Living at the edge: causes and consequences of individual variation in a changing world

Lead Research Organisation: University of Sussex
Department Name: Sch of Life Sciences


Environmental conditions change. How an organism reacts to such changes, for instance in temperature or food availability, can have profound consequences for its survival and reproduction (i.e. its fitness) and influence population dynamics. Understanding how organisms are influenced by environmental conditions is a fundamental issue in the biosciences, and can also help conserve species under pressure of rapid human-induced environmental change.

Ecological studies typically address the above problem using species trait averages despite evidence that within-species variation in phenotypic traits is the raw material for adaptive evolutionary change. Within a population, individuals often show consistent behavioural differences ('personality differences') and these may evolve together with physiological, morphological and life-history traits forming 'syndromes' of correlated traits. Environmental conditions are hypothesised to affect the evolution of these syndromes but empirical evidence is lacking currently. Given that correlated trait evolution probably also affects individual fitness, as well as population or community dynamics, it is likely to have profound implications for key evolutionary and ecological processes.

Experimental, multi-trait studies in natural habitats that test the causes and consequences of within-species trait variation and trait covariances (trait 'syndromes') across environmental conditions are needed to advance our understanding of how environmental conditions shape individual variation. Such studies will also enable more accurate predictions about how human-induced environmental change influences populations and species. We will conduct such an experimental, multi-trait study. This is possible because we have identified a well-suited study organism, a flightless forest-dwelling ground beetle with immediate response to changes in environmental conditions and limited dispersal power, allowing us to address our hypotheses in rigorous experiments.

We will test whether individuals of our model species vary systematically in their trait values (strength at which a trait is expressed) and covariances among behavioural, physiological and morphological traits across environmental conditions. We will assess the underlying mechanisms and fitness consequences of this differentiation. We will test whether trait differences predict individual survival and reproduction in different environmental conditions, including environmental change, and will assess resulting consequences on population dynamics. We will study individuals at forest cores and edges (edges are habitat boundaries with altered environmental conditions, usually through land use change), and will identify the main environmental variables that shape individual differences. We will conduct a combination of translocation and enclosure experiments to expose individuals to different environmental conditions and measure their reaction to change, and the fitness consequences thereof.

Our project will provide novel insights into causes and consequences of within-species trait variation and covariances, and their interplay with environmental conditions. Our study will be one of the first to address the role of within-species variation on short- and longer-term responses to changed environmental conditions using a multi-trait, covariance approach spanning behaviour, morphology, metabolism and fitness within and across generations. For the first time, we will assess experimentally the role of within-species trait variation and covariances on individuals' response to and fitness consequences of edge effects in an insect species under natural conditions. Our project will also provide insight into the mechanisms underlying effects of human-induced environmental change on insects in particular, and animals more generally.


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