An individual-level approach to understanding responses to climate in wild ectotherms

Lead Research Organisation: University of Exeter
Department Name: Biosciences


How ecosystems will change in response to changes in climate is one of the pressing questions of our times. 'Cold blooded' animals (ectotherms) such as insects and other invertebrates play key roles in terrestrial ecosystems, so understanding how they will be affected by climate change is of key importance.

Temperature influences every aspect of the lives of ectotherms, setting boundaries on what they can or cannot do and dictating their vital metabolic rates. Ectotherms perform their physiological functions within a range of tolerable temperatures, and critical functionalities such as locomotion, reproduction and growth are strongly temperature-dependent. Many ectotherms absorb radiation from sunlight and exchange heat with their immediate microenvironments. The body temperature of an ectotherm can differ substantially from the ambient air temperature. Many species also use behaviour to regulate body temperature, for instance by moving in and out of the sun. Although there is abundant evidence for behavioural thermoregulation in ectotherms, we don't know how much potential this provides for ectotherms to adjust to changes in climate by changing their behaviour.

The main way in which environmental science forecasts how changes in climate will affect the distribution of species is by extrapolating from current distributions and climates. The weakness of his approach is that we know that ambient air temperatures are a poor surrogate for the climatic conditions that affect the thermal performance of organisms. We have carried out pilot experiments in a meadow in Northern Spain where we have been monitoring a natural population of field crickets. These show that crickets frequently reach 20 degrees above the air temperature by basking in the sun and that they move in and out of their burrows in order to regulate their temperature.

The aim of this project is to address key questions that relate to how we can predict the temperature that individual ectotherms will experience based on the climate and hence how climate affects the viability of populations. These questions are:

1. What is the relationship between climate data and the temperatures that individual ectotherms experience?
2. How do individual body temperature profiles impact fitness in nature?
3. What is the potential for plastic and evolutionary adaptation to climate?

We will use our cricket population to answer these questions with the aim of extrapolating what we learn in crickets to allow us to make predictions about a huge range of other species. Crickets are a fairly typical temperate insect species with a single generation each year. We will exploit the fact that we already have 12 years of video recordings of individually tagged crickets - more than a million hours of recordings of crickets moving in and out of their burrows. We will combine these data with data from a weather station we have had on-site since 2006. This will allow us to quantify how individuals change their behaviour in response to temperature - how hot they allow themselves to get, and how tightly they control their temperature. Using DNA fingerprinting that we have already carried out we can count how many offspring each individual has in the following generation which allows us to measure the reproductive success of crickets according to how they respond to the climate.

We will combine these video archive studies with field experiments. Firstly we will directly measure the effect of sunshine on the growth rate of juvenile crickets. Secondly, we will compare behavioural thermoregulation between high and low altitude populations to see if behaviour alone can allow a single species to live in a wide range of thermal environments. Thirdly we will conduct a translocation experiment to see if there are genetic differences in how individuals from cold environments manage their temperature compared to individuals from warm environments.

Planned Impact

The project will contribute to efforts to predict the biological impacts of climate change by combining our thermal modelling framework with a vast data archive on the behaviour of wild crickets. We are highly motivated to transcend the boundaries of academia to contribute to efforts to anticipate, and hopefully ameliorate, negative effects of climate change. The main academic outcomes of this project will be insights into the extent to which insect populations already possess the capacity to exploit a wide range of temperature regimes and/or the potential they have to rapidly evolve to do so. This is a broad question so making a direct link to policy and practise will be challenging, but we believe there are ways to immediately exploit our findings. In the medium term we are confident that our findings will help to mitigate risks associated with the effect of changing climate on crop pests benefitting stakeholders in agriculture. Within the period of the project our major impact plans are to increase public understanding of the interactions between environmental change and the resilience of natural populations. This aspect of our impact plan builds on the work carried out in our previous WildCrickets NERC projects. In addition to standard activities (publishing and promoting the work) we will engage in the following impact activities:

Insect pest risk assessment for agri-business
Our long-term work with Defra entails developing crop pest and disease risk models for the whole of the UK, driven by microclimate datasets. At present our models assume a simple relationship between pest development rates and accumulated degree-days close to the ground as indicator of likely emergence. What is missing is a detailed understanding of how insects behaviourally exploit their microenvironments to modify their body temperature. This behaviour will have a major impact on development rates and hence the risk of pest outbreak. Our aim will be to use the insights gained in this project to improve the accuracy of our existing pest risk models. This is a challenge, but we are optimistic about being able to generalise from our model species because the heat budget models we will develop are based on fundamental physics and hence will be widely translatable to other organisms provided appropriate information on surface reflectance and body shape are specified. After initial consultation with plant health scientist in Defra, with whom we already work, we will identify a manageable number of pest species and improve the models we have already developed and applied to the whole of the UK. We will work closely with Defra to present these in a user-friendly format on web-platforms with appropriate guidance. We anticipate these will be used by Defra's plant health scientists to carry out more accurate pest risk assessments, guide emergency responses to pest disease outbreaks and deliver guidance on crop pest management.

Communication and Outreach
Our study provides an excellent opportunity to engage with school pupils and members of the general public. We will work with local teachers to develop lesson plans that use a modified version of our existing online Cricket-Tales game ( We will redesign the interface to optimise it for use in lessons including modifying our server setup to allow functions for local data download by classes. We will employ two data collection assistants who will curate example data sets using existing data from online players and assist the PI and CI in visiting schools to trial and develop lessons. Our modified software will provide teachers with a novel way of presenting students with an interactive data collection interface, which students will then use along with a pool of existing data from other players to design their own scientific studies. This process will be followed by data manipulation exercises, presenting their findings, and finally reviewing their methodology and conclusions.


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