Heat freezes niche evolution

Araújo, Ferri-Yañez et al. Heat freezes niche evolution. Ecology Letters, early view.

ele12155-fig-0001

Some pretty exciting datasets used in this study (above)


Will Pearse

Will Pearse

I’m sorry everyone, because a number of work commitments (including preparing for ESA) mean I haven’t been able to spend the time I would normally devote to PEGE this week. I’m particularly annoyed, because this paper has a story, and stories require sitting in a quiet room with a beer and thinking, which I really don’t have right now.

Let’s assume that the tropical origin theories are right, and that the tropics are a huge source of diversity. If so, I completely buy more variability in cold tolerance – that’s what allowing species to spread towards the poles, and that’s what’s allowing species to radiate out into new niches. We should expect variation, because it’s that variation that’s driving speciation / it’s speciation that’s driving that variation.

When I look at the evolution of species traits, I assume I can measure them fairly accurately, and describe them with a single value. Well, this paper (and in particular figure 7a) really makes me think I should stop doing that, because tolerances seem to be things that are described by distributions with long (or at least variable) tails, and quite strong asymmetries. Perhaps even some kind of linkage with the traits that underly cold tolerance, and how those work physiologically, might help. So, maybe it’s time to crack out that dusty old physiology textbook!


Lynsey McInnes

Lynsey McInnes

Oops, I’ve managed to pick a paper that merits more consideration than either Will and I have had time to give it this week. But in the spirit of publishing PEGE more or less on time each week (less this week given Latvian wifi collapse), here are some initial thoughts on this paper.

Well, it looks like we are finally beginning the next generation of niche conservatism type analyses and that physiology is about to take centre stage. For a while now, we have been bandying about the notion that we can’t really look at niches by summarising the different climates found within species’ range polygons, that really niches relate to physiology and that we need to address physiological mechanisms head on. However, physiological traits are way harder to measure! The authors here do a great job of collating all available date on physiological tolerances and asking some interesting questions with this dataset (as an aside, I am extremely fond of papers that dare to use data from variety of sources and measuring slightly different things, rather than restricting themselves to more ‘perfect’ homogeneous datasets).

They conclude that upper thermal limits are much less variable than lower ones and that this indicates that upper limits are much more conserved. This in turn suggests that species living in regions close to these limits are most likely to be most screwed in the face of increasing temperatures. I really need more time to think about this, but on first glance, this sounds pretty reasonable and sits well with similar assessments of latitudinal gradients of climate change risk that have not used real physiological data.

I really appreciated that authors tackled head on what their results mean for all those studies (mine included) that make loose handwavey gestures that realised niches should be correlated in some nicely linear way with fundamental niches. I also liked the way they highlight how their findings deal (another) blow to using bioclimatic modelling to make robust assessments of species likely responses/range movements in the face of climate change.

Some thoughts that popped into my head…

How are these results affected by there just not being higher temperatures around at the moment? And by there being more species in the tropics, with smaller ranges? Is there any conflation going on?

Are there any experimental evolution studies around that have selected for increased temperature tolerance/looked at the genetic mechanisms behind this? (I expect yes!)

What is the relationship between upper and lower thermal limits and the absolute range of thermal tolerance for each species? (Not sure what I mean here, but I think I mean what about the physiology analogue of the effect of range size/intraspecific variation?).

How would these results change if studied in an explicitly phylogenetic context (harping back to my musings on what is niche conservatism without the ‘phylogenetic’ bit?).

Given the apparent complexity in species’ (thermal) niches is there any real hope that we are able to make accurate predictions of species’ likely responses to climate change (and then go on to use these predictions to take useful conservation decisions)? The typical trio – move, evolve, perish – still stand but how much progress have we made in working out what is more likely (my feeling is most species will have a bit of all three in different/overlapping parts of the range). Pragmatically, maybe we need to give up on these species by species assessments and instead look at emergent community/ecosystem assessments to insure healthy ecosystems (whatever that might mean) rather than persistence of individual species. I.e. go more macro instead of less?

Alternatively, if our aim is not necessarily to conserve, but just to understand what on earth is going on and how niches ‘work’, it looks like we are going to have heat up a lot more organisms on hot plates and digitise a few less maps…

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3 Responses to Heat freezes niche evolution

  1. Pingback: Niche syndromes, species extinction risks, and management under climate change | PEGE Journal Club

  2. kitesandwind says:

    Hello

    I found this page by chance, and I could not stop reading your fitting analyses of all these papers including this one on thermal niche that I coauthored with Ferri, Araujo et al. It has been a great and stimulating to compile all this and we are very happy to trigger questions like those presented here. I am working now on how could we make sense of available information on species, communities and climate change scenarios and provide guidance, advice or some sort of suggestions for ecosystem management in a changing world. Thanks for sharing your brainstorming and hope we can brainstorm together some time somewhere!

    • lynsey83 says:

      Hi Fernando, Thanks for your comment. Great that you found the blog – and liked it! Are you guys pursuing any extensions of the analyses presented here? I really liked that you addressed physiological mechanisms head on; it would be great to hear more about what you have in the pipeline. I’d also be really keen to hear about your work on ecosystem management. I do believe that is the perspective we need to take if we want to achieve any practical conservation successes! Cheers, Lynsey

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