While debates rage among humans over the value of promiscuity, the argument is settled among honey bees. New evidence from several scientific studies suggests that queen bees who mate with multiple males are able to build healthier hives that are more productive, well-fed, and disease-resistant than hives where the queen mated only once.
Every summer, queen bees who hope to form new colonies seek out gatherings of male drones, mating with as many as twelve or fifteen drones before flying off with a swarm of worker bees to start building a new home. The queen's mating days are over — now she'll spend the rest of her life laying eggs with the sperm she got during that one crazy summer. The queen has a special organ where she stores the sperm she got from all her consorts, and she's able to mete out one sperm for every egg she lays.
But queens raised in captivity are generally inseminated just once, with a male carefully chosen by beekeepers to be genetically sound. Wellesley College bee ecologist Heather Mattila wondered if preventing honey bees from promiscuous mating, the way they do in the wild, might be causing problems. Specifically, she wondered if there were a connection to the deadly colony collapse disorder that's claimed the lives of 30 percent of beehives every year for the past decade. So she and her team set out to study the differences between hives with single-mated queens and hives with multi-mated ones. What they found was extraordinary.
Like humans, bees carry thousands of types of bacteria in their guts to aid in digestion and health. Among bees, however, gut bacteria are crucial for food production as well as digestion. Nearly all bee food and honey is processed using the microbes in their guts, where they transform pollen into "bee bread," a food they store for months in their combs. Mattila and her team discovered that bee colonies with a single father had far fewer types of these food-processing microbes in their guts — and far more potentially hazardous, disease-causing microbes.
In a paper published yesterday in PLoS One, Mattila and her colleagues describe the outcome of their experiment. They note that colonies with promiscuous queens were apparently more disease resistant and well fed. This is likely because the genetic diversity from multiple fathers endowed the colony with more microbial richness and thus more nutritious diets for the bees. It's possible that honey bee colonies need multiple fathers to fend off diseases like colony collapse disorder.
Previous experiments, also conducted by Mattila, had revealed that colonies with multiple fathers build combs more quickly and forage for food more effectively than their single-father counterparts. This means that multi-father colonies are more likely to survive their first winter after founding a new hive. Given that only about 20 percent of new colonies survive their first year, this would put strong selection pressure on queens to become polyandrous. After all, a hive built on promiscuity is a hive that's healthy and productive.
Mattila wants to encourage beekeepers to mate their hive queens with multiple males, to promote genetic diversity and hopefully make hives more resistant to colony collapse.
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