Ecological and evolutionary effects of climate change on rainforest food webs

Lead Research Organisation: University of Oxford
Department Name: Zoology

Abstract

Ecological communities are complex, interacting networks of species, linked by competition, mutualism, predation and parasitism. In the 'Origin of Species', Charles Darwin famously wrote of 'an entangled bank', comprising a bewildering richness of species and an even more complex web of connections among them. Fundamentally, ecologists and evolutionary biologists seek to unravel this complexity, by establishing why species occur where they do, why they replace each other under certain conditions, and how the species interactions that make up ecosystems will change as environments change.

As the climate warms and extreme events become more frequent, existing connections between species are changing in strength, or being severed completely; and new connections are forming as species change in abundance and shift their distributions (e.g. colonising cooler habitats, while becoming locally extinct in warmer habitats). Biologists use information about the range of temperatures where species currently occur to predict where species will occur in a future, warmer world. However, better predictions about the consequences of climate change will be possible if we can also take into account changing interactions between species, as well as the potential for species to evolve to cope with new conditions.

We urgently need to test how whole food webs of interacting species are structured by biological processes (e.g. competition and predation) and by temperature, and how these ecological networks will respond to climate change. It is also important to test the extent to which current adaptive divergence across species' geographical ranges will increase their resilience to future climate change. To achieve this, our project will exploit a unique model system (Drosophila fruit-flies and parasitic wasps that are associated with them, called parasitoids) in a high-diversity ecosystem threatened by climate change (Australian tropical rainforests). With this system we will use field observations, field transplant experiments and mathematical models to test: (i) what determines species' local distributions and food web structure; (ii) the responses of natural and simulated networks of interacting species to simulated climate change; and (iii) the underlying mechanisms driving these changes, including the effects of genetic variation among populations within species and the potential for rapid evolutionary adaptation to warmer temperatures. The outcome will be a better and more predictive understanding of how climate change will affect the biotic interactions that characterise biodiversity and underpin the functions and services of natural ecosystems.

Planned Impact

We have identified three categories of beneficiary:

(1) The General Public:
The UK public has an enormous interest in wildlife, and a particular fascination with rainforests. People are concerned about how biodiversity is responding to climate change, and the future consequences of biodiversity loss for human economies, climate stability, and our health and happiness.

(2) Policy-makers and conservation organisations:
The ability to predict species' responses to climate change is critical for conservation, agriculture and medicine, but the mechanisms governing these responses remain poorly understood. An important knowledge gap concerns the direct influence of climate on species distributions versus its effects via interacting species and habitats. Our work will thus be of interest to policy-makers, landscape-planners and stakeholders in agriculture and medicine who are concerned by how climate change may alter interactions among invertebrates, with relevance for species acting as disease vectors, agricultural pests or invasive alien species in natural and managed landscapes.

(3) Wider society:
By examining the mechanisms driving observed changes to species distributions resulting from climate change, our research will contribute to UK leadership in predicting the regional and local impacts of environmental change. Of particular importance at the moment is defining a safe "operating limit" for key environmental pressures. Of these pressures, there is greatest uncertainty about biodiversity loss, and how it will reduce planetary resilience in the face of anthropogenic climate change. Our research will contribute new data to the evidence base that will empower society to respond to global climate change. It will do this by refining forecasts of how species and ecological communities respond to the interacting effects of climate change and interacting species. In particular, our data will address these issues in tropical rainforests which are the planet's most species-rich ecosystems, and also amongst the most sensitive to climate change.

Publications

10 25 50

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O'Brien EK (2022) Environmental variation and biotic interactions limit adaptation at ecological margins: lessons from rainforest Drosophila and European butterflies. in Philosophical transactions of the Royal Society of London. Series B, Biological sciences

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Segar ST (2020) The Role of Evolution in Shaping Ecological Networks. in Trends in ecology & evolution

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Wong MKL (2019) Trait-based ecology of terrestrial arthropods. in Biological reviews of the Cambridge Philosophical Society

 
Description We have been able to use novel molecular biology techniques to document and quantify the interactions between rainforest fruit flies and the parasitic wasps that consume them. We have documented how the organisation of these food webs changes along environmental gradients. We have also succeeded in establishing laboratory cultures of these species, allowing us to measure their performance under different climate change scenarios, and experimental work that explores the response of sets of interacting species to a a range of perturbations.
Exploitation Route Our host-parasitoid study system is now available to researchers as a tractable model system in population and community ecology, for both field and laboratory work.
Sectors Agriculture

Food and Drink

Environment

 
Description Escaping the enemy: spatial ecology of rainforest tree-insect interactions
Amount £418,844 (GBP)
Organisation The Leverhulme Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 02/2022 
End 02/2027
 
Description The ecological and evolutionary legacy of extreme climatic events for food web resilience
Amount £503,905 (GBP)
Funding ID NE/X000117/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 01/2023 
End 12/2025
 
Title Data from: Temperature fluctuations during development reduce male fitness and may limit adaptive potential in tropical rainforest Drosophila 
Description Understanding the potential for organisms to tolerate thermal stress through physiological or evolutionary responses is crucial given rapid climate change. Although climate models predict increases in both temperature mean and variance, such tolerances are typically assessed under constant conditions. We tested the effects of temperature variability during development on male fitness in the rainforest fly Drosophila birchii, by simulating thermal variation typical of the warm and cool margins of its elevational distribution, and estimated heritabilities and genetic correlations of fitness traits. Reproductive success was reduced for males reared in warm (mean 24°C) fluctuating (± 3°C) versus constant conditions but not in cool fluctuating conditions (mean 17°C), although fluctuations reduced body size at both temperatures. Male reproductive success under warm fluctuating conditions was similar to that at constant 27°C, indicating that briefly exceeding critical thermal limits has similar fitness costs to continuously stressful conditions. There was substantial heritable variation in all traits. However, reproductive success traits showed no genetic correlation between treatments reflecting temperature variation at elevational extremes, which may constrain evolutionary responses at these ecological margins. Our data suggest that even small increases in temperature variability will threaten tropical ectotherms living close to their upper thermal limits, both through direct effects on fitness and by limiting their adaptive potential. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
URL https://datadryad.org/stash/dataset/doi:10.5061/dryad.3f8v2
 
Title Drosophila-parasitoid interactions along an elevation gradient in an Australian rainforest, 2016 
Description The dataset contains records of Drosophila flies and associated parasitic wasps collected along two elevational (temperature) gradients from Australian rainforest site. The data is presented at the individual Drosophila pupae level. It describes patterns of parasitism levels from 14 sites and the structure of quantitative food webs at six sites. Also included are temperature records from each site. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
URL https://catalogue.ceh.ac.uk/id/85657c4c-54c9-4d02-a262-455ea1c38d95
 
Title Environmental variation and biotic interactions limit adaptation at ecological margins: lessons from rainforest Drosophila and European butterflies 
Description Models of local adaptation to spatially varying selection predict that maximum rates of evolution are determined by the interaction between increased adaptive potential owing to increased genetic variation, and the cost genetic variation brings by reducing population fitness. We discuss existing and new results from our laboratory assays and field transplants of rainforest Drosophila and UK butterflies along environmental gradients, which try to test these predictions in natural populations. Our data suggest that: (i) local adaptation along ecological gradients is not consistently observed in time and space, especially where biotic and abiotic interactions affect both gradient steepness and genetic variation in fitness; (ii) genetic variation in fitness observed in the laboratory is only sometimes visible to selection in the field, suggesting that demographic costs can remain high without increasing adaptive potential; and (iii) antagonistic interactions between species reduce local productivity, especially at ecological margins. Such antagonistic interactions steepen gradients and may increase the cost of adaptation by increasing its dimensionality. However, where biotic interactions do evolve, rapid range expansion can follow. Future research should test how the environmental sensitivity of genotypes determines their ecological exposure, and its effects on genetic variation in fitness, to predict the probability of evolutionary rescue at ecological margins. This article is part of the theme issue 'Species' ranges in the face of changing environments (Part II)'. 
Type Of Material Database/Collection of data 
Year Produced 2022 
Provided To Others? Yes  
URL http://datadryad.org/stash/dataset/doi:10.5061/dryad.q573n5tkg
 
Title cassandRa 
Description This package for the open source R software is designed to work with incompletely sampled ecological bipartite networks. It does two jobs. First, it includes a function to try and identify likely missing links, by fitting a whole suite of models. Second, it includes an easy way to do some basic sampling bootstrapping, to test how robust results are to variations in sample sizes. 
Type Of Material Data analysis technique 
Year Produced 2020 
Provided To Others? Yes  
Impact n/a 
URL https://cran.r-project.org/web/packages/cassandRa/vignettes/
 
Description Hrcek student co-supervision 
Organisation University of South Bohemia
Country Czech Republic 
Sector Academic/University 
PI Contribution Involved as a formal collaborator on funding applications. Will co-supervise 2 PhD students and 1 postdoc working on topics closely aligned to the NERC grant
Collaborator Contribution Staff time devoted to work that benefits both institutions
Impact None yet
Start Year 2016
 
Description Ilmington School visit and talk 2019 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Owen Lewis gave a 30 minute talk and Q&A about tropical rainforests, climate change, deforestation and biodiversity with 55 Key Stage 2 children and their teachers at Ilmington Primary School, Warwickshire.
Year(s) Of Engagement Activity 2019
 
Description Invited seminar, Liverpool University 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact Invited seminar on tropical forests at the University of Liverpool, 14th February 2019.
Year(s) Of Engagement Activity 2019
 
Description School Visit (Ilmington) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Talk and Q&A with 30 Year 3 students on rainforest ecology and conservation, linked to their class topic 'Rainforests'.
Year(s) Of Engagement Activity 2017
 
Description Talk to Biodiversity Group, Stretton-on-Fosse village hall 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Informal talk, presentation and Q&A to 50 members of the public attending a local Biodiversity Group Annual event.
Year(s) Of Engagement Activity 2017