What could the trouble with the bumble bee be:
It has been well known for years that the honey bee is in decline.  What I have more recently learned is that the bumble bee is also in decline.  Sometimes a species declines quite swiftly. (Mark J. F. Brown The Trouble with Bumble Bees NATURE vol. 469 no. 7329 January 13, 2011 page 169)

Like honey bees bumble bees are pollinators of commercial significance and breeding them and shipping them around is an industry.  I have suggested that in the case of honey bees commercial lots with hundreds of hives being trucked in and out are the source of excessive genetic diversity.  There are simply more different lines of bee being crossed than the epigenetics of the insects can endure.  That idea, of course, is not popular.

I would have suspected the same of bumble bees.  The standard explanations are habitat loss and disease or parasites.  Habitat loss would not seem to be too great a problem if it pays to truck hives in.  The disease or parasite possibility is now attracting attention.  According to the article, that is also a bit difficult to establish.  They think maybe bees imported from Europe have brought with them pests that were not native to North America.  Hence the native species that had not evolved resistance were vulnerable.

Perhaps so.  But this time, at last, they have actually looked at the genetic diversity of the bees.  It is unusually low for bees.  Well that is hardly a slam dunk for saying that the fault lies with excess diversity.  If the interbreeding of too many different hides is at fault, of course, the problem would not necessarily be visible in the diversity of the genes themselves.  Wipe out enough bees and the survivors will of necessity have fewer different genes. 

Just because the evidence is consistent with excessive outbreeding of course does not mean there is evidence for excessive outbreeding.  I’m very happy they looked at the genetic issue.  If they get around to comparing epigenetic patterns in the bees I shall be prepared to say that this time my own explanation is not the truth and that at last there is one piece of valid evidence against the whole process. 

Of course if it ultimately turns out to be disease, then the issue is moot.

Or maybe it’s insecticides.  (Juliet L. Osborne Bumblebees and Pesticides NATURE vol. 491 no. 7422 November 1, 2012 page 43 and Richard J Gill et al Combined Pesticide Exposure Severely Affects Individual- and Colony-Level Traits in Bees page 105 in the same issue)

There have been 72,087 visitors so far.

Home page