Macroevolutionary perspectives to environmental change

Condamine et al. 2013. Ecology Letters: early view. DOI:10.1111/ele.12062. Macroevolutionary perspectives to environmental change.

Below, we give our first impressions of this article. Please comment below, or tweet Will or Lynsey (maybe use #pegejc). Think of this as a journal club discussion group!


Lynsey McInnes

Lynsey McInnes

For our second post, we picked a monster by accident. This is a mammoth perspective paper on the potential of macroevolution to provide insights into expected environmental change. It’s good, it’s comprehensive, it’s kinda hard to get through in one reading. I commend anyone that did.

So, my commentary is going to be a bit haphazard and mostly just the thoughts that came to mind after my fourth skim. It should also be prefaced with the info that I’ve just turned my back a bit on macro-scale approaches because I’d become frustrated with all the patchings-over and arm waving necessary to get from pattern to process with data at this scale. Having said that, smarter people than me can probably make that leap and it be meaningful (i.e., a lot of the recent research cited here: note the prevalence of refs from 2011 and 2012 – this field is moving fast!).

I thought the authors did a great job of provided a measured perspective on the potential for macroevolution to provide practical insights into the effects of contemporary environmental change. They highlight that today our environment is changing extremely rapidly, potentially way more rapidly than in the past (although this may just be because we can’t resolve time to such narrow intervals in the past). They take great pains to highlight how dodgy extinction rate estimates from reconstructed phylogenies are (but indicate the sorts of conditions where estimates might be more reliable). They emphasise that extinction risk today might have different correlates to in the past (and outline neat ways to test for this). They collate and summarise a ton of (mostly very recent) paleo- and phylo- research in an accessible and intelligent way.

A tiny rant – so much on whales! Which demonstrates a point that I think the authors would also agree with: data availability remains an issue. The most robust contributions from macroevolution seem to be ones consisting of a mix of good paleo- and phylo- (here, reconstructed phylogenies of extant lineages) data. And this data is patchy or absent for most groups – except whales… How much are our inferences curtailed by lack of data versus lack of signal of past events in that data?

Cross-talk. One thing I did think the authors could have mentioned (in an otherwise comprehensive overview) is the potential lack of communication with researchers generating the data and researchers developing methods to analyse this data. Although there are (probably quite a few) exceptions, my view is that there is a small band of researchers developing ever more complex models that are then applied by another set of researchers on their painstakingly built phylogenetic dataset. A more fruitful method might be for more cross-talk between methodsy and data people so that data is collected and compiled explicitly to answer interesting questions with powerful methods. For instance, the authors end with a brief discussion of the impact of interaction networks and ecological traits on species’ responses to environmental change. What data would be most useful to start modelling these questions and who is best placed to generate it? THAT development would be exciting!

A random selection of other thoughts that came to mind:

Would macroevolutionary perspectives be most useful in conjunction with microevolutionary ones? As global change is so rapid, microevolutionary/ecological responses are the ones we are going to be able to measure. How do these translate into macroevolutionary change (i.e., what types of short-term responses are retained to be detected at the macro-scale – if we knew that, we could (maybe) look for such signals in existing phylogenies)?

Will we ever be able to confidently identify clades nested in larger phylogenies that have been diversifying according to some homogeneous process (or rather will we ever be able to identify higher-level units a la Barraclough 2010)? It seems like if we can do this we’ll be in a much stronger position to infer how past environmental change or past biotic interactions have influenced clade dynamics.

More generally, are we approaching the point where we’ve extracted all the information we can from macro-scale data, or are we just waiting on more sophisticated models/methods?

Finally, in 10 or 100 or 1000 years time, what will the tree of life look like?


Lynsey McInnes

Lynsey McInnes

Everything Lynsey said about this being a big paper is correct, but I think we’d both recommend you stick with it because it covers so much ground. One of the best things a paper can do is make you think, and I really enjoyed reading this paper with a beer in hand to fuel my thoughts!

Lynsey mentioned data availability, and while the authors mention foraminifera quite a few times, they only briefly mention Ezard et al. I like this paper for two reasons: firstly, it has some of my friends on it (…), and secondly, they assess extinction rates using a dataset where we can be almost certain that we caught most of the extinction and speciation events that mattered. Estimating extinction rates from molecular phylogenies is hard (the authors discuss this) – and sometimes it’s really hard to do. Should we (/could we) be shifting our efforts to systems like foraminifera where we have more precise data? This naturally leads me to wonder to what degree taxa differ in their extinction and speciation rates, and what impact this could have on the field…

I think there’s a weird disconnect between conservation biologists and evolutionary biologists, and (as someone who works on eco-evolutionary stuff) I really enjoyed their discussion of how conservation biologists could focus on areas that generate phylogenetic diversity. I think things like the EDGE list are a really good way of helping the general public place evolutionary dynamics in the wider context of conservation biology, but maybe we could do more to link these two areas. Conserving particular areas because they are evolutionary sources of biodiversity is one way, but could we start using information about the way in which species originated to help us better model how they are likely to respond in the future? For example, maybe species that radiated in ‘favourable’ conditions are more likely to go extinct when faced with difficult environmental conditions – a bit like cichlid species being lost when Lake Victoria becomes more polluted. Perhaps that’s stupid, but aren’t there other (fairly tractable) examples we could use?

A few small (probably increasingly silly) questions to finish off. There’s a lot of debate in ecology about spatial scaling, and the extent to which processes at the local (micro) scale apply at the global (macro) ecological scale. If conservation actions are more micro-scale in their application (we can’t make a protected area the size of Brazil, for example), does this reduce the utility of these kinds of historical analyses when trying to understand present-day change? Land-use change is distributed across the planet different to many previous drivers of extinction – does this matter for these kinds of studies?

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5 Responses to Macroevolutionary perspectives to environmental change

  1. yaelsnail says:

    I promise to comment on this paper too. But so far I have only had time and mental capacity to sit down with it twice. I guess I have two more times to go!

  2. yaelsnail says:

    I’ve finally made my way through this paper – first of all, thanks again Will and Lynsey for choosing an interesting read with lots of things to think about and discuss.

    In general I like this paper and see it as a valuable first attempt to lay out a framework for how macroevolutionary research can offer insight into the likely effects of current environmental change. It’s a timely subject, and made the environmentalist part of me feel a little easier about being an academic instead of an activist. I also like the real integration of paleontology and phylogenetics, the suggestions for areas where methods should be developed, and as you guys commented already, the presentation of many nice examples. Lots to keep thinking about.

    With that overall positive feeling in mind, I have some critical comments as well.

    Big issues:
    First, I was disappointed by the English in this paper. I know very well that English is a tricky language for everyone, especially non-native speakers, and do not fault the authors for that. They could have asked a native speaker to check over the manuscript (or perhaps they did! in which case next time they should find a better one …), but actually I am disappointed in the editors of Ecology Letters. Who copy edited this manuscript? I found 2 bad typos (e.g. “descent” instead of “decent”) and many instances of incorrect grammar. And, why did no-one notice that an “apparition” is not the same as a “first appearance” in the fossil record?? Maybe I am being overly picky and sensitive, but some good copy editing would have made this article much easier for me to read.

    Second, I am skeptical of some points in the “Vulnerability and Evolutionary Potential” section.
    – I don’t think that “the processes generating biodiversity” is a good definition of “evolutionary potential;” neither do I see those processes as a high conservation priority. Seems to me that speciation, adaptation, etc will continue on this planet as long as there are any species alive. Rather, it makes more sense to me that we should try to preserve as much of the phylogenetic diversity/evolutionary history that current species represent as possible (alongside the most useful/potentially useful species, the cutest species, the most inspiring species, the easiest species to protect, whatever your other prioritization metric of choice).
    Furthermore, even if we could predict which clades or taxa would diversify fastest in the future – and this seems like a very tough goal to me, because of the need to integrate clade traits, the abiotic environment, and interactions with the biotic environment, all of which will be changing through time as species adapt and move and speciate and go extinct and the environment changes – even if we could make this prediction, how does this relate to which species/regions are higher priority? Are clades that are diversifying faster or that will diversify faster more worth saving than clades that diversify slowly? Should we not protect the coelocanth or ginkgo at all, since they’ve been crap diversifiers in the last millions of years, and might be unlikely to speciate in the near future?
    In addition, while I generally support integrating as much information into conservation planning as possible, including the long-term, macroevolutionary future, practically I wonder how important it is for conservation planning. There are so many immediate conservation challenges … and so many simple rules that we already know, such as “bigger, less fragmented reserves will protect more species for longer.” How much will it help us in conserving biodiversity to know which areas could gain the most new species in the next 100,000 years? That said, I think information on what has influenced extinction rates/vulnerability in the past could be massively helpful in avoiding as much extinction as possible now. I’m just skeptical of the value of predicting/considering future speciation.
    Anyway we could argue back and forth here, and I think that would be good – I just don’t want anyone to automatically think “Diversification is good, we should protect regions and clades with higher diversification.”
    – One question that I don’t think was mentioned, but seems vitally important in this context, is “how much is past vulnerability to extinction/diversification correlated with vulnerability/diversification later on or now?” In other words, how much is vulnerability to extinction/diversification determined by static traits of clades, and how much by the environment/changing traits? How much will understanding the past histories of clades or regions help us understand their futures? I think this needs study.

    Some smaller issues:
    – In a few places the authors mention “current” speciation or extinction or diversification results estimated from phylogenetic trees. Do any phylogenetic methods really measure *current* rates, or rather do they measure rates of the last million years/few hundred thousand years? On a macroevolutionary timescale, the last million years would count as current … but on a conservation timescale, not at all. I suspect that for truly *current* rates we need to look at different data … eg. numbers of subspecies, genetic differentiation within species, historical records of extinctions. In the context of such data, perhaps for example deserts and polar regions would not seem as much like biodiversity sinks, and the tropics less like biodiversity sources.
    – Is it still valid to talk about “background rates” of speciation and extinction? To me that term implies an unchanging rate that is occasionally punctuated by unusual events such as mass extinctions, but in more and more studies (including examples in this paper) we see evidence of speciation and extinction rates changing often/continuously through time or across clades. If speciation and extinction rates change all the time, what is the “background” and what is an unusual “foreground” event?
    – I like the general idea of Figure 2 but am not convinced that those are the only possibilities. Why can’t you have a fast recovery in species numbers with an exponential curve, for instance? Also, the curves don’t totally match the scenarios in the text. The authors say that diversity-dependent diversification should show a pattern like in 2a, and “time for speciation” should show a pattern like in 2c. So what does the pattern in 2b mean?? I’m not convinced that it will be so easy to look at the pattern of diversification and from that deduce the major diversity dynamics.
    – This goes back to what I said above about my doubts that we can really predict much in detail about diversification rates in the future – I am not impressed by Figure 6. Looks cool, but I think it follows a way oversimplified approach, that makes it seem like we can predict a lot more than we really can. I would hate to see a figure like this presented to conservation or government officials as anything other than a VERY SPECULATIVE assessment. I think we need to retain the big perspective of how much data we actually have, how much certainty we have, and thus how well we can actually predict the future in detail (rather than just identifying broad tendencies). A map like this makes it seem like we know a lot more, and are much more certain about the future, than we actually are.

    Oops, it seems I had a lot to say. Next time pick a simpler paper and I will be less long winded =)

  3. yaelsnail says:

    ps. regarding my last point about how much can we really know about diversification in the past or future … I meant to plug Lynsey’s 2011 paper (http://rspb.royalsocietypublishing.org/content/278/1722/3294.abstract) here – I think it’s a good example of how sometimes, the past is just opaque to us. There is a limit to how much we can figure out.

  4. lynsey83 says:

    Thanks for adding your thoughts, Yael.
    What I mostly took away from your reply was that we should be aware that we are perhaps further away from using macroevolutionary insights to provide sound guidance for on-the-ground conservation action than this article suggests. I think you are right! I’m not sure if the gulf can really ever be reconciled, but your suggestion to focus at much finer scales seems relevant (subspecies, available genetic variation, microevolutionary responses to change – but then you are not really applying a macroevolutionary perspective, more a microevolutionary one). I just read a really cool review of the importance and value in looking at impact of climate change on genetic diversity within populations and species (Pauls et al. 2013 Mol Ecol doi: 10.1111/mec.12152) and it again highlighted to me that if we want to incorporate potential evolutionary responses into our understanding of the impact of climate change, this is the scale we should be looking at. Alternatively, we just have to be a lot more stringent in delimiting the scope of the macroevolutionary perspective for providing insights on responses to environmental change. Partitioning out the impact of traits vs. environment (and how these might interact) on past extinction risk (and past diversification potential if you are keen on picking ‘winners’) might be a good place to focus?

  5. yaelsnail says:

    I guess my actual biggest criticism is that I am skeptical that it’s worth our time now to worry about how we are affecting future speciation. It seems to me like the real, pressing problem at the moment is extinction – and if we do a good job to stop extinction from taking out a lot of our current diversity, then speciation will continue on its own just fine. I’m wary of making too strong a statement here because I largely study speciation, not extinction … and I would like my own work to have some practical value … but in the end I do believe that the *practical* conservation value of macroevolutionary research lies in understanding extinction.

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