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

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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.