ORCC: Interindividual variation in acclimatization capacity as a facilitator of population responsiveness to a changing climate

Understanding how animals respond to temperature change is of increasing importance as climates become more variable and extreme weather events increase in frequency. Yet much debate exists about whether species will be able to respond to global change – and if so, how will they do it? Many animals living in temperate climates, like those across the northern U.S., already harbor the capacity to cope with temperature changes: they do so every time the seasons turn, and they even do so on shorter time scales, like from day to night.

The birds at the local bird feeder are a great example of this. On a cold winter day, they turn up their internal engines to produce more heat, and they visit the feeder more often to fuel their engines. When the temperature warms up, they turn those internal heaters down to save energy.

The ability to make these changes to their physiology may be especially beneficial when the weather turns rapidly, like when a winter storm hits, for example. But are some individuals better at changing this internal physiology than others? And if so, how do they do this?

And what does this mean for their ability to withstand temperature changes? Using automated birdfeeders to track birds across the winter season, this project will make connections between an individual’s ability to change its physiology in response to temperature, its genetics, and its survival. These findings will then be incorporated into the National Audubon Society’s models with the goal of improving predicted responses to climatic change and informing conservation action.

Accurately documenting the capacity for natural populations to respond to environmental variation is a core challenge of biology. When environmental fluctuations occur on short temporal scales relative to the lifetime of an individual, the ability to reversibly modify trait values can allow individuals to optimally match their phenotype to the environment.

Determining the causes and consequences of variation in this phenotypic flexibility is critical to our understanding of individuals’ capacity to cope with accelerating global change and for realistic projections of species’ viabilities in the future. This pursuit necessarily requires linking genotype to phenotype to fitness, though such connections remain rare.

Existing empirical evidence demonstrates that temperature variability drives spatial patterns of variation in physiological flexibility across the range of a small songbird, the Dark-eyed Junco (Junco hyemalis). This project will now quantify: (1) patterns of variation in junco physiological flexibility across a thermal variability gradient; (2) energetic costs of flexible phenotypic changes; (3) selection on physiological flexibility in the wild; and (4) spatial and temporal changes in allele frequencies for loci associated with physiological flexibility.

These aims will be achieved using field mark-resight studies, repeated physiological assays, controlled laboratory experiments, and whole-genome resequencing to quantify the costs and benefits of flexibility and determine flexibility’s potential to evolve in response to environmental change. Taken together, this work will identify the adaptive benefit of junco physiological flexibility and provide a mechanistic understanding of the ability of natural populations to respond to global change.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.