Wild insects matter too
Honeybees are not the only insects whose fertility is impacted by extreme heat. Scientists expect that worsening heat waves could impair fertility of beetles, bumblebees, flies, moths and wasps — and those are just some of the ones we know about.
For whole populations, the trends are even more concerning. In the flour beetle, Tribolium castaneum, the sons of heat-stressed fathers can have impaired fertility, despite never having experienced the heat themselves. Scientists predict widespread wild bumblebee declines as the frequency of heat events increase to “untenable” extremes. And the temperatures at which male fruit flies lose their fertility do a better job of explaining their geographic distributions than the hottest temperatures at which they can survive do.
But honeybees can adapt to their environment, and with the help of beekeepers, they will probably adapt to hotter temperatures too. Subspecies from the Middle East have a higher tolerance to hot and arid conditions than those native to Europe, for example, whereas colonies propagated in Canada show evidence of selection for cold tolerance.
Even so, honeybee colonies only produce new queens about once a year when they prepare to swarm, or produce a new colony. This means that, relative to quickly reproducing insects like mosquitoes, they are by this metric disadvantaged for adapting to rapidly changing conditions.
Luckily, queen honeybees can compensate for this disadvantage by mating with multiple males, assuming they have not been killed in a recent heat wave. This increases the genetic diversity of their colonies, which is the fodder on which natural selection acts.
Canadian beekeepers also import around 250,000 queens each year, adding a constant flow of new genetics. These days, the queens mainly arrive from California and Hawaii, but other exporters include Chile, Australia, Ukraine and New Zealand, among others. This may be a benefit or a hindrance, depending on how genetic diversity balances with local adaptation, but it does promote new combinations of genes that could help deal with new challenges.
Bees are the bellwethers
Despite the losses noted by beekeepers, honeybees, as a species, will almost certainly persist as the climate changes. But not all insects will be so lucky. Bumblebee, wasp and many ant queens, which are also produced annually during the summer, generally mate with one or a few males, with limited opportunities for gene flow, and may be less capable of adapting.
Heat waves are clearly not the only challenge insects face: Habitat loss, pesticides and pathogens are also important. And two months after British Columbia lifted the state of emergency, a devastating flood displaced families yet again, as well as untold numbers of native bees hibernating in the ground.
Insects are critical players in ecosystems around the world, and with many terrestrial species already declining, research on how climate change will impact their fertility is vital. We pay attention to honeybees because we rely on them for pollinating crops, but they are not the only ones on which we depend. We know that the conditions during the 2021 heat dome are sufficient to reduce fertility of honeybees, which should raise alarm bells about the wild insects who don’t have keepers.