Collaborative Research: OPUS: Synthesizing multi-decadal and multi-site data to promote understanding of key questions in stochastic demography

The geographical ranges of most species across the Earth are made up of multiple populations (all individuals of that species in a defined area) and these populations often experience quite different conditions. In addition, how the environment will change in the future will also differ among populations and will ultimately determine whether each population persists, which in turn will determine whether the entire range of a species will contract, expand, or shift in space.

In the face of environmental change, such shifts in geographical ranges can have important implications for ecosystem health and human well-being. Given the variation in climate across time and space for populations of even a single species, to understand and predict how geographical ranges will shift with changing climate requires both long-term and multi-population studies.

This project will synthesize data collected over decades (up to 29-years to date) for a total of 40 populations of two species of tundra plants that are widely distributed across western North America. Tundra plants are especially suited to studies of geographical range shifts driven by climate warming, because they are adapted to cold climates but can also benefit to some degree from warming.

The researchers will use the long-term data to examine how survival, growth, and reproduction of the tundra plants respond to variation in multiple, measured environmental factors (both climatic and non-climatic) at multiple spatial scales (from the scale of individual plants to the scale of entire regions), and will assess how year-to-year variation and long-term trends in those factors are likely to either enhance abundance or increase extinction risk of those plants within populations and thus increase or decrease the geographical ranges of the species. All the data on both performance of individual plants and environmental factors affecting that performance will be made publicly available for any future studies of how environmental changes affect geographical range shifts.

The three questions this research aims to address are, first, how does demographic buffering – the evolution of reduced temporal variance in demographic rates (survival, growth, reproduction, and recruitment), especially those that most influence population growth – arise from responses of those rates to specific climatic drivers? Second, what role do differences in demographic responses to environmental variation between individuals within populations, between populations in a region, and between regions play in reducing temporal variance in population growth and thus enhancing species persistence locally, regionally, and across entire geographical ranges?

Third, do long-term demographic data reveal evidence of adaptive demographic lability – an increase in the population growth rate due to temporal variation in vital rates caused by nonlinear responses to climate, the opposite of demographic buffering - and if so, does its presence depend on the type of environmental driver (e.g., abiotic vs. biotic drivers)?

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.