Honeybee Tracheal Mites and Evolution

After perusing the recent micro/macro-evolution mailbag article, I started wondering about the evolutionary status of honeybee tracheal mites.

When was in college, 10+ years ago, I took a beekeeping class. The professor was one of those old guys who knew everything about his subject: in this case, bees. During a discussion of honeybee parasites, we talked at length about tracheal mites, which were, and still are, decimating wild bee populations.

One comment that this professor made was interesting. Apparently, there was no evidence that tracheal mites existed previous to about 1900. If they had existed, the thought was that someone would have noticed, since they’re pretty lethal to bees.

The current thinking was that tracheal mites were another form of the body mites that live on the outside of honeybees, and that tracheal mites had, perhaps, evolved within the last hundred years or so. If this were true, then this would be a rather rare example of a new species appearing in modern times.

My question is: Does anyone know more about the evolutionary status of tracheal mites? My impression was that, at the time, there was little evidence for or against the theory outlined above. Nevertheless, it’s intriguing enough that I’d think someone had followed it up. So: fact? fallacy? still to be decided?

http://www.ag.ohio-state.edu/~ohioline/hyg-fact/2000/2164.html

http://www.colostate.edu/Depts/CoopExt/PUBS/INSECT/05584.html

http://www.udel.edu/entomology/dmcaron/public_html/surveyresults.htm

http://bluehen.ags.udel.edu/deces/beekeeping/tracheal%20mites.htm

http://www.ifas.ufl.edu/~mts/apishtm/threads/tracheal.htm

This site has a fascinating history of the “myth” of the mite, and of the early years of Isle of Wight disease. Even up until the 1920s, some authorities were still maintaining that there was no such thing as “tracheal mites”, preferring to blame nosema (a disease) or unusually cold winter weather for the die-offs.
http://www.ifas.ufl.edu/~mts/apishtm/apis91/apjun91.htm

Here’s the good ol’ USDA–it’s not a myth.
http://www.barc.usda.gov/psi/brl/mite-aw.htm

The USDA also says this:

So apparently it’s been around the beekeeping world for a while, but only invaded the U.S. relatively recently. (There’s a marvelous quote in the ifas.ufl.edu website, from the early years, saying something like, “If those Americans think they’ll never have mites in their bees, they’ve got another think coming.”)

I have trouble believing that not one but THREE species of bug have suddenly popped into existence since about 1900. I think it’s more likely that this was a problem that was just undetected or misunderstood, until people had microscopes and the mindset of “scientific inquiry” to find out exactly what it was that was killing the bees.

I don’t know why a new species of mite would suddenly evolve to take advantage of a new ecological niche, when I don’t see a new ecological niche. People have been keeping bees for hundreds of years. Granted, they haven’t always been keeping them in scientifically designed hives, with supers and things like that, and a new queen bee every spring from Sears Roebuck, but still.

Also, if it was a totally new species, I would think that at least one of the Ag Departments I cited would have mentioned it, but not a peep out of anybody. It’s just all “these are new in the United States”, not “this is a new species”. My gosh, if it was a totally new species, I would think that somebody would have won a prize for discovering it, or written a book, at the very least.

I suggest that it’s possible you mis-heard or misunderstood the prof, or that he misspoke himself, or that he was just plain wrong.

Hey! Some good research.

Duck Duck Goose says,

I think, perhaps, the wording I used was unclear, and, admittedly, some of the details were foggy. Using the citations you provided, let me rephrase what I said above:

The current thinking was that the tracheal mite, Acarapis woodi, had recently evolved from previously existing external body mites, A. externus. Only one species has evolved, from one of the other mite species. The ecological niche utilized (honeybee tracheas) was not perhaps new, but was underutilized. Supporting this thinking are a few facts:

[ul][li]Tracheal mites had not been documented before the turn of the century.[/li][li]Tracheal mites decimate bee populations, particularly wild ones where beekeepers aren’t around to save the hive.[/ul][/li]The logic, then, is: If tracheal mites had existed before 1900, they would have killed off the bee populations very rapidly. Bees were not killed rapidly, therefore, tracheal mites did not exist before 1900.

Duck Duck Goose also says,

I agree, which is why I was looking for information.

No, I think I heard correctly. However, I should also emphasize that this was presented, by the professor, as a big “maybe.” Nothing’s proven, it’s just an elegant theory. I tried to include some caveats in the OP, evidently they weren’t strong enough. You are correct, though: the absence of anything written about the evolution of mites is in itself a strong argument.

Nonetheless, 'tis an interesting puzzle: Why are honeybees dying now at record rates when they never did before? I was hoping someone coud shed some light on this.

I didn’t stop to read all the links I saw (Google brought up 1,458 hits for “tracheal mites”), but in passing I noticed some mention of simply breeding resistant bees. Apparently they’re starting to notice that some hives just don’t get sick, and they’re starting to track down the reason why.

Also, it seems, from what I know of modern industrialized beekeeping, and from what I read at some of the Ag Dept. sites, that the explosion in tracheal mites is exacerbated by the way the big commercial beekeepers truck their hives up and down the country, pollinating crops. I noticed (also in passing) mentions of this as the number one cause of the quick dissemination of tracheal mites across the U.S., within a surprisingly short period of time (especially when you compare it to how slowly fire ants and African “killer” bees are expanding their ranges.)

It’s possible that in 10 or 20 years the situation will stabilize, the way that fire ants and African bees seem to have stabilized. Here in Illinois, I haven’t heard a “killer bees are coming!” news story in a long time.

I also thought it was interesting that the first line of defense, in all the websites I looked at, was towards more organic methods of control, as opposed to quantities of chemicals. One method involves vegetable oil and menthol–what an amazingly simple idea. Dow Chemical is definitely out of the loop on this one, I think. No bad thing, IMHO.

But if it is definitely a new species, still I would have thought that somebody would have noticed, you know? Some geek entomologist who LIVES for mites, that sort of thing.

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Could it be that the bee that introduced the mite to America was the African “Killer” Bee? Perhaps the mite is less malevolent to African bees or that no one particularly cares if wild African bee colonies die off.

Not stabilized at all. Here’s an article From Jan, 1999. There is a graphic there showing them in five states so far (CA, Nev, NM, TX and Az). According to this site, they’ve only been in the US for less than ten years. The question is how far North will they be able to go and still survive the winter.

I forgot to say, about the OP, that an alternate theory is that the tracheal mites have been present for a long time in some isolated part of the world, and in 1900 got carried elsewhere through international trade or travel.

Changes in science and in beekeeping around 1900 were such that it is incredibly naive to believe that simply because the mites were first detected then, that they only then had come into existence. Moreover, there are 8 different species of honeybees, and only ONE was being examined for mites. It is entirely possible that A. woodi existed on another species of Apis, like the Asian A. cerana, and was transferred to A. mellifera early this century, when beekeepers first began trying to raise A. cerana in Europe. We’ll probably never know.

Well, it seems like there are several possibilities.

a) Tracheal mites existed on a genetically resistant form (species or sub-species) of honeybee and crossed over onto the commercial variety fairly recently, where they have been wreaking havoc.

b) Tracheal mites are actually a recent mutation of a previously harmless mite that was always around commercial honeybees but did no damage.

c) Some combination of a and b.

So, the questions are, what evidence can we muster? I know that the current commercial form of honeybee is fairly homogenous, genetically speaking, so a disease that afflicts one spreads rapidly through populations.
Is there any species of domestic bee that is immune to the mites? I heard a rumour that the africanized bees are partially resistant, and that is one reason why they are spreading so rapidly through former domestic honeybee territory. I can’t back that up, though.

"Changes in science and in beekeeping around 1900 were such that it is incredibly naive to believe that simply because the mites were first detected then, that they only then had come into existence. Moreover, there are 8 different species of honeybees, and only ONE was being examined for mites… " – Doug Yaneka

That is true, but IF(and yes, it’s a big IF)the tracheal mites were a recent mutation, THEN the effects on the honeybee population would be about the same as they are now: massive dieoffs, and eventually replacement by resistant forms. This process is accelerated by human involvement, as Duck Duck Goose and Zenbeam have noted.

Furthermore, if these tracheal mites are an import from somewhere else, and if they get isolated from their original carriers (whatever they were)and habitat (wherever it was), and manage to survive in a resistant strain of domestic honeybee, in another few centuries they will be a new species, by way of divergent evolution.

So either way you look at it, it’s still a pretty neat process.

Hmph. You guys evidently don’t read your Bibles. It’s right there in Genesis: “And Noah begat Ham, and Ham begat Yehiel, and Yehiel begat Phred, and Phred begat Tracheal Mites.”

Horseshit, Dex. You know damn well that the Hebrew word for “young woman” was mistranslated as “tracheal mites” sometime in the third century. Umm… even though there were no tracheal mites in the third century. I guess it was a divinely inspired mistranslation.