more solar parks / farms ‘springing up’. Whilst they do create clean energy, they also take up a lot of land, and it is important to see if such solar parks can offer other commercial or environmental benefits. One suggestion is to place honeybee hives on such parks. The bees could provide a pollinating service to surrounding crops / farmland. Researchers at Reading and Lancaster Universities have studied detailed land cover maps / crop distribution patterns to estimate the economic value of deploying honeybees in solar parks. Their investigations suggest that a variety of crops from oil seed rape, soft fruits to apples and pears could benefit from such an arrangement. The benefits would vary across the UK, with the benefits being greatest in the East and South of the country. Care would need to be exercised though to ensure the placing of hives did not disturb the foraging of wild pollinators, such as carder bees, hoverflies etc. Are plants sulphur deficient? Much has been written about the importance of plants nutrients, especially NPK; that is to say nitrogen, phosphorus and potassium. However, little is said about sulphur. However, researchers in Groningen, Graz and Cologne have been looking at the effects of sulphur deficiency, particularly in relation to the colour and shape of the flowers formed. The work focused on Brassica rapa, a member of the mustard family. When it was subject to ‘mild’ sulphur stress (by limiting the sulphate in the growth medium), the flowers that formed were smaller and paler - not the usual bright yellow. They were also likely to be mis-shapen. Colour and shape are features by which pollinators recognise flowers and then visit them. Pollen production by the flowers was also affected; smaller pollen grains were formed. This may in turn affect the pollinators who visit the flowers foraging for food. In the relatively recent past, sulphur deficiency may not have been a problem due to acid rain, which would percolate through the soil, forming sulphates. [In the twentieth century, acid rain formed as a result of the release of sulphur dioxide (and nitrogen oxides) into the air through the burning of fossil fuels. However, various clean air acts have ensured that there is now much less SO2 in the air.] Annual rings, water availability and earthquakes. Christian Mohr (scientist from the University of Potsdam) was studying the transport of sediments in rivers in Chile in 2010 when a massive earthquake shook coastal areas of the country. When he was able to return to his studies, he noticed that streams in the valleys were flowing faster. He reasoned that this was because the earthquake has literally shaken up the soil, so that it was now more permeable and ground water could more easily flow down from the ridges. As a result of increased water supply, he thought that trees down in the valleys would grow more than those on the ridges. He and colleagues drilled out plugs of wood from valley trees and ridge trees, and back in Potsdam they examined the tree rings under a microscope. They also looked at the uptake of different isotopes of carbon as a measure of photosynthesis. They found that trees from the valley floor experienced a small but noticeable growth after the earthquake, and this lasted for weeks or months, whereas the trees of the ridges grew more slowly. It is possible that analyses like these, when combined with other information, could help identify significant historic disturbances. Rising temperatures. Recent years have seen periods of very hot temperatures, Such extreme weather events have been seen not only in the UK but across the globe (Arizona , Victoria Australia, Indonesia). Extreme heat (and drought) have been known throughout history, but it would seem that extreme events are now more common. The first two decades of this century are among the warmest on record; this warming is associated with increasing levels of greenhouse gases (due to human activity). Prolonged heat is not without its effects on us, it leads to sweating, teaches, fatigue, dehydration and heat exhaustion. The very young and the elderly are most at risk from ‘heat waves’. A 2003 heatwave across Europe is said to have caused several thousand 'excess' deaths’, mainly of the elderly. Even gradual but sustained warming of the climate can have its effects. For example, Silwood Park (Imperial’s research station) has commented that though it is now November, they have not recorded a single frosty night - normally they would expect to have three in a ‘normal’ October. Snowdrops are appearing earlier, and some migratory species are changing their pattern / timing of migration. Across the world, different species are being affected in different ways. Thick billed murres (type of guillemot, found in and around the Hudson Bay) have a high metabolism to deal with the cold waters into which they dive - they are cold adapted animals. On warm days (when the temperature is 21cC or above) they are dying whilst sitting on their nests - incubating their eggs. They struggle to keep cool, if they spend more time in the water then they leave their eggs exposed to predators (like gulls and arctic foxes). Similarly boreal and arctic bumblebee species are sensitive to heat stress, succumbing to stupor; other work indicates that some European / mediterranean species are now to be found in areas of the arctic circle - as a result of changing climatic ‘norms’. Wild dogs are adapted to deal with heat, but if the temperature goes beyond a certain point they stop hunting, consequently their pups / offspring are less likely to survive. Warming temperatures not only affect animals but they also contribute to the increasing number of harmful algal blooms (in lakes and off shore regions). These blooms can be dangerous to many animals (including humans) and when they die back they ‘suck’ oxygen out of the water - creating ‘dead zones’. One species of alga (Karlodinium veneficum) which is known to produce toxins has been shown to acclimatise to higher temperatures (up to 30cC). As climate change and research continues, we will no doubt see further examples of how animals and plants are being affected by changing temperatures / climate .
Heat, bumblebees and foraging
Silwood Park is part of Imperial College, a postgraduate campus, located some 25 miles west of central London, near Ascot. It is a centre for research and teaching in ecology and allied disciplines. The campus includes areas of wet woodlands, acid grasslands, traditional orchards and parkland. The veteran and ancient trees support an significant number of rare species of insects, lichens and fungi that depend on decaying wood. Silwood is the heart of the wildlife corridors for the surrounding area. Read more...