You know it’s hot when it’s too hot to ….

16 01 2014
© T. Brandon

© T. Brandon

My post’s title might be a good candidate title for a punk song in the 2030s (maybe by a re-incarnation of the Dead Kennedys).

I am currently sitting under my solar-powered ceiling fan as Adelaide is declared the world’s hottest city (and not in the funky, cultural, fun way), and I can’t help but contemplate climate change models predicting the fate of biodiversity over the coming decades. Because it’s far, far too hot to work outside, I’m perusing the latest interesting articles on the subject and I came across this recent little gem.

Also recommended on F1000Prime by Ary Hoffman, the paper, Using physiology to predict the responses of ants to climatic warming, by Sarah Diamond and colleagues touches on many aspects of climate predictions that need to be considered. I summarise these briefly here.

While no physiologist, I have dabbled in the past, although up until quite recently I didn’t see that physiology per se had much to do with conservation. It turns out that climate change has spawned an entire sub-discipline called ‘conservation physiology‘, which focuses inter alia on how species can/will/might respond and adapt to a warmer, climatically disrupted world.

What struck me about Diamond & colleagues’ paper was that yet again, it’s not as simple as heat-stressing a species experimentally and making a prediction on its future distribution (ecology is complex). No, the complexity comes in various forms that makes each species a little different from each other. Using North American ant species subjected to various warming scenarios in large (5 m) enclosures, they found the following:

  1. They confirmed the now well-understood phenomenon that low-latitude species are more vulnerable to climate change because they are already near their thermal tolerance limits. This is despite higher-latitude species experiencing greater rates of warming.
  2. While some species might not necessarily show a reduction in ‘thermal foraging niche’ (that is, the amount of time and area over which they can forage) with warming, the growth rate of their colonies (i.e., a great proxy for fitness in ants) can decline nonetheless. So even though they can bring back the bacon (so to speak), there might be less of it and of a lower quality that the overall growth rate of the colony declines.

The take-home message is that even though an individual of species X might be able to survive a particular heatwave event, overall its population’s fitness might still decline (or be sub-optimal) such that its long-term persistence probability declines. Surviving is one thing; being able to spawn the next healthy generation is another.

This complexity reminds me of the tired, old argument against worrying about inbreeding depression: many inbred populations survive and even proliferate under the right environmental conditions, so why worry about genetic issues in conservation? The fact is that inbreeding leads to suboptimal fitness (survival, reproduction, etc.), making the persistence probability of species on average decline, thus increasing extinction risk. Stay tuned very shortly for an entire paper on this subject that will be out shortly in Biological Conservation.

CJA Bradshaw


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2 responses

17 01 2014
takver

Interesting post. I don’t have any background in biology to speak of, but I discovered that climate change could have some unexpected impacts on tropical species while writing up some research in 2012 on global warming impact on the life cycle physiology of one tropical species.
http://takvera.blogspot.com.au/2012/02/tropical-insects-face-catastrophic.html

I’m sure Jello Biafra would appreciate your starting comment. Had the pleasure of meeting him in the 1980s. He’d appreciate the humour.

17 01 2014
CJAB

Thanks. That would have been an interesting meeting. Very clever (and irreverent man).

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