Varroa mites have appeared on the island of Oahu. These parasites of bees are a known cause of colony death. The current worry is for the honey industry. But I expect crops may suffer too if the island loses its hives. 1
Bee immunity
We’ve spent some time on the big bee die off (although not on the mobile phones) as have many other blogs and newspaper articles. In the US, the problem has reached epidemic proportions and has raised serious concerns about the future of several crops that depend to a large degree on bee pollination. Unfortunately recent evidence seems to suggest that the problem, which has been called Colony Collapse Disorder (CCD) has been spotted in Europe, as well. The cause or causes of CCD are unknown, but the list includes the usual suspects ranging from transgenic crops and pathogens to global warming and newly developed pesticides. Oh yes, and cell phones.
So the e-publication of a paper due to appear in the Journal of Heredity 2 (behind a paywall) is timely. It describes the heritability and genetic variation of a gene called abaecin which is a key component of the immune system of bees.
Bees, like nearly all eukaryotes, have an innate immunity, but are generally thought to lack the additional adaptive immune response, which we and most other vertebrate species have. That is to say insects can’t get the ‘flu and respond by making specific antibodies to the virus (In fairness, the notion that insects do not have an adaptive immune system has been challenged recently by studies in Drosophila. 3 )
To find out whether abacein expression differed between bee populations, scientists at the US Department of Agriculture crossed several unrelated males into a homogeneous maternal background and then challenged the offspring with Paenibacillus larvae. This is the bacterium that causes American foulbrood, a widespread larval disease of bees. Subsequent measurements in affected larvae showed that the level of abaecin was moderately heritable but highly variable, differing by as much as 10,000 times between different lines. Why this is variation exists at all is a matter of speculation, but it might be due to selective pressures: an arms race between hosts and different pathogen strains or species.
At any rate an understanding of the components of the immune response in bees at the molecular level and the realization that there appears to exist considerable genetic variation that could be exploited would seem to offer one of the more promising approaches to selection for pathogen resistance. Whether that will stop CCD is anyone’s guess 4.
First study of global pollinator value
Back in October 2006 the Royal Society published an online version of a comprehensive study that was the first attempt to put a global value on pollinators. It attracted some attention back then, at The Worsted Witch, who got it from Science Daily. We missed it at the time 5, but as the paper version has just been published, that’s enough reason to revisit it 6.
Very briefly, the article shows that 87 of the leading 115 crops depend to varying degrees on animal pollination. These 87 crops represent 35% of the world’s food production. While a few food plants are pollinated by birds or bats, the most important pollinators are, of course, honeybees, domesticated and wild. This is particularly troublesome in light of the various threats to the domesticated bee. The authors conclude that agricultural intensification jeopardizes wild bee populations and plead for more research into landscape management practices that would enhance wild bee viability.
Interestingly, I couldn’t find an actual cash value for pollination services in the article, but maybe I didn’t look hard enough.
Buzz on GM crops and bees
We’ve written a bit here about pollinator problems. The looming shortage of bees in the US, and in Spain. We pointed to a piece that said maybe the problems in the US weren’t any worse than they had been, just better reported. Maybe the problem is monoculture? Throughout the recent buzz of hive-related news, though, we’ve ignored a few items that laid the blame on GMO crops. Why? Because they seemed a bit shrill, maybe even a tad one-sided. But a long and apparently comprehensive piece in the German news magazine Der Spiegel is neither shrill nor one-sided. And it seems to adduce good evidence that bees who are suffering a parasite infestation are abnormally susceptible to pollen from maize engineered to express the Bt bacterial toxin from Bacillus thuringiensis.
The work Der Spiegel reports is a long way from conclusive. But it does give pause for thought, and it is causing huge excitement among opponents of GM in all its forms. At the very least, it deserves a closer look. But wouldn’t it be weird if it proved true? And how would industrial agriculture respond?
The rich tapestry of life
I hope I can finish posting this before the battery runs out on my laptop. It’s been one long power cut after another for the past couple of days and the one we’re experiencing at the moment started more than three hours back. Anyway, I thought this piece in EurekAlert really interesting and I couldn’t wait to blog about it. There’s this rare endemic plant on Mauritius called Trochetia blackburniana, you see, and it happens to be pollinated by the equally endemic gecko Phelsuma cepediana. But this is a day gecko, which means that to avoid predators they have to spend a lot of time hiding, and their favourite place for doing that is among the spiky leaves of Pandanus shrubs. Now, I’m not sure about Mauritius, but in lots of other places around the Indian and Pacific Oceans, Pandanus is a really useful plant: the fruits are eaten, the leaves woven into mats, people recognize and maintain dozens of varieties etc etc. So here’s something else that Pandanus is important for: protecting the pollinators of a rare Mauritian endemic.
P.S. Incidentally, Trochetia blackburniana, which is in the Malvaceae, seems to be one of the very few species of plants with coloured nectar.
Correction: Trochetia is actually in the Sterculiaceae. Apologies. Please read the comments for more interesting stuff on this genus.