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Unusual Suspects: Have you met Drosophila?

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Climate change is contributing to rapid species extinction, of which we humans will hope to avoid. I’m going to take a moment to look at an unusual suspect – a species you might not have thought of when considering the consequences of climate change.

Those of you who took first year university level Biology will probably remember Drosophila –  the humble fruit fly. With their short life span of around two weeks, they’re a great way to see genetics in action and I spent several weeks in a lab raising and then cataloguing Drosophila during my first year.

So why are these flies going to be one of the first climate change victims and should we even care?

Fruit flies are annoying and difficult to swat, but everybody’s got to eat, and spiders, frogs, some ants and beetles find fruit flies really tasty (another win for much-maligned spiders!).

But Drosophila, like some humans, don’t deal with change well, specifically temperature change. Some researchers in my hometown of Melbourne, Australia published a paper last month looking at the upper thermal limits of
Drosophila, and their heat resistance isn’t good. They are ectothermic (cold blooded) which means they use the conditions around them to regulate their body heat. So when their climate changes, they get uncomfortable quickly.

The worst heat resistance results for Drosophila were between 10 – 23 degrees latitude North, which is roughly from Colombia up to Baja in Mexico. Two of the ways in which animals can evolve to meet climate pressures is to migrate, or to evolve.

With their short lifespan, it would seem Drosophila would have a fighting chance at quick evolution, but the researchers found the species had a ‘limited evolutionary capacity to evolve and alter upper thermal limits’.

Which leaves migration as Drosophila’s other option and could mean an increase in fruit fly numbers in new areas. Will we be seeing large increases in the fruit fly population in BC similar to the pine beetle?

 Fruit fly migration will also have ramifications for all the frogs, spiders and ants that rely on fruit flies for their dinner and have been left behind, or are not able to migrate as easily.

The researchers concluded: “Thus, although studies of genetic variation and geographic variability in heat resistance point to some evolutionary adaptive potential, this may not be enough under current Intergovernmental Panel on Climate Change scenarios.”

Which means for the poor Drosophila that no matter how fast they try to fly to new lands, it’s likely climate changes that are happening at much greater speed than has ever been seen in geological history will mean they may not survive.

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