Ecology Live with Enrico Rezende: Temperature effects in organisms and communities

The British Ecological Society is broadcasting free online talks on the latest ecological research during the coronavirus lockdown period. In this talk, Enrico Rezende of the Pontificia Universidad Católica de Chile talks about temperature effects in organisms and communities.

Why is global warming a major concern? Temperature affects biological processes in multiple ways, and warming impacts ecological communities across the world. In this talk, Enrico discusses how temperature affects organisms at different levels of organisation and the conceptual frameworks that thermal biologists currently employ to study this pressing issue.

REFERENCES

REFERENCES
• Mannion, P. D., Upchurch, P., Benson, R. B., & Goswami, A. (2014). The latitudinal biodiversity gradient through deep time. Trends in Ecology & Evolution 29: 42-50.
• Tittensor, D. P., Mora, C., Jetz, W., Lotze, H. K., Ricard, D., Berghe, E. V., & Worm, B. (2010). Global patterns and predictors of marine biodiversity across taxa. Nature 466: 1098-1101.
• Pachauri, R. K., et al. (2014). Climate change 2014: synthesis report. Contribution of Working Groups I, II and III to the fifth assessment report of the Intergovernmental Panel on Climate Change (p. 151). IPCC.
• Urban, M. C. (2015). Accelerating extinction risk from climate change. Science 348: 571-573.
• Huey, R. B., & Kingsolver, J. G. (1989). Evolution of thermal sensitivity of ectotherm performance. Trends in Ecology & Evolution 4: 131-135.
• Sinclair, B. J., et al. (2016). Can we predict ectotherm responses to climate change using thermal performance curves and body temperatures?. Ecology Letters 19: 1372-1385.
• Rezende, E. L., & Bozinovic, F. (2019). Thermal performance across levels of biological organization. Philosophical Transactions of the Royal Society B, 374: 20180549.
• Deutsch, C. A., Tewksbury, J. J., Huey, R. B., Sheldon, K. S., Ghalambor, C. K., Haak, D. C., & Martin, P. R. (2008). Impacts of climate warming on terrestrial ectotherms across latitude. Proceedings of the National Academy of Sciences 105: 6668-6672.
• Dillon, M. E., Wang, G., & Huey, R. B. (2010). Global metabolic impacts of recent climate warming. Nature 467: 704-706.
• Pinsky, M. L., Eikeset, A. M., McCauley, D. J., Payne, J. L., & Sunday, J. M. (2019). Greater vulnerability to warming of marine versus terrestrial ectotherms. Nature 569: 108-111.
• Araújo, M. B., Ferri‐Yáñez, F., Bozinovic, F., Marquet, P. A., Valladares, F., & Chown, S. L. (2013). Heat freezes niche evolution. Ecology Letters 16: 1206-1219.
• Hoffmann, A. A., Chown, S. L., & Clusella‐Trullas, S. (2013). Upper thermal limits in terrestrial ectotherms: how constrained are they? Functional Ecology 27: 934-949.
• Rezende, E. L., Castañeda, L. E., & Santos, M. (2014). Tolerance landscapes in thermal ecology. Functional Ecology 28: 799-809.
• Kearney, M. R., Gillingham, P. K., Bramer, I., Duffy, J. P., & Maclean, I. M. (2020). A method for computing hourly, historical, terrain‐corrected microclimate anywhere on Earth. Methods in Ecology and Evolution 11: 38-43.

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Enrico has answered a number of the questions we didn't have time for during the live talk. We've posted them here in the comments.

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Javiera Chinga: Thanks for this very interesting talk. You showed that plants behave similar to some animals in terms of performance curves. In a goblal warming scenario: do you think plants will be more impacted as they cannot move (may be leading to longer exposure time)?
R: Thank you for the kind words. That’s a really good question, and my impression is that water availability will determine the outcome of different plant communities. Leaf evaporation tends to decrease temperatures locally and across entire ecosystems, such as in the Amazon rainforest, and therefore I would argue that rising temperatures may not be a major concern per se but its impact in precipitation regimes might.

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mehmet topkaya: Great talk! As I know (correct me if I am wrong) when diversity is higher than the ecosystem is stronger, so maybe the impact in total in tropical could be lower even though the populations have lower tolerance?
R: Thank you for the kind words. The association between diversity and resilience has been a major area of research in community ecology, and for small perturbations such as the introduction of new species or a local extinction, this may be true. However, global warming constitutes a massive perturbation that cannot be readily accommodated by ecological communities, and this is why partly all models suggest that tropical regions will be more severely impacted.

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Saket Shrotri: nice talk. My question is related to changes in intra-year variations and how to incorporate them into the models? Because of climate change the daily max-min temp may vary drastically and this may affect phenology of the organisms.
R: Thank you, glad you liked it! I hear you, in my opinion one of the main weaknesses of current approaches is that they fail to incorporate temperature changes at very small temporal windows (i.e., within years, months or days). We are currently working precisely on this problem.

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Eleanor Barr: Is there research or practical trials looking into how habitats could be managed to maintain the temperature of the local species? e.g. in Scotland riparian habitat on river banks have been reintroduced to create better conditions for spawning of fish, etc.
R: Yes, efforts to prevent deforestation and active engagement in reforestation have a direct impact on the availability of microclimates and also provide a local thermal buffer to rising temperatures (as mentioned above, leaf evaporation works as an ecological cooling system). Artificial shelters that reduce the impact of solar radiation constitutes another possibility. Interestingly enough, this area of research is also important in urban environments since cities are generally a couple of degrees warmer than their surrounding environments.

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Rodrigo Kruger: to improve niche models, how could we include species abundance in these models in different co2 emission scenarios?
R: Very difficult question, since species abundance is highly variable and can fluctuate dramatically over time. What can be done, however, is to quantify relative mortality rates with probabilistic models (i.e., what’s the fraction of the population that is expected to be affected by temperature).

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Marc Cadotte: How do the thermal ecology predictions interact with gains and losses of habitats?
R: That’s an excellent question. The shortest answer is that habitat loss will generally result in more homogeneous environments and, in the case of deforestation, in exposure to higher temperatures and thermal extremes. These are synergic effects that, together with the impact of habitat loss on precipiation regimes, might ultimately explain the desertification we are observing in several regions of the globe.

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Lianne Allen-Jacobson: Have you compared performance for the same organism using different types of traits (population, organism, cellular)? Do they predict the same thermal maximum?
R: This was our prediction in Rezende & Bozinovic (2019), and now we have empirical data for Drosophila. Indeed both CTmax and thermal breadth decreased at higher levels of organization, we are currently working on the manuscript and hope to submit it soon.

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Jonathan Bonfanti: Thanks for your presentation E. Rezende, here my question : what do you think about threshold effects in high latitudes (that you said less threatened by climate change) ? Would local communities reach faster their "cumulative thermal stress" limit instead of their CTmax, since they live in relatively lower Temp than in tropics ?
R: That’s hard to say, but the limited data available suggests that this is not the case. Organisms at high latitudes exhibit surprisingly decent tolerance to high temperatures, which is partly explained by high seasonality at high latitudes and relatively warm summers (thermal minima vary substantially more than maxima across latitudes).

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Giulio Biondi: The temperature referred to in the previous graph is the average environmental temperature to which the organism is exposed?
R: In principle, the thermal performance curve indicates how performance would change instantaneously with temperature since time is not explicitly considered. In reality, most researchers work with temperature averages of some sort (daily averages, etc).

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How to separate the effects of temperature vs. parasites on metabolism?
R: It is possible to estimate this experimentally by exposing insects with and without parasites to a thermal stress. In general, parasitism is expected to decrease thermal tolerance due to synergic effects (i.e., it is a combined stress), but this may not always be the case depending on the sensitivity of the parasite to the thermal stress itself, as discussed in the previous response.

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Nicolás Berrios: Can we expect that vertebrates in higher latitudes would have a better performance with rising temperatures ? I’m thinking in large herbivores.
R: Possibly. For ectotherms higher temperatures may result in a large activity window both daily and seasonally and, for endotherms, reduced energy requirements for thermoregulation. With regards to herbivores in particular, the potential impact of climate change on plant biomass is an indirect impact that should be taken into consideration.

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João Felizardo: Thanks for the great presentation! Regarding positive feedback on global warming and microbiologic C emissions. With higher CTmax points for this microbes can we expect a higher relevance of this C route?
R: Difficult to say because carbon and oxygen emissions vary respectively with respiration and photosynthetic rates, and how warming temperatures will impact these processes varies across regions and lineages. Therefore, while one might expect higher microbiological carbon emissions as temperatures rise, it is unclear how this will ultimately impact the concentration of greenhouse gases in the atmosphere.

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Boris Tinoco: What do we know about thermal tolerances of organisms across elevations?
R: Intuitively one would expect that organisms at higher altitudes would exhibit performance curves displaced towards lower temperatures (i.e., lower critical limits and thermal optima), and there is some empirical evidence that this is the case. However, this trend is often not obvious not only due to the limitations of current empirical approaches, but also because there is a lot of gene flow between populations at different elevations.

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Ciaran Higgins: Is biodiversity expected to increase in temperate regions?
R: Only due to the influx of species from other regions, even though this will be a relatively low number in comparison to those species that might not make it. Consequently, my guess is that biodiversity will decrease less in temperate regions in comparison to the tropics.

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Luiz Cortez: There is any chance that tropical organisms to change their distributions to the warming temperate zones?
R: As answered during the talk, yes. Several organisms are already moving as nicely summarized in a paper by Terry Root in Nature a couple of years ago.

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Ritu Yadav: What about plants? do we have any study which shows plants are also migrating due to increase in temperature?
R: Yes, there are studies showing how plant populations are displacing towards higher latitudes. The problem with plants, however, is that this process involves differential recruitment of seedlings and is considerably more difficult to study in the laboratory with the approaches that I described in the talk.

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Charly Crump: Is the reason that organisms living in equatorial habitats are impacted more due to the fact that those environments tend to be more species rich?
R: That depends. Indirect effects will likely be more pronounced because of cascading effects (coextinctions) that are expected to be higher in more species rich regions. However, the impacts that I discussed in the talk result primarily from differences in current temperatures, and the fact that a small increase in temperatures in the tropics will result in higher vulnerability on a species by species basis.

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Anonymous Attendee: What is the potential for thermal adaptation to play a role in predicted effects of climate change?
R: Great question, many would argue that it will definitively have a role. After all, this is not the first time that lineages have encountered major changing climatic conditions and here we are. The main problem is to diagnose which lineages might be able to cope with rising temperatures and adapt, and which are more vulnerable and might go locally extinct.

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Anonymous Attendee: Do you have any further reading to suggest on this?
R: The references included in this talk are now available in the Youtube page. Having said that, I highly recommend Michael Angilletta’s book “Thermal Adaptation: A Theoretical and Empirical Synthesis” and Andrew Clarke’s “Principles of Thermal Ecology: Temperature, Energy and Life”.