Today's online version of the San Francisco Chronicle published another follow-up article about last week's rampage of bees in Concord, CA. The gist is that seven bees sent to the state Department of Food and Agriculture for testing, and the results showed that they did not possess Africanized alleles. This finding has led some to conclude that the bees that did the attacking were ordinary European honey bees. This, in turn, is a dangerous conclusion because the logical continuation of the thought process is that any hive of ordinary European honey bees kept in managed hives could suddenly and without warning become super aggressive. Let me address the study results as reported in the Chronicle, and then we can talk about the repercussions to beekeepers in California.
Thought #1: First of all, only seven bees were examined for Africanization. Seven out of several tens of thousands of bees in the colony. So yeah, sampling error is a problem.
Thought #2: Worker honey bees, all of which are female, are diploid. They inherit nuclear chromosomes from both parents. This is the same as happens for other diploid animals such as humans and most likely every other animal you would think of. The workers' brothers, the drones, are haploid; they develop from unfertilized eggs and thus carry nuclear DNA only from their mother, the queen.
Thought #3: The test used by the state looked for the presence of Africanized alleles in the mitochondrial DNA (mtDNA) of the seven bees that were examined. In sexually reproducing animals, the female gamete (egg) is much larger than the male gamete (sperm). The sperm provides DNA to the zygote that results from fertilization, but little else. All of the other cellular components, including mitochondria, come from the egg. Mitochondria are nifty little bean-shaped organelles, evolutionarily derived from some sort of aerobic bacterium-type critter, that are the "powerhouses" of cells. They are the site of cellular respiration, where glucose molecules are broken down and the energy within the chemical bonds is released to fuel the cell's activities. Mitochondria, as descendants of formerly free-living bacteria, possess their own DNA and are self-replicating units within eukaryotic cells. Because a diploid organism inherits mitochondria only from its mother, mtDNA can be used to trace maternal lineages through time.
Thought #3.5: A hive of European honey bees contains a European queen and her progeny. Her daughters, the workers, obtained half of their DNA from her and half from their fathers. A virgin queen mates with 12-15 drones on her mating flight before returning to her hive to begin laying. If some of the drones she mates with have Africanized alleles, then some proportion of her daughters will as well.
Thought #4: The results of the test used by the state cannot be correctly interpreted as indicating that there were no Africanized bees in the aggressive hive in Concord. Period. If the state wants to test for Africanized alleles, looking only in the mtDNA isn't going to do the trick. They can examine every single damn bee in the hive, and all they will find is the same mtDNA that the European queen has. They are looking in the wrong damn place--they need to examine the nuclear DNA for Africanized alleles. Now, there could always be something unusual about the mitochondrial genome of honey bees that I'm not aware of, which would mess up my entire argument. However, I am not the only person who thinks that relying on mtDNA to determine Africanization tells the whole story. Eric Mussen, apiculturist emeritus at the UC Davis Department of Entomology and Nematology, said more or less the same thing a week ago, right after the attack happened.
Repercussions for beekeepers: Well, any beekeeper knows that public hysteria about bees is a real thing. Many people are frightened of honey bees and don't want them around. Responsible beekeepers take measures to ensure that their bees are not a nuisance or danger to the public. We really want to do the right thing for our neighbors as well as for our bees. Shoddy science reported as fact doesn't help our cause.