Understanding within- and between-population variation in responses to climate variability and extreme climatic events

Human-driven climate change is leading to increases in average temperature that are having profound impacts on the natural world, including breakdowns in species interactions, shifts in species ranges, and population collapse and species extinctions. Alongside overall warming, climate change is expected to lead to changes in climate variability and in the frequency, duration, and severity of extreme climatic events, such as heat waves. Increased climate variability and extreme events may lead to more severe effects on organisms than more gradual climate warming because they lead to larger relative changes in climatic variables, such as temperature, over short timescales. In doing so, they are more likely to expose organisms to conditions that affect their performance. Consequently, we need to understand how climate variability and extreme climatic events affect the survival and reproduction of organisms, the degree to which evolutionary change provides a means for species to adapt to continued change, and whether there are environmental factors that act to exacerbate or ameliorate the effects of increased climate variability or extreme climatic events.

Progress to understand the impacts of climate variability and extreme climatic events in the wild has been limited largely by the difficulty of collecting appropriate data. This is because such studies require climatic data at a temporal and spatial resolution relevant to wild populations, information on the survival and reproduction of large numbers of wild individuals, measures of individual phenotypes in wild systems, and detailed information on environmental characteristics, such as resource availability or habitat quality.

We propose to use an ecological system that has been extensively used to study the effects of changing average climate - passerine birds exploiting caterpillars as a food source in deciduous woodlands - to examine how variation in climate variability and extreme climatic events generate variation in survival and reproduction. First, we will use data from one of the longest running studies of a wild animal - the study of great tits (Parus major) in Wytham Woods, near Oxford for which data exist for almost 60 years under standardised conditions. We will use these data to explore the links between climate at a variety of spatial scales, measures of habitat variation, and how these are linked to individual reproductive data and to individual fitness. We will then expand on this single-population study by using datasets from 27 studies of great tits across Europe, to quantify continent-wide patterns in the relationship between climate variability/extremes an survival and reproduction of these birds, and explore differences between populations and between species in these relationships.

Using the approach outlined above, our work will provide novel insights into: (1) the immediate consequences of variation in climate variability and extreme climatic events on survival and reproduction, and thus potentially on population health; (2) the influence of these climatic changes on natural selection at both the local and European scale; and (3) the role of environmental heterogeneity in modifying the effects of climate variability/extreme climatic events. These insights can then be used to forecast how future changes in climate variability/extreme climatic events may influence populations and species, better predict the potential for evolution to help species cope with continued human-driven climate change, and pinpoint ways that conservation can use variation in the environment, between individuals, and between populations, to minimise the effects of continued climate change on biodiversity.