As the local natural beekeeping group, we’ve got to know and respect Filipe. The recent article in The Guardian about his findings at Blenheim has led to some heated debate in the Twittersphere. In the following article, Guy Thompson addresses some of the controversy.
By Guy Thompson
This piece in the Observer has caused a bit of a stir. Clearly aimed at engaging the general public, I can see why it has been annoying in some circles. Prof. Jeff Ollerton – @jeffollerton on Twitter – is right to say that “extraordinary claims require extraordinary proof” but, in fact, what is being seen at Blenheim is not, IMHO, extraordinary: it is pretty much what you would expect to see given the circumstances: the pristine nature and extent of the woodland and the absence of modern bee management from the entire estate.
OxNatBees member using binoculars to scan a Blenheim oak for nests
Local ecotypes of honey bees were the norm in the UK until very recently. Globalisation has made honey bee imports much easier and events such as the Isle of Wight disease around 1902 gave impetus to the international trade in bees (and their genes). The current genetic uniformity of honey bees in Britain is driven by constant high volumes of imports of queen bees that dilute the native genes, and also by unrestricted movement of stocks within the UK. Most British honey bees are now, for better or worse, cross breeds. Whether any examples of “native” honey bees can be found in mainland Britain is hotly debated but there is acceptance that elements of the “native” genetics are still to be found. (I put “native” in italics only because I don’t want to cloud this with arguments about whether honey bees are or are not actually native to the UK).
However, it has been shown that, by various mechanisms, if dilution is halted, these cross-breeds revert, over time, to the native genotype. How? Well various mechanisms are possible – partial reproductive isolation or cryptic patrilines for example – but even a simple fitness model with just a few percentage points difference in survival rates will show measurable population differences in just a few generations. Survival of the fittest. The fact is that honey bees can revert towards “native” quite quickly and many examples of this have been documented, even in situations where non-local genes are to be found quite close by.
Many things can drive the speed of this reversion, in particular the ability to naturally swarm (reproduce by fission), size constraints on the nest cavity (which also drives swarming) and a freedom from other stressors (poor forage, reduced pesticide impacts, low inter-colony disease transfer). Therefore, in an environment such as Blenheim, one would expect the speed of any reversion to be at the top end of the range. Interestingly, all those same factors – swarming, nest size, healthier conditions – also permit the bees to deal more effectively with one of their main problems, the varroa mite and its associated diseases. Whether this amounts to resistance – as indicated by the Observer article – or is simply an increased resilience in those populations needs investigating but, regardless, what effectively is in place at Blenheim is a rapid breeding programme with “survival” as the only selection factor.
Filipe checking nest. Photo (c) Guy Thompson
The small nest cavity point is very interesting and, again, worthy of further investigation. At Blenheim, any potential cavity spotted by the forestry team has, wherever accessible, been assessed and recorded. Accurately measuring the cavity volume is very tricky several tens of metes up a tree with bees (or wasps or hornets) often in attendance. However, a camera endoscope and a long arm can often allow a good estimate of the cavity: if it is occupied an infrared image can also reveal the nest extent at least so that it can be broadly categorised (sub 20 litres, 20-40 litres, etc.,.).
Both at Blenheim and on the Boughton Estate, where a similar project is underway (see @BehcHoneybee on Twitter), the occupied cavities appear to be often quite small – maybe half of the 40 litre “ideal” defined by the work of Prof. Seeley in the USA). More work needed again, but the same small cavities that drive swarming can also mean that the combs are regularly honey bound, causing breaks in the brood cycle that are very much to the detriment of the dreaded varroa mite. Furthermore, the generally high humidity in natural cavities, especially when nectar is being evaporated into honey, is not conducive to varroa reproduction. All in all, it would not be entirely surprising to find that these free living colonies have sufficiently different host-parasite relationships that keep the varroa mite at bay.
Typical landscape in the woods. Filipe is indicating a nest.
In terms of foraging pressure on the landscape, small colonies have very small impacts compared to standard commercial hives. This is not just a question of scale – more bees equals more pressure – but the increased wall thickness reduces heat losses: less energy used means less need to collect nectar. Furthermore, a generally smaller entrance size for natural sites (which the bees can control themselves with propolis) reduce thermal losses even further. Finally,and importantly, there is no beekeeper to remove the honey regularly – whatever is taken for human consumption has to be recouped from the environment with obvious implications for other foragers. All in all, the almost 50 colonies found at Blenheim probably equate (in terms of landscape pressure) to no more that 5 commercial hives. Add into that the availability of the forage and propolis from the extensive broadleaf tree cover on the estate – and remember honey bees are a creature of the forest – and the relative impact of the honey bees (relative to other pollinators) is further lessened. It is quite telling that 500 potential nest sites have been found but only 50 occupied: not a picture of the all-devouring honey bee that is sometimes painted.
Whilst I agree with some entomologists who have pointed out that proper DNA analysis of the Blenheim bees is a necessary step in assessing whether the “wild heirs of lost British honeybee” have been found, I also think this misses the point. The arduous work Filipe Salbany has done in a single year on the estate is a tiny opening of a window into a very special environment for study of not just these small bee colonies, but their interactions with other pollinators and the wider landscape. It is a tribute to the project that they have sought to prevent managed beekeeping on and around the estate, and that there is therefore no honey production (meaning that pollinator resources to the largest extent possible for the use of pollinators).
“This work has just begun” is the real message of Blenheim and I think the Observer article is unfortunate only in the sense that it focusses on the sensationalism (in order to sell papers?) rather than the reality, which is that what is being seen at Blenheim can, if the landscape is sufficiently pristine, be seen anywhere. Pesticides, managed beekeeping, etc, etc almost always cloud the picture…. at Blenheim you can get a clear uninterrupted view and that is rare.
Guy Thompson (@pguythompson on Twitter)
Oxfordshire Natural Beekeeping Group 
DNA. Are you texting all the colonies or just selected ones?
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Some samples have already been sent for preliminary testing, but the plan is to sample EVERY colony this winter. By doing it in winter you avoid the issue of bees drifting between nests. However, this involves a LOT of climbing, and some nests are more accessible than others, so Filipe may not manage to access every one.
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Nice summary of the work Guy, and more balanced than the Observer piece, thanks for writing it.
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Thanks, Guy. In The Lives of Bees, 2019, Seeley’s picture of wild nests still relies on his 1970s work (in his usual modest, honest way he acknowledges where he was wrong, like a true scientist). One forest of ferals in New England! Isn’t it bizarre that there hasn’t been more knowledge generated in nearly half a century? That’s why, as you say, Felipe Salbany’s citizen science is so important. It’s the kind of science that Darwin respected — drawing on ‘amateurs’ all over the world, including the lower-class pigeon breeders of London, whose skills he could only marvel at — and engaged in himself, as in his earthworm book. Sitting down before fact as a little child, as Huxley put it.
Still on Seeley, I’m reminded of his Arnot Forest studies, where he proved a genetically independent feral population had survived the varroa bottleneck, in the face of the ‘common knowledge’ that ferals had been exterminated by varroa and restocked by recent hive escapes.
I thought the pile-on was upsetting, by people who should know perfectly well that journalists generally get science wrong. I hope Felipe is OK.
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Thanks Tim. Always remember that Seeley’s work was conducted in N America where honey bees are certainly not native, having been introduced in the 1600s. Various projects in the UK – including at Blenheim – are finding results that contradict his work on various fronts, such as natural nest spacing, nest sizes, etc.,. Guy
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Seeley proved no such thing, “survived a varroa bottleneck”. The Arnot forest (while a bit bigger than Blenheim), is surrounded by farmland with honeybees stocked in hives, including bee breeders which have selected and imported lineages. In fact some of the surprising mitochondrial DNA in the Seeley analysis proves that very fact (Syrian lineage mDNA), the Arnot was restocked with exotic bees.
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I think Seeley did show that a population had developed resistance to (or tolerance of) to varroa, but whether they were (i) genetically different and (ii) whether this difference was what contributed to their resilience seems to me to be in need of clarification. Another reason to be supportive of projects like Blenheim and Boughton Estate.
Your point about the surrounding landscape is interesting. Genetic reversion appears to be able to proceed even when populations are not isolated. In the case of Blenheim, one hypothesis might be that the overall pressure (due to the free swarming of the unmanaged colonies) is outwards from the well populated site: this would tend to push the reversion process along but would not, I agree, ensure complete genetic isolation. However, a thought to consider …. if each colony is swarming on average once a year, say, and if the population density is stable, this implies that the mortality rate is ~50%. That alone would cause a very significant pressure on the varroa populations in these free-living colonies …. One has to wonder if this, possibly bolstered by the items I mention in my piece, is what is allowing the apparent “continuation” of the overall wild population.
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