Propolis and hygienic behaviour

Interesting looking report in December that bees with high propolis production have enhanced hygienic behaviour (clearing pin-killed pupae) though the graphs aren't altogether convincing. These bees were Africanized so relatively resistant to mites already. I know nothing about the genetics of propolis production … they started with crosses between high propolis (HP) producing colonies to make their test colonies. It's not clear from the paper whether the resulting test colonies showed similar levels of propolis production as the parental ones.

If you kill the pop-up window on the link you can read the paper on screen.

OK, here's my assessment from a quick read.

The differences between the F1 colonies from high propolis x low propolis crosses and the other combinations are small. I'm a little surprised that they declare them to be 'significant' and would have liked to see more details of the stats. For example, they didn't even declare a p value for differences in % pin killed brood between all crosses. They *did* say that low propolis x low propolis F1s compared to others had a (non-significant) p value of 0.2 but why not one for comparing all crosses? Usually you look at all the independent data to derive a level of significance of the differences.

Assuming that there are significant differences, what do they mean?

Here are three possibilities.

1. Chance, due to different sub-populations.

Let's imagine (no idea if it is true) that there is an eastern and a western race of Africanised Brazilian honeybees.

Population A. More or less bald. Pale yellow. Good at collecting propolis. Hygienic.

Population B. Hairy. Dark. Doesn't like collecting propolis. Can't be bothered with hygiene.

(Purely ficticious. Any resemblance to real populations living or dead is purely coincidental.)

AxB - intermediate for hairs, colour, propolis, hygiene. Do we claim hairiness is connected to propolis collection or colour to hygiene? No.

2. Genetic linkage. Scenario 1 applied once upon a time. But things have become very mixed. There is still a slight tendency for propolis collection to go with hygiene as there are genes controlling both on the same stretch of chromosome and they still tend to go together.

3. There is a real biological link between propolis collection and hygiene as the genes controlling the tendency to perform one behaviour tend to also affect the other. Not completely inconceiveable that bees that like ripping things apart (hygiene) also tend to like patching things up again (propolis collection). But it is a bit of a stretch.

Next step is to go and design experiments that discriminate these possibilities.