This study will use models to ask how individual variation in survival and reproductive rates affects population extinction risk. The investigators will examine both genetic and environmental causes of variation in demographic rates. They will develop a method for modeling growth of populations in which individuals vary in their growth rates and their birth and death rates. They will use the extensive body of research on these rates in plant populations, by compiling a database from published and unpublished research on this topic. Statistical analyses of the data will allow conclusions about the pervasiveness of variation in demographic rates.
This research is important because models from demography are used widely in conservation, epidemiology, wildlife management, control of weeds and pest animals, and in social policy. Almost uniformly, these models treat individuals in a population - after accounting for differences due to sex, age, or size - as though they all have the same chances of surviving or giving birth. Recent research has shown that sometimes this assumption of homogeneity within populations can lead to substantial errors when estimating population growth rates and extinction risks. A key aim is to develop methods that help researchers determine when they need to account for demographic variation.
