Blog 5: Queen-Worker-Bee Conflict

Explain the conflict between queens and workers. Who wins and why? Are there any exceptions?

There exists and reproductive conflict between worker daughters and their queen mother. In social insects--such as bees--here occurs a very distinct sex-determination system that governs where selective pressure is placed when speaking in terms of reproduction. This system is called haplodiploidy. The father only has one set of genes to pass along, so the probability that an ant will share the same paternal genes as her sister is 100%. So the degree of relatedness for two sisters is:

(1 x ½) + (½ x ½) = ¾.

A typical female bee is genetically more closely related to her sister than to her mother or her daughters. This is why female workers would favor a 3:1 ratio, of producing more sisters rather than their own daughters. But this comes with a caveat-- their mother queen must only mate with one drone in order to ensure greater relatedness between the offspring sisters. If the queen is inseminated by more than one male, selective pressures will shift and cause daughter workers to reproduce their own young, since it guarantees a greater degree of genetic relatedness and therefore greater percentage of genetic fitness.

The queen’s genes however can benefit best if she invests equally in both sexes, supported by Fischer calculations on optimal sex ratios done by Trivers and Hare. Using 20 species of ants, Trivers and Hare estimated sex ratios in terms of investment in reproductives and found a 3:1 female to male ratio. “Workers are running the show for their own benefit.” With this study Trivers and Hare found that it was the workers who “won” the conflict between workers and queen because it was them who had the greatest investment in the offspring.

Since the workers were the ones making the greatest investment in caring for the offspring –they could therefore manipulate the sex ratio towards their benefit, that is, to a 3:1 female : male ratio. Exceptions to this included that in species that have “slaves” (ants from other colonies) caring for the offspring the queen has a greater ability to manipulate the ratios through the slaves since the queen can escape the slaves’ countermeasures because they do not work on her, being that she is totally unrelated to them.