It's the Inbreeding!

I do not find the claim that certain Bumblebee species are disappearing from the UK because they are too genetically similar to resist parasites and disease very convincing(http://www.bbc.co.uk/news/science-environment-11199779). It is certainly true that the eusocial lifestyles of certain bees, ants and wasps results in members of the hive or colony being genetically very similar but I suspect that changes in agricultural and horticultural practices (or even climate?) play much bigger roles here. In the case of zoo animals there was a marked tendency to blame inbreeding for failures to reproduce endangered captive species. The claim is often made in the absence of having a clear measure of genetic variance (other than using often dubious 'geneological charts') but without being able to specify a reason (e.g. diet, social structure etc). I suspect that something similar is going on here.