The fungal disease known as white-nose syndrome has absolutely obliterated certain species of North American bats, as I’m sure you know. One hope has been that it would cause a winged-mammal version of population resistance, where removing all the competing bats allows a few genetic variants who are less affected by the disease to thrive, spreading their resistance to future generations.
That’s what happens when we blast germs with antibiotics, so why couldn’t it happen when bats get blasted by fungal disease?
Alas, mammals are not bacteria. A Forest Service study (see it here) found no evidence that bats are evolving resistance.
So what is causing the apparent survival of a few scattered populations of little brown bats, which is the most affected species? “We propose that mechanisms other than adaptive immunity are more likely driving current persistence of little brown bats in affected regions,” the authors note.
Basically, some bats are changing habits to cope with the disease. The fungus mostly kills bats by waking them up during their long winter torpor, which depletes energy and keeps them from surviving until insect food appears in the spring. Bats that survive the fungus manage to shrug off at least some of these waking impulses, or else they have the habit of eating more in the fall so they have better fat supplies to make it through the winter.
Either way, no magic DNA bullet is going to save them.
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But isn’t that an evolution of the bats? The bats that can NOT “hrug off at least some of these waking impulses, or else they have the habit of eating more in the fall so they have better fat supplies to make it through the winter” die, so the traits of the survivors are passed on to the offspring. Tat sounds like the DEFINITION of evolution, to me.
Good point. I, and the study, meant there’s no sign of genetic evolution but you’re right that species can split based on actions as well as genetics. A big difference: New behavior isn’t usually passed down to generations, but genetic changes are.
Gene B. is correct; the tendency to “shrug off waking impulses” would likely have a basis in the genome. You’d have to know whether the waking impulse is induced by chemical or physical means and the genetic trait would be an insensitivity to that impulse. That insensitivity could be passed on to the next generation.
I came here to make almost the exact same comment at Gene B. I’m no expert, but that sounds just like evolution to me, too.
Me too,