by Dave Goulson
Our bumper data set of bee visits to flowers also allowed me to investigate a different question, relating to competition between bumblebees. When I was an undergraduate, I was taught about a classic study conducted on the bumblebees of Colorado in the 1970s by an Australian named Graham Pyke. He hiked up and down mountains counting bumblebees in a rather similar way to our surveys of the Polish mountains, but he had a different interest. He was looking for evidence that bumblebees compete with one another. Bumblebees of different species all tend to be pretty similar in shape, size and in their basic biology. Of course some are a little smaller or larger, or more or less furry, and they differ in colour, but they are all flying about together feeding on broadly the same resources – flowers. Back in the 1930s, a Russian ecologist named Georgy Gause had proposed the ‘competitive exclusion principle’, which eventually became known as Gause’s Law. This states that two species that use exactly the same resources (which might be food, nest sites or anything else needed for survival) cannot coexist. The point is that whichever is the superior competitor will win the competitive battle, and exclude its rival. He demonstrated this in lab experiments using two species of Paramecium, microscopic freshwater protozoans related to Amoeba. In any particular conditions of water quality and food availability one or other of his types of Paramecium would always eventually win out. Bumblebees seemed like an interesting system to see whether such things happened in the real world, and this is what Pyke set out to discover.
Pyke gathered data on which species of bumblebee occurred at different altitudes as he climbed up each of a number of mountains, and he discovered that there were only ever three or four species found in abundance in any particular mountain meadow. When he looked at them more closely, he found that there was always one short-tongued species, one with a medium tongue and one with a long tongue. As you might expect, the short-tongued bees fed on shallow flowers, the long-tongued bees fed mainly on deep flowers, and the bees with medium-length tongues fed mostly on flowers that were in between, so that the three species carved up the available flower resources between them and avoided competition. The particular species that were present changed with altitude, and sometimes from mountain to mountain. In addition, a fourth species, the western bumblebee, was also present at most sites, but this is a nectar robber like the red-tailed robber bee in Poland. Moreover, the western bumblebee specialised in stealing nectar from very deep flowers normally visited by hummingbirds, so it didn’t compete at all with the other species. Pyke’s data suggested that Gause was correct – bumblebee communities were structured by competition, so that species with similar tongue lengths did not coexist. Only species that differed in tongue length – and so tended to visit different flowers – could thrive together. One can make parallels with Darwin’s finches, where the different species have evolved different shaped bills to carve up the resources between them and minimise competition – some have long thin bills for gleaning insects, others slightly fatter bills for crushing small seeds, and still others have fat bills for crunching big seeds and nuts.
Our Polish data didn’t seem to fit Gause’s Law. We had found up to fifteen species living alongside one another, sometimes in a single meadow. Admittedly, for the long-tongued bees only one species, the garden bumblebee, was usually common, with just a few ruderal bumblebees turning up alongside them. Similarly, the common carder was usually by far the most abundant of the medium-tongued bees, even though there were quite a few shrill, red-shanked and brown-banded carders about. But amongst the short-tongued bees there were often four or five common species living together – buff-tails, white-tails, early, tree and broken-banded bumblebees. According to Gause, one species should have outcompeted all the others. As they say in the film Highlander, ‘There can be only one.’ So what was going on?
When I looked more closely at the flowers that they were visiting, it turned out that these short-tongued bees actually did tend to visit different flowers, though there was quite a bit of overlap. White-tailed bumblebees were often on umbellifers (hog-weed, angelica, and so on), which the others seemed to avoid. The tree bumblebees went mad for willowherb, while the broken-banded bumblebees were very keen on knapweeds (we saw very few harebells in Poland, the flower they had historically favoured in the Netherlands, UK and Belgium). Even though the different species are equipped with near-identical mouthparts, the bees were somehow dividing up the resources and minimising competition. Quite how they arrived at this equitable distribution of resources we don’t know. We also have no idea why this doesn’t happen in Colorado. It could possibly be because bumblebees have lived in Europe for thirty to forty million years, while they have only been in America for about twenty million years, so perhaps they have had more time to evolve into more specialised niches here. I don’t find this idea particular convincing, since twenty million years is surely quite a long time in anyone’s book, but it is the best idea that I have managed to come up with so far. There is so much that we still do not understand about the way communities of animals and plants interact with one another.
These comparisons highlighted just how rich the Polish bumblebee community is compared to what remains in the UK. Of course the Gorce Mountains are far from an exact replica of what Britain used to be like before intensive farming, but they perhaps give some idea. I think that Frederick Sladen would have felt quite at home, at least as far as the abundance of different bees and flowers are concerned. I’m not so sure how he would have felt about all the sausages.
I would not wish to condemn the farmers of this region to a life of back-breaking labour, but I hope that this backwater of rural life has remained unchanged since I visited. It may sound patronising, but there was no obvious poverty, and the people we met seemed happy enough. Like crofters in the Uists, they live in a beautiful, unspoiled place, eating healthy food, much of it grown by themselves or their near-neighbours. Are they better or worse off than those of us who spend our days commuting through traffic to work, then sitting at a workstation or in a meeting while daydreaming of our annual holiday to a Greek island? I don’t know the answer to that question, but purely from the perspective of the bees I hope things have not changed, though I fear that change is inevitable. Just as in the Outer Hebrides, I wonder if young folk will be content to take over their small family farm in rural Poland. What’s more, major external factors are at play – Poland joined the European Union in 2004, two years before our visit. The Common Agricultural Policy must be a contender for one of the most unfair, opaque and perverse bundles of legislation ever concocted by man, and I fear that it may bring an end to the extraordinary biodiversity that has until recently thrived in parts of Poland and elsewhere in Eastern Europe. The CAP was introduced in the late 1950s, with the primary goal of increasing food production through subsidies for modernisation of farming and guaranteed prices for crops, regardless of demand. This goal seems laudable, particularly in the context of a Europe that had seen nearly two decades of food rationing and shortages brought on by the Second World War. The downsides of the policies were that we subsidised the destruction of the European countryside to make way for industrial farming, created huge surpluses of food, flooded the world market with cheap, subsidised produce, and gave EU farmers an artificial advantage over farmers in developing countries, thus condemning millions of farmers elsewhere in the world to a life of poverty. The CAP has been revised countless times, but has not fundamentally changed. In essence, it still involves taking staggering amounts of EU taxpayers’ money and using it to subsidise industrial farming, giving the bulk of it to multinational farming corporations and Europe’s major landowners, all of whom are already pretty well off by anyone’s standards, while giving tiny amounts to small-scale farmers, those striving for more sustainable food production and farms in marginal areas – the ones that might justifiably deserve our support. Land-grabbing – the buying up of large tracts of farmland by multinationals, usually accompanied by the displacement of local people and industrial-scale
farming – is something associated mainly with Africa and South America, but in recent years it has begun across Eastern Europe, particularly in countries such as Romania, Serbia, Hungary and Ukraine. In Poland, purchase of land by foreign corporations requires a special permit, but this law expired in 2016 so it will be possible for multinational farming corporations to buy up land, which remains cheap, and roll out their industrial model of farming, while being heavily subsidised by us taxpayers. In February 2015, Polish farmers used their tractors to block roads across the country in protest at these threats to their livelihoods, but whether they can hold back the tide of ‘progress’ remains unclear.
There is a positive side to this story. The fact that taxpayers’ money is used to subsidise farming across Europe means that taxpayers have every right to demand a say in how that money is spent. With a major overhaul to redirect funds from large corporations to small-scale farmers, to encourage sustainable, environmentally friendly farming practices and local food production, the Common Agricultural Policy could make life better for farming communities, rather than subsidising their destruction. Of course it is not easy to make such major changes, but that is no reason not to try. Perhaps that is a story for another day, or even another book.
CHAPTER FOUR
Patagonia and the Giant Golden Bumblebee
Consider the bee
Is it aware of its mortality?
Does it fear surprise?
Does it see many ghosts with its many eyes?
Mal Campbell, from ‘Worship the Ant’
On 1 January 2012 I flew from Glasgow via Heathrow and Frankfurt to Buenos Aires, accompanied by Jessica Scriven, a PhD student of mine who was studying the population genetics and ecology of the cryptic bumblebeefn1 in the UK. The weather in Scotland, where we were based at the time, had been decidedly dreichfn2 through December, so we were both looking forward to a few weeks of southern-hemisphere summer sunshine. Our self-imposed mission was to investigate the impact of European buff-tailed bumblebees on the native fauna and flora of South America. Rumours suggested that something pretty disastrous was afoot, something that threatened the future of all of the bumblebees of South America, and I wanted to see first-hand what was going on, and whether there might be any possible solution.
South America is the only part of the southern hemisphere to have naturally occurring bumblebees. Most bumblebee species live in the northern hemisphere; we think they originated somewhere in the eastern Himalayas some forty million years ago, and they spread through the temperate old world, west to Poland and eventually to Benbecula, east to Siberia and then across the Bering Strait to Alaska and hence to the rest of North America. With their large size and big furry coats, they tend to overheat in warm climates, so they never ventured south towards the Equator except in the Americas, where there is a more or less continuous chain of mountains linking the Rockies down through Central America to the Andes in South America. A few especially adventurous bees made their way down through the cooler habitats provided by these mountains, reaching South America somewhere between four and fifteen million years ago. They must have liked what they found, for they diversified, and today South America supports twenty-four known native bumblebee species. They include some really odd bumblebees, such as Bombus atratus, which has managed to adapt to live in the steamy tropical lowlands of South America, not a habitat one normally associates with bumblebees. It is an entirely black bumblebee with dark, smoky wings that superficially resembles a carpenter bee, and it is reputed to be absolutely ferocious in defence of its nest. Its life cycle is quite different to ‘normal’ bumblebees, for colonies can last for several years, there being no need for a winter diapause. There can also be up to eight active queens in a single nest, though apparently they fight a lot and eventually all but one are killed. Just as in Europe, some South American bumblebees have undergone major declines, most likely driven by intensive farming. For example Bombus bellicosus (the bellicose bumblebee?), a bee of open grasslands in Brazil, Uruguay and northern Argentina, is believed to be extinct in much of its former range. It used to be found in the area around Buenos Aires, but seems to have disappeared, and there have been very few records from anywhere in the last twenty-five years.
There was one particular bumblebee that I really wanted to see: Bombus dahlbomii, claimed to be the largest bumblebee species in the world, a creature that would make the great yellow seem like a mosquito by comparison. What is more, this wondrous beast was said to have a magnificent golden pelt (I can’t quite bring myself to use the term fleece for the fur of a bumblebee). Such is their size, the queens are said to resemble flying golden mice, their generous proportions helping them to keep warm in the bleak, windy climate of Patagonia and Tierra del Fuego. This is the only native bumblebee found in the southern half of Argentina and Chile, and it is a creature strongly associated with the great mountain chain of the Andes. Unfortunately, local scientists were reporting the rapid demise of this splendid species following the invasion of South America by European bumblebees.
Man’s enthusiasm for taking bees from one part of the world and releasing them in another appears to remain unchecked, despite the well-documented catastrophes that have occurred due to other invasive species running amok, such as mink and grey squirrels in the UK, or cane toads and rabbits in Australia. We have spread honeybees, natives of Europe and Africa, to every country in the world excluding Antarctica, and we have also deliberately carried numerous other bees, including various bumblebees and a host of small, solitary bee species, from one continent to another. In the late 1980s, Chilean agronomists imported ruderal bumblebees from New Zealand to help with clover pollination. Ruderal bumblebees are not natives of New Zealand, but were taken there from Kent in 1885 for precisely the same reason; New Zealand farmers had noticed that their red clover set no seed, and had worked out that this was because there were no bumblebees to pollinate it. Just as in Poland today, the New Zealanders of the 1880s and Chilean farmers of the 1980s used clover as a ley crop to improve soil health. It is not clear why the Chileans were unhappy with the pollination provided by the native dahlbomii, but perhaps they were too few in the lowland areas where clover tends to be grown – dahlbomii is more a species of the mountains and cool, wet forests. Whatever their reasoning, ruderal bumblebees were shipped in with little thought for the consequences and soon became established.
Chile is an oddly shaped country, an immensely long sliver of land more than 3,000 kilometres from north to south, squeezed between the Pacific to the west and the Andes to the east. It stretches from the Atacama Desert in the north, one of the driest places on Earth, to rain-sodden Tierra del Fuego in the south, the closest land mass to Antarctica. The ruderal bumblebees were introduced near the capital Santiago, which is very roughly in the middle of Chile, and from there they spread both north and south, eventually being halted by the two climatic extremes.
In 1994 the first ruderal bumblebees were recorded in neighbouring Argentina. If your geography is a little rusty, Argentina lies east of the north-south chain of the Andes. It is as long as Chile, but roughly triangular in shape, widening from Tierra del Fuego (ownership of which is uneasily split between Argentina and Chile) to a rather bulbous mid and upper section which borders Brazil, Bolivia, Paraguay and Uruguay. Like Chile, the climate varies enormously from the icy, windswept south to high-mountain deserts in the north-west and subtropical forests in the north-east. The Andes are the second highest mountain range in the world, providing a formidable barrier between Chile and Argentina for most of their length, which is fortunate for there is little love lost between the two countries. However, near San Martin de los Andes in Argentina they are lower, with passes through the mountains no higher than about 700 metres. It is through these passes that ruderal bumblebees are thought to have flown, and soon they became abundant in the lush, temperate forests of southern beech and araucaria (monkey puzzle) surrounding San Martin. For a number of years they seemed to live alongside dahlbomii. Both
are long-tongued species, so they visit similar, deep flowers, and there was concern that the two species might have read about Gause’s Law in an ecology textbook and worked out that they should not be able to coexist. If ruderal bumblebees proved to be the superior competitor, perhaps they would wipe out the native dahlbomii. In particular, both bee species loved to feed upon the beautiful scarlet and purple flowers of the native fuchsias. Carolina Morales, a scientist based at the Universidad Nacional del Comahue in San Carlos de Bariloche, just to the south of San Martin, has been studying bumblebees in the region since the 1990s. She has counted numbers of different bumblebee species over many years and came to the conclusion that dahlbomii was a little less common following the arrival of ruderal bumblebees, but that there had been no dramatic impact. For a while, all was well – the two bumblebees seemed blissfully unaware of Gause’s Law, and were able to get along with one another without disaster. Unfortunately, that was not the end of the story.
